Optical element, optical device, and imaging apparatus

Abstract

To provide an optical element that achieves lens adhesion with high reliability and stability.SOLUTION: A PMO lens 13 has an optical effective surface 13f through which an optical axis O passes, and a side face 13b formed on the outside in a radial direction of the optical effective surface 13f. A plurality of fine projections P including a periodic pattern are formed on the side face 13b. An adhesion pool 12c is provided between the PMO lens 13 and a lens holder 12 holding the PMO lens 13. The side face 13b having the fine projections P and the lens holder 12 are fixed to each other with an adhesive 14 injected into the adhesion pool 12c.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an optical element, an optical device, and an imaging device. [Background technology]

[0002] In recent years, plastic molded lenses made from resins such as acrylic have increasingly been used as a type of aspherical lens, primarily in small lens barrels.

[0003] A method of fixing a plastic molded lens to a lens holder using an adhesive without applying heat or pressure is often used. Patent Document 1 discloses a technique for performing a hydrophilic treatment and then bonding the plastic lens to a lens holding frame with an ultraviolet-curing adhesive (UV adhesive). Patent Document 2 also discloses a technique for fixing an optical element used in an imaging device in a small device, in which the surface roughness of at least one surface of the outer periphery of the optical element is made larger than the surface roughness of the optically functional surface of the optical element, thereby increasing the surface area and adhesive strength. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2018-180535 [Patent Document 2] Japanese Patent Application Laid-Open No. 2005-193646 Summary of the Invention [Problem to be solved by the invention]

[0005] However, UV adhesives and plastic molded lenses have poor adhesive properties, and may peel off when stored in harsh temperature environments or subjected to drop impact tests. Furthermore, the hydrophilic treatment disclosed in Patent Document 1 may increase costs. Furthermore, the optical element disclosed in Patent Document 2 is used in imaging devices for small devices such as digital still cameras and mobile phones, but is insufficient as a solution for interchangeable lens devices, which use larger optical elements.

[0006] An object of the present invention is to provide an optical element that achieves highly reliable and stable lens bonding. [Means for solving the problem]

[0007] In order to achieve the above object, the present invention provides an optical element having a first surface through which an optical axis passes and a second surface formed radially outward of the first surface, wherein a plurality of convex portions including a periodic pattern are formed on the second surface, a plurality of gaps are provided between the optical element and a holding member that holds the optical element, and the second surface having the convex portions and the holding member are fixed by adhesive injected into the gaps. [Effects of the Invention]

[0008] According to the present invention, an optical element can be provided that achieves highly reliable and stable lens bonding. [Brief explanation of the drawings]

[0009] [Figure 1] 1A is a perspective view of a PMO lens 13 according to Example 1. FIG. 1B is a partial cross-sectional view of the PMO lens 13 taken along the cross-sectional line IB-IB in FIG. [Figure 2] FIG. 2 is a perspective view of the lens holder assembly 11 of the first embodiment. [Figure 3] 3A is a partial cross-sectional view taken along the line III-III in Fig. 2. FIG. 3B is a partial cross-sectional view showing a state in which adhesive 14 has been dropped. [Figure 4] (A) is a perspective view of a fine protrusion P. (B) is a partial cross-sectional view of a PMO lens 13. [Figure 5] (A) is an enlarged perspective view of the micro-protrusion P. (B) is a plan view of the micro-protrusion P. (C) is a cross-sectional view of the micro-protrusion P taken along the cross-sectional line VC-VC in FIG. 5(B). (D) is a cross-sectional view of the micro-protrusion P taken along the cross-sectional line VD-VD in FIG. 5(B). [Figure 6] FIG. 10 is a partial cross-sectional view of a PMO lens 23 according to a second embodiment. [Figure 7] FIG. 10 is a partial cross-sectional view of a lens holder assembly 21 according to a second embodiment. [Figure 8] FIG. 10 is a partial cross-sectional view of a PMO lens 33 according to a third embodiment. [Figure 9] FIG. 10 is a partial cross-sectional view of a lens holder assembly 31 according to a third embodiment. [Figure 10] 3A and 3B are cross-sectional views showing the configuration of a mold 15. FIG. [Figure 11] FIG. 1 is a schematic diagram illustrating an example of the configuration of an imaging device. DETAILED DESCRIPTION OF THE INVENTION

[0010] Example 1 Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Fig. 1(A) is a perspective view of a PMO lens 13 (plastic molded lens, optical element) according to a first embodiment of the present invention. Fig. 1(B) is a partial cross-sectional view of the PMO lens 13 taken along the section line IB-IB in Fig. 1(A). Fig. 2 is a perspective view of a lens holder assembly 11 according to the first embodiment, with the adhesive 14 not shown. Fig. 3(A) is a partial cross-sectional view taken along the section line III-III in Fig. 2, in which the lens holder assembly 11 is cut along a plane including the optical axis O and viewed in the direction of the arrow. Fig. 3(B) is a partial cross-sectional view of a state in which the adhesive 14 has been applied.

