JP2024062808A - Lens and lens manufacturing method - Google Patents

Abstract

[Problem] To provide a lens with markings that are easy to manufacture and do not affect the positional accuracy or shape accuracy of the lens. [Solution] A lens (10) that is a press-molded glass product and has lens surfaces (11, 12) on both sides in the optical axis direction and an annular edge portion (13) provided on the outer periphery of the lens surfaces, the edge portion having a flat surface (15) that is provided on the outer periphery of at least one of the lens surfaces on both sides in an annular shape surrounding the lens surface and is approximately perpendicular to the optical axis (X1), a stepped surface (17) that is provided on the outermost periphery of the edge portion in an annular shape surrounding the flat surface and is concave in the optical axis direction relative to the flat surface, and a marking (18) that is provided in the same radial region as the stepped surface, is convex in the optical axis direction relative to the stepped surface, and does not protrude in the optical axis direction relative to the flat surface. [Selected Figure] Figure 2

Description

The present invention relates to lenses and methods for manufacturing lenses.

Lenses may be provided with markings that indicate various types of information. For example, markings to indicate the eccentric orientation of a lens are known. A typical lens has an edge portion (also called a flange portion) on the periphery of the optically functional portion that has the lens surface, and markings are often provided on the edge portion (for example, Patent Documents 1 and 2).

Methods of marking lenses by printing, painting, vapor deposition, etc. are known. With these methods, the marking is formed using a material different from the lens after the lens is molded, and this has the problem of reduced production efficiency and increased manufacturing costs due to the additional steps.

A method is also known in which a marking consisting of a convex or concave portion is formed on part of the edge when the lens is press-molded using a molding die (metal mold). This method has the advantage of being highly efficient in production, as the marking shape is formed simultaneously when the lens is molded, and does not require any equipment or process to apply the marking later.

The position of a lens in an optical device is managed by its position in the optical axis direction of the optical system, its position in the direction perpendicular to the optical axis (perpendicular to the optical axis), and its inclination with respect to the optical axis. The lens is held by fixing its edge to a lens holding member (lens frame, lens barrel, etc.), and the edge serves as the lens position reference. For example, the edge has a plane perpendicular to the optical axis on at least one of the front and rear sides in the optical axis direction, and the lens position in the optical axis direction is determined based on this plane. In some cases, the edge has a cylindrical outer periphery centered on the optical axis, and the lens position in the direction perpendicular to the optical axis is determined based on this outer periphery.

When a convex portion protruding from the edge is provided as a lens marking, there is a risk that the convex portion may interfere with the lens mounting portion of the lens holding member, other adjacent lenses, spacers that adjust the distance between lenses, etc. Furthermore, when a minute convex portion protruding from the outer surface of the lens is provided as a marking, there is a risk that the convex portion may be chipped or otherwise damaged.

To address this issue, Patent Document 3 describes a flange portion provided on the outer periphery of the lens surface of a plastic lens, in which a step is provided on part of the flange surface on one side, and a marking is injection molded integrally with the marking surface of the step, with the highest part of the marking being lower than the highest surface of the flange surface.

JP 2004-191493 A International Publication No. 2019/208455 JP 2010-186550 A

Patent Document 3 is a technology that targets plastic lenses manufactured by injection molding of resin material. Injection molding of resin material makes it easy to form complex or minute shapes, and there are fewer restrictions when forming lenses that include steps or markings as described above.

In contrast, glass molded lenses, which are manufactured by press molding a glass material, are processed by heating to a high temperature range where the glass softens, so a mold with high heat resistance must be used, and there are many restrictions on the mold structure. For example, instead of a metal mold, which is easy to process, a ceramic mold, which is hard and difficult to process, may be used. In addition, when factors such as the ductility of glass during pressing and the contraction of glass due to cooling after pressing are taken into consideration, there are also restrictions on the lens shape that can be obtained by transferring the shape of the mold with high accuracy. Therefore, glass molded lenses have more restrictions on the formation of markings than plastic lenses, and it is necessary to find suitable marking conditions for glass molded lenses.

The present invention was made based on the above-mentioned awareness, and aims to provide a lens with markings that are easy to manufacture and do not affect the positional accuracy or shape accuracy of the lens, and a method for manufacturing the lens.

One aspect of the present invention is a press-molded glass lens having lens surfaces on both sides in the optical axis direction and annular edge portions provided on the outer periphery of the lens surfaces, the edge portions being characterized in that they have a flat surface that is provided on the outer periphery of at least one of the lens surfaces on both sides in an annular shape surrounding the lens surfaces and is substantially perpendicular to the optical axis, a stepped surface that is provided in an annular shape surrounding the flat surface at the outermost periphery of the edge portions and is concave in the optical axis direction relative to the flat surface, and a marking that is provided in the same radial region as the stepped surface, is convex in the optical axis direction relative to the stepped surface, and does not protrude in the optical axis direction relative to the flat surface.

