JP2019200221A - Micro-lens array, optical writing device, and image forming apparatus - Google Patents

Abstract

To provide a micro-lens array that can prevent image degradation caused by distortion of a glass substrate generated due to expansion and contraction of resin, an optical writing device, and an image forming apparatus.SOLUTION: A micro-lens array 200 consists of two lens arrays 200a, 200b, and the lens array 200a comprises: a glass substrate 220; a plurality of resin lens arrays in which resin lenses 211a, 212a, 213a, 212b, and 213b are lined up along a main scanning direction on a substrate surfaces 220a, 220b of the glass substrate 220, the resin lens arrays arranged in parallel in a sub scanning direction; and resin layers 261a, 262a, 263a, 262b, and 263b that are provided respectively to the resin lenses and interposed between the resin lenses and the glass substrate. In the plurality of resin lens arrays, as the resin lens array has resin lenses having a larger lens shape area, the resin layers become thinner.SELECTED DRAWING: Figure 2

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 due to distortion of a microlens array.

  Some electrophotographic image forming apparatuses use a line optical type optical writing apparatus as an optical writing apparatus that forms an electrostatic latent image on a photosensitive member. The line optical type optical writing apparatus forms an image on the photosensitive member by using light emitted from a number of light emitting elements using a microlens array.

  This microlens array is formed by, for example, forming a large number of resin lenses on a glass substrate. Since the resin lens contracts when it is cured, the position of the resin lens can change when the glass substrate is warped by this contraction. Then, since the image formation state on the photoconductor changes, the image quality may be deteriorated.

  In order to deal with such a problem, for example, with respect to the warpage in the out-of-plane direction of the glass substrate, a technique of forming resin lenses having the same shape on both surfaces of the glass substrate has been proposed (see, for example, Patent Document 1). In this way, since the shrinkage force of the resin acting on the glass substrate is the same on both surfaces of the glass substrate, warping can be prevented.

  As for the warpage in the in-plane direction of the glass substrate, when the number of resin lenses is sufficiently large, the warpage can be suppressed by randomly changing the shape of the resin lens (for example, Patent Document 2). reference).

JP 2011-118423 A JP 2005-148427 A

  In a plan view from the optical axis direction of the microlens array, an optical writing device in which light emitting elements are periodically arranged two-dimensionally may have different distances from the light emitting elements to the photoconductors. For example, when a plurality of light emitting element arrays extending in the main scanning direction are arranged in parallel in the sub scanning direction and the distance from the light emitting element to the photoconductor is different between the light emitting element arrays, it corresponds to the light emitting element array. When 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, but different resin lens rows. The resin lenses to which they belong must have different shapes.

  In such a case, if all the resin lenses cannot be made the same shape, the shape of the resin lens cannot be changed randomly, so that the glass substrate is warped only by applying the above prior art. It cannot be suppressed.

  When warping in the in-plane direction occurs on the glass substrate, the positional relationship between the resin lenses changes, and the positional relationship between the light emitting element and the resin lens corresponding to the light emitting element varies, so the imaging performance varies from resin lens to resin lens. End up. If there is periodicity in the change in the shape of the resin lens, periodicity also appears in density changes due to variations in imaging performance, making it easy to visually recognize, so deterioration in image quality is inevitable.

  The present invention has been made in view of the above-described problems, and provides a microlens array, an optical writing device, and an image forming apparatus that can suppress image deterioration due to distortion of a glass substrate. With the goal.

  To achieve the above object, a microlens array according to the present invention includes a glass substrate and a resin lens array in which a plurality of resin lenses having the same shape are arranged along a first direction on the substrate surface of the glass substrate. However, a lens optical system arranged in a plurality of rows in a second direction different from the first direction, and a resin layer integrally formed with the resin lens and sandwiched between the resin lens and the glass substrate In the plurality of resin lens arrays, the resin lens array having a larger lens shape area of the resin lens has a thinner resin layer interposed between the resin lens belonging to the resin lens array and the glass substrate. It is characterized by.

