Lens and lens mold

Abstract

To provide a lens capable of reducing size and weight of a lens holding portion while securing optical performance.SOLUTION: A lens comprises: an optical function portion (41) which is a press-molded product of glass, has lens surfaces (43, 44) on both sides in an optical axis direction, and has volumetric absorbing portions (46, 47) for allowing a shape error accompanied by press molding around the lens surfaces, and an edge portion (42) made of a material different from the glass of the optical function portion and coupled with the optical function portion. The edge portion includes: a cylindrical portion (42a) having a cylindrical shape with an optical axis as a center and fixed to surround an outer peripheral surface of the optical function portion; and an annular portion (42b) of which thickness in the optical axis direction is smaller than the length of the cylindrical portion in the optical axis direction, and which extends from the outer peripheral surface of the cylindrical portion in a direction orthogonal to the optical axis. The length L of the cylindrical portion in the optical axis direction and the width W of the annular portion in the direction orthogonal to the optical axis satisfy W / L≥0.8.SELECTED DRAWING: Figure 8

Description

[Technical field]

[0001] The present invention relates to a lens and a lens molding die. [Background technology]

[0002] In recent years, the mounting of imaging means in portable electronic devices such as smartphones has become widespread, and there is an increasing demand for imaging means that are small and have high performance. The lens that constitutes the imaging means is required to be as small and lightweight as possible while satisfying such requirements as high optical performance and the ability to be positioned with high accuracy relative to a holding member that holds the lens.

[0003] Generally, a lens has a flange on the periphery of a main body portion that has a lens surface and functions optically, and the position is determined by fixing the flange to a holding member. The position of the lens is managed by the position in the optical axis direction, the position in the direction perpendicular to the optical axis, and the inclination with respect to the optical axis of the optical system. For example, the flange has a plane perpendicular to the optical axis at least on either the front or rear of the optical axis direction, and the lens position in the optical axis direction is determined based on this plane. In addition, the flange may have a cylindrical outer peripheral surface that surrounds the optical axis, and the lens position in the direction perpendicular to the optical axis (hereinafter referred to as the direction perpendicular to the optical axis) may be determined based on this outer peripheral surface.

[0004] As another form of positioning a lens, the edge portion has a tapered surface that is neither parallel nor perpendicular to the optical axis, and this tapered surface is used as a reference to manage the position along the optical axis and the position perpendicular to the optical axis together.

[0005] As part of efforts to reduce the size and weight of lenses, it is desirable to thin the edges in the direction of the optical axis. However, due to the following reasons, there are limitations to the degree of freedom in the shape and structure of the edges of glass lenses, making it difficult to sufficiently thin the edges.

[0006] In glass molded lenses manufactured by press-molding a glass preform in a molding die, a volume absorbing portion is provided at the edge to absorb various errors related to the capacity and supply position of the glass preform, the volume of the internal space (mold space) of the molding die, etc. The volume absorbing portion is a portion that allows for variations in shape according to the various errors described above, and is set so that the corner R value of the corner is the minimum allowable value when the fluctuating mold space volume is at the lower limit and the glass volume is at the upper limit, and the corner R value is set so that the central value of the up and down fluctuations in the volume is the design center.

[0007] Because the volume absorbing portion is a portion that allows for variation in shape, the area of ​​the edge that is the volume absorbing portion cannot be used to position the lens relative to the holding member. If the area of ​​the edge used for positioning the lens is not sufficiently secured, the positional accuracy and stability of the lens will deteriorate. Therefore, the edge must have dimensions that allow for highly accurate positioning, and the dimensions of the volume absorbing portion that absorbs errors during molding must also be added, which restricts the miniaturization of the edge.

[0008] Another issue with glass molded lenses is that they are prone to cracking and breakage in areas where the angle changes sharply due to their small thickness. For this reason, there are limitations on how thin the edges can be made due to the need to ensure the strength of the edges themselves.

[0009] When molding a glass molded lens, if there is a narrow space in the mold, it is difficult to spread the glass preform, so the temperature must be increased to reduce the viscosity of the glass preform. Therefore, in order to form a thin edge, the glass preform must be heated to a temperature higher than the temperature required to form the lens surface, which may deteriorate the precision and appearance quality of the lens surface.

[0010] For the reasons mentioned above, there is a limit to how thin the edge of a glass molded lens can be made, and a solution to this problem has been sought.A known technology for positioning a lens without relying on the edge is to provide a frame member (holder) made of a different material, such as metal, on the outer periphery of the lens, and mold the lens by press molding while integrating it with the frame member (for example, Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0011] [Patent Document 1] Japanese Patent Application Publication No. 3-167514 [Patent Document 2] Patent No. 3679489 [Patent Document 3] JP 2008-88027 A Summary of the Invention [Problem to be solved by the invention]

[0012] In the invention of Patent Document 1, a molded glass lens has an edge portion including a flat surface perpendicular to the optical axis on the outside of the aspheric lens surface, and a metal frame member is provided on the outside of the edge portion. Therefore, it could not solve the above-mentioned problem that it is difficult to make the edge portion thin due to manufacturing constraints of the glass molded lens.

[0013] Furthermore, in the conventional technologies in which a frame member is provided on the outer periphery of a glass molded lens, including Patent Documents 1, 2, and 3, no specific conditions were presented for realizing a reduction in the size and weight of the lens holding portion without impairing optical performance with regard to the dimensional relationship between the glass molded lens and the frame member.

[0014] The present invention has been made based on the above-mentioned problem awareness, and has an object to provide a lens that can reduce the size and weight of the lens holding portion while ensuring optical performance.

[0015] Another object of the present invention is to provide a lens molding die capable of manufacturing, with high precision, a lens having a compact and lightweight lens holding portion. [Means for solving the problem]

[0016] A lens according to one embodiment of the present invention is a press-molded glass product, and includes: an optical functional part having lens surfaces on both sides in the optical axis direction and a volume absorbing part around the lens surfaces that allows for shape errors associated with press molding; and an edge part made of a material different from the glass of the optical functional part and connected to the optical functional part, wherein the edge part has a cylindrical shape centered on the optical axis and includes a tube part that surrounds and is fixed to an outer circumferential surface of the optical functional part; and an annular part that has a thickness in the optical axis direction smaller than the length of the tube part in the optical axis direction and extends from the outer circumferential surface of the tube part in a direction perpendicular to the optical axis, and is characterized in that the length L of the tube part in the optical axis direction and the width W of the annular part in the direction perpendicular to the optical axis satisfy the following condition (1). (1) W / L≧0.8

[0017] It is preferable that a length L of the cylindrical portion in the optical axis direction and a width W of the annular portion in the direction perpendicular to the optical axis satisfy the following condition (2). (2) W / L≦10

[0018] The edge portion is preferably made of metal.

[0019] It is preferable that the annular portion extends from one end in the optical axis direction of the outer circumferential surface of the cylindrical portion in a direction perpendicular to the optical axis.

[0020] It is preferable that the inner peripheral surface of the cylindrical portion of the edge portion is blackened.

[0021] The edge portion may be such that the entire outer surfaces of the cylindrical portion and the annular portion are blackened.

[0022] A lens molding mold of one embodiment of the present invention is a lens molding mold in which a lower mold and an upper mold are brought close to each other to press-mold the lens, wherein the lower mold has an annular portion holding surface located around the lens forming surface that forms the lens surface of the optical function portion and holds the annular portion of the edge portion, and an annular damming protrusion located around the annular portion holding surface and protruding above the annular portion holding surface, and is characterized in that when the lower mold and the upper mold are brought close to each other to press-mold the lens, the damming protrusion determines the outer edge position of the annular portion.

[0023] It is preferable that the upper mold has a tubular portion forming surface located around a lens forming surface that forms the lens surface of the optical function portion and determines the position of the outer peripheral surface of the tubular portion of the edge portion, and an opposing surface located around the tubular portion forming surface and facing the annular portion holding surface and damming protrusion of the lower mold. Effect of the Invention

[0024] According to the present invention, a lens is formed by an optical functional part having a lens surface and a volume absorption part, and a flange part provided on the outside of the optical functional part, and the flange part comprises a cylindrical part that surrounds and is fixed to the outer peripheral surface of the optical functional part, and an annular part that protrudes from the outer peripheral surface of the cylindrical part in a direction perpendicular to the optical axis, and by further satisfying predetermined conditions for the length of the cylindrical part in the optical axis direction and the width of the annular part in the direction perpendicular to the optical axis, it is possible to obtain a lens in which the lens holding part can be made small and lightweight while maintaining optical performance.

[0025] Furthermore, according to the present invention, it is possible to obtain a lens molding die for manufacturing the above-mentioned lens with high precision. [Brief description of the drawings]

[0026] [Figure 1] FIG. 1 is a cross-sectional view showing a conventional lens molding die for press-molding a glass molded lens. [Diagram 2] 1A to 1C are cross-sectional views showing a conventional process for press-molding a glass molded lens. [Diagram 3] 1A to 1C are cross-sectional views showing a conventional process for press-molding a glass molded lens. [Figure 4] FIG. 1 is a cross-sectional view of a conventional glass molded lens. [Diagram 5] FIG. 2 is a cross-sectional view showing a lens molding die for press-molding the lens of the present embodiment. [Figure 6] 4A to 4C are cross-sectional views showing a process of press-molding the lens of the present embodiment. [Figure 7] 4A to 4C are cross-sectional views showing a process of press-molding the lens of the present embodiment. [Figure 8] FIG. 2 is a cross-sectional view of the lens of the present embodiment. [Figure 9] FIG. 2 is a front view of the lens of the present embodiment. [Figure 10] FIG. 2 is a cross-sectional view of a lens unit in which the lens of the present embodiment is attached to a lens barrel. [Figure 11] FIG. 2 is a cross-sectional view of a lens unit in which the lens of the present embodiment is attached to a lens barrel. [Figure 12] FIG. 2 is a cross-sectional view showing a lens in which the inner peripheral surface of the cylindrical portion at the edge is blackened. [Figure 13] FIG. 2 is a cross-sectional view showing a lens in which the entire outer surface of the edge has been blackened. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0027] First, a conventional glass molded lens and its manufacture will be described with reference to Figures 1 to 4. Figures 1 to 3 show the configuration and operation of a lens molding die 10, and Figure 4 shows a glass molded lens 20 formed by the lens molding die 10.