The thickness t1 of the edge portion in the optical axis direction at the flat surface, the thickness t2 of the edge portion in the optical axis direction at the marking, and the thickness t3 of the edge portion in the optical axis direction at the stepped surface are set so that t1>t2>t3.

When the lens diameter of the lens is D, the inner diameter of the flat surface in contact with the lens surface is d ₁ , and the outer diameter of the flat surface in contact with the step surface is d ₂ , it is preferable that the following condition (1) is satisfied.
(1) (0.7D+ _0.3d1 )< _d2 <D-0.2

It is preferable that a chord-direction width w of the marking perpendicular to the radial direction of the lens at a position where the marking is provided satisfies the following condition (2).
(2) w ≧ 0.05 mm

It is preferable that a radial width L of the marking parallel to the radial direction of the lens at a position where the marking is provided satisfies the following condition (3).
(3) L≧0.2 mm

It is preferable that the step surface is parallel to the flat surface.

It is preferable that the markings be polygonal, arcuate, or elliptical when viewed along the optical axis.

The present invention also provides a manufacturing method for manufacturing a lens having the above-described configuration, which is characterized in that a mold member having a press surface including a lens forming surface for forming the lens surface, a flat annular portion located on the outer periphery of the lens forming surface for forming the flat surface, a stepped annular portion located on the outer periphery of the flat annular portion for forming the stepped surface, and a groove portion that is concave in the press direction relative to the stepped annular portion for forming the marking is used to press a glass preform with the mold member to mold the lens to which the shape of the press surface has been transferred.

The present invention provides a lens with markings that are easy to manufacture and do not affect the positional accuracy or shape accuracy of the lens, as well as a method for manufacturing the lens.

1 is a diagram showing the front surface side of a glass molded lens of the present embodiment as viewed along the optical axis. 2 is a diagram showing the rear surface side of the glass molded lens of the present embodiment as viewed along the optical axis. FIG. FIG. 2 is a cross-sectional view taken along line III-III in FIG. FIG. 2 is a cross-sectional view taken along line IV-IV in FIG. FIG. 2 is an enlarged view of a marking provided on a glass molded lens and its surroundings. FIG. 2 is a cross-sectional view showing a molding die for producing the glass molded lens of the present embodiment. FIG. 2 is a perspective view showing a pressing surface of an upper die that constitutes a molding die. FIG. 13 is a diagram showing a modified example of the marking.

The lens of this embodiment and its manufacturing method will be described below with reference to the drawings. Figs. 1 to 4 show a glass molded lens 10, which is the lens of this embodiment. Fig. 1 shows the front side of the glass molded lens 10, and Fig. 2 shows the rear side of the glass molded lens 10. Figs. 3 and 4 show the glass molded lens 10 in a cross section including the optical axis X1. In the glass molded lens 10, the direction along the optical axis X1 is defined as the optical axis direction. The direction perpendicular to the optical axis X1 may be called the direction orthogonal to the optical axis, or the radial direction of the glass molded lens 10.

Glass molded lens 10 has a convex lens surface 11 and a concave lens surface 12 on both sides in the optical axis direction. When glass molded lens 10 is incorporated into an optical device, lens surface 11 becomes the front surface in the optical axis direction, and lens surface 12 becomes the rear surface in the optical axis direction. Note that the front-to-rear direction of glass molded lens 10 is an example and is not limited to this.

The glass molded lens 10 has an annular edge portion 13 on the outer periphery of the optical function portion including the lens surface 11 and the lens surface 12. The edge portion 13 has a first flat surface 14 on the front side located on the outer periphery side of the lens surface 11, a second flat surface 15 on the rear side located on the outer periphery side of the lens surface 12, and a cylindrical outer periphery surface 16 centered on the optical axis X1. The first flat surface 14 and the second flat surface 15 are each a plane perpendicular to the optical axis X1. The distance between the first flat surface 14 and the second flat surface 15 is the maximum thickness of the edge portion 13 in the optical axis direction (thickness t1 shown in FIG. 3). The outer periphery surface 16 is the surface that constitutes the outermost edge in the radial direction of the glass molded lens 10, and the diameter of the glass molded lens 10 (lens diameter D shown in FIG. 2) is defined as the diameter of the outer periphery surface 16.

Furthermore, a step surface 17 and a marking 18 are provided on the rear surface side of the edge portion 13. The step surface 17 is located on the outer periphery side of the second flat surface 15, and is formed in an annular region surrounding the second flat surface 15. In other words, the annular second flat surface 15 is formed on the outer periphery side of the lens surface 12, and the annular step surface 17 is formed on the outer periphery side of the second flat surface 15. The step surface 17 is provided on the outermost periphery of the rear surface of the edge portion 13, and the outer edge of the step surface 17 and the outer periphery surface 16 are in contact.