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

  Further, regardless of the shape of the resin lens, the distance between the lens unit interface passing through the optical axis of each resin lens and in contact with the resin layer between any two resin lenses is as follows. L1 and L2 respectively, the lens shape area of each resin lens is 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. Sometimes it is desirable that the following relational expression is satisfied but equal:

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

Moreover, the said resin layer is continuously provided over several resin lenses along the substrate surface of the said glass substrate, and thickness may change continuously.

  The resin lens array and the resin layer are disposed on both substrate surfaces of the glass substrate, and the sum of the volumes of the resin lens array and the resin layer disposed on one substrate surface is the other. It may be equal to the sum of the volumes of the resin lens array and the resin layer disposed on the substrate surface.

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

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

  The light emitting point may be an OLED.

  The image forming apparatus according to the present invention includes the optical writing device according to the present invention.

  In this way, since the resin layer of the resin lens array having a larger lens shape area of the resin lens is thinner, the distortion of the microlens array is suppressed by making the resin volume distribution uniform on the substrate surface of the glass substrate. Can do.

1 is a diagram illustrating a main configuration of an image forming apparatus according to an embodiment of the present invention. 1 is a diagram illustrating a main configuration of an optical writing device 100. FIG. It is a figure which shows the main structures of the light source substrate. It is the top view which looked at the lens array 200a from the light source substrate 200 side. 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. It is a table | surface which illustrates the dimension of the lens array 200a. It is a figure which shows the structure of the microlens array which concerns on the modification of this invention. It is a top view which illustrates the micro lens array where the P direction and the Q direction are orthogonal. It is a top view which illustrates the microlens array which has four resin lens rows which arranged the resin lens along the P direction. (A) is a table | surface which illustrates the precondition for designing the dimension of a resin lens and a resin layer, (b) is a table | surface which illustrates the dimension of the resin lens and resin layer which met the precondition shown to (a). It is. (A) is a cross-sectional perspective view illustrating a mold having the same height between core blocks, and (b) illustrates a mold in which the height of the core block is adjusted according to the thickness of the resin layer. It is a cross-sectional perspective view.

Hereinafter, embodiments of a microlens array, an optical writing apparatus, 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 the 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) colors. The image forming units 110Y, 110M, 110C, and 110K include photosensitive drums 101Y, 101M, 101C, and 101K that rotate in the direction of arrow A, respectively.

  Around the photosensitive drums 101Y, 101M, 101C, and 101K, along the outer peripheral surface thereof, charging devices 102Y, 102M, 102C, and 102K, optical writing devices 100Y, 100M, 100C, and 100K, and developing devices are sequentially provided 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 arranged.

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

  Since the organic EL has an area in the light emitting portion, the beam diameter at the image forming point is greatly different from other light emitting methods such as LEDs in that it is determined by the light emitting area × optical magnification. OLED-PH makes the beam diameter uniform by optimizing the light emission area and shape according to the optical magnification, even when the optical magnification must be changed by design for each light emitting point due to the different conjugate lengths. be able to.

  Further, when the light emitting units having an area are arranged in an array, the light source substrate tends to be enlarged, but in this embodiment, the light source substrate is divided into a plurality of unit substrates as will be described later, and wiring and the like are arranged. By increasing the mounting area of the circuit components, the substrate area of the light source substrate in a plan view from the optical axis direction is reduced.

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

  The cleaning devices 105Y, 105M, 105C, and 105K neutralize charges remaining on the outer peripheral surfaces of the photosensitive drums 101Y, 101M, 101C, and 101K after the primary transfer, and remove residual toner. In the following description, YMCK characters are omitted when a configuration common to the image forming units 110Y, 110M, 110C, and 110K is described.

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

  The two rollers constituting 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 synchronization 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). Transcription).

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

The image forming apparatus 1 further includes a control unit 150. When receiving a print job from an external apparatus such as a PC (Personal Computer), the control unit 150 controls the operation of the image forming apparatus 1 to execute image formation.
[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, and 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 stacking unit substrates 231, 232, and 233 in the optical axis direction. Light emitting point groups 241, 242, and 243 are arranged in the main scanning direction on the unit substrates 231, 232, and 233, respectively, and constitute light emitting point group rows 251, 252, and 253. The light emission point group 243 includes light emission points 303 arranged in a staggered manner, and the light emission point groups 241 and 242 are the same.