[0028] The lens molding die 10 is composed of a body die 11, a lower die 12, and an upper die 13. The body die 11 is cylindrical in shape and has an internal space surrounded by an inner peripheral surface 11a which is a cylindrical surface. The central axis X1 of the lens molding die 10 is an axis line that extends in the vertical direction through the center of the inner peripheral surface 11a. The lower end surface 11b and the upper end surface 11c of the body die 11 are each surfaces perpendicular to the central axis X1. The internal space of the body die 11 penetrates in the vertical direction and opens to the lower end surface 11b and the upper end surface 11c.

[0029] The lower mold 12 has an insertion part 12a inserted from below into the internal space of the body mold 11, and a large diameter part 12b provided at the bottom of the insertion part 12a and having a larger diameter than the insertion part 12a. The upper mold 13 has an insertion part 13a inserted from above into the internal space of the body mold 11, and a large diameter part 13b provided at the top of the insertion part 13a and having a larger diameter than the insertion part 13a. The outer peripheral surfaces of the insertion parts 12a and 13a can slide in the vertical direction relative to the inner peripheral surface 11a of the body mold 11, but movement in a direction perpendicular to the central axis X1 is restricted. In other words, the lower mold 12 and the upper mold 13 can move in the vertical direction relative to the body mold 11 with the centers of the lower mold 12 and the upper mold 13 aligned to coincide with the central axis X1.

[0030] The lower die 12 has a press surface 14 at the upper end of the insertion portion 12a. The press surface 14 has a concave lens forming surface 14a and an edge forming surface 14b located around the lens forming surface 14a. The upper die 13 has a press surface 15 at the lower end of the insertion portion 13a. The press surface 15 has a concave lens forming surface 15a and an edge forming surface 15b located around the lens forming surface 15a.

[0031] The lower die 12 can be inserted into the body die 11 up to a position where the large diameter portion 12b abuts against the lower end surface 11b. The upper die 13 can be inserted into the body die 11 up to a position where the large diameter portion 13b abuts against the upper end surface 11c. The positions at which the lower die 12 and the upper die 13 are each inserted furthest into the body die 11 are called the press movement ends. As shown in FIG. 1, when the lower die 12 and the upper die 13 reach their respective press movement ends, the press surface 14 and the press surface 15 face each other with a predetermined gap between them in the vertical direction, and a die space S1 is formed that is surrounded by the press surface 14, the press surface 15, and the inner circumferential surface 11a.

[0032] When molding a glass molded lens 20 using the lens molding die 10, as shown in Fig. 2, a spherical glass preform PF1 made of glass that is to be the base material of the glass molded lens 20 is placed on the press surface 14 of the lower die 12. The concave shape of the lens forming surface 14a holds the glass preform PF1 at a position on the central axis X1. The lower die 12 is held at a press moving end with the large diameter portion 12b abutting against the lower end surface 11b, and the lower die 12 is supported from below so that the insertion portion 12a does not come off the body die 11. The glass preform PF1 may be supplied onto the press surface 14 with the insertion portion 12a removed downward from the body die 11, or may be supplied from the upper end side of the body die 11 with the insertion portion 12a inserted into the body die 11.

[0033] The glass preform PF1 is softened by heating it above its glass transition temperature, and the upper die 13 with the insertion portion 13a inserted into the body die 11 is pressed downward. The glass preform PF1 is pressed between the pressing surface 15 of the descending upper die 13 and the pressing surface 14 of the lower die 12 whose descent is restricted, and the glass preform PF1 is deformed.

[0034] When upper die 13 is lowered to the press movement end shown in Fig. 3, glass preform PF1 takes a shape corresponding to mold space S1. Then, after cooling to a prescribed temperature, lens forming die 10 is disassembled, and the molded glass molded lens 20 can be removed. Glass molded lens 20 is a lens onto which the surface shapes of pressed surface 14, pressed surface 15, and inner circumferential surface 11a are transferred.

[0035] The direction along the optical axis Xa of the glass molded lens 20 is defined as the optical axis direction, and the direction perpendicular to the optical axis Xa is defined as the direction orthogonal to the optical axis. The direction orthogonal to the optical axis can also be called the radial direction of the glass molded lens 20.

[0036] As shown in Fig. 4, the glass molded lens 20 has a convex lens surface 21 to which the surface shape of the lens forming surface 14a is transferred, and a convex lens surface 22 to which the surface shape of the lens forming surface 15a is transferred, on both sides (front and back) in the optical axis direction. The glass molded lens 20 further has an annular edge portion 23 around the lens surface 21 and the lens surface 22. The edge portion 23 is a region surrounded by a first plane 23a to which the surface shape of the edge forming surface 14b is transferred, a second plane 23b to which the surface shape of the edge forming surface 15b is transferred, and an outer peripheral surface 23c to which the surface shape of the inner peripheral surface 11a of the barrel mold 11 is transferred. The first plane 23a and the second plane 23b are planes perpendicular to the optical axis Xa, and the outer peripheral surface 23c is a cylindrical surface centered on the optical axis Xa.

[0037] When manufacturing glass molded lens 20 using lens forming mold 10, various errors occur, such as a capacity error in glass preform PF1, a volume error in mold space S1 of lens forming mold 10, and deviation in the supply position of glass preform PF1. Glass molded lens 20 has volume absorbing portions 24 and 25 at the outer circumferential corners of edge portion 23 to absorb the effects of these errors.

[0038] Specifically, the volume absorbing portion 24 is formed by connecting the first plane 23a and the outer peripheral surface 23c so as to form a rounded corner shape (R-shaped corner) that is more inward than the corner shape that would be formed if the first plane 23a and the outer peripheral surface 23c were extended and intersected as they are. The volume absorbing portion 25 is formed by connecting the second plane 23b and the outer peripheral surface 23c so as to form a rounded corner shape (R-shaped corner) that is more inward than the corner shape that would be formed if the second plane 23b and the outer peripheral surface 23c were extended and intersected as they are. The volume absorbing portion 24 and the volume absorbing portion 25 are portions that allow for variations in shape according to the above-mentioned various errors. Therefore, the shapes of the volume absorbing portion 24 and the volume absorbing portion 25 shown in FIG. 4 are examples, and the shapes of the volume absorbing portion 24 and the volume absorbing portion 25 vary depending on the degree of error. By providing the volume absorbing portion 24 and the volume absorbing portion 25, the other portions of the glass molded lens 20 can be formed with high accuracy.

[0039] On the other hand, since the glass molded lens 20 cannot be positioned with respect to the lens barrel of the lens unit at the volume absorption parts 24 and 25, the size of the surface of the edge part 23 that serves as a reference for positioning the glass molded lens 20 becomes relatively small by providing the volume absorption parts 24 and 25 on the edge part 23. For example, when the width of the edge part 23 in the direction perpendicular to the optical axis is constant, the width of the first plane 23a and the second plane 23b in the direction perpendicular to the optical axis becomes smaller as the formation range of the volume absorption parts 24 and 25 in the direction perpendicular to the optical axis becomes larger. When the glass molded lens 20 is positioned in the optical axis direction using the first plane 23a and the second plane 23b, if the width of the first plane 23a and the second plane 23b in the direction perpendicular to the optical axis becomes small, there is a risk that the positioning accuracy and the stability of the holding will deteriorate when the glass molded lens 20 is attached to the lens barrel of the lens unit. Furthermore, when the thickness of edge portion 23 in the optical axis direction is constant, the larger the range in which volume absorbing portions 24 and 25 are formed in the optical axis direction, the smaller the optical axis direction length of outer circumferential surface 23c in edge portion 23. When outer circumferential surface 23c is used to position glass molded lens 20 in the direction perpendicular to the optical axis, if the optical axis direction length of outer circumferential surface 23c becomes small, there is a risk that the positioning accuracy and holding stability will deteriorate when glass molded lens 20 is attached to the barrel of a lens unit.

[0040] Therefore, edge portion 23 needed to have a sufficient dimension to obtain the positioning function, and also needed to have a dimension to obtain the error absorbing function of volume absorbing portions 24 and 25, which restricted the miniaturization of edge portion 23. In other words, the positioning function of glass molded lens 20 and the error absorbing function during molding were concentrated in edge portion 23, which was one of the restricting factors in the miniaturization of edge portion 23.