As shown in Figures 3 and 4, the step surface 17 is formed at a position lower than the second flat surface 15 and has a shape that is concave in the optical axis direction with respect to the second flat surface 15. The thickness in the optical axis direction from the first flat surface 14 to the step surface 17 (thickness t3 shown in Figure 3) is smaller than the thickness in the optical axis direction from the first flat surface 14 to the second flat surface 15 (thickness t1 shown in Figure 3).

The marking 18 is located on an extension of the step surface 17 in the circumferential direction centered on the optical axis X1. In other words, the marking 18 is provided in the same radial region as the step surface 17 and is located on the outer circumferential side of the second flat surface 15. The marking 18 has a shape that is convex in the optical axis direction relative to the step surface 17. The amount of protrusion (height) of the marking 18 from the step surface 17 in the optical axis direction is slightly smaller than the distance in the optical axis direction from the step surface 17 to the second flat surface 15. Therefore, the marking 18 is provided at a position lower than the second flat surface 15 in the optical axis direction and does not protrude in the optical axis direction relative to the second flat surface 15. The conditions under which the marking 18 does not protrude in the optical axis direction will be described later.

Figure 5 is an enlarged view of the marking 18 and its surroundings. The marking 18 is substantially rectangular when viewed from the rear of the glass molded lens 10. The inner diameter end of the marking 18 contacts the outer edge of the second flat surface 15, and a pair of substantially parallel side walls 18a extend from the inner diameter end of the marking 18 toward the outer diameter end 18b.

The marking 18 functions as an information display section that shows various information related to the glass molded lens 10. Examples of information shown by the marking 18 include the circumferential orientation (eccentricity orientation) of the glass molded lens 10, the serial number of the glass molded lens 10, and the production lot. In the illustrated embodiment, an example is shown in which only one marking 18 is provided, but it is possible to show desired information by providing multiple markings or by making the shapes of the multiple markings different. Furthermore, when multiple markings are provided, the content of the information can also be distinguished by making the circumferential positional relationship (spacing) different.

Since the marking 18 is provided as part of the shape of the glass molded lens 10, the marking 18 is formed at the same time as the glass molded lens 10 is press molded. After the lens is molded, there is no need to apply marking in a separate process using a material other than glass, which results in excellent production efficiency.

When providing a marking as part of the shape of a lens, which is a press-molded glass product, the mold (metal die) used to mold the lens must also be considered. Molds for press-molding glass molded lenses are used in high-temperature environments where the glass material is melted, so there are restrictions on the materials they can be made from. In addition, because it is necessary to reliably transfer the shape of the mold to the glass material when molding the lens, it is difficult to use complex molds with partially abrupt changes in shape.

For example, ceramics are used as the material for molds for glass molded lenses. In general, ceramic molds are more likely to have limited freedom in shape in terms of workability compared to metal molds, and are often difficult to manufacture. More specifically, it is difficult to process ceramic molds with a high degree of freedom in shape by turning with a cutting tool, and they are restricted to being machined into a simple shape by grinding with a grinding wheel.

When a simple convex portion protruding from the outer surface of the lens is provided as the marking on the lens side, a concave portion is provided in the mold at a location corresponding to the marking. Providing a minute concave portion for forming a marking on a ceramic mold is advantageous in terms of ease of mold manufacture, since it can be achieved with a small amount of grinding work, etc. However, simply using a convex portion transferred from the concave portion of the mold as the marking on the lens side will result in the marking protruding from the outer surface of the lens, and there is a risk that the marking will interfere with the lens frame, lens barrel, other lenses, spacers, etc. when the lens is incorporated into an optical device, making it impossible to position the lens with high precision. Furthermore, a marking in the shape of a minute convex portion protruding from the outer surface of the lens is easily damaged.

Making the marking on the lens side a concave portion can avoid the risk of the marking interfering with or damaging other components. On the other hand, if the marking is simply a tiny concave portion, then a tiny protrusion must be provided on the mold to form the concave portion. To provide a tiny protrusion on the mold, processing such as grinding must be performed on a wide area other than the convex portion to leave the convex portion, which makes processing the mold more difficult and increases the amount of processing work. In addition, there is a problem in that the tiny protrusions provided on the mold are easily damaged.

The glass molded lens 10 of this embodiment is provided with a step surface 17 that is concave in the optical axis direction relative to the second flat surface 15, and a marking 18 that is convex in the optical axis direction is provided on the step surface 17, and the marking 18 is set to a height that does not protrude from the second flat surface 15 in the optical axis direction. In other words, the marking 18 is contained within the optical axis direction range between the step surface 17 and the second flat surface 15, and does not protrude from the second flat surface 15 in the optical axis direction. Therefore, it is possible to prevent the marking 18 from interfering with another member that abuts against the second flat surface 15 to perform positioning. Examples of such another member include a lens frame or lens barrel to which the glass molded lens 10 is attached, another lens adjacent to the glass molded lens 10, and a spacer that adjusts the distance between multiple lenses. As a result, the mounting position of the glass molded lens 10 can be appropriately managed by the edge portion 13 including the second flat surface 15. In addition, the marking 18 that does not protrude from the second flat surface 15 in the optical axis direction has a low risk of breakage.