  In the present embodiment, an OLED (Organic Light Emitting Diode) is used as the light emitting point 303. Since an OLED can form a light emitting region in a planar shape, a beam diameter at an imaging point corresponding to the OLED can be set by setting a multiplication value of the area of the light emitting region of the OLED and the optical magnification. it can. Therefore, even if the optical magnification must be changed for each light emitting point by design because of 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 There is an advantage that the diameter can be made uniform. In addition, you may use light emitting elements other than OLED as a light emission point.

  In general, the light emitting points are all arranged in the same plane, but the light emitting points are all in the same plane due to wiring restrictions, manufacturing restrictions, spatial restrictions when arranging the light emitting board, etc. When it is not suitable to arrange in the inside, it is effective to arrange the light emitting points in a plurality of planes as in this embodiment.

  The light source substrate 230 is divided into unit substrates 231, 232, and 233 for each of the light emission point group rows 251, 252, and 253. The unit substrates 231, 232, and 233 have distances L1, L2, and L2 from the photosensitive drum 101, respectively. L3 is individually positioned by a holder (not shown) so as to be L3. The distances L1, L2 and L3 are so-called conjugate lengths.

  For this reason, the conjugate lengths of the unit substrates 231, 232, and 233 can be individually adjusted. For example, when 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 having different conjugate lengths are mounted on the same substrate. If this is the case, the imaging performance in any one of the routes must be sacrificed under the condition that the adjustment value differs for each conjugate length level.

  On the other hand, if the light emission points are grouped for each conjugate length level and the light emission points are mounted on different unit substrates for each group as in the present embodiment, the adjustment value is individually set for each conjugate length level. Therefore, it is possible to optimize each level of imaging performance without sacrificing other levels of imaging performance. Such a configuration is not limited to the case where the number of unit substrates is three, and not only in the conjugate length corresponding to the optical path length, but also in the main scanning direction and the sub scanning direction orthogonal to the optical axis direction. This is also effective when adjusting a shift component, which is a displacement, or an error of a tilt component of the substrate surface with respect to the optical axis direction.

  In addition to the conjugate length, errors in shift components and tilt components can be individually corrected for each of the unit substrates 231, 232 and 233. Therefore, deterioration in image quality due to these errors can be suppressed, so that high image quality can be achieved.

In addition, the OLED has a relatively large light emitting area, and a large number of OLEDs are arranged in an array. Therefore, if the light source substrate 230 is a single substrate, the OLED is increased in size. On the other hand, if a circuit such as a wiring other than the OLED is provided at a location where the plurality of unit substrates 231, 232 and 233 are overlapped as described above, the area of the light source substrate 230 viewed from the optical axis direction can be reduced. Can do.
[3] Configuration of Microlens Array 200 Next, the configuration of the microlens array 200 will be described.

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

  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. The resin lenses 212b and 213b sandwich the resin layers 262b and 263b with the glass substrate 220.

On the other hand, the resin lens 211b is a resin lens having a larger resin volume than 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 the resin layer. Yes. In this way, since the resin volume in the microlens array 200 can be minimized, the stress applied to the microlens array 200 due to the contraction and expansion of the resin can be minimized. Further, the amount of resin used in the microlens array 200 can be reduced to reduce the cost, and the microlens array 200 can be reduced in size and weight. The resin lenses 211a and 211b make the emitted light of the light emitting point group 241 parallel light. 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 200 b is formed by forming resin lenses 251 on both surfaces 220 a of a glass substrate 250.

  While the distance from the unit substrates 231, 232 and 233 to the glass substrate 220 differs for each unit substrate 231, 232 and 233, the distance from the glass substrate 250 to the photosensitive drum 101 is constant regardless of the resin lens 251. Yes. For this reason, all the resin lenses 251 have the same shape. Therefore, even if the resin lens 251 contracts or expands, the glass substrate 250 does not warp because the contraction amount and the expansion amount are equal between the resin lenses. 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 the main scanning direction, respectively, and constitute resin lens rows 401, 402, and 403.