[0011] The lens holder assembly 11 is one element that constitutes the lens unit 100 (optical device, see FIG. 11), which is part of a digital camera or camera module. The optical axis O represents the optical axis center of the lens unit 100 and the optical axis center of the PMO lens 13. The lens holder assembly 11 is composed of the PMO lens 13 and a lens holder 12 (holding member) that holds the PMO lens 13.

[0012] The PMO lens 13 of Example 1 has an optically effective surface 13f (first surface) including the optical axis O, and a non-optically effective surface (surface in range E, second surface) formed radially outward from the optically effective surface 13f. The optically effective surface 13f is a surface through which light passes, and the passing light reaches the image sensor 200b (see FIG. 11) and an image is formed thereon. On the other hand, the non-optically effective surface is a surface on which light does not reach the image sensor 200b and an image is not formed thereon even if it enters. The optically effective surface 13f is formed on both the object side and the image side. On the other hand, the non-optically effective surface in range E is composed of an abutment surface 13a, a side surface 13b (second surface), an outer shoulder surface 13g, etc. The abutment surface 13a abuts against the lens holder 12. In Example 1, a plurality of fine protrusions P (convex portions) described below are formed on the side surface 13b.

[0013] As shown in Fig. 2, the lens holder 12 has an inner peripheral surface 12b and an adhesive pool 12c (gap portion). As shown in Fig. 3(A), the lens holder 12 has a lens receiving surface 12a that receives the abutment surface 13a of the PMO lens 13. The adhesive pool 12c is located between the lens holder 12 and the PMO lens 13 and is formed by the area surrounded by the bottom surface 12d, inner wall surface 12e, and side surface 13b of the PMO lens 13.

[0014] In this embodiment, adhesive 14 is injected into adhesive pools 12c of lens holder 12 to bond and fix two components, PMO lens 13 and lens holder 12. Typically, adhesive pools 12c are evenly spaced around optical axis O. In Figure 2, three adhesive pools 12c are provided at regular angular intervals, for example, 120 degrees, around the circumference of optical axis O.

[0015] The up-down direction in Figure 3(A) is the optical axis direction, and the PMO lens 13 is arranged relative to the lens holder 12 so that the PMO lens 13 is placed on the upper side of the lens holder 12 in the optical axis direction. The lens receiving surface 12a of the lens holder 12 and the abutment surface 13a of the PMO lens 13 are each finished with high dimensional precision, and the surfaces of each surface are generally finished smoothly. The position of the PMO lens 13 in the optical axis direction is determined by abutting the abutment surface 13a against the lens receiving surface 12a. In this embodiment, there is no gap in the optical axis direction when they are abutted.

[0016] Returning to FIG. 2, a gap 12f exists between the lens holder 12 and the PMO lens 13 in the radial direction perpendicular to the optical axis O. The gap 12f is a space provided to align the optical axes of the lens holder 12 and the PMO lens 13. The presence of this gap 12f makes it possible to optimally adjust the position of the PMO lens 13 relative to the lens holder 12 in the direction perpendicular to the optical axis for each individual lens. This allows the entire lens unit (not shown) including the lens holder assembly 11 to achieve optimal optical performance, such as suppressing aberrations. Depending on the individual lens, adjustments may be made, such as intentionally shifting the axes of the lens holder 12 and the PMO lens 13. Therefore, even within a single lens, the gap 12f may be wide or narrow in some places, and the state of this gap varies depending on the individual lens. As can be seen in FIG. 3(A), the lens receiving surface 12a extends further outward (to the right in the figure) than the abutting surface 13a of the PMO lens 13. This extension is intended to ensure contact between the lens receiving surface 12a and the contact surface 13a when the position of the PMO lens 13 is moved relative to the lens holder 12 during the optical adjustment.

[0017] In recent years, in response to growing demands for smaller and higher performance camera lenses, the use of aspherical lenses has increased in interchangeable lenses and other camera lenses. Aspherical lenses can eliminate lens aberrations without increasing the number of lens elements, making them effective for reducing lens size and improving performance. However, plastic molded lenses are characterized by greater thermal deformation and pressure distortion than glass lenses, posing challenges when it comes to fixing them to lens holding members. For example, fixing plastic molded lenses to lens holding members using thermal caulking, as with glass lenses, results in distortion of the lens's optical surface, making it difficult to employ this fixing method.

[0018] Additionally, UV adhesives are often used for ease of assembly, but if the UV adhesive and plastic molded lens separate, the lens will move from its ideal position, resulting in a deterioration of optical performance. In worse cases, the plastic molded lens will come off, making photography impossible. Separation between the UV adhesive and plastic molded lens is particularly likely in environments with temperature changes, such as high and low temperatures, due to the different linear expansion coefficients of the lens holder, plastic molded lens, and UV adhesive. The main cause of this is incompatibility between the plastic molded lens and UV adhesive materials, which results in insufficient adhesive strength.