Figures 6A and 6B show the configuration and operation of a molding die 30 for producing a glass molded lens 10.

The molding die 30 is composed of a body die 31, a lower die 32, and an upper die 33. The lower die 32 and the upper die 33 are die members having a pressing surface 41 and a pressing surface 44 facing each other. The body die 31 is cylindrical in shape and has an internal space surrounded by an inner peripheral surface 34, which is a cylindrical surface. The central axis X2 of the molding die 30 is an axis that passes through the center of the inner peripheral surface 34 and extends in the vertical direction. The lower end surface 35 and the upper end surface 36 of the body die 31 are each perpendicular to the central axis X2. The internal space of the body die 31 penetrates in the vertical direction and opens to the lower end surface 35 and the upper end surface 36.

The lower mold 32 has an insertion portion 37 that is inserted from below into the internal space of the body mold 31, and a large diameter portion 38 that is provided below the insertion portion 37 and has a larger diameter than the insertion portion 37. The upper mold 33 has an insertion portion 39 that is inserted from above into the internal space of the body mold 31, and a large diameter portion 40 that is provided above the insertion portion 39 and has a larger diameter than the insertion portion 39. The outer peripheral surfaces of the insertion portions 37 and 39 can slide vertically relative to the inner peripheral surface 34 of the body mold 31, but movement is restricted in a direction perpendicular to the central axis X2. In other words, the lower mold 32 and the upper mold 33 can move vertically relative to the body mold 31 with their centers aligned to coincide with the central axis X2.

The lower die 32 has a press surface 41 at the upper end of the insertion portion 37. The press surface 41 has a concave lens forming surface 42 and an edge forming surface 43 located on the outer periphery of the lens forming surface 42. The edge forming surface 43 is a surface perpendicular to the central axis X2.

The upper die 33 has a press surface 44 at the lower end of the insertion portion 39. The press surface 44 has a convex lens forming surface 45 and an edge forming surface 46 located on the outer periphery of the lens forming surface 45.

Figure 7 is a perspective view showing the press surface 44 of the insertion portion 39 of the upper die 33. The edge forming surface 46 has a flat annular portion 46a, a stepped annular portion 46b, and a groove portion 46c. The flat annular portion 46a is formed in an annular range surrounding the outer periphery of the lens forming surface 45, and constitutes an annular plane perpendicular to the central axis X2. The stepped annular portion 46b is formed in an annular range surrounding the outer periphery of the flat annular portion 46a, and is an annular protruding portion that protrudes from the flat annular portion 46a in the direction along the central axis X2. The stepped annular portion 46b has a plane perpendicular to the central axis X2.

The groove portion 46c is provided in a portion of the circumference of the stepped annular portion 46b, and is a portion that is concave in the press direction (direction along the central axis X2) relative to the stepped annular portion 46b. The groove portion 46c is a groove that extends in the radial direction of the press surface 44, with its inner diameter end communicating with the flat annular portion 46a and its outer diameter end communicating with the outer peripheral surface of the insertion portion 39. The bottom surface of the groove portion 46c is located slightly higher (protruding) than the flat annular portion 46a in the direction along the central axis X2.

The edge forming surface 46 of the press surface 44 has a simple structure with a concentric flat annular portion 46a and a stepped annular portion 46b on the outside of the lens forming surface 45, so it can be easily formed when manufacturing the upper mold 33. For example, the flat annular portion 46a and the stepped annular portion 46b can be formed by grinding with a grinding wheel that rotates around an axis parallel to the central axis X2.

The groove portion 46c can be formed by forming the stepped annular portion 46b in a shape that is continuous around the entire circumference, and then thinning a part of the stepped annular portion 46b by grinding with a grinding wheel. The groove portion 46c is a through groove that extends in the radial direction of the press surface 44 and crosses the stepped annular portion 46b, so it can be formed by a simple process. For example, the groove portion 46c can be formed by grinding with a small grinding wheel that rotates around an axis perpendicular to the central axis X2. The configuration in which the bottom surface of the groove portion 46c is higher (protruding) than the flat annular portion 46a in the direction along the central axis X2 has an effect on the ease of processing when forming the groove portion 46c after forming the stepped annular portion 46b.