  The resin lens rows 401, 402, and 403 are juxtaposed in the sub-scanning direction. Further, the resin lens rows 401, 402, and 403 are shifted from each other in the main scanning direction, and connect 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. The direction Q obliquely intersects with the arrangement direction P (main scanning direction) of the resin lenses 211, 212, and 213. In FIG. 4, the case where the crossing angle between the directions P and Q is 30 degrees is illustrated, but when the directions P and Q are not parallel, the crossing angle is 90 degrees (FIG. 5) and other angles other than 30 degrees. There may be.

  As described above, the resin lenses 211 a, 212 a, and 213 a are two-dimensionally and periodically arranged on the glass substrate 220, and are arranged side by side to correspond to the writing width on the outer peripheral surface of the photosensitive drum 101. Yes. The resin lenses adjacent along the direction Q have different shapes. These resin lenses are for forming an image of light emitted from light emitting point groups having different distances (conjugate lengths) to the image carrier (photosensitive member).

  The resin layers 261a, 262a and 263a are also arranged in the same manner as the resin lenses 211a, 212a and 213a. As shown in FIG. 5, the area occupied by each resin layer in a plan view from the optical axis direction is the center 212cc of the resin lens 212c corresponding to the resin layer 262c and the center of the resin lenses 212r and 212l adjacent in the direction P. The straight lines 502r and 502l along the direction Q and the centers 212cc and the centers 211c and 213c of the resin lenses 211 and 213 adjacent to the resin lens 212c in the direction Q pass through the respective midpoints 501r and 501l with the 212rc and 212lc. And are surrounded by straight lines 502b and 502t along the direction P through the middle points 501b and 501t. The region occupied by the resin layer has the same shape in plan view from the optical axis direction.

  On the other hand, the resin layers 261a, 262a, 263a have different thicknesses, and the resin layers 262b, 263b have different thicknesses. In this embodiment, the case where there is no resin layer corresponding to the resin lens 211b is taken as an example, and 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. Since the shapes of the resin lenses are different from each other, 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, and the smaller the volume of the resin lens, The thickness of the resin layer is increased. In this way, the resin contraction force increases as the resin volume increases, and the resin volume is the same between the resin lenses. Therefore, distortion is caused in both the in-plane direction and the out-of-plane direction of the light source substrate 200. Can be suppressed.

  Microlens array 200 has a resin-glass two-layer structure when resin lenses are formed only on one surface of glass substrate 220. In this two-layer structure, when a temperature change occurs, distortion occurs so that the glass substrate 220 bends in the out-of-plane direction due to the difference in linear expansion between the glass and the resin. On the other hand, if resin lenses are formed on both substrate surfaces so as to sandwich the glass substrate 220, a three-layer structure of resin-glass-resin is formed, and there are layers having the same linear expansion coefficient across the glass.

  In this way, the difference in linear expansion generated on one side of the resin-glass acts in a direction that cancels out the difference in linear expansion generated on the opposite glass-resin layer, thereby eliminating the occurrence of distortion of the glass substrate 220. Can do. In particular, in the present embodiment, the total resin volume is the same between the substrate surface 220a and the substrate surface 220b of the glass substrate 220, and the linear expansion difference is equal between the two substrate surfaces of the glass substrate 220. 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 region φ1a. The resin lens 212a has a core thickness L2a and a lens shape area φ2a, and the resin lens 213a has a core thickness L3a and a lens shape area φ3a. The core thickness L is the thickness of the resin lens at the optical axis position, and is equal to the protruding amount from the upper surface of the resin layer. The lens shape area φ is the outer diameter of the area where the resin lens has a shape on the glass substrate 220.

Since the volume of the resin lens is determined by the square of the cross-sectional area in the cross section including the optical axis, and the cross-sectional area is proportional to the product of the core thickness L and the lens shape region φ, the volume ratio between the resin lenses having different shapes is the core thickness. 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 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 the dimensions of the resin lens and the resin layer according to this embodiment. The lens surface height is a height from the main surface of the glass substrate 220 to the highest position of the resin lens. As shown in FIG. 7, if the dimensions according to the present embodiment are employed, the ratio of the resin volume obtained by adding the resin lens and the resin layer between the resin lenses can be set to 1.00. Therefore, since the warp of the microlens array can be suppressed, excellent image quality can be achieved.
[4] Modifications As described above, the present invention has been described based on the embodiments. However, the present invention is not limited to the above-described embodiments, and the following modifications can be implemented. .
(4-1) In the above embodiment, the case where the resin volumes of the resin lenses and the resin layers corresponding to the resin lenses are the same has been described as an example, but the present invention is limited to this. Needless to say, the following may be added to this.