[0019] In this embodiment, too, a UV adhesive is used as the adhesive 14, taking assembly workability into consideration. The adhesive 14 is dripped into the adhesive pool 12c of the lens holder 12, and UV irradiation is performed while the adhesive 14 is dripped, causing the adhesive 14 to harden. This fixes the relative positions of the lens holder 12 and the PMO lens 13, restricting movement in both the optical axis direction and the direction perpendicular to the optical axis. The PMO lens 13 is fixed in place by contacting the adhesive 14 on its side surface 13b. The lens holder 12 is fixed in place by contacting the adhesive 14 on the bottom surface 12d and inner wall surface 12e of the adhesive pool 12c.

[0020] As mentioned above, the adhesive 14 and the PMO lens 13 are incompatible materials, making it difficult to achieve sufficient adhesive strength. In contrast, UV adhesives are compatible with polycarbonate, a common material for the lens holder 12, and can achieve sufficient adhesive strength. Furthermore, the surface area in contact with the adhesive 14 is larger for the lens holder 12 than for the PMO lens 13. Therefore, in most cases, peeling occurs at the interface between the UV adhesive and the PMO lens 13 during drop impact tests or environmental tests.

[0021] Here, the micro-protrusions P provided on the surface of the PMO lens 13 of this embodiment will be described with reference to Figures 4(A) and (B). Figure 4(A) is an enlarged view of the side surface 13b on which the micro-protrusions P are provided, and is an enlarged perspective view showing the state of the side surface 13b. Figure 4(B) is a partial cross-sectional view of the region on which the micro-protrusions P are formed, as viewed in the direction indicated by the arrow in Figure 1(A).

[0022] A plurality of micro-protrusions P are formed on the side surface 13b of the PMO lens 13 in a regular, periodically repeating pattern. The micro-protrusions P have a mountain-like shape with the side surface 13b as the base, and include at least substantially the same shape, or all of them have substantially the same shape, or a combination of substantially the same shapes, and their dimensions, such as height, are also substantially the same. The side surface 13b includes a large-diameter portion 13d on the larger-diameter side of the PMO lens 13 and a small-diameter portion 13e on the smaller-diameter side. Note that although the micro-protrusions P are only provided on a portion of the side surface 13b in FIG. 1(A), in reality, the micro-protrusions P are provided around the entire circumference of the side surface 13b.

[0023] Next, the fine protrusions P will be described in detail using Figures 5(A) to (D). Figure 5(A) is an enlarged perspective view of one of the fine protrusions P. The white background represents the side surface 13b. Two fine protrusions P are shown, and a perspective view from the opposite side has been added to make the shape easier to understand. The arrows in Figure 5(A) indicate the direction of the large diameter portion 13d on the side surface 13b, which has a larger diameter, and the direction of the small diameter portion 13e on the side surface 13b, which has a smaller diameter.

[0024] The angle from the side surface 13b to the apex of the fine protrusion P varies depending on the direction, and the shape is not a perfect cone, but appears to extend in the optical axis direction of the PMO lens 13 as a whole.

[0025] The angle of the slope of the peak of the fine protrusion P varies depending on the location, with the small diameter portion 13e side being a steeper slope and the large diameter portion 13d side being a gentler slope. On the other hand, the longitudinal direction of the side surface 13b (the circumferential direction of the optical axis O) is an even steeper slope than the small diameter portion 13e side. This is due to the manufacturing method of the PMO lens 13 and the fine protrusion P, which will be described later.

[0026] 5(B) is a plan view of the fine protrusion P, as seen from a direction perpendicular to the side surface 13b. The left-right direction of the figure is the optical axis direction, with the left side being the large-diameter portion 13d side and the right side being the small-diameter portion 13e side. The up-down direction of FIG. 5(B) is the circumferential direction of the optical axis O.

[0027] Figure 5(C) is a cross-sectional view of the fine protrusion P as seen in the direction of the arrow at cross-sectional line VC-VC in Figure 5(B). The left-right direction in the figure is the optical axis direction, with the left side being the large-diameter portion 13d side and the right side being the small-diameter portion 13e side. The slope on the large-diameter portion 13d side is an inclined surface that has an angle B with respect to side surface 13b, and the slope on the small-diameter portion 13e side is an inclined surface that has an angle A with respect to side surface 13b. The height of the fine protrusion P from side surface 13b is H.

[0028] Figure 5(D) is a cross-sectional view of the fine protrusions P as seen in the direction of the arrow at the cross-sectional line VD-VD in Figure 5(B). The left and right sides of Figure 5(D) are the circumferential direction of the optical axis O. The inclined surfaces are inclined surfaces having an angle C with respect to the side surface 13b, and both the left and right inclined surfaces in Figure 5(D) have approximately the same angle C. Angle C is greater than angles A and B. As in Figure 5(C), the height of the fine protrusions P from the side surface 13b is H.

