WO2014119737A1 - Compound eye optical system, image capture device, and method for producing compound eye optical system - Google Patents

Abstract

Provided are: a high-resolution, ultrathin compound eye optical system that is lightweight and capable of ensuring a reduction in cost due to a simple molding; and a method for producing the compound eye optical system. In the case of a side gate in which a resin injection part (14) is positioned on a side of a lens array (10), the lens array (10) sometimes warps slightly in the direction of the gate. In the case of the compound eye optical system (100), equivalent performance is demanded in lens arrays (10, 20, 30) that are substantially the same size, therefore, molding conditions etc. are similar, and the direction and magnitude of warp are similar in the plurality of lens arrays (10, 20, 30). At that time, as described above, when gates (GA), in other words, resin injection parts (14, 24, 34) are aligned in the same direction and the lens arrays (10, 20, 30) are stacked on one another, the warps of the lens arrays (10, 20, 30) align, making it difficult for problems such as interval variations and eccentricity of lens elements (10a, 20a, 30a) due to differences in the warps of the lens arrays (10, 20, 30) to occur.

Description

Compound eye optical system, imaging apparatus, and compound eye optical system manufacturing method

The present invention relates to a compound-eye optical system having a plurality of compound optical systems formed by stacking lens arrays, an imaging device incorporating the compound-eye optical system, and a compound-eye optical system manufacturing method.

As a compound eye optical system used in a compound eye imaging device that forms a plurality of images on an image sensor using a plurality of lenses and reconstructs one image from the obtained images, a plurality of resin lens arrays are used. An axial stack is known. For example, Patent Document 1 discloses an optical array in which three types of lenses are adjacently integrated in the direction perpendicular to the optical axis as a compound eye optical system, and two molded products are stacked in the vertical direction in the optical axis direction. A single-piece optical element is disclosed.
Patent Document 2 discloses a lens array assembly in which a plurality of lens arrays made of a synthetic resin, in which a plurality of lenses and a positioning portion are integrally formed, are overlapped so that the lenses are aligned on the same optical axis. ing.
However, the compound eye optical system of Patent Document 1 is formed of a photocurable resin and is not formed of a thermoplastic resin. Although the photocurable resin is lightweight as a material, the molding process is relatively complicated, and cost reduction is not easy. Further, since the viscosity of the photo-curing resin before curing is very low, there is a problem such as leakage from the mold, and there is a problem that molding by injection molding is difficult.
The lens array assembly of Patent Document 2 uses a plurality of lens arrays molded by resin injection from the side of the mold into the mold, and is related to the optical performance of the lens array and the distance from the gate. There is no description about the shrinkage of the molded article, and sufficient studies have not been made on securing optical performance when a plurality of lens arrays are laminated.

JP 2005-338505 A JP 2000-227505 A

The present invention has been made in view of the above-mentioned background art, and aims to provide a compound eye optical system that is lightweight, can ensure cost reduction by simple molding, has a high image quality, and is ultra-thin, and a method for manufacturing the same. To do.
Another object of the present invention is to provide a small and high-performance imaging apparatus incorporating the compound eye optical system.

In order to solve the above problems, a compound eye optical system according to the present invention is a compound eye optical system obtained by superimposing a plurality of lens arrays each having a lens element molded in a thermoplastic resin and arranged two-dimensionally. Each lens array has a resin injecting portion, and each resin injecting portion is disposed on the side of the lens array and is disposed corresponding to the same reference direction with respect to the arrangement of the lens elements.

An imaging apparatus according to the present invention includes the compound eye optical system described above, a sensor array provided corresponding to a plurality of lens arrays, and an image processing unit that performs processing on an image signal detected by the sensor array. Is provided.

The compound eye optical system manufacturing method according to the present invention includes a step of molding a plurality of lens arrays each having two-dimensionally arranged lens elements by injection of a thermoplastic resin, and superimposing the plurality of lens arrays. The compound eye optical system manufacturing method comprising the steps of: obtaining a compound eye optical system, wherein the resin injection portions of the lens array are arranged corresponding to the same reference direction with respect to the arrangement of the lens elements.

In the compound eye optical system, since the resin injection portion formed in the lens array is arranged on the side of the lens array, when the thermoplastic resin is injected into the mold space via the gate corresponding to the resin injection portion, etc. The resin can be easily supplied to a portion corresponding to the thin portion of the lens array, and the obtained lens array can be highly accurate. In addition, since the resin injecting portions of the plurality of lens arrays are arranged corresponding to the same reference direction with respect to the arrangement of the lens elements, the resin injecting portions protrude when the lens array or the compound eye optical system is stored in the case. However, it is only necessary to provide a relief on one side of the case, so that it is easy to incorporate the lens array and to improve positioning accuracy. In addition, it is known that the resin shrinkage differs depending on the distance from the gate. However, if the lens array is stacked with the gate, that is, the resin injection portion aligned in the same direction, the difference in shrinkage will be the same, and the optical axis of all lens elements will be the same. The alignment can be performed with relatively high accuracy. Furthermore, in the case of a side gate in which the resin injection portion is arranged on the side of the lens array, the lens array may be slightly warped along the gate direction, and in the case of a compound eye optical system, the size is approximately the same. Since the lens array requires the same performance, the molding conditions and the like are similar, and the direction and amount of warping are also similar in the plurality of lens arrays. At that time, if the lens array is stacked with the gates or resin injection portions aligned in the same direction as described above, the warp of the lens array is aligned. Problems are less likely to occur.