[0041] In addition, generally, glass molded lenses are prone to cracking and breakage in areas where the thickness is small and the angle change is steep. In the case of the glass molded lens 20 shown in FIG. 4, the boundary between the convex lens surface 21 and the first plane 23a and the boundary between the convex lens surface 22 and the second plane 23b are particularly prone to cracking and breakage. Therefore, even if the edge portion 23 is thinned in the optical axis direction regardless of the restrictions imposed by the volume absorbing portion 24 and the volume absorbing portion 25, there is a problem that the smaller the thickness of the edge portion 23, the higher the risk of cracking and breakage. Therefore, in the glass molded lens 20, the reduction in size of the edge portion 23 (particularly, the reduction in thickness in the optical axis direction) is restricted from the viewpoint of ensuring the strength of the edge portion 23 itself.

[0042] Furthermore, when molding a glass molded lens, attention must be paid to the fluidity of the glass preform within the space of the lens molding die. In the mold space S1 of the lens molding die 10 shown in Figure 1, the space is wide in the central portion between the lens forming surfaces 14a and 15a, and the space is narrow in the peripheral portion between the edge forming surfaces 14b and 15b.

[0043] In order to spread the glass preform PF1 in the narrow space around the mold space S1 during pressing, it is necessary to lower the viscosity of the glass preform PF1. That is, in order to form the edge portion 23 in the glass molded lens 20 that is thinner in the optical axis direction than the effective diameter portion (the range of the lens surface 21 and the lens surface 22), it is necessary to spread the glass preform PF1 with a lower viscosity in the narrow space around the mold space S1. In order to lower the viscosity of the portion where the edge portion 23 is formed, it is necessary to raise the temperature of the glass preform PF1 to a temperature (for example, a second temperature) higher than the temperature (for example, a first temperature) required to spread the portion where the lens surface 21 or the lens surface 22 is formed. If the lens surface 21 or the lens surface 22 that can be formed at the first temperature is formed at a second temperature higher than the first temperature, the effect of thermal contraction after molding becomes large, and the precision and appearance quality of the lens surfaces 21 and 22 may be deteriorated compared to when they are formed at the first temperature.

[0044] As edge portion 23 is made thinner in the optical axis direction, the space for forming edge portion 23 in mold space S1 becomes narrower, making it more difficult to extend glass preform PF1, and making it necessary to further reduce the viscosity of glass preform PF1 during molding (i.e., heating to a higher temperature). As a result, it becomes more difficult to ensure the precision and appearance quality of lens surfaces 21 and lens surfaces 22. In other words, from the perspective of ensuring the quality of the effective diameter portion of glass molded lens 20, including lens surfaces 21 and lens surfaces 22, there are restrictions on making edge portion 23 smaller (particularly, making it thinner in the optical axis direction).

[0045] As a countermeasure when spreading the glass preform PF1 over the thin and easily cracked edge portion 23, it is known to provide a release film that suppresses cracking, or to perform a surface treatment on the glass preform PF1 to make it less likely to crack. However, when such a release film or surface treatment is applied to prevent cracking, there are problems in that the outer surface of the glass molded lens 20 becomes more susceptible to clouding, and the surface precision of the outer surface of the glass molded lens 20 becomes unstable.

[0046] When the glass molded lens 20 is molded by the lens molding die 10, if the upper die 13 is lowered to pressurize the glass preform PF1, the pressure applied to the glass preform PF1 from the lens forming surface 15a of the upper die 13 may cause the outer periphery of the glass preform PF1 to curve upward, and the outer periphery of the glass preform PF1 may contact the lens forming surface 15a before the inner periphery of the glass preform PF1. Alternatively, the outer periphery of the glass preform PF1 may curve downward, and the outer periphery of the glass preform PF1 may contact the lens forming surface 14a before the inner periphery of the glass preform PF1. In such a case, gas is sealed between the glass preform PF1 and the lens forming surface 15a or between the glass preform PF1 and the lens forming surface 14a, causing a so-called gas trap. The gas trap causes the glass molded lens 20 to have a defective shape.

[0047] In order to avoid gas trapping, the radius of curvature of the glass preform PF1 needs to be smaller than the radius of curvature of the lens forming surface 14a and the lens forming surface 15a of the lens forming die 10 by a predetermined amount. However, in order to form the glass molded lens 20 including the volume of the edge portion 23, the required volume of the glass preform PF1 becomes large, making it difficult to set a small radius of curvature of the glass preform PF1. For the various reasons mentioned above, there is a limit to how small the edge portion 23 can be made, and there is also a limit to the measures of reducing the amount of the glass preform PF1 to avoid gas trapping.

[0048] Unlike the glass molded lens 20 shown in Fig. 4, a type of glass molded lens is known in which the edge is provided with a plurality of steps to separate a positioning function part and a volume absorbing part. Also known is a type of glass molded lens in which a volume absorbing part is provided that protrudes in the optical axis direction from the positioning function part at the edge. In each of these types of glass molded lenses, the volume absorbing part or the positioning function part is a curved edge with an irregular shape, which is disadvantageous in terms of strength and makes it difficult to mold the positioning function part with high precision.

[0049] In view of the various problems with conventional glass molded lenses as described above, the present invention provides a lens in which the lens holding portion can be made smaller and lighter while maintaining optical performance. Also, the present invention provides a lens molding die capable of manufacturing such a lens with high precision. This invention is based on the idea that the above problems can be solved by configuring a lens with an optical functional portion made of a press-molded glass product and including a lens surface, and an edge portion made of a material different from the glass of the optical functional portion and provided on the outside of the optical functional portion, the optical functional portion being provided with the minimum necessary configuration to fulfill the optical function and the function of absorbing errors during molding, and the edge portion being responsible for the function of positioning the lens.

[0050] Next, a lens according to an embodiment to which the present invention is applied and its manufacture will be described with reference to Fig. 5 to Fig. 9. Fig. 5 to Fig. 7 show the configuration and operation of a lens molding die 30, and Fig. 8 and Fig. 9 show a lens 40 of this embodiment formed by the lens molding die 30. The direction along the optical axis Xb of the lens 40 is the optical axis direction, and the direction perpendicular to the optical axis Xb is the direction orthogonal to the optical axis. The direction orthogonal to the optical axis can also be called the radial direction of the lens 40.

[0051] The lens molding die 30 is composed of a body mold 31, a lower mold 32, and an upper mold 33. The body mold 31 is cylindrical in shape and has an internal space surrounded by an inner peripheral surface 31a which is a cylindrical surface. The central axis X2 of the lens molding die 30 is an axis line extending in the vertical direction through the center of the inner peripheral surface 31a. The body mold 31 has a body mold lower end surface 31b at its lower end and a body mold upper end surface 31c at its upper end. The body mold lower end surface 31b and the body mold upper end surface 31c are each surfaces perpendicular to the central axis X2. The internal space of the body mold 31 penetrates in the vertical direction and opens to the body mold lower end surface 31b and the body mold upper end surface 31c.

[0052] The lower mold 32 has an insertion part 32a inserted from below into the internal space of the body mold 31, and a large-diameter part 32b provided below the insertion part 32a and having a larger diameter than the insertion part 32a. The upper mold 33 has an insertion part 33a inserted from above into the internal space of the body mold 31, and a large-diameter part 33b provided above the insertion part 33a and having a larger diameter than the insertion part 33a. The outer peripheral surfaces of the insertion parts 32a and 33a can slide in the vertical direction relative to the inner peripheral surface 31a of the body mold 31, but movement in a direction perpendicular to the central axis X2 is restricted. In other words, the lower mold 32 and the upper mold 33 can move in the vertical direction relative to the body mold 31 with the centers of the lower mold 32 and the upper mold 33 aligned to coincide with the central axis X2.

[0053] The lower mold 32 has a lens forming surface 34, an annular portion holding surface 35, and a blocking protrusion 36 at the upper end of the insertion portion 32a. The lens forming surface 34 is a surface involved in the formation of an optical function portion 41 described later, and the annular portion holding surface 35 and the blocking protrusion 36 are surfaces involved in the formation of an edge portion 42 described later. The lens forming surface 34 is a concave surface that is deepest at the center on the central axis X2 and becomes shallower toward the outer periphery. The annular portion holding surface 35 is a surface perpendicular to the central axis X2, and is an upward-facing annular surface provided in an annular range centered on the central axis X2 around the lens forming surface 34. The blocking protrusion 36 is formed around the annular portion holding surface 35, and is an annular protrusion that protrudes upward relative to the lens forming surface 34 and the annular portion holding surface 35. The upper surface of the blocking protrusion 36 is an annular surface perpendicular to the central axis X2. The inner peripheral surface of the blocking protrusion 36 is a cylindrical surface centered on the central axis X2.

[0054] The upper mold 33 has a lens forming surface 37, a tube forming surface 38, and an opposing surface 39 at the lower end of the insertion portion 33a. The lens forming surface 37 is a surface involved in the formation of an optical function portion 41 described later, and the tube forming surface 38 and the opposing surface 39 are surfaces involved in the formation of an edge portion 42 described later. The lens forming surface 37 is a concave surface that is deepest at the center on the central axis X2 and becomes shallower toward the outer periphery. The tube forming surface 38 is a cylindrical surface that protrudes downward from the outer edge of the lens forming surface 37, and is formed as the inner peripheral surface of a cylinder centered on the central axis X2. The opposing surface 39 is a surface perpendicular to the central axis X2, and is provided in an annular range centered on the central axis X2 around the tube forming surface 38. In other words, the tube forming surface 38 and the opposing surface 39 form an annular protrusion that protrudes downward around the lens forming surface 37.