For the above reasons, the upper die 33 can be manufactured efficiently. Furthermore, the structure in which the groove portion 46c is part of the stepped annular portion 46b that continues in the circumferential direction does not have any minute protruding portions on the press surface 44, and there is little risk of breakage. In this way, the press surface 44 has a structure that is easy to manufacture even when the material of the upper die 33 is ceramic, and is less likely to break.

Returning to FIG. 6, the process of press molding using the mold 30 will be described. When molding the glass molded lens 10 using the mold 30, as shown in FIG. 6A, a spherical glass preform PF made of glass, which is the base material of the glass molded lens 10, is placed on the press surface 41 of the lower mold 32. The concave shape of the lens forming surface 42 holds the glass preform PF in a position on the central axis X2. The lower mold 32 is held in a position where the large diameter portion 38 abuts against the lower end surface 35, and the lower mold 32 is supported from below by a pedestal (not shown) so that the insertion portion 37 does not come off the body mold 31. The glass preform PF can be supplied onto the press surface 41 with the insertion portion 37 removed downward from the body mold 31, or from the upper end side of the body mold 31 with the insertion portion 37 inserted into the body mold 31.

The glass preform PF is heated above its glass transition temperature to soften it, and the upper die 33 with the insertion portion 39 inserted into the body die 31 is pressed downward. The glass preform PF is pressed between the pressing surface 44 of the descending upper die 33 and the pressing surface 41 of the lower die 32, whose descent is restricted, and the glass preform PF is deformed.

When the upper mold 33 is lowered to the press movement end shown in FIG. 6(B), the glass preform PF takes a shape corresponding to the mold space surrounded by the press surface 41, the press surface 44, and the inner peripheral surface 34. Then, by cooling to a predetermined temperature and disassembling the molding die 30, the molded glass molded lens 10 can be removed. The glass molded lens 10 is a lens to which the surface shapes of the press surface 41, the press surface 44, and the inner peripheral surface 34 have been transferred.

More specifically, the inner peripheral surface 34 of the body mold 31 forms the outer peripheral surface 16 of the glass molded lens 10. The lens forming surface 42 of the lower mold 32 forms the lens surface 11, and the edge forming surface 43 forms the first flat surface 14 of the edge portion 13.

On the rear side of the glass molded lens 10, the lens forming surface 45 of the upper mold 33 forms the lens surface 12, the flat annular portion 46a forms the second flat surface 15, the stepped annular portion 46b forms the stepped surface 17, and the groove portion 46c forms the marking 18.

As described above, in the glass molded lens 10, the marking 18 has a non-protruding shape that does not protrude beyond the second flat surface 15 or the outer peripheral surface 16, and therefore a structure is realized in which the marking 18 does not interfere with incorporation into an optical device and the marking 18 is less likely to be damaged. In the molding die 30, a structure is realized in which the stepped annular portion 46b and groove portion 46c for forming the marking 18 are easy to manufacture and each portion, including the groove portion 46c, is less likely to be damaged. Therefore, the above configuration has advantages for both the glass molded lens 10 and the molding die 30. Furthermore, by manufacturing using the molding die 30, the glass molded lens 10 having the marking 18 can be obtained efficiently and at low cost.

The preferred conditions for the glass molded lens 10 will now be described in more detail. First, it is preferable that the step surface 17 is continuous over the entire circumferential direction centered on the optical axis X1, except for the marking 18, and surrounds almost the entire outer periphery of the second flat surface 15. This simplifies the shape of the step surface 17, making it easier to ensure strength. In addition, the thickness of the edge portion 13 in the area where the step surface 17 is formed is made uniform, so there is no bias in the amount of shrinkage that accompanies cooling of the glass after press molding, making it easier to achieve a highly accurate lens shape.

The step surface 17 and the marking 18 are preferably provided on the outermost periphery of the edge portion 13. Although the thickness of the edge portion 13 differs partially at the marking 18, the second flat surface 15 is present between the marking 18 and the lens surface 12, so that even if the amount of shrinkage varies near the marking 18 during cooling after pressing, the shape accuracy of the lens surface 12 is not affected and the optical performance is not impaired. In addition, even if the amount of shrinkage varies at the step surface 17 during cooling after pressing due to the difference between the thickness of the edge portion 13 at the second flat surface 15 (thickness t1 in FIG. 3) and the thickness of the edge portion 13 at the step surface 17 (thickness t3 in FIG. 3), the outermost periphery of the edge portion 13 can absorb the variation in the amount of shrinkage, so that the shape accuracy of the lens surface 12 inside the second flat surface 15 is less likely to be affected.

For example, unlike this embodiment, if the positions of the second flat surface 15 and the step surface 17 are reversed and the step surface and marking are provided on the outer periphery adjacent to the lens surface 12, the shape accuracy of the lens surface 12 may be affected by variations in the amount of shrinkage during cooling due to differences in thickness at the step surface and marking locations.