For example, the resin volume of the resin layer corresponding to the resin lens may be reduced as the resin volume of the resin lens is increased. In such a microlens array, there are a resin lens having a lens shape region φ1 and a resin lens having a lens shape region φ2,
φ1> φ2 (3)
The thickness T1 of the resin layer corresponding to the resin lens in the lens shape area φ1 and the thickness T2 of the resin layer corresponding to the resin lens in the lens shape area φ2 are:
T1 <T2 (4)
It becomes a relationship like this.

  If it does in this way, the difference of the resin volume which match | combined the resin lens and the resin layer with the resin lenses from which resin volume differs can be made small. Therefore, the difference between the shrinkage and expansion force of the resin caused by the difference in resin volume is reduced, so the amount of cooling shrinkage after injection molding and the amount of expansion when heat is applied are at any location 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 resin volume of the resin lens and the resin layer, the higher the effect of suppressing the in-plane distortion of the microlens array. Therefore, the difference in the resin volume may be reduced to such an extent that the degradation of the image quality due to the distortion of the microlens array cannot be visually recognized, and it is sufficient in practical use even if the resin volumes are not exactly the same.

  When measuring the lens shape region 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 region φ, and a microscope or the like is used. It can be measured by optical observation. When the boundary between the resin lens and the resin layer is polygonal, the lens shape region φ can be obtained by approximating the polygon with a circle and measuring the diameter of the approximate circle.

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

If the lens shape region φ of the resin lens and the thickness T of the resin layer are measured using the method as described above, it is confirmed whether or not the measured value satisfies the relationship 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 between the resin lenses.

  When molding a resin lens and a resin layer by injection molding using a mold, the optical surface of the resin lens is formed by fitting the core block into the mold. By adjusting the position of the 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 a resin lens. For this reason, if the height of the top is different for each resin lens, the height of the core block must be adjusted for each resin lens. It becomes difficult to adjust accurately.

  Further, when the height of the top portion is different for each resin lens, the thickness of the resin is different for each resin lens. As a result, when resin lenses having different thicknesses are arranged in the pressing 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 a problem that when the glass substrate is cracked, the yield is lowered.

For these problems, if the height from the substrate surface of the glass substrate 220 to the top of the resin lens is the same between the resin lenses, there is no need to adjust the height of the core block for each resin lens. The dimensional accuracy of the microlens array can also be improved. Moreover, since the load concerning a glass substrate at the time of shaping | molding can be equalized, the crack of a glass substrate can be suppressed and shaping | molding stability can be improved.
(4-2) In the above embodiment, the case where the thickness of the resin layer changes discontinuously between resin lens rows has been described as an example, but it goes without saying that the present invention is not limited to this. Instead, it may be as follows.

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

  Therefore, it goes without saying that the thickness of the portions of the resin layers 260a and 260b other than the resin lens continuously changes in a plan view from the optical axis direction. In order to continuously change the height of the resin layers 260a and 260b in this way, it is desirable that the conjugate length is monotonously changed along the sub-scanning direction.

By doing so, it is possible to reduce the punching resistance when the lens array is injection-molded, so that it is possible to improve the mold release property. Accordingly, when a large number of microlens arrays are continuously formed using the same mold repeatedly, 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, but it is needless to say that the present invention is not limited thereto. Instead of this, a resin layer may be sandwiched between all the resin lenses of the microlens array and the glass substrate.