[0029] Next, a manufacturing method for the PMO lens 13 and the fine protrusions P will be described with reference to Figure 1(A). The PMO lens 13 is a resin lens, and is injection molded using an injection molding die (mold) for molding resin lenses. Injection molding is a manufacturing method in which molten resin material is heated to a high temperature and injected into the die, and the part is removed when it has cooled and solidified.

[0030] 10(A) and (B) are cross-sectional views of a mold 15 used for injection molding a PMO lens 13. Fig. 10(A) shows the state in which a molten resin material heated to a high temperature is injected into the mold and then cooled and hardened. The PMO lens 13 is molded between an upper piece 15a and a lower piece 15b. The sprue and runner parts that pour the resin into the mold are not shown.

[0031] Figure 10(B) is a cross-sectional view of the upper and lower pieces 15a and 15b separating to remove the PMO lens 13. Either the upper and lower pieces 15a and 15b separate upward or downward at the mold split portion 15c shown in Figure 10(A), allowing the PMO lens 13 to be removed. Note that although arrows indicating the direction of movement are attached to the upper and lower pieces 15a and 15b, in reality, only one of them moves. The mold 15 is configured as described above, and with this in mind, we will return to Figure 1(B) to continue the explanation.

[0032] The PMO lens 13 has an optically effective surface 13f and a non-optically effective surface. The mold surface corresponding to the optically effective surface 13f is machined with extremely high precision and finished with a very fine surface roughness. The optically effective surface 13f is a part of the PMO lens 13, and is the surface through which light rays pass through the lens unit including the lens holder assembly 11 and reach the imaging surface. The imaging surface is the surface of a sensor such as a CMOS sensor or CCD sensor, and the light received by the sensor surface of these sensors is converted into an electrical signal to generate an image. Therefore, if the shape of the optically effective surface 13f is not as designed, image quality will deteriorate. The same applies if the optically effective surface 13f is contaminated.

[0033] The non-optically effective surface is a part of the PMO lens 13, and light passing through it does not reach the imaging surface. Therefore, even if the accuracy or surface roughness is inferior to that of the optically effective surface 13f, it does not affect the quality of the captured image. Because it is a surface that does not affect the captured image, it is common to use this non-optically effective surface for holding the lens and adhesively fixing the lens.

[0034] The mold surface corresponding to the side surface 13b has minute recesses (recessed portions) (not shown) regularly and periodically arranged. The PMO lens 13 can be removed from the mold 15 by separating the pieces of the mold 15 into two pieces in the front and rear directions of the optical axis at a mold separation portion 15c present inside the mold 15. In this embodiment, the mold separation portion 15c is located at the intersection of the surface connected to the optically effective surface 13f and the side surface 13b. This is the same location as the large-diameter portion 13d in Figure 4(B). The side surface 13b is formed at an angle D with respect to the optical axis O, allowing the two pieces to separate smoothly. The angle D of the side surface 13b is set so that the adhesive 14 does not form a wedge in the direction in which the PMO lens 13 is removed from the lens holder 12.

[0035] The molten resin material injected into the mold 15 fills it according to the shape of the mold 15, molding the shape of the PMO lens 13. At the same time, the resin flows into a concave shape (not shown) provided on the side surface 13b, forming fine protrusions P. Although the concave shape is not shown, it is a concave shape provided in the mold 15, and has a shape without undercuts when viewed from the direction of movement of the mold 15 (usually the same as the optical axis direction). Because of the shape without undercuts, the PMO lens 13 can be smoothly separated from the mold 15 without restricting mold movement. However, because the concave shape is very fine, the resin material does not completely fill the concave shape, and the shape of the concave shape is not transferred as is. The inside of the concave shape is not completely filled with resin, and cooling begins once filling of the other parts is completed. After cooling and solidification, the mold 15 separates into two halves, bounded by the mold split portion 15c. In this embodiment, the piece forming the upper side is fixed at the mold split portion 15c shown in Figure 1(B), and the piece forming the lower side moves downward along the optical axis O, thereby making it possible to remove the PMO lens 13. As mentioned above, the concave shape is formed to have no undercuts when viewed from the direction of movement of the mold 15 so that the resin and the piece of the mold 15 can separate without resistance.

[0036] The fine protrusions P are formed by incompletely filling the recessed shape on the side surface 13b, which is inclined relative to the optical axis O, with resin, and therefore, as mentioned above, the angle of the slope of the mountain varies depending on the location.

[0037] Next, the effects of this embodiment will be described. As shown in Figure 3(B), adhesive 14 is dropped into adhesive pool 12c provided on lens holder 12, and side surface 13b of PMO lens 13 and the surface of fine protrusions P are all covered with adhesive 14. Similarly, bottom surface 12d other than fine protrusions P is also covered with adhesive 14. After that, UV light is irradiated to harden adhesive 14, completing the process, and side surface 13b and fine protrusions P are covered with hardened adhesive 14.