1A and 1B are a plan view and a side sectional view for explaining the compound eye optical system and the like of the first embodiment. It is a conceptual perspective view explaining the stacking method of the some lens array which comprises a compound eye optical system. 3A and 3B are a plan view and a side sectional view illustrating one lens array constituting the compound eye optical system. 4A and 4B are a partially enlarged cross-sectional view and a cross-sectional conceptual diagram illustrating the lens array molding die shown in FIG. 3A and the like. It is a figure explaining the effect of contraction at the time of stacking of a lens array. It is a figure explaining the effect of the bending at the time of stacking of a lens array. It is a perspective view explaining the compound-eye optical system of 2nd Embodiment. It is a typical perspective view explaining the compound-eye optical system of 3rd Embodiment.

[First Embodiment]
As shown in FIGS. 1A and 1B and the like, the compound eye optical system 100 of the present embodiment is a laminated body in which a first lens array 10, a second lens array 20, and a third lens array 30 are bonded together. The first to third lens arrays 10, 20, and 30 are flat members extending in parallel to the XY plane. These lens arrays 10, 20, and 30 are stacked in the Z-axis direction perpendicular to the XY plane.

The first lens array 10 on the + Z side (upper side of the drawing) of the compound-eye optical system 100 is a molded product made of a thermoplastic resin and has a rectangular (including square) outline in plan view. The first lens array 10 includes a plurality of lens elements 10a, each of which is an optical element, and a support portion 10b that supports the plurality of lens elements 10a from the periphery. The plurality of lens elements 10a constituting the first lens array 10 are two-dimensionally arranged on square lattice points (16 × 4 × 4) arranged in parallel to the XY plane. That is, the lens elements 10a are arranged in a matrix along four orthogonal reference directions DR1, DR2, DR3, DR4. The array region of the lens elements 10a is a rectangular frame RL having a rectangular outline, like the first lens array 10 as a whole. Each lens element 10a has a convex first optical surface 11a on one main surface 10p side, and a convex second optical surface 11b on the other main surface 10q side. Both optical surfaces 11a and 11b are aspherical surfaces, for example.

The first lens array 10 has ribs 12 protruding in the −Z direction from the main surface 10q along the four surrounding sides S1, S2, S3, and S4. The ribs 12 of the first lens array 10 function as spacers for the second lens array 20 adjacent thereto. A block-shaped resin injection portion 14 protrudes from the center of one side S4 in the fourth reference direction DR4 (−X side in the drawing) of the first lens array 10. The resin injecting portion 14 is a gate mark corresponding to the gate at the time of molding, and can be excised in advance before the first lens array 10 is laminated, but is left for simplification of the process. In addition, when the resin injection part 14 is removed and the side surface SF4 corresponding to one side S4 is flattened or a depression is formed in this, the excision trace remains, and this excision trace is referred to as the resin injection part 14. . Here, the side S4 provided with the resin injection portion 14 is parallel to one side RL4 in the fourth reference direction DR4 (−X side in the drawing) of the rectangular frame RL in which the lens elements 10a are arranged. It extends. The resin injecting portion 14 is disposed outside the center of the side RL4 so as to face one side RL4 of the rectangular frame RL. In this case, the resin injecting portion 14 can be arranged corresponding to the arrangement frame of the lens elements 10a, and the characteristic deterioration caused by the resin injection process described later can be made to correspond to the arrangement frame of the lens elements 10a. The resin injecting portion 14 does not need to completely coincide with the center of the side S4 as viewed from the Z direction (the same applies to resin injecting portions 24 and 34 described later). For example, the resin injection portions 14, 24, 34 of the lens arrays 10, 20, 30 may be provided so as to be shifted from the center and deviated to the same side in the side S <b> 4.

The second lens array 20 is a molded product made of a thermoplastic resin and has a rectangular outline in plan view. The second lens array 20 includes a plurality of lens elements 20a, each of which is an optical element, and a support portion 20b that supports the plurality of lens elements 20a from the periphery. The plurality of lens elements 20a are two-dimensionally arranged on square lattice points (16 × 4 × 4) arranged in parallel to the XY plane. That is, the lens elements 20a are arranged in a matrix along the four orthogonal reference directions DR1, DR2, DR3, DR4. The array region of the lens elements 20a is a rectangular frame RL having a rectangular outline, like the second lens array 20 as a whole. Each lens element 20a has a convex first optical surface 21a on one main surface 20p side and a concave second optical surface 21b on the other main surface 20q side. Both optical surfaces 21a and 21b are aspherical surfaces, for example.

The second lens array 20 has ribs 22 protruding in the −Z direction from the main surface 20q along the four surrounding sides S1, S2, S3, and S4. The ribs 22 of the second lens array 20 function as spacers for the third lens array 30 adjacent thereto. A block-shaped resin injection portion 24 protrudes from the center of one side S4 in the fourth reference direction DR4 (−X side in the drawing) of the second lens array 20. The resin injecting portion 24 is a gate trace corresponding to the gate at the time of molding, and can be excised in advance before the second lens array 20 is laminated, but is left for simplification of the process. In addition, also when the resin injection part 24 is removed and the side surface SF4 is flattened or a depression is formed in the side surface SF4, the cut trace is referred to as the resin injection part 24. Here, the side S4 provided with the resin injection part 24 is parallel to one side RL4 in the fourth reference direction DR4 (−X side in the drawing) of the rectangular frame RL in which the lens elements 20a are arranged. It extends. The resin injecting portion 24 is disposed outside the center of the side RL4 so as to face one side RL4 of the rectangular frame RL.

The third lens array 30 is a molded product made of a thermoplastic resin and has a rectangular outline in plan view. The third lens array 30 includes a plurality of lens elements 30a, each of which is an optical element, and a support portion 30b that supports the plurality of lens elements 30a from the periphery. The plurality of lens elements 30 a are two-dimensionally arranged on square lattice points (16 × 4 × 4) arranged in parallel to the XY plane. That is, the lens elements 30a are arranged in a matrix along the four orthogonal reference directions DR1, DR2, DR3, DR4. The array region of the lens elements 30a is a rectangular frame RL having a rectangular outline, as in the third lens array 30 as a whole. Each lens element 30a has a concave first optical surface 31a on one main surface 30p side, and a convex second optical surface 31b on the other main surface 30q side. Both optical surfaces 31a and 31b are aspherical surfaces, for example.