[0055] When forming the lens 40 by press molding, the positions where the insertion portion 32a of the lower die 32 and the insertion portion 33a of the upper die 33 are inserted most into the body die 31 are called the press movement ends of the lower die 32 and the upper die 33. As shown in FIG. 5, when the lower die 32 and the upper die 33 reach their respective press movement ends, the lens forming surface 34 and the lens forming surface 37 face each other with a predetermined gap therebetween in the vertical direction, and a mold space S2 is formed between the lower die 32 and the upper die 33. The mold space S2 is a space surrounded by the lens forming surface 34, the annular portion holding surface 35, and the blocking protrusion 36 of the lower die 32, and the lens forming surface 37, the cylindrical portion forming surface 38, and the opposing surface 39 of the upper die 33. The opposing surface 39 faces both the annular portion holding surface 35 and the upper surface of the blocking protrusion 36.

[0056] As an example, the position where the large diameter portion 32b abuts against the barrel mold lower end surface 31b can be set as the press movement end of the lower mold 32. Also, the position where the large diameter portion 33b abuts against the barrel mold upper end surface 31c can be set as the press movement end of the upper mold 33. Alternatively, the press movement end of the upper mold 33 may be determined by a configuration other than the large diameter portion 33b abutting against the barrel mold upper end surface 31c.

[0057] 8 and 9, the lens 40 is composed of an optical function part 41 made of glass and an edge part 42 surrounding the outside of the optical function part 41. The edge part 42 is made of a material different from the glass of the optical function part 41, and in this embodiment, the edge part 42 is made of metal. The softening temperature of the metal constituting the edge part 42 is equal to or higher than the glass transition temperature of the glass constituting the optical function part 41. As an example, the edge part 42 is made of copper.

[0058] The edge portion 42 is prepared in advance before the optical function portion 41 is press-molded using the lens molding die 30, and has a cylindrical tube portion 42a centered on the optical axis Xb of the lens 40, and an annular ring portion 42b extending from the outer peripheral surface of the tube portion 42a in a direction perpendicular to the optical axis. The length of the tube portion 42a in the optical axis direction is L, and the thickness of the tube portion 42a in the optical axis direction is t1. The width of the ring portion 42b in the optical axis direction is W, and the thickness of the ring portion 42b in the optical axis direction is t2. The thickness t1 of the tube portion 42a in the optical axis direction is smaller than the width W of the ring portion 42b in the optical axis direction. The thickness t2 of the ring portion 42b in the optical axis direction is smaller than the length L of the tube portion 42a in the optical axis direction. The ring portion 42b extends in the optical axis direction from one end of the outer peripheral surface of the tube portion 42a in the optical axis direction, and when the edge portion 42 is viewed in a cross section along the optical axis Xb, it has an L-shape as shown in FIG. 8.

[0059] When molding the lens 40 using the lens molding die 30, the edge portion 42, which has been formed in advance into an L-shaped cross section, is attached to the inside of the lens molding die 30, as shown in FIG. 6. The edge portion 42 is held by the lower die 32 with the lower surface of the annular portion 42b placed on the annular portion holding surface 35 and the outer edge of the annular portion 42b facing the inner peripheral surface of the blocking protrusion 36. By holding the annular portion 42b by the annular portion holding surface 35, the position of the edge portion 42 in the direction along the central axis X2 is determined. In addition, since the edge portion 42 is held so as to fit inside the blocking protrusion 36, the mounting position of the edge portion 42 in the direction perpendicular to the central axis X2 can be easily determined. With the edge portion 42 held by the lower die 32, the tube portion 42a protrudes upward from the outer edge of the lens forming surface 34, and the tip of the tube portion 42a is located above the upper surface of the blocking protrusion 36. Furthermore, the upper surface of the annular portion 42b is substantially flush with the upper surface of the damming protrusion 36. The upper surface of the annular portion 42b may protrude slightly above the upper surface of the damming protrusion 36.

[0060] As shown in FIG. 6, the edge portion 42 is placed inside the lens forming mold 30, and a spherical glass preform PF2 made of glass that is the base material of the optical function portion 41 is placed on the lens forming surface 34 of the lower mold 32. The concave shape of the lens forming surface 34 holds the glass preform PF2 at a position on the central axis X2. The lower mold 32 is held at the press moving end where the large diameter portion 32b is in contact with the barrel mold lower end surface 31b, and the lower mold 32 is supported from below so that the insertion portion 32a does not come off the barrel mold 31. The glass preform PF2 may be supplied onto the lens forming surface 34 with the insertion portion 32a removed downward from the barrel mold 31, or may be supplied from the upper end side of the barrel mold 31 with the insertion portion 32a inserted into the barrel mold 31. Although the glass preform PF2 is spherical in FIG. 6, a glass preform having a shape other than a sphere may be used.

[0061] The glass preform PF2 is softened by heating it above its glass transition temperature, and the upper die 33 with the insertion portion 33a inserted into the body die 31 is pressed downward. The glass preform PF2 is pressed between the lens forming surface 37 of the descending upper die 33 and the lens forming surface 34 of the lower die 32 whose descent is restricted, and the glass preform PF2 is deformed.

[0062] 7, the glass preform PF2 becomes an optical function part 41 having a shape corresponding to the mold space S2. More specifically, since an edge part 42 is arranged on the periphery of the mold space S2, the optical function part 41 is press-molded in the inner region of the edge part 42 in the mold space S2, and the outer periphery of the optical function part 41 is closely fixed to the inner periphery surface of the tube part 42a, and the optical function part 41 and the edge part 42 are joined together.

[0063] In addition, when the upper die 33 is lowered, the tube-forming surface 38 of the upper die 33 comes into contact with the outer circumferential surface of the tube portion 42a of the edge portion 42, and the opposing surface 39 comes into contact with the upper surface of the annular portion 42b of the edge portion 42. When the upper die 33 is moved to the press movement end, a pressing force is applied from the upper die 33 to the edge portion 42, and the edge portion 42 is slightly plastically deformed. In detail, the tube-forming surface 38 of the upper die 33 determines the position of the outer circumferential surface of the tube portion 42a, and the shape of the tube portion 42a is adjusted. The annular portion 42b is sandwiched between the annular portion holding surface 35 of the lower die 32 and the opposing surface 39 of the upper die 33 to form the front and back surfaces in the optical axis direction, and the outer edge position is determined by the inner circumferential surface of the blocking protrusion 36. In this way, in the mold space S2, the edge portion 42 is also press-molded in addition to the optical function portion 41 to be finished into the final shape.

[0064] Once the optical function portion 41 and the edge portion 42 have been press molded as described above, the lens 40 can be taken out by cooling to a prescribed temperature and then disassembling the lens molding die 30.

[0065] The edge portion 42 may be made of a metal having a higher coefficient of thermal expansion than the material constituting the lens forming die 30, and the outer edge of the annular portion 42b of the edge portion 42 may be disposed with a small clearance inside the blocking protrusion 36 of the lower die 32 before being heated to soften the glass preform PF2. In this case, the edge portion 42 expands when heated, and the edge portion 42 comes into close contact with the lens forming die 30 by utilizing the difference in the coefficient of thermal expansion. Specifically, the expansion of the edge portion 42 causes the outer edge of the annular portion 42b of the edge portion 42 to come into close contact with the inner circumferential surface of the blocking protrusion 36. By configuring the lens molding die 30 so that the central axis X2 of the lens molding die 30 and the optical axis Xb of the molded lens 40 coincide with each other with high precision, the edge portion 42 which expands when heated is brought into isotropic contact with the inner peripheral surface of the blocking protrusion 36, improving the decentering precision with respect to the lens molding die 30, and it is possible to obtain a lens 40 in which the central position of the edge portion 42 is coaxial with the optical function portion 41 with high precision.

[0066] In this manner, a lens 40 having a hybrid structure is formed, which is composed of an optical function part 41 that is a press-molded product of glass and a metal edge part 42. As shown in Fig. 8, the optical function part 41 of the lens 40 has, on both sides (front and back) in the optical axis direction, a convex lens surface 43 to which the surface shape of the lens forming surface 34 is transferred, and a convex lens surface 44 to which the surface shape of the lens forming surface 37 is transferred. The lens 40 of this embodiment is an aspherical lens in which the lens surface 43 and the lens surface 44 are both aspherical. The lens according to the present invention is not limited to an aspherical lens, and can also be applied to a spherical lens.

[0067] The outer peripheral portion of the optical function part 41 is an outer peripheral surface 45 that is fixed in close contact with the inner peripheral surface of the tube part 42a of the edge part 42. The outer peripheral surface 45 is a cylindrical surface centered on the optical axis Xb by following the inner peripheral surface of the tube part 42a. The length L of the tube part 42a in the optical axis direction covers the entire length of the outer peripheral surface 45 of the optical function part 41 in the optical axis direction, and prevents glass from flowing out beyond the tube part 42a to the outside in the direction perpendicular to the optical axis (the annular part 42b side of the edge part 42) when the optical function part 41 is molded. Therefore, the shape of the outer peripheral surface 45 of the optical function part 41 is controlled with high precision by the tube part 42a.

[0068] The outer circumferential corners of the optical function portion 41 have volume absorption portions 46 and 47 for absorbing the effects of errors during molding by the lens forming mold 30. The errors during molding include a capacity error in the glass preform PF2, a volume error in the mold space S2 of the lens forming mold 30, and deviations in the supply position of the glass preform PF2 to the lens forming mold 30.

