JP2013035713A - Method for predicting molding difficulty of aspheric glass molded lens, and method for designing lens system including the aspheric glass molded lens - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a method for predicting molding difficulty which predicts the molding difficulty of an aspheric MO lens (glass molded lens) for which the key is not present so far, and becomes the key to request the change of the design shape itself of the aspheric MO lens.SOLUTION: In the method for predicting the molding difficulty of an aspheric glass molded lens in which at least one of the R1 surface and R2 surface is a rotationally symmetric aspheric surface represented by an aspheric surface expression, inclinations of the R1 surface and R2 surface are calculated respectively by differentiating once the aspheric surface expressions of the R1 surface and R2 surface, and on the basis of an expression of an inclination ratio obtained by dividing any one of the inclination of the R1 surface and the inclination of the R2 surface by the other, the molding difficulty is determined.

Description

  The present invention relates to a method for predicting the molding difficulty when molding an aspheric glass lens and a design method for a lens system including an aspheric glass mold lens.

  Conventionally, the moldability of a glass mold lens (hereinafter referred to as an MO lens) has been determined by an empirical method such as glass material, center thickness, lens diameter, presence / absence of lands, meniscus shape, and the like. For example, in the case of a convex meniscus lens having the same center thickness with the same glass material, it has been said that a better surface shape can be obtained with a smaller lens diameter.

Japanese Examined Patent Publication No. 61-32263

  However, in the field of press molding, a reality is that aspherical MO lenses with extremely low yields that do not fit the rule of thumb frequently occur. The manufacturing process of the aspherical MO lens is the shape specification of the aspherical lens (n (glass material) determined by the orderer (for example, camera (lens) manufacturer) to the contractor (for example, mold manufacturer) based on the lens design). ), R (radius of curvature), d (thickness) and rotationally symmetric aspherical shape data, rnd-aspherical surface data), and the contractor has the shape of the aspherical MO faithful to the shape specification. It has a relationship of molding a lens. The same applies when the contractor is a division of a camera manufacturer. In such a relationship, even if the aspherical MO lens that has been ordered is inferior in moldability and yield is poor, the side of the contractor who molds the molded lens using various press machines cannot (or hardly) cope with it. . In other words, even if the shape is difficult to shape (low yield), the contractor does not request the orderer to change the aspherical shape, and there is no basis for the change request. Met. As a result, it is difficult for a lens system including an aspherical MO lens that is difficult to be molded to obtain stable and high optical performance. According to the present inventors, the biggest problem is that, conventionally, there is no clue as to what causes the molding quality of the aspherical MO lens, and it has been determined only by an empirical method. is there.

  An object of the present invention is to predict a molding difficulty level of an aspherical MO lens, which has not had a clue in the past, and to obtain a molding difficulty level prediction method that is a key to request a change in the design shape of the aspherical MO lens itself. And Furthermore, the present invention warns the difficulty of molding and prompts a change in the design itself when the design result includes an aspherical MO lens that is difficult to mold in the design of a lens system including an aspherical lens. The purpose is to obtain a design method (program) that can be used.

  The present inventors have found that deformation stress applied to glass at the time of molding is affected by the surface shape, that the deformation stress can be classified into agglomeration / divergence, and molding is easy if the deformation stress is agglomerated. On the other hand, with the assumption that it is difficult to form by diverging, and therefore it is possible to predict the difficulty of forming an aspherical shape if the aggregation and divergence of deformation stress can be predicted, the rotationally symmetric aspherical shape can be predicted. The present invention was completed by trying to predict the molding difficulty of the surface shape from the aspherical surface as an index.

The present invention provides a method for predicting the molding difficulty of an aspheric glass mold lens in which at least one of the R1 surface and the R2 surface is a rotationally symmetric aspheric surface expressed by the following aspherical expression (1): Inputting lens data including the rotationally symmetric aspheric data of the R2 surface; calculating the slopes of the R1 surface and the R2 surface by differentiating the aspherical expression (1) of the R1 surface and the R2 surface once. And dividing one of the inclination of the R1 surface and the inclination of the R2 surface by the other to obtain an equation of an inclination ratio that is an index of the molding difficulty.

  In the method for predicting the molding difficulty of the aspherical glass mold lens of the present invention, the equation of the slope ratio between the R1 surface and the R2 surface is further differentiated once or more, and the differential equation is used as an index of the molding difficulty. it can.

  More specifically, the inflection point is used as an index of the inflection point whether or not an inflection point is included in an inclination ratio between the R1 surface and the R2 surface, or an expression obtained by further differentiating the expression of the inclination ratio at least once. When there is a point, it can be predicted that molding is difficult, and when there is no inflection point, molding is easy.