The third lens array 30 has ribs 32 protruding in the −Z direction from the main surface 30q along the four surrounding sides S1, S2, S3, S4. The ribs 32 of the third lens array 30 function as spacers for the sensor array 60 adjacent thereto. A block-shaped resin injection portion 34 protrudes from the center of one side S4 in the fourth reference direction DR4 (−X side in the drawing) of the third lens array 30. The resin injecting portion 34 is a gate mark corresponding to the gate at the time of molding, and can be excised in advance before the third lens array 30 is laminated, but is left for simplification of the process. In addition, also when the resin injection part 34 is removed and the side surface SF4 is flattened or a depression is formed in the side surface SF4, the cut trace is referred to as the resin injection part 34. Here, the side S4 provided with the resin injection portion 34 is parallel to one side RL4 in the fourth reference direction DR4 (−X side in the drawing) of the rectangular frame RL in which the lens elements 30a are arranged. It extends. The resin injecting portion 34 is disposed outside the center of the side RL4 so as to face one side RL4 of the rectangular frame RL.

In the above, the first lens array 10 and the second lens array 20 constituting the compound-eye optical system 100 are joined with a photo-curing adhesive. That is, the lower end surface of the rib 12 of the first lens array 10 is bonded to the upper main surface 20p of the second lens array 20 via the adhesive. The second lens array 20 and the third lens array 30 are joined with a photo-curing adhesive. That is, the lower end surface of the rib 22 of the second lens array 20 is bonded to the upper main surface 30p of the third lens array 30 via the adhesive. The compound eye optical system 100 obtained by stacking and joining the first to third lens arrays 10, 20, and 30 is a two-dimensional array of a number of compound optical systems 2 that are a number of individual lens systems. ing. Specifically, the compound optical system (single lens system) 2 is arranged on square lattice points (4 × 4 16 points) arranged in parallel to the XY plane. That is, the composite optical system 2 is arranged in a matrix along four orthogonal reference directions DR1, DR2, DR3, DR4. In the compound eye optical system 100, the first to third lens arrays 10, 20, and 30 are resin injection portions 14, 24, and 34 outside the center of a specific side RL4 among the four sides RL1 to RL4 of the rectangular frame RL. Is prominent. That is, the resin injecting portions 14, 24, and 34 are arranged in the first to third lens arrays 10, 20, and 30 so as to align with a specific reference direction DR4 among the reference directions DR1, DR2, DR3, and DR4.

As shown in FIG. 1B, the imaging apparatus 1000 incorporating the compound eye optical system 100 includes, in addition to the compound eye optical system 100 described above, a sensor array 60 provided corresponding to the plurality of lens arrays 10, 20, and 30. And an image processing unit 65 that performs processing on an image signal detected by the sensor array 60. Here, the compound eye optical system 100 is bonded to the sensor array 60 and accommodated in a rectangular frame-like case 50. An opening 51 is formed in the case 50 at a position corresponding to the lens element 10 a such as the lens array 10.

The compound-eye optical system 100 has the compound optical system (single-lens system) 2 arranged two-dimensionally along the XY plane as described above. In the sensor array 60, CMOS (Complementary Metal Metal Oxide Semiconductor) and other solid-state imaging devices 61 are formed in a two-dimensional array corresponding to each composite optical system 2. Each compound eye optical system 100 includes three lens elements 10a, 20a, and 30a. By appropriately performing the optical design of these lens elements 10a, 20a, and 30a, the compound-eye optical system 100 generally has (1) an optical system that observes the same field of view by a plurality of compound optical systems 2, and (2) a plurality of The compound optical system 2 is used as either one of the optical systems for observing different fields of view. In this embodiment, the compound-eye optical system 100 is used in the super-resolution method (1). In this case, the lens elements 10a, 20a, and 30a constituting each composite optical system 2 and the corresponding solid-state imaging device 61 in the sensor array 60 are completely centered on the optical axis AX so that their fields of view coincide with each other. Arranged to match.

When the compound-eye optical system 100 is used for super-resolution image detection, the compound optical system 2 constituting the compound-eye optical system 100 enables observation of the same field of view at the same time, and each compound optical system 2 has the same field of view. Then, each solid-state image sensor 61 converts an image from the same field of view into an electrical image signal. The image processing unit 65 appropriately performs image processing on the image signal output from the solid-state imaging device 61, and obtains a high-resolution image with the same visual field from a low-resolution image with the same visual field. When the compound-eye optical system 100 is used in a super-resolution system, each composite optical system 2 has substantially the same optical design. This means that, for example, all the lens elements 10a constituting the first lens array 10 have substantially the same shape. In this way, in the super-resolution system application, a lens array having the same shape is molded. Therefore, in the injection molding, the flow of resin is the same, and each lens element 10a constituting the first lens array 10 is the same. It is easy to get the accuracy. On the contrary, when the shape of the lens element is different as in the field division method, it is difficult to obtain a stable shape with a large change in thickness. Since the super-resolution method requires very high optical performance, the lens shape and the accuracy of decentration are very strict. Therefore, the effect that the resin injection portions 14, 24, and 34 are arranged in the same direction is more easily exhibited in the super-resolution direction than the field division. When the compound eye optical system 100 is used in the super-resolution method, the chromatic aberration and the focus position may be different for each composite optical system 2, so that it is “same” instead of “same” as described above. It expresses.