[0069] The volume absorbing portion 46 is formed by connecting the boundary between the lens surface 43 and the outer peripheral surface 45 so as to form a rounded corner shape (R-shaped corner) that is more inward than the corner shape that would be obtained if the lens surface 43 were extended with the designed lens surface shape and intersected with the outer peripheral surface 45. The volume absorbing portion 47 is formed by connecting the boundary between the lens surface 44 and the outer peripheral surface 45 so as to form a rounded corner shape (R-shaped corner) that is more inward than the corner shape that would be obtained if the lens surface 44 were extended with the designed lens surface shape and intersected with the outer peripheral surface 45. The volume absorbing portion 46 and the volume absorbing portion 47 are portions that allow for variations in shape according to the above-mentioned various errors. Therefore, the shapes of the volume absorbing portion 46 and the volume absorbing portion 47 shown in FIG. 8 are only examples, and the shapes of the volume absorbing portion 46 and the volume absorbing portion 47 vary depending on the degree of error.

[0070] By providing the volume absorbing parts 46 and 47, it is possible to prevent the influence of errors during press molding from affecting other parts of the optical function part 41, and to form the lens surfaces 43 and 44 with high precision. Furthermore, the volume absorbing parts 46 and 47 do not have shapes that protrude or recess sharply from the optical function part 41, but have shapes that smoothly connect the lens surfaces 43, 44 and the outer circumferential surface 45, so that the optical function part 41 is less likely to crack or break due to the volume absorbing parts 46 and 47.

[0071] In this way, the volume absorbing portion 46 and the volume absorbing portion 47 can absorb errors that occur during press molding of the optical function portion 41. Also, the position reference surface for positioning the lens 40 is provided by the edge portion 42, not the optical function portion 41. That is, in the lens 40, the edge portion 42 has a positioning function, and the optical function portion 41 has a function of absorbing errors during press molding.

[0072] 10 shows a lens unit 50 incorporating a lens 40. The lens unit 50 includes a cylindrical lens barrel 51, and a lens barrel space 52 penetrating in the optical axis direction is formed inside the lens barrel 51. The lens barrel space 52 is formed with a position restriction surface 53 extending in a direction perpendicular to the optical axis, a large diameter cylindrical surface 54 extending in the optical axis direction from the outer edge of the position restriction surface 53, and a small diameter cylindrical surface 55 extending in the optical axis direction from the inner edge of the position restriction surface 53. The size of the inner diameter of the large diameter cylindrical surface 54 is equal to or larger than the outer diameter of the annular portion 42b in the edge portion 42 (i.e., the diameter of the lens 40).

[0073] The lens 40 is inserted into the barrel 51 from the open end of the large diameter cylindrical surface 54 (the end opposite the position restriction surface 53) with the lens surface 44 facing forward in the insertion direction. When the annular portion 42b of the edge portion 42 abuts against the position restriction surface 53, the insertion of the lens 40 in the optical axis direction is restricted, and the position of the lens 40 in the optical axis direction is determined. In other words, the annular portion 42b constitutes a position reference surface that determines the position of the lens 40 in the optical axis direction. By determining the position in the optical axis direction via the annular portion 42b extending in a direction perpendicular to the optical axis, highly accurate positioning with excellent stability can be achieved.

[0074] The position of lens 40 in the direction perpendicular to the optical axis relative to barrel 51 can be determined by the abutment of the outer circumferential surface of tube portion 42a of edge portion 42 with small diameter cylindrical surface 55 of barrel 51. By determining the position in the direction perpendicular to the optical axis via tube portion 42a extending in the optical axis direction, highly stable and accurate positioning can be achieved.

[0075] As another embodiment, the position of lens 40 in the direction perpendicular to the optical axis relative to barrel 51 can be determined by abutting the outer edge of annular portion 42b of flange 42 with large-diameter cylindrical surface 54 of barrel 51.

[0076] As yet another embodiment, a clearance may be provided between the small diameter cylindrical surface 55 or the large diameter cylindrical surface 54 and the outer peripheral portion of the edge portion 42, which allows the position in the direction perpendicular to the optical axis to be adjusted, and an alignment structure may be provided to determine the position of the lens 40 in the direction perpendicular to the optical axis when the lens 40 is fixed to the lens barrel 51.

[0077] The lens 40, whose position has been determined in this manner, is fixed inside the lens barrel 51. The lens 40 can be fixed to the lens barrel 51 by various means. For example, the edge portion 42 can be adhered to the position restriction surface 53.

[0078] As shown in Figure 11, it is also possible to fix (screw) the lens 40 to the lens barrel 51 by forming a screw hole 56 on the position control surface 53 of the lens barrel 51, forming a through hole 57 penetrating in the optical axis direction in the annular portion 42b of the edge portion 42, and screwing a fixing screw 58 into the screw hole 56 on the position control surface 53 through the through hole 57 in the annular portion 42b.

[0079] Alternatively, after inserting lens 40 into lens barrel 51, another fixing member can be inserted into space 52 within the lens barrel, and lens 40 can be fixed by clamping annular portion 42b of edge portion 42 between position control surface 53 and the fixing member.

[0080] 10 and 11 show an example in which only lens 40 is disposed inside lens barrel 51, the optical system of lens unit 50 may be configured with a plurality of lenses. In this case, it is also possible to position another lens inserted into lens barrel 51 after lens 40 in the optical axis direction using annular portion 42b of edge portion 42 as a reference (by abutting against annular portion 42b of edge portion 42).

[0081] The edge portion 23 of the glass molded lens 20 shown in FIG. 4 is based on the thickness of the outermost circumference of the optical effective diameter (the outer edge portion of the lens surfaces 21 and 22) and has a structure that extends in the direction perpendicular to the optical axis while maintaining the thickness. In the glass molded lens 20 whose entirety including the edge portion 23 is made of glass, if the shape is changed abruptly from the lens surfaces 21 and 22 to the edge portion 23, cracks and breakage are likely to occur, so there is a restriction that the entire edge portion 23 is formed based on the shape of the outermost circumference of the optical effective diameter. Furthermore, the edge portion 23 requires a thickness of the volume absorption portion 24 and the volume absorption portion 25 on both sides of the outer circumferential surface 23c in the optical axis direction. Therefore, it is difficult to reduce the thickness of the edge portion 23 in the optical axis direction in the glass molded lens 20. Furthermore, if the thickness of the edge portion 23 in the optical axis direction changes abruptly in the middle of the direction perpendicular to the optical axis, the edge portion 23 made of glass is likely to crack or break, so the thickness of the edge portion 23 in the optical axis direction must be uniform overall. Therefore, it is difficult to reduce the weight of the edge portion 23 of the glass molded lens 20 by partially thinning or hollowing out the edge portion 23 .

[0082] In the lens 40 of this embodiment, in order to obtain the desired optical performance, a predetermined thickness is required in the optical axis direction at the outermost periphery of the optical effective diameter of the optical functional part 41 (the outer edge parts of the lens surfaces 43 and 44). In other words, the minimum thickness in the optical axis direction of the outer periphery 45 of the optical functional part 41 is restricted by the optical performance of the lens 40. However, only the optical functional part 41 is molded from glass, and the edge part 42 on the outside of the optical functional part 41 is formed from metal, which is a different material from the optical functional part 41. Therefore, the edge part 42 can be formed with a high degree of freedom in shape without considering the risk of cracking or breaking the optical functional part 41.

[0083] For example, edge portion 42 of lens 40 does not require a shape for absorbing errors during lens molding, such as volume absorbing portion 46 and volume absorbing portion 47, so edge portion 42 can be easily made thin in the optical axis direction.

[0084] Furthermore, the edge portion 42 of the lens 40 is composed of a tube portion 42a extending in the optical axis direction along the outer circumferential surface 45 of the optical function portion 41, and an annular portion 42b extending from the outer circumferential surface of the tube portion 42a in the optical axis orthogonal direction. The thickness t1 of the tube portion 42a in the optical axis orthogonal direction is smaller than the size of the entire edge portion 42 in the optical axis orthogonal direction (the width W of the annular portion 42b from the outer circumferential surface 45 of the optical function portion 41 to the outer edge of the annular portion 42b). Furthermore, the thickness t2 of the annular portion 42b in the optical axis direction is smaller than the size of the entire edge portion 42 in the optical axis direction (the length L of the tube portion 42a in the optical axis direction). In other words, the edge portion 42 is composed of the tube portion 42a which is thin in the optical axis orthogonal direction and the annular portion 42b which is thin in the optical axis direction. Therefore, compared to a configuration in which an edge portion of the same thickness as the optical axis direction thickness of the outer peripheral surface 45 of the optical functional portion 41 protrudes in a direction perpendicular to the optical axis (such as a configuration of edge portion 23 of glass molded lens 20), edge portion 42 having an L-shaped cross-sectional structure consisting of a cylindrical portion 42a and annular portion 42b is configured to be compact and lightweight.

[0085] As can be seen from a comparison between edge portion 42 of lens 40 of this embodiment shown in Fig. 8 and edge portion 23 of glass molded lens 20 shown in Fig. 4, edge portion 42 of this embodiment has a hollowed-out structure in which only a portion (two sides) of edge portion 23 with a rectangular cross section remains, and can achieve a significant weight reduction compared to edge portion 23. For example, when optical function portion 41 of lens 40 is formed from the same glass material as glass molded lens 20, lens 40 can be made about 5 to 10% lighter than glass molded lens 20.

[0086] On the other hand, as shown in Figures 10 and 11, the area of ​​edge portion 42 of lens 40, which abuts against lens barrel 51 to position lens 40, is equal to or greater than that of edge portion 23 of glass molded lens 20, and edge portion 42 enables lens 40 to be positioned with high precision.