With such a configuration, since the resin layer is continuous between all the resin lenses formed on the same substrate surface, the distribution of the stress applied to the glass substrate 220 due to the shrinkage and expansion of the resin is determined on the substrate surface. Can be uniform along. Therefore, the generation of distortion in the in-plane direction of the glass substrate 220 can be further effectively suppressed.
(4-4) In the above embodiment, when the three types of resin lenses 211a, 212a, and 213a having different shapes form the resin lens rows 401, 402, and 403 arranged so as to be shifted from each other in the main scanning direction. However, it is needless to say that the present invention is not limited to this, and the following may be used instead.

  For example, as shown in FIG. 9, the resin lens rows 401, 402, and 403 are not displaced 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 are used. The direction Q connecting the optical axis centers may be arranged so as to coincide with the sub-scanning direction.

Further, as shown in FIG. 10, four types of resin lenses 1011a, 1012a, 1013a, and 1014a having different shapes are arranged in resin lens rows 1001, 1002, 1003, and 1004 arranged so as to be shifted from each other in the main scanning direction. It 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 do.
(4-5) In the above embodiment, the case where the resin lens rows 401, 402, and 403 are disposed on different unit substrates 231, 232, and 233 has been described as an example. However, the present invention is not 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 these resin lens rows having the same conjugate length are arranged on the same unit substrate. In this way, since the position and inclination of the unit substrate can be collectively adjusted for the resin lens rows having the same conjugate length, the microlens array 200 can be efficiently manufactured without the adjustment effort.
(4-6) In the above embodiment, the example of the dimensions of the resin lens and the resin layer is described. However, it goes without saying that the present invention is not limited to this, and the following may be used instead. FIG. 11A shows dimensions that are preconditions to be considered when determining the dimensions of the resin lens and the resin layer. For example, the object height is the outer diameter of the light emitting point group in plan view from the optical axis direction. NAO is the F number, and NA is the effective F number. Further, the panel thickness, the panel refractive index n, and the panel-lens distance are dimensions relating to the light source substrate, and the lens diameter R is a curvature diameter when the lens surface is a Kyoto surface.

FIG. 11B illustrates the dimensions of the resin lens and the resin layer that meet the above preconditions. For example, the lens surface vertex interval represents the distance in the P direction between adjacent resin lenses. The lens surface vertex distance (sub) is the distance in the Q direction between adjacent resin lenses. In this way, the resin volume of the resin lens and the resin layer can be perfectly matched with two significant figures, so that excellent image quality can be achieved by suppressing the distortion of the microlens array. Can do.
(4-7) In the above modification, the case where adjustment of the height of the core block is facilitated 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 to this. Instead of or in addition to this, the following may be used.

  As shown in FIG. 12A, when a microlens array is molded using molds 1201, 1202 and core blocks 1200a, 1200b, and 1200c, the resin lenses having different resin layer thicknesses are used. If all the core blocks used for molding are at a height h, the height must be adjusted by the thickness of the resin layer for each core block.

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

On the other hand, 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, as shown in FIG. It is sufficient to individually adjust the height of the core blocks 1200a, 1200b, and 1200c so that the upper surfaces of 1200a, 1200b, and 1200c are all at a height H from the upper surface of the mold 1202. For this reason, the trouble of height adjustment can be saved and height accuracy can be improved.
(4-8) In the above embodiment, the case where the shape of the resin layer for each resin lens is a parallelogram in plan view from the optical axis direction has been described as an example, but the present invention is limited to this. Needless to say, the shape may be other than a parallelogram. Further, the thickness of the resin layer corresponding to the resin lens does not need to be constant for each resin lens, and the resin volume of the resin layer corresponding to the resin lens increases as the resin volume of the resin lens decreases. For example, the effect of suppressing the distortion of the microlens array due to the expansion and contraction of the resin can be obtained.

In order not to affect the optical characteristics of the resin lens, light passing through the lens surface of the resin lens passes through an interface other than the interface between the resin layer and the glass substrate among the resin layer interfaces. It is desirable to design the shape of the resin layer so that it does not occur. Specifically, it is preferable that the lower surface of the resin lens (virtual plane facing the glass substrate side) is in contact with the upper surface of the resin layer (virtual surface in contact with the resin lens).
(4-9) Although not specifically mentioned in the above embodiment, in order for the resin volumes of the resin lenses and the resin layer to be equal between the resin lenses, the following conditions must be satisfied.