In order to obtain high resolution by the super-resolution method, it is better that the number of individual eyes constituting the compound-eye optical system 100, that is, the number of compound optical systems 2 is larger. For example, in the case of a 2 × 2 array, since only four composite optical systems 2 are provided, the maximum number of pixels is four times (twice in the length direction). For this reason, the effect on high resolution and thinning is small, and there is little difference in ability from a monocular system using one lens for one sensor. Therefore, it is preferable to have at least 3 × 3 composite optical systems 2. Thereby, the compound eye optical system 100 can be thinned, and the degree of improvement in super-resolution when the entire image is synthesized from a single eye can also be increased.

When the number of pixels of the solid-state imaging device 61 for the composite optical system 2 constituting the compound-eye optical system 100 is Ni and the number of pixels after super-resolution processing is Ns, the following conditional expression (3)
Ns / Ni> 5 (3)
It is desirable to satisfy. In order to improve the resolution (number of pixels) by the super-resolution method, the performance of the original lens is required to be high to some extent. That is, in order to recover or improve the pixels smaller than the pixels provided corresponding to the individual composite optical systems 2, the spatial frequency corresponding to the number of pixels after super-resolution is used for each composite optical system 2. Lens performance is required. The requirement for the decentering of the lens elements 10 a, 20 a, and 30 a required for that purpose requires a smaller accuracy than the pixel pitch of the composite optical system 2. In other words, the compound-eye optical system 100 in which the accuracy of the shape and decentering of the lens elements 10a, 20a, and 30a is increased to easily improve the performance of each composite optical system 2 is suitable for the super-resolution system. .

Regarding the first to third lens arrays 10, 20, and 30 constituting the compound eye optical system 100, the lens elements 10a, 20a, and 30a in the gate vertical direction crossing the gate GA corresponding to the resin injection portions 14, 24, and 34 are arranged. When the maximum interval is P and the single pixel pitch of the solid-state image sensor 61 provided corresponding to the single-eye compound optical system 2 in the sensor array 60 is d, the following conditional expression (4)
20> (P / d) / 1000 (4)
Meet. As the distance between the lens elements 10a, 20a, 30a in the first to third lens arrays 10, 20, 30 increases, the eccentricity tends to increase, and the eccentricity accuracy is related to the pixel pitch. In particular, when extremely high performance such as super-resolution is required, deterioration becomes a problem even with a deviation of about the pixel pitch. However, by setting the range of the conditional expression (4), a compound with less eccentricity can be obtained. The optical system 2 effectively improves the resolution after super-resolution processing.

FIG. 2 is a perspective view conceptually illustrating the structure and manufacturing method of the compound-eye optical system 100. In the compound eye optical system 100, the first lens array 10, the second lens array 20, and the third lens array 30 are sequentially joined. These lens arrays 10, 20, and 30 are formed of resin injection portions 14, 24, 34 are stacked at the same rotation position. As described above, in the case of the present embodiment, since the positions of the resin injection portions 14, 24, and 34 are made to coincide with any one of the reference directions DR1, DR2, DR3, and DR4, the protrusion from the compound-eye optical system 100 is increased. It gathers in one place and is easy to incorporate into the case 50 and alignment. Further, these lens arrays 10, 20, and 30 are formed of a thermoplastic resin and have a problem of heat shrinkage and bending. However, the lens arrays 10, 20, and 30 are based on the resin injection portions 14, 24, and 34. When the directions are aligned, it is easy to match the directionality and tendency of heat shrinkage and deflection between the lens arrays 10, 20, and 30, and centering in each composite optical system 2 becomes relatively easy.

Hereinafter, the reason why the resin injection portions 14, 24, and 34 are arranged on the same side that is any one of the four sides S1, S2, S3, and S4 with reference to the fixed side will be described.

3A and 3B are a plan view and a side sectional view of the first lens array 10. The resin injection portion 14 of the first lens array 10 is formed on the side S4 or the side surface SF4. This is because the first lens array 10 is obtained by molding a thermoplastic resin by a side gate method. The compound-eye optical system 100 is attracting attention from the viewpoint of reducing the thickness of the imaging apparatus 1000 in applications such as a super-resolution method. Various compound-eye optical systems have been proposed so far, but the requirements necessary to achieve ultra-thinness with high image quality using a lightweight resin (thermoplastic resin) that is excellent in cost reduction are proposed. There was nothing to do. In the present embodiment, it is proposed that not only the first lens array 10 constituting the compound-eye optical system 100 but also the other lens arrays 20 and 30 are molded from a thermoplastic resin to achieve high image quality while being ultra-thin.

When the lens arrays 10, 20, and 30 are molded from a thermoplastic resin, there is a problem of whether to use a side gate or a pin gate. In the case of a pin gate, the resin injecting portion is formed in the vertical direction. However, since the inflow direction of the resin and the spreading direction are perpendicular to each other, there is a disadvantage that it is difficult for the resin to enter the thin portions of the lens arrays 10, 20, and 30. On the other hand, in the case of the side gate, since the inflow direction of the resin and the spreading direction are almost the same, the resin can easily enter the thin portions of the lens arrays 10, 20, and 30, and the shape of the compound eye optical system 100 is required to be accurately transferred. This is advantageous as a manufacturing method. In the case of a pin gate, the gate is automatically cut at the time of mold release, but since the gate is cut in such a way that it is torn, the vicinity of the gate of the lens is locally deformed, which is disadvantageous for molding a highly accurate lens. It is. On the other hand, in the case of a side gate, the gate is released without being cut, and is cut using a gate cutting machine or the like in a later process, so that local deformation is unlikely to occur in the gate portion, and a highly accurate lens is formed. Is advantageous.