[0038] In environments with temperature changes, such as high and low temperatures, the linear expansion coefficients of the lens holder 12, PMO lens 13, and adhesive 14 are different, resulting in stress at the interface that tries to separate them. Referring to FIG. 3(B), the side surface 13b and the surface of the micro-projection P are all covered with adhesive 14, and shear stress acts on the micro-projection P in response to the force that tries to separate the adhesive 14 from the side surface 13b. Shear stress is particularly strong on the slopes at angles C and A, which form large angles with the side surface 13b. This shear stress increases the force that resists the force that tries to separate the PMO lens 13 and adhesive 14 at the interface between them, making the interface between the PMO lens 13 and adhesive 14 less likely to separate even when the temperature environment changes. Furthermore, shear stress acts not only when the temperature environment changes but also when an impact such as a drop is applied, making peeling less likely to occur. Therefore, the PMO lens 13 does not move from its initial position, and optical performance is less likely to deteriorate. According to the present invention, it is possible to provide an optical element that achieves highly reliable and stable lens bonding without incurring disadvantages such as increased costs, increased size, and impaired assembly.

[0039] Next, we will explain more preferable shapes of the fine protrusions P. The larger the angle formed by the inclined surface of the fine protrusions P with the side surface 13b, the greater the shear stress. Furthermore, the higher the height H of the fine protrusions P, the greater the shear stress. Furthermore, the greater the number of fine protrusions P, the greater the shear stress. The number of fine protrusions P can be changed depending on how many recessed shapes are provided in the mold 15. The arrangement of the fine protrusions P can be changed depending on the arrangement of the recessed shapes provided in the mold 15.

[0040] Furthermore, the angles A, B, C and height H of the slopes of the fine protrusions P can be changed by changing the shape and depth of the concave shape provided in the mold 15 and the molding conditions for injection molding the PMO lens 13. Referring to Figures 1(A), 4(B), 5(C), and 5(D), by increasing the angle D of the side surface 13b with respect to the optical axis O, it is possible to increase the angles A, B, and C, and also the height H. However, increasing the angle D has the disadvantage of increasing the outer diameter of the PMO lens 13.

[0041] On the other hand, the surface precision of the optically effective surface 13f of the PMO lens 13 varies greatly depending on the molding conditions, and poor molding conditions can prevent precision matching the shape of the mold 15 or result in instability, such as variations between individual units. As a result, the initial optical performance of the lens unit 100 and the imaging device deteriorates. In many cases, increasing the angle of the slope of the fine protrusions P, increasing their height, or increasing their number increases the resistance when the mold 15 and the PMO lens 13 separate, thereby worsening the precision of the optically effective surface 13f.

[0042] In other words, these parameters and the surface precision of the optically effective surface 13f are in a trade-off relationship. In other words, it is not appropriate to determine molding conditions with the objective of controlling only the number of fine protrusions P or the angle and height of the inclined surfaces, and it is necessary to strike a balance with the surface precision of the optically effective surface 13f.

[0043] In this way, the number of fine protrusions P, the angles A, B, C of the slopes, the height H, and the molding conditions during molding influence each other and are in a contradictory relationship, so it is necessary to set optimal conditions.

[0044] In this example, a laser processing machine was used to process recesses into the mold surface in order to precisely control the shape, number, and arrangement of the fine protrusions P. By controlling the laser output and conditions of the laser processing machine, it is possible to process the recesses into the desired shape and depth.

[0045] Furthermore, by arranging the recessed shapes regularly and periodically, it is possible to provide a large number of recessed shapes per unit area. This makes it possible to increase the number of fine protrusions P. However, if the recessed shapes are spaced too close together, they may not be transferred properly during molding. Furthermore, if the spaces are too close together, mold processing is difficult in the first place. Even if processing is possible, thin-walled portions may be formed in the mold 15, making the mold weak and potentially damaging the mold 15 during processing or molding. In other words, the recessed shapes must be spaced appropriately, not only in shape but also in shape. Similarly, if the recessed shapes are spaced too close together, the transfer of the mold shape during molding will be unstable, and the molded fine protrusions P will not have the desired shape. Conversely, if the spaces between the recessed shapes are too large, a sufficient number of fine protrusions P will not be formed. In this example, the recessed shapes were spaced at intervals of 50 μm to 150 μm.

[0046] Furthermore, not only can the number of fine protrusions P be increased, but the desired number of fine protrusions P can be provided evenly, which eliminates the deterioration of the surface precision of the optically effective surface 13f of the PMO lens 13. For example, if the fine protrusions P are sparsely spaced and densely spaced in some locations in the circumferential direction of the side surface 13b, the balance during molding or when the mold 15 is separated from the resin will be lost, and the surface precision of the optically effective surface 13f will deteriorate.