[0087] Therefore, when attempting to obtain the same positional accuracy and stability between glass molded lens 20 and lens 40, edge portion 42 of lens 40 can be constructed to be smaller and lighter than edge portion 23 of glass molded lens 20.

[0088] The metal edge 42 can easily achieve a level of thinning that is difficult to achieve with the glass edge 23 that is integrally formed with the glass molded lens 20. For example, it is difficult to form a structure such as a cylindrical portion 42a that is thin in the direction perpendicular to the optical axis or a ring-shaped portion 42b that is thin in the optical axis direction with high precision using glass, and even if it can be formed with glass, it is prone to breakage. In contrast, the metal edge 42 has the advantage that it is easy to form a thin and highly accurate shape by pressing a metal plate. In addition, the metal edge 42 can restore its shape by elastic deformation against a certain degree of external force, so there is little risk of cracking or irreversible deformation occurring even if the edge 42 is thinned.

[0089] In manufacturing the lens 40 using the lens molding die 30 described above, the edge portion 42, which already has a cylindrical portion 42a and annular portion 42b, is held in the lower die 32, and when the optical function portion 41 is press-molded, the edge portion 42 is plastically deformed to be finished into a final shape. According to this manufacturing method, the shape accuracy of the lens surfaces 43, 44 of the optical function portion 41 and the shape accuracy of the cylindrical portion 42a and annular portion 42b of the edge portion 42 are all collectively controlled by the press surfaces (lens forming surface 34, annular portion holding surface 35, blocking protrusion 36) of the lower die 32 and the press surfaces (lens forming surface 37, cylindrical portion forming surface 38, opposing surface 39) of the upper die 33, so that the relative shape accuracy of the optical function portion 41 and the edge portion 42, and the shape accuracy of the entire lens 40 can be improved.

[0090] Furthermore, because metal edge 42 is not light-transmitting, it is possible to obtain a light-shielding effect that blocks harmful light that passes through the outside of lens surfaces 43, 44 of lens 40. For example, in the glass molded lens 20 of Fig. 4, edge 23 is light-transmitting, so it is necessary to apply a light-shielding paint or attach a light-shielding material to edge 23. In contrast, edge 42 of lens 40 itself has light-shielding properties, which has the advantage that such time and effort is not required.

[0091] In order to improve the light blocking ability of the edge portion 42, a blackening treatment may be applied to the outer surface of the edge portion 42 to suppress light reflection. The outer surface of the edge portion 42 refers to the part that appears when the edge portion 42 is in a single state (before being combined with the optical function portion 41), and the inner peripheral surface of the tube portion 42a that is fixed to the outer peripheral surface 45 of the optical function portion 41 when the lens 40 is completed is also included in the outer surface of the edge portion 42. The blackening treatment of the outer surface is a process for preventing the color and luster of the metal (base metal) that is the material of the edge portion 42 from being exposed to the outer surface as it is, thereby reducing light reflection. The blackening treatment is not limited to making the outer surface of the edge portion 42 completely black, and may be any treatment that exhibits a predetermined or higher reflection reduction effect compared to when the base metal of the edge portion 42 is exposed. In Figs. 12 and 13, the part on the outer surface of the edge portion 42 that has been blackened is indicated by a thick line.

[0092] 12 shows an example in which a blackening treatment is performed on the inner peripheral surface of the tube portion 42a of the edge portion 42. By performing a blackening treatment on the inner peripheral surface of the tube portion 42a that constitutes the inner surface of the optical path surrounding the optical function portion 41, it is possible to suppress internal reflection on the inner peripheral surface of the tube portion 42a and improve the optical performance of the lens 40.

[0093] 13 shows an example in which the entire outer surface of edge portion 42 is blackened, and the inner circumferential surface, outer circumferential surface, and tip surface of tubular portion 42a, and the front, back, and outer edge of annular portion 42b are all blackened. In other words, edge portion 42 is configured such that the non-blackened portion (base metal) is not exposed to the outer surface. In a thin edge portion 42, the entire outer surface may be blackened in this manner to enhance the effect of suppressing harmful stray light.

[0094] In addition, when lens 40 is incorporated into lens barrel 51 as shown in Figures 10 and 11, if the outer surface of tubular portion 42a of edge portion 42 and small diameter cylindrical surface 55 of lens barrel 51 are in close contact with each other and light does not enter the outer surface of tubular portion 42a, it is also possible to choose to blacken the inner surface of tubular portion 42a and the entire annular portion 42b and not blacken the outer surface of tubular portion 42a.

[0095] It is difficult to blacken the inner peripheral surface of the tube portion 42a after the optical function portion 41 and the edge portion 42 are joined together. For this reason, it is advisable to blacken the inner peripheral surface of the tube portion 42a at a stage before the optical function portion 41 is press-molded using the lens molding die 30, that is, while the edge portion 42 is still a single unit.

[0096] Of the edge portion 42, the outer peripheral surface and tip surface of the cylindrical portion 42a and the entire annular portion 42b can be blackened even after the optical function portion 41 and the edge portion 42 are joined. Therefore, the portions other than the inner peripheral surface of the cylindrical portion 42a may be blackened before press molding of the optical function portion 41 by the lens molding die 30, or may be blackened after press molding.

[0097] As a method of blackening treatment performed on the outer surface of the edge portion 42, for example, oxidation by heating a metal, chemical conversion treatment, plating treatment, etc. can be applied. In the case of oxidation by heating a metal, the outer surface of the edge portion 42 is oxidized by heating in an atmosphere containing oxygen, and the metallic luster is removed and blackened. As an example of chemical conversion treatment, the edge portion 42 is immersed in an alkaline aqueous solution to form a black oxide film (iron tetraoxide film) on the outer surface of the edge portion 42. As an example of plating treatment, plating such as black nickel plating or black chrome plating is performed on the outer surface of the edge portion 42. In addition, since heating for softening the optical function portion 41 is not performed after press molding of the optical function portion 41 using the lens molding die 30, and the heat resistance conditions are relaxed, it is also possible to use a method such as applying a black paint made of synthetic resin for the blackening treatment after press molding.

[0098] 9, an information display section 48 may be provided on the edge portion 42. Examples of the information display section 48 include a reference mark indicating the circumferential orientation of the lens 40, a product serial number, and a two-dimensional code including information such as the specifications of the lens 40. The metal edge portion 42 makes it easy to provide the information display section 48 and also makes it easy to increase the visibility of the information display section 48. Suitable positions for providing the information display section 48 include the front or back surface in the optical axis direction of the annular portion 42b, the outer circumferential surface of the tube portion 42a, and the like.

[0099] Optical function part 41 of lens 40 does not have a positioning function for lens 40, and has a structure in which lens surfaces 43 and 44, which function as optical surfaces, are connected by a simple peripheral shape (peripheral surface 45, volume absorption part 46, and volume absorption part 47). Therefore, optical function part 41 does not have a thin protruding part like edge part 23 in glass molded lens 20 in Fig. 4, and does not have a part where the surface angle changes sharply like the boundary between lens surface 21 and first plane 23a in glass molded lens 20, so the risk of cracking or breakage is reduced compared to glass molded lens 20, and it is advantageous in terms of strength.

[0100] In addition, in the lens molding die 30, the edge portion 42 is disposed in the outer peripheral region of the mold space S2, and the cylindrical portion 42a blocks the extension of the glass preform PF2 toward the outer peripheral side of the mold space S2, so there is no need to extend the glass preform PF2 into the narrow space on the outer peripheral side of the mold space S2 during molding. Therefore, the extension of the glass preform PF2 within the optically effective area (lens surfaces 43 and 44 formed by the lens forming surfaces 34 and 37) where high quality is required in terms of appearance and surface precision can be achieved at a relatively low temperature (a value close to the glass transition temperature of the glass preform PF2), which is advantageous for improving the quality of the appearance and surface precision of the optical function part 41.

[0101] Furthermore, because the optical functional part 41 does not have any fragile parts like the edge part 23, measures such as providing a release film to suppress cracking or special surface treatment of the glass preform PF2 are not required (or the measures can be reduced) when molding the optical functional part 41 with the lens molding die 30. As a result, clouding of the outer surface of the optical functional part 41 and instability in surface accuracy caused by the release film or surface treatment do not occur, which is also advantageous in terms of improving the quality of the appearance and surface accuracy of the optical functional part 41.

[0102] Lens surfaces 21 and 22 of glass molded lens 20 in Fig. 4 and lens surfaces 43 and 44 of lens 40 in Fig. 8 have almost the same design shape, but as can be seen from a comparison between Fig. 2 and Fig. 6, the glass preform PF2 used to form optically functional portion 41 of lens 40 requires a smaller amount of glass preform PF2 than the glass preform PF1 used to form glass molded lens 20. In addition, since the small amount of glass preform PF2 is a spherical body with a smaller radius of curvature than the glass preform PF1, the risk of gas trap generation during pressing is reduced by creating lens surfaces 43 and 44 of lens 40 from glass preform PF2 rather than creating lens surfaces 21 and 22 of glass molded lens 20 from glass preform PF1. In addition, by using glass preform PF2, which is smaller than glass preform PF1, the degree of freedom in lens design shape can be increased.

[0103] As described above, the lens 40 of the present embodiment is constructed by combining an optical function portion 41 made of glass with an edge portion 42 made of a material (metal) different from the glass of the optical function portion 41. This makes it possible to ensure high optical performance and strength in the optical function portion 41 while making the edge portion 42 small and lightweight, thereby providing various advantages over the glass molded lens 20 shown as a comparison example.