FIG. 4A is a diagram for explaining a mold for molding the first lens array 10. The mold apparatus 70 includes a first mold 71 and a second mold 72. The first mold 71 and the second mold 72 are mold-matched at the mold-matching surface PL, and a cavity 70 a is formed between the molds 71 and 72. The first mold 71 is formed with a transfer surface 71c for transferring the shape on the main surface 10p side of the first lens array 10 so as to face the cavity 70a, and the second mold 72 has a first lens. A transfer surface 72c for transferring the shape on the main surface 10q side of the array 10 is formed. The transfer surfaces 71c and 72c have a plurality of optical transfer portions 71g and 72g arranged two-dimensionally at a part thereof in order to transfer the optical surfaces 11a and 11b of the lens element 10a. The second mold 72 is also formed with a transfer surface 72f for forming the rib 12. In the mold apparatus 70, a gate GA communicating with the cavity 70a is formed. The gate GA is provided adjacent to the transfer surface 72 f of the rib 12.

FIG. 4B is a cross-sectional view illustrating the entire structure of the mold apparatus 70. A runner RA is connected to the cavity 70a of FIG. 4A through a gate GA, and the runner RA is connected to the sprue SP on the resin supply side. As a result, the molten resin J from the sprue SP fills the runner RA and fills the cavity 70a through the gate GA. By separating the first mold 71 and the second mold 72 after cooling the molten resin J, a sprue portion 81 corresponding to the sprue SP, a runner portion 82 corresponding to the runner RA, and a gate corresponding to the gate GA. A molded product 80 including a portion 83 and a lens array body 84 corresponding to the cavity 70a is formed. Here, the gate part 83 is subjected to a gate cut process, and the first lens array 10 is obtained by the resin injection part 14 that is the remaining part of the gate part 83 and the lens array body 84 ahead. When the molding as described above is performed, a process such as removing a gate cut burr is required for the resin injection portion 14 after the gate cut process. Such removal of the gate cut burr is simple in the side gate method in which the resin injection portion 14 is formed in the periphery, but is not necessarily simple in the pin gate method or the like.

3A, the arrangement and shape of the resin injection portion 14 in the first lens array 10 will be considered. In the illustrated example, the resin injecting portion 14 is disposed at a position corresponding to the center of the side S4 or the side surface SF4. On the other hand, as indicated by the alternate long and short dash line, the resin injection portion 14 ′ is formed near the end of the side S4 or the side surface SF4, or the resin injection portion 14 ″ is formed at the corner where the pair of sides S1 and S4 intersect. However, in the resin injection portion 14 'closer to the end, the distance to the farthest lens element 10a is larger than in the case of the resin injection portion 14 arranged at the center, and the resin injection portion in the corner portion. 14 ″ further increases compared to the case of the resin injection portion 14 ′ whose distance to the farthest lens element 10a is closer to the end. In order to increase the surface accuracy of the lens elements 10 a constituting the first lens array 10, it is necessary to apply sufficient pressure to a portion corresponding to the lens elements 10 a in the cavity 70 a of the mold apparatus 70. For this reason, in the mold apparatus 70, when the transfer portion of one of the lens elements 10a is far from the gate GA, the pressure loss increases, and the surface accuracy of the lens element 10a is likely to decrease. Therefore, the transfer portion of the lens element 10a is preferably as close to the gate GA as possible. In order to make the transfer portion of the lens element 10a and the position of the gate GA closest, the gate GA is not located on a specific side of the first lens array 10. It is desirable to arrange corresponding to the center of S4 or side surface SF4. As a result, it can be said that in the first lens array 10, it is desirable that the resin injection portion 14 is disposed at the center of the specific side S <b> 4 or the side surface SF <b> 4 or in the vicinity thereof. Thereby, the pressure loss of resin can be suppressed and each lens element 10a can be shape | molded by comparatively high quality.

The cross-sectional area of the gate GA shown in FIG. 4A is desirably large from the viewpoint of ensuring the surface accuracy required for each lens element 10a. That is, in order to mold each lens element 10a with high accuracy, it is better that the molten resin J has good fluidity, and the lateral width of the gate GA (that is, the resin injection portion 14) is set to D with reference to FIG. When the vertical width of the gate GA (that is, the resin injection portion 14) is h, it is desirable that the gate cross-sectional area (D × h) is large. Here, the lateral width (gate width D) of the gate GA or the resin injecting portion 14 is good in fluidity, but if it is too wide, gate cut processing becomes difficult.
1mm ≦ D ≦ 10mm
The range. Further, the vertical width h of the gate GA or the resin injection portion 14 is preferably large, but generally cannot be larger than the flange height H.
0.5 ≦ h / H ≦ 1.0
The range. More preferably,
0.5 ≦ h / H ≦ 0.8
The range.

Furthermore, in order to mold the thin first lens array 10 and the like without causing the filling failure of the cavity 70a, it is necessary to appropriately set the cross-sectional size of the first lens array 10 and the like. Specifically, referring to FIG. 3B, each lens array 10, 20, 30 has a minimum thickness T, and the length of each lens array 10, 20, 30 in the gate direction, that is, the ± X direction, is L. The following conditional expression (1)
10 <L / T <60 (1)
Meet. Conditional expression (1) sets the ratio of the length and the thinness in the gate direction of the lens arrays 10, 20, and 30 in an appropriate range in order to achieve good filling and a thin optical system. By making it smaller than the upper limit of conditional expression (1), it is not too long in the depth direction, the flow of the resin is ensured, and the resin can be filled well. On the other hand, by making it larger than the lower limit of the conditional expression (1), the lens array 10, 20, 30 does not become excessively thick, and a thin compound eye optical system 100 can be realized. Thereby, the fluidity of the molten resin J can be ensured during molding while making the lens arrays 10, 20, and 30 thin.