[0047] In other words, by forming the concave shape by laser processing, it is possible to control not only the shape of the fine protrusions P, but also the density and arrangement of the fine protrusions P. This makes it possible to stabilize the surface precision of the optically effective surface 13f of the PMO lens 13, while at the same time improving the adhesive strength between the PMO lens 13 and the adhesive 14 and suppressing peeling when the temperature environment changes or when the lens is dropped. However, it should be noted that it is not necessarily a necessary condition that the fine protrusions P be arranged regularly or periodically.

[0048] In conventional technology, a method has been used to increase the surface roughness of the UV adhesive by applying a matte finish to the mold and transferring the mold's surface shape. However, the surface shapes obtained by sandblasting and chemical etching, which are widely known methods for applying a matte finish to a mold, were insufficient as a countermeasure. In particular, in environments with severe temperature changes, the surface roughness achieved by the matte finish alone did not solve the problem of the plastic molded lens and UV adhesive peeling apart.

[0049] Table 1 shows the angles A, B, C, and height H of the inclined surface of the fine protrusions P, as well as the test results for adhesive peeling in the temperature environment test. In Table 1, ◯ indicates that no adhesive peeling occurred after the temperature environment test, and × indicates that adhesive peeling occurred and the optical performance deteriorated. [Table 1]

[0050] From Table 1, it was found that the height H should be approximately 4 μm or more, but that a height H of 3 μm to 20 μm is more preferable. It was also found that any one of angles A, B, and C should be 35 degrees or more. Although not shown in Table 1, it was also found that the larger the angles A, B, and C, the greater the adhesive strength, making it less likely that the PMO lens 13 and adhesive 14 will peel off. Similarly, it was also found that the higher the height H, the greater the adhesive strength, making it less likely that the PMO lens 13 and adhesive 14 will peel off. It was also found that peeling will not occur if the spacing between the fine protrusions P is in the range of 50 μm to 150 μm.

[0051] In contrast, the above-described shape cannot be obtained by the matte finish applied to a mold by sandblasting or chemical etching, as proposed in the prior art. It is impossible to precisely control the arrangement and pitch of the fine protrusions P, and they can only be processed at wide intervals compared to laser processing. At least, they cannot be processed at narrow intervals such as 50 μm to 150 μm as in this embodiment. Furthermore, it is impossible to process the entire processed surface without any variation in density. With regard to the angle and height of the inclined surface of the fine protrusions P, it may be possible to create the shapes listed in Table 1, but they cannot be processed at narrow pitches such as in this embodiment.

[0052] On the other hand, in machining processes using a machining center or other machine tools, it is possible to control the layout and spacing, but it is also impossible to process at a narrow pitch.Furthermore, it is impossible to process a concave shape of this size.

[0053] That is, laser processing is the only mold processing method that can achieve the fine protrusions P at a narrow pitch, without density variations, regularly and periodically, and with a predetermined slope angle and height, as in this embodiment.

[0054] 1(B) and 3(B), the angle D of inclination of the side surface 13b of the PMO lens 13 in this embodiment is reverse tapered with respect to the direction in which the lens is inserted into the lens holder 12. As can be seen from FIG. 3(B), this relationship prevents the adhesive 14 from forming a wedge in the direction in which the PMO lens 13 is removed from the lens holder 12 (upward of the optical axis O). Naturally, a forward taper provides a stronger bond between the PMO lens 13 and the lens holder 12, but this embodiment has been shown to be sufficiently effective even under such reverse taper conditions. In other words, it can be said that the effect is even greater when the PMO lens 13 is reverse tapered.

[0055] In Example 1, gap 12f is provided, allowing adjustment of PMO lens 13 relative to lens holder 12 in a direction perpendicular to the optical axis. However, gap 12f is not necessarily provided, as PMO lens 13 may be positioned and fixed relative to lens holder 12. Positioning may be achieved by fitting the outer diameter of PMO lens 13 to the inner diameter of lens holder 12, or by providing a positioning pin on one side and a positioning hole on the other side, and inserting the pin into the hole. In this example, PMO lens 13 may or may not be positioned and fixed relative to lens holder 12.

[0056] Although a UV adhesive is used as the adhesive 14 in the above description, other types of adhesives can also be used. The same effect can be obtained regardless of the type of adhesive.

[0057] In addition, in this embodiment, the fine protrusions P are formed by transferring the concave shape provided in the mold 15 used to mold the resin lens by injection molding, but this embodiment is not limited to this. Any other means, such as machining or etching, that can provide the fine protrusions P can be applied.

[0058] Furthermore, in this embodiment, the fine protrusions P are provided around the entire circumference of the side surface 13b around the optical axis, but they do not need to be provided around the entire circumference. The fine protrusions P are shaped to prevent peeling from the adhesive 14, so they need only be provided in the areas to be bonded. For example, the fine protrusions P may be provided only in the areas (phases) corresponding to the three locations where the adhesive pools 12c are provided in Figure 2. Preferably, the adhesive 14 is arranged evenly around the optical axis, such as in three locations every 120 degrees.