In addition, if the step surface 17 and the marking 18 are located on the outermost periphery of the edge portion 13, it is easy to carry out processing such as adjusting the shape of the marking 18 later, and there is an advantage in that there is little risk of damaging the lens surface 12 when processing the marking 18.

As shown in Figure 3, when the thickness of the edge portion 13 is defined based on the first flat surface 14, it is preferable that the thickness t1 of the edge portion 13 at the second flat surface 15, the thickness t2 of the edge portion 13 at the marking 18, and the thickness t3 of the edge portion 13 at the step surface 17 satisfy the relationship t1 > t2 > t3. By satisfying this condition, the marking 18 protrudes in the optical axis direction from the step surface 17 and is easy to see, and a shape in which the marking 18 does not protrude in the optical axis direction from the second flat surface 15 can be realized.

The difference between the thickness t1 of the edge portion 13 at the second flat surface 15 and the thickness t3 of the edge portion 13 at the step surface 17 is preferably about 10 μm to 30 μm. If the difference between the thickness t1 and the thickness t3 is less than 10 μm, it may be difficult to form the step surface 17 and the marking 18 in a good shape, or the visibility of the marking 18 may be impaired.

If the difference between thickness t1 and thickness t3 is too large, the thickness of edge portion 13 at step surface 17 will be too small, causing a problem of reduced strength at the outer periphery of edge portion 13. In addition, the step between flat annular portions 46a and 46a on press surface 44 of upper die 33 of mold 30 will be too large, increasing the effort and cost required to shape press surface 44.

When the lens diameter, which is the diameter of glass molded lens 10 (the outer diameter size defined by outer peripheral surface 16), is D, the inner diameter of the inner edge side of second flat surface 15 that is in contact with lens surface 12 is _d1 , and the outer diameter of the outer edge side of second flat surface 15 that is in contact with step surface 17 is _d2 , it is preferable to satisfy the following condition (1).
(1) (0.7D+ _0.3d1 )< _d2 <D-0.2

By satisfying the lower limit of condition (1), a necessary and sufficient dimension can be ensured for the width of the second flat surface 15 in the radial direction of the glass molded lens 10, and the glass molded lens 10 can be positioned with high precision using the second flat surface 15. Furthermore, by satisfying the upper limit of condition (1), the width of the step surface 17 in the radial direction of the glass molded lens 10 is not too small, making it easier to ensure the shape precision of the step surface 17 and the marking 18.

Furthermore, the width ((D-d ₂ )/2) of step surface 17 in the radial direction of glass molded lens 10 is preferably 0.2 mm or more. When glass molded lens 10 is formed by press working using mold 30, the cross-sectional shape of the boundary between step surface 17 and outer circumferential surface 16 is, strictly speaking, not a right angle as shown in Figures 3 and 4, but a curved, rounded corner shape. Since it is difficult to control the shapes of step surface 17 and marking 18 with high precision at this rounded corner location, the minimum radial width at which step surface 17 can be effectively formed is approximately 0.2 mm, taking into account the range occupied by the rounded corner shape.

As shown in FIG. 5, the chord width w of the marking 18 is the dimension perpendicular to the radial direction of the glass molded lens 10 at the position where the marking 18 is provided. In the marking 18, the chord width w is the width connecting a pair of side walls 18a at the shortest distance.

It is preferable that the chord-direction width w of the marking 18 satisfies the following condition (2).
(2) w ≧ 0.05 mm

By satisfying condition (2), it is possible to obtain a marking 18 with excellent visibility. In addition, by satisfying condition (2), the width of the groove portion 46c of the upper die 33 for forming the marking 18 is not too small, and the workability when manufacturing the upper die 33 can be improved. Conversely, if the chord direction width w of the marking 18 falls below condition (2), problems arise in that the visibility of the marking 18 is reduced and the workability of the groove portion 46c in the upper die 33 becomes high.

It is preferable that the chord-direction width w of the marking 18 is not too large, even if condition (2) is satisfied. If the chord-direction width w is too large, the shape distortion caused by shrinkage of the marking 18 during cooling after pressing becomes significant, and this may affect the shape accuracy of the edge portion 13 and the lens surfaces 11 and 12 on the inner periphery thereof.

As shown in FIG. 5, the dimension of the marking 18 in a direction parallel to the radial direction of the glass molded lens 10 at the position where the marking 18 is provided is defined as the radial width L. In the marking 18, the width in the direction in which the pair of side walls 18a extend when viewed along the optical axis X1 is the radial width L. The radial width L represents the width in a direction perpendicular to the chord width w.

It is preferable that the radial width L of the marking 18 satisfies the following condition (3).
(3) L≧0.2 mm

By satisfying condition (3), a marking 18 with excellent visibility can be obtained. In addition, by satisfying condition (3), the length of the groove portion 46c of the upper die 33 for forming the marking 18 is not too small, and the workability when manufacturing the upper die 33 can be improved. Conversely, if the radial width L of the marking 18 falls below condition (3), the visibility of the marking 18 will be reduced.