Further, referring to FIG. 3A, each lens array 10, 20, 30 has a gate width in the gate vertical direction that crosses the gate GA corresponding to the resin injection portion 14, 24, 34, that is, the gate width in the ± Y direction as D, Conditional expression (2) below, where W is the length of each lens array 10, 20, 30 in the gate vertical direction, that is, the ± Y direction.
1.3 <W / D <25 (2)
Meet. Conditional expression (2) sets the ratio of the length of the lens array 10 and the like in the vertical direction of the gate to the gate width in an appropriate range in order to improve the filling and facilitate the gate cut process. By making it smaller than the upper limit of conditional expression (2), the size of the gate GA can be ensured, the fluidity can be kept good, and the occurrence of poor filling can be suppressed. On the other hand, by making it larger than the lower limit of conditional expression (2), the gate GA can be narrowed to some extent and the gate cut processing can be facilitated. Thus, the gate cut processing is facilitated by making the lateral width of the gate GA larger than a certain extent and maintaining the fluidity of the molten resin J while preventing the lateral width of the gate GA from becoming too large.

Even if the mold apparatus 70 as shown in FIG. 4B or the like is used under the conditions that can ensure the fluidity and transferability of the molten resin J as described above, the first lens array 10 and the like may be deformed after molding. . That is, the molded lens array body 84 or the first lens array 10 contracts when the pressure loss during molding increases, and generally shrinks in a portion near the gate GA and shrinks in a portion away from the gate GA. . Therefore, if the gate GA or the resin injecting portions 14, 24, and 34 are made to coincide with each other when the lens arrays 10, 20, and 30 are laminated, the contraction state or tendency of the lens arrays 10, 20, and 30 coincide with each other. Therefore, it becomes easy to match the centers of the lens elements 10a, 20a, and 30a in each compound optical system 2 constituting the compound-eye optical system 100, and the optical performance of each compound optical system 2 can be achieved with a small amount of decentering. It is expected to get as high as possible.

FIG. 5 is a conceptual diagram exaggerating the contraction of the first and second lens arrays 10 and 20. Rectangular outlines 10m and 20m indicated by phantom lines (one-dot chain lines) indicate a case where the first and second lens arrays 10 and 20 are ideally shaped and no contraction occurs. In practice, molding shrinkage occurs such that the displacement due to shrinkage increases as the distance from the gate GA increases due to pressure loss at the time of injection, resulting in trapezoidal contours 10 m and 20 m indicated by solid lines. The lattice axes 8a and 8b of the molded product indicated by the solid lines are distorted as compared with the original accurate lattice axes 7a and 7b indicated by the phantom lines. However, since molding contraction showing the same tendency occurs in both the first lens array 10 and the second lens array 20, the lens elements 10a and 20a constituting the first and second lens arrays 10 and 20 are mutually connected with the optical axis AX. Are maintained in a consistent state, and the resolution of each composite optical system 2 and thus the resolution of the imaging apparatus 1000 can be increased.

Further, in the case of a side gate as in the mold apparatus 70 shown in FIG. 4A, the lens array body 84 or the first lens array 10 is moved in the gate direction due to the asymmetry of the lens array body 84 (for example, the presence of the ribs 12). May be slightly warped in the gate vertical direction at each position along the line. The compound-eye optical system 100 for applications such as super-resolution includes lens arrays 10, 20, and 30 having substantially the same size, and equivalent performance is required for each. For this reason, the molding conditions and the like are also similar, and the direction and amount of warpage between the plurality of lens arrays 10, 20, and 30 are also similar. Therefore, when the lens arrays 10, 20, and 30 are stacked as described above, the warp of the three lens arrays 10, 20, and 30 is copied by matching the gate GA or the resin injection portions 14, 24, and 34 with each other. Problems such as interval fluctuations and occurrence of eccentricity due to such warpage are less likely to occur or are reduced.

FIG. 6 is a conceptual diagram exaggerating the warp of the lens arrays 10, 20, and 30 in an easily understandable manner. In the illustrated example, the lens arrays 10, 20, and 30 are slightly bent downward with the ribs 12, 22, and 32 as the distance from the resin injection portions 14, 24, and 34 corresponding to the gate GA is increased. The bending methods of the arrays 10, 20, and 30 are substantially the same, and in each compound optical system (single-lens system) 2 constituting the compound-eye optical system 100 obtained by stacking the lens arrays 10, 20, 30, lenses The relative position between the elements 10a, 20a, 30a is kept uniform. The warpage of the lens arrays 10, 20, and 30 is considered to occur due to differences in shrinkage due to resin pressure, temperature, and resin flow orientation during molding. Although the warpage can be reduced by optimizing the molding conditions, it is not easy to achieve the micrometer accuracy required for the compound-eye optical system 100 for applications such as super-resolution. Therefore, the warp of the lens arrays 10, 20, and 30 is left, and the resin injection portions 14, 24, and 34 are made to coincide with each other, so that the relative arrangement of the lens elements 10 a, 20 a, and 30 a can be easily made accurately. The accuracy of the optical system 100 can be improved.

As described above, by aligning the angles of the lens arrays 10, 20, and 30 with respect to the resin injection portions 14, 24, and 34, the specific composite optical system 2 close to the resin injection portions 14, 24, and 34 is used. The influence of birefringence is likely to occur, and the superposition of these tends to cause a large deterioration in performance compared to the surroundings. Therefore, it is desirable that the individual lens arrays 10, 20, and 30 have a small amount of birefringence. For this reason, it is conceivable to select a material for molding the lens arrays 10, 20, and 30 to reduce the birefringence amount. Generally, the photoelastic coefficient of the resin for molding each lens array 10, 20, 30 is 50 × 10 ⁻⁷ (cm ² / Kgf) or less, preferably 30 × 10 ⁻⁷ (cm ² / Kgf). The following. Accordingly, the photoelastic coefficient of the resin forming the lens elements 10a, 20a, and 30a is kept small, the performance of the lens arrays 10, 20, and 30 is maintained at a certain level or more, and the compound optical system 2 or compound eye in which these are stacked. The performance of the entire optical system 100 can also be improved.