[0059] In this embodiment, the PMO lens 13 has a circular shape when viewed from the optical axis direction, but it may have a rectangular shape or a shape with a part D-cut, and the fine protrusions P may be provided on the side surface 13b thereof.

[0060] In addition, although it has been described in this embodiment that the recessed shape is not completely filled with resin, it is possible to completely fill the recessed shape by adjusting the shape of the recessed shape, molding conditions, etc. This embodiment is also applicable in such a case.

[0061] Furthermore, in this embodiment, the PMO lens 13 has been described as an example, but it does not necessarily have to be a plastic molded lens, and other types of lenses such as glass molded lenses may also be applicable in some cases. Furthermore, in other cases, the present invention may be applied with appropriate modifications within the scope of the spirit of the present invention.

[0062] Example 2 Example 2 will be described in detail below with reference to Figures 6 and 7. Figure 6 is a partial cross-sectional view of a PMO lens 23 of Example 2. Figure 7 is a partial cross-sectional view of a lens holder assembly 21 of Example 2. The description of this example will focus on differences from Example 1, and will omit parts that are common to Example 1.

[0063] In Example 1, the fine protrusions P are formed on the side surface 13b of the PMO lens 13. However, the fine protrusions P may also be formed on the outer shoulder surface 23g (second surface) of the optically effective surface 23f of the PMO lens 23. That is, the fine protrusions P may be provided on the outer shoulder surface 23g (the upper surface in the drawing) that smoothly connects to the optically effective surface 23f, and the outer shoulder surface 23g may be bonded to the upper surface of the lens holder 12 with adhesive 14 so as to connect them. In this case, the adhesive 14 may be injected so that it enters the radial gap 12f (gap portion) that exists between the lens holder 12 and the PMO lens 23.

[0064] Example 3 Example 3 will be described in detail below with reference to Figures 8 and 9. Figure 8 is a partial cross-sectional view of a PMO lens 33 of Example 3. Figure 9 is a partial cross-sectional view of a lens holder assembly 31 of Example 3. The description of this example will focus on differences from Example 1, and will omit parts that are common to Example 1.

[0065] In Example 1, the surface of the abutment surface 13a of the PMO lens 13 is smoothly finished. The position of the PMO lens 13 in the optical axis direction is determined by abutting the abutment surface 13a against the lens receiving surface 12a, and there is no gap in the optical axis direction when the abutment is in place. However, the fine protrusions P may be formed on the abutment surface 33a (second surface) that abuts the lens holder 12. That is, the fine protrusions P may be provided on the abutment surface 33a (the surface on the lower side in the drawing), which is an optically ineffective surface formed radially outward of the optically effective surface 33f of the PMO lens 33, and the abutment surface 33a and the lens receiving surface 12a of the lens holder 12 may be bonded with adhesive 14. In this case, a gap exists in the optical axis direction between the lens receiving surface 12a of the lens holder 12 and the abutment surface 33a of the PMO lens 33, and the adhesive 14 is injected so that the adhesive 14 fills the gap.

[0066] In this way, fine protrusions P are provided on the surface including the contact surface 33a of the PMO lens 33, and the PMO lens 33 is bonded to the lens receiving surface 12a of the lens holder 12. In this case, it is difficult to precisely correct the dimensions of the contact surface 33a of the PMO lens 33, and the position of the PMO lens 33 in the optical axis direction varies due to variations in the thickness of the adhesive 14. However, by providing fine protrusions P, it is possible to prevent the PMO lens 33 and the adhesive 14 from peeling off.

[0067] (Application example) 11 is a schematic diagram showing an example configuration of a camera device 200 (image capture device) that uses a lens unit 100 to which the present invention is applied. The image capture device includes the lens unit 100 and the camera device 200, which is made up of a camera body 200a having an image sensor 200b that captures an image of an object formed by the lens unit 100. The image capture device may also be configured such that the lens unit 100 is detachably attached to the camera body 200a of the camera device 200.