  The resin volume VL of the resin lens is a distance from the lens unit interface passing through the optical axis of the resin lens and contacting the resin layer to the apex of the lens optical surface, and the lens shape area of the resin lens is φ. sometimes,

である。

It is.

  The resin volume VT of the resin layer has an area S and a thickness T.

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 resin volume combining the resin lens and the resin layer is

である。

It is.

  Accordingly, in order for the resin volumes of the resin lens and the resin layer to be equal between different resin lenses, the following relational expression must be satisfied.

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 distance from the lens unit interface passing through the optical axis of each resin lens and contacting the resin layer to the vertex of the lens optical surface is L1 and L2, respectively, and the lens shape area of each resin lens is 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.

In this way, it is possible to optimize the resin layer thickness and the lens parameters when minimizing the resin volume difference between the resin lenses.
(4-10) In the above embodiment, the case where the image forming apparatus 1 is a tandem color printer has been described as an example. However, it is needless to say that the present invention is not limited thereto. A color printer or a monochrome printer may be used. The same applies when the present invention is applied to a single-function machine such as a copying machine equipped with a scanner or a facsimile machine equipped with a facsimile communication function, or a multi-function peripheral (MFP) having these functions. An effect can be obtained.

  The microlens array, the optical writing device, and the image forming apparatus according to the present invention are particularly useful as a device that can prevent image degradation caused by distortion of the microlens array as the resin contracts or expands.

1 ……………………………………………………………… Image forming apparatus 100 ………………………………………………………… ... Optical writing device 101 ………………………………………………………… Photosensitive drum 200 …………………………………………………… Micro lens arrays 220, 250 ... Glass substrates 211a, 212a, 213a ... Resin lenses 211b, 212b 213b, 251 ........... resin lenses 261a, 262a, 263a, 262b, 263b ... resin layer 230 ..................................... 231, 232, 233 ……………………………… Unit substrates 241, 242, 243 …………………………………… 303 .................................................................. light emitting point (OLED)
L1, L2, L3 …………………………………………… Conjugate length

Claims (9)

A glass substrate;
On the substrate surface of the glass substrate, a plurality of resin lens rows in which a plurality of resin lenses having the same shape are arranged along the first direction are arranged in parallel in a second direction different from the first direction. Lens optics,
A resin layer integrally molded with the resin lens and sandwiched between the resin lens and the glass substrate,
In the plurality of resin lens arrays, a resin lens array having a larger lens shape area of the resin lens has a thinner resin layer interposed between the resin lens belonging to the resin lens array and the glass substrate. Lens array. 2. The microlens array according to claim 1, wherein the resin lenses have the same height from the substrate surface of the glass substrate to the top of the resin lens regardless of the shape thereof. Regardless of its shape, the resin lens is between any two resin lenses,
The distances from the lens portion interface passing through the optical axis of each resin lens and contacting the resin layer to the apex of the lens optical surface are L1 and L2, respectively.
The lens shape area of each resin lens is φ1, φ2,
When 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,
The following relational expression is satisfied

The microlens array according to claim 1 or 2, wherein The said resin layer is continuously provided over the some resin lens along the board | substrate surface of the said glass substrate, The thickness is changing continuously, The Claim 1 to 3 characterized by the above-mentioned. The microlens array according to any one of the above. The resin lens array and the resin layer are disposed on both substrate surfaces of the glass substrate,
The sum of the volumes of the resin lens array and the resin layer disposed on one substrate surface is equal to the sum of the volumes of the resin lens array and the resin layer disposed on the other substrate surface. Item 5. The microlens array according to any one of Items 1 to 4. A microlens array according to any one of claims 1 to 5,
For each position corresponding to the resin lens in a plan view, a light source substrate provided with a light emitting point group composed of a plurality of light emitting points, and
The optical writing device, wherein a distance from the light emitting point group to the resin lens corresponding to the light emitting point group is different for each shape of the 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 resin lenses having different shapes are disposed on different unit substrates. 8. The optical writing device according to claim 6, wherein the light emitting point is an OLED. An image forming apparatus comprising the optical writing device according to claim 6.

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