The outer diameter end 18b of the marking 18 may be shaped to reach the outer peripheral surface 16 of the edge portion 13, or the outer diameter end 18b of the marking 18 may be shaped to be located on the inner diameter side of the outer peripheral surface 16.

5 shows a configuration example in which the outer diameter side end 18b of the marking 18 is located on the inner diameter side of the outer circumferential surface 16. That is, the radial width L of the marking 18 is smaller than the width ((D-d ₂ )/2) of the step surface 17 in the radial direction of the glass molded lens 10. In the case of this configuration example, it is guaranteed that the marking 18 does not protrude not only in the optical axis direction but also in the outer diameter direction at the edge portion 13. Therefore, it is possible to prevent the marking 18 from interfering with another member surrounding the outer circumferential surface 16 (for example, the inner circumferential surface of a lens frame or a lens barrel to which the glass molded lens 10 is attached) and to prevent the vicinity of the outer diameter side end 18b of the marking 18 from being damaged. Furthermore, when performing a centering process to adjust the shape of the outer circumferential surface 16 after the press molding of the glass molded lens 10, the centering process area is set so as not to reach the position of the marking 18, thereby preventing the marking 18 from cracking or chipping.

After the glass molded lens 10 is formed using the mold 30, a portion of the outer diameter side of the marking 18 is removed by grinding or other processing to obtain the marking 18 in the shape shown in FIG. 5. By arranging the step surface 17 and the marking 18 on the outermost periphery of the edge portion 13, it becomes easier to perform such post-processing after press molding.

Even in the case where the outer diameter side end 18b of the marking 18 is located on the inner diameter side of the outer circumferential surface 16 when the glass molded lens 10 is completed (the example configuration shown in FIG. 5), it is preferable that the groove 46c of the upper die 33 has a shape in which the outer diameter side end is not blocked and is connected to the outer circumferential surface of the insertion portion 39 (a shape that is longer in the radial direction of the press surface 44 than the radial width L shown in FIG. 5). Groove 46c that is connected to the outer circumferential surface of the insertion portion 39 has the advantage that it is easier to manufacture than a non-penetrating groove with a blocked outer diameter side end.

Unlike the configuration example of FIG. 5, the outer diameter side end 18b of the marking 18 may be shaped to reach the outer peripheral surface 16 of the edge portion 13. This configuration has the advantage that the final shape of the marking 18 can be completed at the stage where the glass molded lens 10 is molded by the molding die 30, and post-processing of the marking 18 can be omitted. However, the outer diameter side end 18b of the marking 18 is set so that it does not protrude outward beyond the outer peripheral surface 16 of the edge portion 13.

The shape of the marking 18 shown in FIG. 5 (approximately rectangular) is just one example, and the glass molded lens 10 can be provided with markings of various geometric shapes, without being limited to this. Modified examples of the marking shape are shown in FIG. 8.

Figure 8 (A) illustrates a marking 20 having a triangular outer edge shape. The marking 20 is a triangle that tapers from the inner diameter side that contacts the second flat surface 15 toward the outer circumferential surface 16 of the edge portion 13.

Figure 8 (B) illustrates a marking 21 with an arched outer edge shape. The marking 21 has a curved shape that tapers from the inner diameter side that contacts the second flat surface 15 toward the outer circumferential surface 16 of the edge portion 13.

Figure 8 (C) illustrates a marking 22 with an elliptical outer edge shape. The marking 22 has an elliptical shape with its major axis extending in the radial direction of the glass molded lens 10.

In this way, the shape of the marking can be appropriately selected from polygons such as rectangles and triangles, arcs, ellipses, etc. The markings of each modified example shown in Figure 8 are easy to finish by machining with a grinding wheel, and the markings can be manufactured efficiently.

The marking shapes are not limited to those shown in Figures 5 and 8, and markings of various geometric shapes can be used, such as polygons other than rectangles and triangles, circles, semicircles, etc.

The glass molded lens 10 in the above embodiment is a convex meniscus lens having a convex lens surface 11 and a concave lens surface 12, but the lens shape to which the present invention is applied is not limited to this and may be a biconvex lens, a biconcave lens, a plano-convex lens, a plano-concave lens, a concave meniscus lens, etc. In addition, the lens surface may be spherical or aspherical.

In the glass molded lens 10 of the above embodiment, the thickness t1 of the edge portion 13 at the second flat surface 15 and the thickness t2 of the edge portion 13 at the marking 18 satisfy the relationship t1>t2. That is, on the rear side of the glass molded lens 10, the marking 18 and the second flat surface 15 are not flush with each other (t1=t2), and the marking 18 is located slightly lower than the second flat surface 15 in the optical axis direction. Alternatively, the marking 18 and the second flat surface 15 can be set to be flush with each other (t1=t2). Therefore, the condition t1≧t2 may be satisfied. In the present invention, "not protruding in the optical axis direction" is a concept that includes the case where the marking 18 and the second flat surface 15 are flush with each other.