[0068] The disclosure of this embodiment includes the following configuration. (Configuration 1) An optical element having a first surface through which an optical axis passes and a second surface formed radially outward of the first surface, a plurality of convex portions including a periodic pattern are formed on the second surface; a gap is provided between the optical element and a holding member that holds the optical element, an adhesive injected into the gap between the second surface having the convex portion and the holding member; (Configuration 2) 2. The optical element according to configuration 1, wherein the plurality of convex portions are formed on the second surface at intervals of 50 μm to 150 μm. (Configuration 3) 3. The optical element according to configuration 1 or 2, wherein the plurality of convex portions are formed in a periodic and regularly repeated pattern. (Configuration 4) 4. The optical element according to any one of configurations 1 to 3, wherein the convex portions include at least a combination of the same shapes. (Configuration 5) 5. The optical element according to any one of configurations 1 to 4, wherein the angle formed between the inclined surface of the convex portion and the second surface is 35 degrees or more for at least a portion of the inclined surface. (Configuration 6) 6. The optical element according to any one of configurations 1 to 5, wherein the height of the convex portion is 3 μm to 20 μm. (Configuration 7) The optical element according to any one of configurations 1 to 6, wherein the optical element is a resin lens, and the convex portion is formed by transferring a concave portion provided in a mold for molding the resin lens by injection molding. (Configuration 8) 8. The optical element according to claim 7, wherein the concave portion of the mold is formed by laser processing. (Configuration 9) the gaps are a plurality of adhesive pools formed on the holding member at regular angular intervals in the circumferential direction of the holding member, The optical element according to any one of configurations 1 to 8, wherein the convex portion is formed on a side surface of the optical element as the second surface. (Configuration 10) The optical element described in configuration 9, characterized in that the side surface is inclined with respect to the optical axis of the optical element and is inclined in a direction that prevents the adhesive from forming a wedge in the direction in which the optical element is removed from the holding member. (Configuration 11) the gap portion is a gap that exists between the holding member and the optical element in the radial direction, 11. The optical element according to any one of configurations 1 to 10, wherein the convex portion is formed on an outer shoulder surface of the first surface serving as the second surface. (Configuration 12) the gap portion is a gap that exists between the holding member and the optical element in the optical axis direction, 12. The optical element according to any one of configurations 1 to 11, wherein the convex portion is formed on the second surface for adjusting the position of the optical element in the optical axis direction. (Configuration 13) the first surface is an optically effective surface through which light passes; 13. The optical element according to any one of configurations 1 to 12, wherein the second surface is an optically ineffective surface and includes an abutment surface that abuts against the holding member. (Configuration 14) 14. An optical device comprising the optical element according to any one of the first to thirteenth aspects and a holding member for holding the optical element. (Configuration 15) 15. An imaging device comprising the optical device according to configuration 14 and an imaging element for capturing an image formed by the optical device. [Explanation of symbols]

[0069] 12 Lens holder (holding member) 12c Adhesion pool (gap area) 12f Gap (gap part) 13 PMO lens (optical element) 13b Side (Second Side) 13f Optically effective surface (first surface) 14 Adhesive 15 Molds 23g Outer shoulder surface (second surface) 33a Contact surface (second surface) 100 Lens unit (optical device) 200 Camera equipment (imaging equipment) 200b image sensor P Fine protrusion (convex shaped part)

Claims

1. An optical element having a first surface through which an optical axis passes and a second surface formed radially outward of the first surface, a plurality of convex portions including a periodic pattern are formed on the second surface; a gap is provided between the optical element and a holding member that holds the optical element, an adhesive injected into the gap between the second surface having the convex portion and the holding member;

2. 2. The optical element according to claim 1, wherein the plurality of convex portions are formed on the second surface at intervals of 50 μm to 150 μm.

3. 2. The optical element according to claim 1, wherein the plurality of convex portions are formed in a periodic and regularly repeated pattern.

4. The optical element according to claim 1 , wherein the convex portions include at least a combination of the same shapes.

5. 2. The optical element according to claim 1, wherein the angle formed between the inclined surface of the convex portion and the second surface is 35 degrees or more in at least a portion of the inclined surface.

6. 2. The optical element according to claim 1, wherein the height of the convex portion is 3 μm to 20 μm.

7. 2. The optical element according to claim 1, wherein the optical element is a resin lens, and the convex portion is formed by transferring a concave portion provided in a mold for molding the resin lens by injection molding.

8. 8. The optical element according to claim 7, wherein the concave portion of the mold is formed by laser processing.

9. the gaps are a plurality of adhesive pools formed on the holding member at regular angular intervals in the circumferential direction of the holding member, 2. The optical element according to claim 1, wherein the convex portion is formed on a side surface of the optical element as the second surface.

10. The optical element described in claim 9, characterized in that the side surface is inclined with respect to the optical axis of the optical element and is inclined in a direction that prevents the adhesive from forming a wedge in the direction in which the optical element is removed from the holding member.

11. the gap portion is a gap that exists between the holding member and the optical element in the radial direction, 2. The optical element according to claim 1, wherein the convex portion is formed on an outer shoulder surface of the first surface serving as the second surface.

12. the gap portion is a gap that exists between the holding member and the optical element in the optical axis direction, 2. The optical element according to claim 1, wherein the convex portion is formed on the second surface for adjusting the position of the optical element in the optical axis direction.

13. the first surface is an optically effective surface through which light passes; 2. The optical element according to claim 1, wherein the second surface is an optically ineffective surface and includes an abutment surface that abuts against the holding member.

14. An optical device comprising: the optical element according to claim 1; and a holding member for holding the optical element.

15. An imaging device comprising the optical device according to claim 14 and an imaging element for capturing an image formed by the optical device.

Images