[0104] Furthermore, by configuring the edge portion 42 with the cylindrical portion 42a and the annular portion 42b as described above, the edge portion 42 can be made thin and lightweight without impairing the positioning performance of the lens 40.

[0105] More specifically, it is preferable that the lens 40 satisfies the following conditions: First, only the edge portion 42 has the function of determining the position of the lens 40 relative to a holding member such as the lens barrel 51 of the lens unit 50.

[0106] The optical function part 41 only has an area including lens surfaces 43 and 44 which are optically functional parts, an outer peripheral surface 45 fixed to the edge part 42, and volume absorbing parts 46 and 47 for absorbing errors during press molding of the optical function part 41, and does not have a function for determining the position of the lens 40 with respect to a holding member such as the lens barrel 51. The shape condition of the optical function part 41 is not only that it does not simply have a function for determining the lens position, but also that it does not include a surface perpendicular to the optical axis such as the front and back surfaces of the annular part 42b of the edge part 42. In other words, the optical function part 41 does not include a shape similar to the edge part of an existing glass molded lens.

[0107] 8, in the flange 42, the length of the cylindrical portion 42a in the optical axis direction is L, and the width of the annular portion 42b in the direction perpendicular to the optical axis is W. Here, it is desirable to satisfy the following conditions (1) and (2). (1) W / L≧0.8 (2) W / L≦10

[0108] The tube portion 42a of the edge portion 42 is coupled to the outer peripheral surface 45 of the optical function portion 41 to make the optical function portion 41 and the edge portion 42 coaxial. Therefore, in order to realize a highly accurate coupling, the tube portion 42a is required to have a length L in the optical axis direction of a predetermined length or more. In detail, it is preferable that the length L in the optical axis direction of the tube portion 42a is approximately the same as the length in the optical axis direction of the outer peripheral surface 45 of the optical function portion 41. If the tube portion 42a is too short with respect to the outer peripheral surface 45 of the optical function portion 41, the coupling accuracy between them cannot be ensured, and the optical function portion 41 and the edge portion 42 may not be appropriately coaxial. Alternatively, during press molding with the lens molding die 30, a part of the glass preform PF2 may flow out from the tube portion 42a to the outer peripheral side, and the shape accuracy of the optical function portion 41 may be reduced.

[0109] If condition (1) is not satisfied, the width W of the annular portion 42b in the direction perpendicular to the optical axis will be insufficient compared to the length L of the tube portion 42a in the optical axis direction, and the position of the annular portion 42b may become unstable when it is brought into contact with the position restriction surface 53 of the lens barrel 51, making it impossible to accurately determine the position of the lens 40. Therefore, it is necessary to ensure a necessary and sufficient length L in the optical axis direction for the tube portion 42a and then satisfy condition (1).

[0110] With regard to condition (1), it is more preferable that W / L≧1.5 is satisfied. In the lens 40 of the present embodiment, the value of W / L is about 1.5.

[0111] Since the outer edge of the annular portion 42b is the outermost circumference of the lens 40, the width W of the annular portion 42b in the direction perpendicular to the optical axis affects the diameter of the lens 40. If the condition (2) is not satisfied, the width W of the annular portion 42b in the direction perpendicular to the optical axis is very large compared to the length L of the tube portion 42a in the optical axis direction, and the diameter of the lens 40 including the edge portion 42 becomes too large, which may hinder the miniaturization of an optical device (such as a lens barrel 51) that houses the lens 40. Alternatively, if the area of ​​the annular portion 42b in the direction perpendicular to the optical axis is too large, it becomes more difficult to control the accuracy of the positioning surface of the annular portion 42b (such as ensuring flatness), which may adversely affect the accuracy of positioning the lens 40 using the annular portion 42b. Therefore, it is preferable to satisfy the condition (2) in consideration of the miniaturization of the optical device in which the lens 40 is mounted and the ease of controlling the position accuracy of the lens 40 within the optical device.

[0112] With regard to condition (2), it is more preferable that W / L≦5 be satisfied.

[0113] However, if there is sufficient space inside the optical device and the restrictions on the diameter of the lens 40 are not strict, condition (2) does not have to be satisfied.

[0114] Furthermore, when the area of ​​the annular portion 42b in the direction perpendicular to the optical axis is large, it is possible to easily control the accuracy of the positioning portion by providing an additional positioning protrusion or the like at a specific location of the annular portion 42b. Therefore, even when such a measure is possible, it is possible to exclude condition (2).

[0115] In this way, by adopting the configuration of lens 40 of the present embodiment and satisfying conditions (1) and (2), it is possible to achieve a smaller edge portion 42 and a significantly lighter weight than conventional glass molded lenses, without compromising optical performance.

[0116] The thicknesses t1 and t2 (plate thickness) of the cylindrical portion 42a and the annular portion 42b constituting the edge portion 42 are set to appropriate values ​​taking into consideration ease of processing, strength, etc. In the lens 40 of this embodiment, the thickness t1 of the cylindrical portion 42a in the direction perpendicular to the optical axis and the thickness t2 of the annular portion 42b in the optical axis direction are both approximately 0.5 mm.

[0117] If the thickness t1 of the cylindrical portion 42a or the thickness t2 of the annular portion 42b is too large, the weight reduction effect achieved by making the edge portion 42 have an L-shaped cross-section hollowed-out structure is diminished. Furthermore, when plastically deforming the edge portion 42 by press molding using the lens molding die 30, if the thickness t1 of the cylindrical portion 42a or the thickness t2 of the annular portion 42b is too large, deformation may be difficult or irregular deformation (sink marks, etc.) may occur, which may result in poor shape accuracy of the edge portion 42 after press molding.

[0118] If the thickness t1 of the cylindrical portion 42a or the thickness t2 of the annular portion 42b is too small, the rigidity of the edge portion 42 may be insufficient, and the precision and strength required for holding the optical function portion 41 and positioning the lens 40 may not be obtained. For example, if the cylindrical portion 42a is too thin, it may deform irregularly, compromising the coaxiality with the optical function portion 41. If the annular portion 42b is too thin, it may deform irregularly, making it impossible to properly position the lens 40.

[0119] As shown in FIG. 8, the diameter of the entire lens 40 defined by the outer edge of the annular portion 42b of the edge portion 42 is defined as the outer diameter D. The diameter of the optical function portion 41 defined by the inner peripheral surface of the cylindrical portion 42a of the edge portion 42 (the outer peripheral surface 45 of the optical function portion 41) is defined as the surface diameter d. The diameter of the optical function portion 41 excluding the radial region where the volume absorption portion 46 and the volume absorption portion 47 are formed (the diameter of the optically effective lens surfaces 43, 44) is defined as the effective diameter e. The dimension in the direction perpendicular to the optical axis of the radial region where the volume absorption portion 46 and the volume absorption portion 47 are formed is defined as the error absorption width R. The maximum thickness of the edge portion 42 in the optical axis direction is defined by the length L of the cylindrical portion 42a in the optical axis direction.

[0120] It is desirable that the outer diameter D and the length L of the cylindrical portion 42a in the optical axis direction (the maximum thickness of the edge portion 42 in the optical axis direction) satisfy the following condition (3) or (4). (3) For 2 mm ≦ D ≦ 5 mm, 0.15≦L≦0.35 (4) For D>5mm, 0.15+(D-5)×0.03≦L≦0.15+(D-5)×0.07

[0121] Conditions (3) and (4) indicate the range of appropriate maximum thickness in the optical axis direction of edge portion 42 relative to the diameter of lens 40. If the lower limit values ​​of conditions (3) and (4) are not met, there is a risk that the positioning accuracy of lens 40, the stability of holding the lens, the strength of edge portion 42, and the like may be adversely affected.

[0122] If the upper limits of conditions (3) and (4) are exceeded, edge portion 42 becomes thick in the optical axis direction and does not satisfy the requirement for thinness. For example, if length L of tube portion 42a in the optical axis direction is too large, when incorporated into barrel 51 of lens unit 50, the space occupied by edge portion 42 in the optical axis direction may become too large, which may result in an increase in the size of lens unit 50.

[0123] In this way, by satisfying the conditions (3) and (4), it is possible to ensure the strength and precision of the edge portion 42 and to thin the edge portion 42. In other words, by employing the lens 40 consisting of the optical function portion 41 and the edge portion 42, it is possible to reasonably satisfy the conditions (3) and (4).

[0124] In the case of glass molded lens 20 ( FIG. 4 ) having lens surfaces 21, 22 of the same shape as lens surfaces 43, 44 of lens 40, if edge portion 23 is formed with a thickness within the range corresponding to conditions (3) and (4), there is an increased probability of cracks or deformation occurring in edge portion 23 or its surroundings, or an increased probability of a decrease in the positioning accuracy of the lens via edge portion 23.

[0125] In this way, by adopting the configuration of lens 40 of this embodiment and satisfying condition (3) or (4), it is possible to achieve a thinner edge portion 42 than a conventional glass molded lens without impairing optical performance.