Specifically, polycarbonate resins EP4000, EP5000 (Mitsubishi Gas Chemical Co., Ltd.), polyolefin resin APEL (Mitsui Chemicals Co., Ltd.) and the like can be used as the material of the lens arrays 10, 20, 30. The photoelastic coefficient of general polycarbonate is 71 × 10 ⁻⁷ (cm ² / Kgf), and the photoelastic coefficients of EP4000, EP5000, and APEL are 30 × 10 ⁻⁷ (cm ² / Kgf) or less. Become.

For the birefringence as described above, the optical transfer portions 71g and 72g formed on the transfer surfaces 71c and 72c of the mold apparatus 70 shown in FIG. 4A can be corrected to reduce the influence of birefringence in advance. It can also be. At this time, the processing of the nested core members 71k and 72k for forming the optical transfer portions 71g and 72g is individually adjusted.

Although not described above, as shown in FIG. 2, the lens arrays 10, 20, and 30 may be provided with alignment marks MA. By using the alignment mark MA to adjust the XYΘ between the lens arrays 10, 20, and 30, or by feeding back the measurement results, it is possible to implement a highly accurate integration. At this time, by providing the alignment mark MA at a location where the displacement between the lens arrays 10, 20, and 30 can be reduced, the point to be adjusted can be adjusted firmly, and the eccentricity is reduced at other locations as a result.

In addition, when the lens arrays 10, 20, and 30 are taken out from the mold apparatus 70, the molded product 80 is ejected by an ejector pin (not shown) provided on one of the first mold 71 and the second mold 72. The lens array main body 84 may be pushed out. Here, if the lens array body 84 or the four corners of the lens arrays 10, 20, and 30 are pushed out in a well-balanced manner, it is possible to suppress the warpage of the lens array body 84 or the lens arrays 10, 20, 30 and the like.

In the compound eye optical system described above, the resin injection portions 14, 24, and 34 formed in the lens arrays 10, 20, and 30 are disposed on the sides of the lens arrays 10, 20, and 30, so that a thermoplastic resin is injected into the resin. When the resin is injected into the mold space through the gate GA corresponding to the portions 14, 24, 34, etc., the resin can be easily supplied to the thin portions of the lens arrays 10, 20, 30, and the obtained lens array 10, 20, and 30 can be made highly accurate. Further, the resin injection portions 14, 24, and 34 of the plurality of lens arrays 10, 20, and 30 are arranged corresponding to the same reference direction DR4 with respect to the arrangement of the lens elements 10a, 20a, and 30a. Therefore, when the lens array 10, 20, 30 or the compound eye optical system 100 is accommodated in the case 50, even if the resin injection portions 14, 24, 34 protrude, it is only necessary to provide relief on one side of the case 50. The arrays 10, 20, and 30 can be easily incorporated, and the positioning accuracy can be easily obtained. In addition, it is known that the shrinkage of the resin differs depending on the distance from the gate GA. However, if the lens arrays 10, 20, and 30 are stacked with the gate GA, that is, the resin injection portions 14, 24, and 34 aligned in the same direction, the shrinkage occurs. Similarly, the optical axis alignment of all the lens elements 10a, 20a, and 30a can be performed with relatively high accuracy. Further, in the case where the resin injection portions 14, 24, 34 are side gates arranged on the sides of the lens arrays 10, 20, 30, the lens arrays 10, 20, 30 may be slightly warped in the gate direction. Further, in the case of the compound eye optical system 100, since the lens array 10, 20, 30 having substantially the same size requires the same performance, the molding conditions and the like are similar, and the plurality of lens arrays 10, 20, 30 warp. The direction and amount of will be similar. At that time, if the lens arrays 10, 20, and 30 are stacked with the gate GA, that is, the resin injection portions 14, 24, and 34 aligned in the same direction as described above, the lens arrays 10, 20, and 30 are warped. Problems such as variations in the distance between the lens elements 10a, 20a, and 30a and occurrence of eccentricity due to differences in warpage between the 10, 20, and 30 are also unlikely to occur.

The imaging apparatus 1000 incorporating the compound eye optical system 100 described above easily increases the accuracy of the shape and decentering of the lens elements 10a, 20a, and 30a, and easily improves the performance of each compound optical system 2 that is a single-eye lens system. It has become. As a result, the image pickup apparatus 1000 is thin and lightweight, but has high quality.

Specific examples will be described below. Table 1 below shows an example in which molding was performed while changing parameters such as the thickness T, length L, gate width D, and length W of the lens arrays 10, 20, and 30.
[Table 1]

Any of Examples 1 to 6 was a high-performance lens array, and the compound eye optical system 100 in which these lens arrays were combined had the expected performance.

[Second Embodiment]
The compound eye optical system according to the second embodiment will be described below. The compound eye optical system of the second embodiment is a modification of the compound eye optical system of the first embodiment, and items not specifically described are the same as those of the first embodiment.

As shown in FIG. 7, the compound-eye optical system 100 of the present embodiment is formed by stacking four lens arrays 10, 20, 30, and 40. In these lens arrays 10, 20, 30, and 40, the positions of the resin injection portions 14, 24, 34, and 44 are oriented in the same reference direction DR4.

[Third Embodiment]
The compound eye optical system according to the third embodiment will be described below. The compound eye optical system of the third embodiment is a modification of the compound eye optical system of the first embodiment, and items not specifically described are the same as those of the first embodiment.