In the above embodiment, the glass molded lens 10 has a step surface 17 and markings 18 (20, 21, and 22) on the outermost periphery of the rear side having the concave lens surface 12, but instead, a similar structure including a step surface and markings may be provided on the outermost periphery of the front side having the convex lens surface 11. In addition, the step surface and markings on the outermost periphery may be provided on only one of the front and rear surfaces of the edge of the lens, or on both the front and rear surfaces of the edge.

In the above embodiment, the glass molded lens 10 has the marking 18 (20, 21, and 22) at only one location in the circumferential direction centered on the optical axis X1, but multiple markings may be provided. Furthermore, when multiple markings are provided, the shapes of the markings may be different. Furthermore, when multiple markings are provided, the spacing between the markings in the circumferential direction may be different.

In the glass molded lens 10 of the above embodiment, the step surface 17 is a flat surface parallel to the second flat surface 15, but the step surface is not limited to a surface parallel to the flat surface at the edge. However, if the step surface includes a shape that changes sharply with respect to the flat surface, there is a risk that the shape precision and strength of the outermost peripheral portion of the edge including the step surface will be impaired, so it is desirable to align the formation direction and surface shape of the step surface and the flat surface as much as possible.

The embodiments of the present invention are not limited to the above-described embodiments or their variations, 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 advances or other derived technologies, it may be implemented using that method. Therefore, the claims cover all embodiments that may fall within the scope of the technical idea of the present invention.

10: Glass molded lens (lens)
11: Lens surface 12: Lens surface 13: Edge portion 14: First flat surface 15: Second flat surface (flat surface)
16: Outer circumferential surface 17: Step surface 18: Marking 18a: Side wall 18b: Outer diameter side end portion 20: Marking 21: Marking 22: Marking 30: Forming mold 31: Body mold 32: Lower mold 33: Upper mold (mold member)
41: Pressed surface 42: Lens forming surface 43: Edge forming surface 44: Pressed surface 45: Lens forming surface 46: Edge forming surface 46a: Flat annular portion 46b: Step annular portion 46c: Groove portion PF: Glass preform X1: Optical axis X2: Central axis of the mold

Claims (8)

A lens which is a press-molded product of glass and has lens surfaces on both sides in the optical axis direction and an annular edge portion provided on the outer periphery of the lens surfaces,
The edge portion is
a flat surface that is provided in an annular shape around the lens surface on the outer periphery side of at least one of the lens surfaces on both sides and is substantially perpendicular to the optical axis;
a step surface that is provided in an annular shape around the flat surface at the outermost periphery of the edge portion and is recessed in the optical axis direction with respect to the flat surface;
a marking provided in the same radial region as the step surface, protruding in the optical axis direction relative to the step surface and not protruding in the optical axis direction relative to the flat surface;
A lens comprising: The lens according to claim 1, characterized in that the thickness t1 of the edge portion in the optical axis direction at the flat surface, the thickness t2 of the edge portion in the optical axis direction at the marking, and the thickness t3 of the edge portion in the optical axis direction at the stepped surface satisfy the relationship t1>t2>t3. 3. The lens according to claim 1, wherein the lens diameter of the lens is D, the inner diameter of the flat surface in contact with the lens surface is _d1 , and the outer diameter of the flat surface in contact with the step surface is _d2 , the lens satisfies the following condition (1):
(1) (0.7D+ _0.3d1 )< _d2 <D-0.2 The lens according to claim 1 or 2, characterized in that a chord-direction width w of the marking perpendicular to a radial direction of the lens at a position where the marking is provided satisfies the following condition (2).
(2) w ≧ 0.05 mm The lens according to claim 1 or 2, characterized in that a radial width L of the marking parallel to a radial direction of the lens at a position where the marking is provided satisfies the following condition (3):
(3) L≧0.2 mm The lens according to claim 1 or 2, characterized in that the step surface is a surface parallel to the flat surface. The lens of claim 1 or 2, characterized in that the marking is polygonal, arcuate, or elliptical when viewed along the optical axis. A method for producing the lens according to claim 1 or 2, comprising the steps of:
a lens forming surface for forming the lens surface;
a flat annular portion located on an outer circumferential side of the lens forming surface and forming the flat surface;
a stepped annular portion located on an outer circumferential side of the flat annular portion and forming the stepped surface;
A groove portion that is recessed in the press direction relative to the stepped annular portion and is used to form the marking;
Using a mold member having a pressing surface,
A method for manufacturing a lens, comprising pressing a glass preform with the mold member to mold the lens having the shape of the pressed surface transferred thereto.

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