[0126] As an additional condition different from the above conditions (3) and (4), from the viewpoint of the operation accuracy and stability of the lens molding die 30 during press molding, it is preferable that the upper limit value of the length L in the optical axis direction of the tube portion 42a in the lens 40 is 40% or less of the outer diameter D. If the edge portion 42 has a thickness exceeding this upper limit value, when the edge portion 42 is arranged inside the lens molding die 30, the fitting length between the insertion portion 33a of the upper die 33 and the inner peripheral surface 31a of the body die 31 and the fitting length between the insertion portion 32a of the lower die 32 and the inner peripheral surface 31a of the body die 31 become small, and the risk of the upper die 33 or the lower die 32 tilting with respect to the central axis X2 during press molding increases. In particular, the smaller the outer diameter D of the lens 40, the smaller each part of the lens molding die 30 becomes, and this tendency becomes stronger. Therefore, by setting the length L in the optical axis direction of the tube portion 42a to the above upper limit value or less, the fitting length of each part of the lens molding die 30 is ensured, and the effect of improving the processing accuracy of press molding can be obtained.

[0127] Moreover, it is desirable that the surface diameter d and the effective diameter e of the optically functional portion 41 of the lens 40 satisfy any one of the following conditions (5), (6), (7), or (8). (5) In the range of 2 mm ≦ e ≦ 5 mm, (de) ≦ 0.5 mm (6) 5 mm <e≦10mmにおいて、(d-e)≦0.7mm (7) 10mm <e≦15mmにおいて、(d-e)≦0.9mm (8) 15mm <e≦20mmにおいて、(d-e)≦1.1mm

[0128] Conditions (5), (6), (7), and (8) indicate the appropriate value of the difference between the surface diameter d and the effective diameter e in the optical function part 41. By satisfying any one of conditions (5), (6), (7), and (8), the volume absorbing parts 46 and 47 can reliably absorb the volume error within the range expected when press-molding the optical function part 41 with a predetermined effective diameter e, and it is possible to create the optical function part 41 having the lens surfaces 43 and 44 with high precision and appearance quality without causing molding defects.

[0129] 8, the difference between the surface diameter d and the effective diameter e of the lens 40 is approximately equal to the error absorption width R × 2. It is preferable that the error absorption width R satisfies the following condition (9), (10), (11), or (12). (9) In the range of 2 mm ≦ D ≦ 5 mm, R ≦ 0.23 mm (10) 5 mm <D≦10mmにおいて、R≦0.35mm (11) 10mm <D≦15mmにおいて、R≦0.45mm (12) 15mm <D≦20mmにおいて、R≦0.55mm

[0130] The dimension of edge portion 42 in the direction orthogonal to the optical axis (width W of annular portion 42b in the direction orthogonal to the optical axis shown in FIG. 8) is calculated by (Dd) / 2. Lens 40 of this embodiment is capable of achieving a thin edge portion 42 while providing a high degree of freedom in the dimensional relationship between width W of annular portion 42b in the direction orthogonal to the optical axis and length L of tube portion 42a in the optical axis direction. However, by satisfying the following condition (13), it becomes easier to achieve a reduction in weight of lens 40 and a stable position of lens 40 when it is incorporated into lens barrel 51. (13) 0.5≦{(Dd) / 2} / L≦30

[0131] The lower limit of {(Dd) / 2} / L within the range of condition (13) is preferably 1.0, more preferably 1.5, and even more preferably 2.0. The upper limit of {(Dd) / 2} / L within the range of condition (13) is preferably 20, more preferably 10, and even more preferably 5.

[0132] In the lens 40 of the above embodiment, the edge portion 42 is made of metal, but it is also possible to select a material other than metal as the edge portion of a lens to which the present invention is applied. For example, the edge portion may be made of ceramics. In this case, it is preferable that the thermal expansion coefficient of the ceramics constituting the edge portion exceeds the thermal expansion coefficient of the material constituting the lens molding die. This allows the ceramic edge portion to expand and adhere to the lens molding die when molding the optical function portion of the lens, improving the decentering accuracy with respect to the lens molding die, and making it possible to obtain a lens in which the edge portion and the optical function portion are coaxial with each other with high accuracy.

[0133] The edge portion 42 in the above embodiment has an L-shaped cross-sectional structure, with the annular portion 42b extending from one end of the tube portion 42a in the optical axis direction, and the other end of the tube portion 42a in the optical axis direction having a completed shape as an end face facing the optical axis direction. The edge portion 42 having this shape has the advantage that it is easy to manufacture by pressing. However, it is also possible to use an edge portion having a shape different from the edge portion 42 in the above embodiment.

[0134] For example, as a modified example, an annular flange may be provided that protrudes from the other end of the tube portion 42a in the optical axis direction (the end opposite to the one end side to which the annular portion 42b extends) toward the center side in the radial direction of the lens 40 (the side approaching the optical axis Xb). That is, the cross-sectional shape of the edge portion may be a crank shape (S shape) instead of an L shape as shown in FIG. 8. This flange has a shape that covers a part of the periphery of the optical function portion 41 (near the volume absorbing portion 47), and can function as a light blocking portion that blocks the progression of light reflected on the inner surface of the tube portion 42a.

[0135] As another modification, it is possible to apply an edge portion having a structure (T-shaped cross-sectional structure) in which the annular portion 42b protrudes in a direction perpendicular to the optical axis from a position midway in the optical axis direction of the cylindrical portion 42a. Even with an edge portion having such a T-shaped cross-sectional structure, it is possible to obtain the effect of reducing size and weight compared to edge portion 23 of glass molded lens 20 shown in FIG.

[0136] In addition, the annular portion 42b of the edge portion 42 in the above embodiment has both surfaces (front and back) in the optical axis direction that are parallel to each other, but a recess or notch may be present in a part of the annular portion 42b. In addition, the cylindrical portion 42a of the edge portion 42 in the above embodiment has a completely cylindrical shape that is continuous all around the circumferential direction centered on the optical axis Xb, but a recess or notch may be present in the middle of the cylindrical portion 42a. In these cases, the outer diameter of the lens 40 and the dimensions of the edge portion 42 are determined based on the remaining parts of each part of the edge portion 42 excluding the recess or notch.

[0137] The embodiments of the present invention are not limited to the above-mentioned embodiments or their modifications, and may be modified, substituted, or altered in various ways without departing from the spirit of the technical idea of ​​the present invention. Furthermore, if the technical idea of ​​the present invention can be realized in a different way due to technological progress or other derived technology, it may be implemented using that method. Therefore, the claims cover all embodiments that may be included within the scope of the technical idea of ​​the present invention. [Explanation of symbols]

[0138] 30: Lens molding mold 31: Body type 32: Lower mold 33: Upper mold 34: Lens forming surface 35: Annular retaining surface 36: Blockage protrusion 37: Lens forming surface 38:Cylinder forming surface 39: Opposite surface 40: Lens 41:Optical function section 42: Edge section 42a:Cylinder part 42b: Circular section 43: Lens surface 44: Lens surface 45: Outer surface 46: Volume absorption part 47: Volume absorption part 48: Information display section 50: Lens unit 51: Telescope tube 52: Space inside the lens barrel 53: Position control surface 54: Large diameter cylindrical surface 55: Small diameter cylindrical surface 56: Screw hole 57:Through hole 58: Screw L: Length of the barrel in the optical axis direction PF2: Glass preform S2: type space W: Width of the annular part in the direction perpendicular to the optical axis X2: Center axis of the lens mold Xb: Optical axis t1: Thickness of the tube in the direction perpendicular to the optical axis t2: Thickness of the annular part in the optical axis direction

Claims

1. an optical function portion which is a press-molded glass product and has lens surfaces on both sides in the optical axis direction and has a volume absorbing portion around the lens surfaces to allow for shape errors associated with press molding; a flange portion made of a material different from the glass of the optical function portion and coupled to the optical function portion; The edge portion is a cylindrical portion having a cylindrical shape centered on an optical axis and surrounding an outer peripheral surface of the optical function portion; a ring-shaped portion having a thickness in the optical axis direction smaller than a length of the cylindrical portion in the optical axis direction and extending from an outer circumferential surface of the cylindrical portion in a direction perpendicular to the optical axis, A lens characterized in that a length L of the cylindrical portion in the optical axis direction and a width W of the annular portion in a direction perpendicular to the optical axis satisfy the following condition (1): (1) W / L≧0.8

2. The lens according to claim 1 , wherein a length L of the cylindrical portion in the optical axis direction and a width W of the annular portion in the direction perpendicular to the optical axis satisfy the following condition (2): (2) W / L≦10

3. 3. The lens according to claim 1, wherein the edge portion is made of metal.

4. 3. The lens according to claim 1, wherein the annular portion extends from one end of the outer circumferential surface of the cylindrical portion in the optical axis direction in a direction perpendicular to the optical axis.

5. 3. The lens according to claim 1, wherein the inner peripheral surface of the cylindrical portion of the edge portion is blackened.

6. 3. The lens according to claim 1, wherein the entire outer surfaces of the cylindrical portion and the annular portion of the edge portion are blackened.

7. A lens molding die for press-molding the lens according to claim 1 or 2 by bringing a lower die and an upper die close to each other, The lower mold is an annular portion holding surface that is located around a lens forming surface that forms the lens surface of the optical function portion and holds the annular portion of the edge portion; a ring-shaped blocking protrusion located around the ring-shaped portion holding surface and protruding above the ring-shaped portion holding surface; A lens molding die, characterized in that when the lower die and the upper die are brought close to each other to press-mold the lens, the blocking protrusion determines the outer edge position of the annular portion.

8. The upper mold is a tube-portion forming surface that is located around a lens forming surface that forms the lens surface of the optical function portion and determines the position of an outer circumferential surface of the tube portion of the edge portion; The lens molding die according to claim 7 , further comprising: an opposing surface located around the periphery of the cylindrical portion forming surface, the opposing surface facing the annular portion holding surface and the blocking protrusion of the lower die.

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