As shown in FIG. 8, the compound eye optical system 100 according to the present embodiment describes a method of stacking the lens arrays 10, 20, 30 in the compound eye optical system 100 including three lens arrays 10, 20, 30. . In this case, the three lens arrays 10, 20, and 30 are configured by arranging a plurality of lens elements 10a, 20a, and 30a on 3 × 3 square lattice points. The three lens arrays 10, 20, and 30 are stacked so that the resin injection portions 14, 24, and 34 are oriented in the same direction.

According to the compound eye optical system of the present embodiment, it is possible to increase the degree of super-resolution (improvement of resolution when obtaining an entire image from a single eye) while suppressing an increase in thickness.

In the above, the present invention has been described according to the present embodiment, but the compound eye optical system of the present invention is not limited to the above embodiment. For example, the outline of the lens arrays 10, 20, 30, 40 in plan view is not limited to a rectangle, but may be a circle or an ellipse.

In the above description, the lens element 10a and the composite optical system 2 are arranged on square lattice points. However, the lens elements 10a, 20a, and 30a can be arranged on rectangular lattice points, triangular lattice points, and the like. is there.

In the above description, the case where three or four lens arrays 10, 20, 30, and 40 are stacked has been described. However, five lens arrays may be stacked. In addition, the improvement in resolution is expected by configuring the compound eye optical system 100 by stacking three or more lens arrays. However, since the error sensitivity becomes severe as the number of sheets increases, if there are three or more lens arrays, the resin injection part corresponding to the gate GA is not aligned in the same direction. The effect of aligning 14, 24, 34, 44 is further enhanced. On the other hand, if the number of lens arrays constituting the compound-eye optical system 100 is more than six, the entire compound-eye optical system 100 becomes thicker, or the performance deterioration at a temperature other than room temperature increases due to the influence of the temperature variation of the resin. Since practicality is lowered, 3 to 5 lens arrays are preferable.

In addition, the arrangement of the lens elements 10a and the composite optical system 2 can be 5 × 5 or more in a matrix form.

In the above embodiment, if necessary, a diaphragm member is provided before and after the compound eye optical system 100 or between each lens array, or a light shielding material is provided on at least one main surface of at least one of the lens arrays. It may be applied to form a diaphragm. A case 50 having a plurality of openings provided corresponding to each lens element may have a diaphragm function.

In the above embodiment, the size, optical surface shape, and the like of the lens elements 10a, 20a, and 30a can be appropriately changed according to the application and function.

Claims (14)

1. A compound-eye optical system obtained by superimposing a plurality of lens arrays each formed of a thermoplastic resin and having two-dimensionally arranged lens elements,
   Each lens array has a resin injection part,
   Each resin injection part is arranged on the side of the lens array, and is arranged corresponding to the same reference direction with respect to the arrangement of the lens elements.
2. In each lens array, the lens elements are arranged in a matrix along four orthogonal reference directions, and the resin injecting portion is arranged on any one of the sides constituting a rectangular frame in which the lens elements are arranged. The compound eye optical system according to claim 1, which is disposed so as to face each other.
3. 3. The compound eye optical system according to claim 2, wherein each lens array has a rectangular outline corresponding to the rectangular frame, and the resin injecting portion is provided on a central outer side of any side of the rectangular outline.
4. Each lens array has the following conditional expression 10 <L / T, where T is the minimum thickness of the lens array and L is the length of the lens array in the gate direction in which the gate corresponding to the resin injection portion of the lens array extends. <60
   The compound eye optical system according to any one of claims 1 to 3, wherein
5. Each lens array has the following conditional expression 1 where D is the gate width in the gate vertical direction across the gate corresponding to the resin injection portion of the lens array, and W is the length of the lens array in the gate vertical direction. 3 <W / D <25
   The compound eye optical system according to any one of claims 1 to 4, wherein
6. The compound eye optical system according to any one of claims 1 to 5, wherein the plurality of two-dimensionally arranged composite optical systems obtained by superimposing the plurality of lens arrays have substantially the same shape. .
7. The compound eye optical system according to any one of claims 1 to 6, wherein each of the plurality of compound optical systems observes the same visual field.
8. The compound eye optical system according to claim 7, wherein the plurality of compound optical systems are arranged in an array number of 3 × 3 or more.
9. The compound-eye optical system according to any one of claims 1 to 8, wherein three or more and five or less lens arrays are stacked as the plurality of lens arrays.
10. A compound eye optical system according to any one of claims 1 to 9,
    A sensor array provided corresponding to the plurality of lens arrays;
    An image processing apparatus comprising: an image processing unit that performs processing on an image signal detected by the sensor array.
11. A plurality of two-dimensionally arrayed composite optical systems obtained by superimposing a plurality of lens arrays are for observing the same field of view.
    The imaging apparatus according to claim 10, wherein the image processing unit performs super-resolution processing of an image signal detected by the sensor array.
12. The following conditional expression Ns / Ni> 5, where Ni is the number of single-eye pixels of the sensor provided corresponding to each composite optical system in the sensor array, and Ns is the number of pixels after super-resolution.
    The imaging device according to claim 11, wherein:
13. The maximum distance between the lens arrays in the gate vertical direction across the gate corresponding to the resin injection portion of the lens array is P, and the individual pixel pitch of the sensor provided corresponding to each compound optical system in the sensor array is d. The following conditional expression 20> (P / d) / 1000
    The imaging device according to any one of claims 11 and 12, which satisfies:
14. Molding a plurality of lens arrays each having two-dimensionally arranged lens elements by injection of a thermoplastic resin;
    A method for producing a compound eye optical system comprising a step of obtaining a compound eye optical system by superimposing a plurality of lens arrays,
    A compound eye optical system manufacturing method in which resin injection portions of the lens array are arranged corresponding to the same reference direction with respect to the arrangement of lens elements.

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