In the aspect of the design method of a lens system including an aspheric glass mold lens in which at least one of the R1 surface and the R2 surface is a rotationally symmetric aspheric surface expressed by the following aspherical expression (1), Inputting lens data including the rotationally symmetric aspheric surface data for the R1 surface and the R2 surface; and by differentiating the aspherical expression (1) of the R1 surface and the R2 surface once, the inclinations of the R1 surface and the R2 surface are respectively determined. A step of calculating; a step of dividing one of the inclination of the R1 surface and the inclination of the R2 surface by the other to obtain an equation of the inclination ratio; and the equation of the inclination ratio of the molding difficulty of the aspheric glass mold lens. It is characterized by including a stage as an index.

  In the design method of the lens system including the aspheric glass mold lens of the present invention, the expression of the slope ratio between the R1 surface and the R2 surface can be further differentiated once or more, and the differential expression can be used as an index of the molding difficulty.

  At the stage of determining the molding difficulty level, the R1 plane and R2 plane slope ratio, or the formula of the same slope ratio further differentiated one or more times is used as an index of the molding difficulty level. When there is an inflection point, it can be predicted that molding is difficult, and when there is no inflection point, molding is easy.

  A step of giving a warning when it is determined that molding is difficult in the step of determining the molding difficulty can be further included.

  In the design method of the lens system including the aspheric glass mold lens according to the present invention, the slope ratio of the R1 surface and the R2 surface, or the formula of the slope ratio is further changed to a formula obtained by differentiating at least once at the stage of determining the molding difficulty. When the inflection point is included, the aspherical data is redesigned, and as long as there is a redesigned solution, the slope ratio of the R1 and R2 planes, or the formula of the slope ratio is further differentiated one or more times. The design can continue until there are no inflection points in the equation.

  If there is no redesign solution even after redesigning the aspherical data, any one of the production of a null lens, the use of a multi-stage press, the application of a side contact sleeve to a press die, and the modified polishing of a molded lens 1 The adoption of the above method can be determined.

  According to the present invention, the molding difficulty level of an aspherical MO lens can be easily predicted from lens data including a rotationally symmetric aspherical expression. For this reason, the prediction of the difficulty of molding can be fed back to the lens design department to promote the change of the aspherical shape, and the aspherical MO lens that can be easily molded can be replaced. Also, at the lens design stage, warn of the difficulty of molding an aspherical MO lens, or continue redesigning as long as there is a redesigned solution in the aspherical form, without waiting for feedback from the molding site. Therefore, it is possible to design an aspherical MO lens (including) lens system that is easy to achieve, and as a result, a stable and high-performance lens system can be obtained at low cost.

It is image sectional drawing when pressing a glass sphere with an upper and lower shaping | molding die, and shape | molding into a biconvex lens with an edge. (A) (B) is a graph which shows the coordinate system of the design state of a lens shape, and a press state. It is a graph which shows the example of inclination distribution of the entrance plane (R1 surface) and exit surface (R2 surface) of a lens. It is the figure which classified the distribution shape and moldability of inclination ratio dR1 _/ 2 of the R1 surface and R2 surface of a lens. (A) and (B) are sectional views showing examples of lens shapes of the sample lens 1 and the sample lens 2. It is a comparison figure which shows the distribution shape of the inclination ratio dR1 _/ 2 of the sample lens 1 and the sample lens 2, prediction of moldability, and the actual molding result of the R1 surface. It is a comparison figure which shows the distribution shape of the inclination ratio dR1 _{/ 2} of the sample lens 1 and the sample lens 3, a moldability prediction, and the actual molding result of the R1 surface. It is a graph which shows the example of a shape of d'R1 _{/ 2} which further differentiated the formula of inclination ratio dR1 _{/ 2} . It is a graph which shows the example of another d'R1 _{/ 2} shape. The distribution shape of d′ R _1/2 obtained by differentiating the slope ratio dR _1/2 between the R1 surface and the R2 surface of the sample lens 4, the sample lens 5, and the sample lens 6, the moldability prediction, and the actual molding result of the R1 surface FIG. It is a comparison figure which shows the specific Example about the double convex MO lens of a double-sided aspherical surface. It is a comparison figure which shows the specific Example about the double concave MO lens of a double-sided aspherical surface. It is a comparison figure which shows the specific Example about the double-sided aspherical convex meniscus MO lens. It is a comparison figure which shows the specific Example about the concave meniscus MO lens of a double-sided aspherical surface. It is a comparison figure which shows the specific Example about a single-sided aspherical biconvex MO lens. It is a comparison figure which shows the specific Example about a single-sided aspherical biconcave MO lens. It is a comparison figure which shows the specific Example about a single-sided aspherical convex meniscus MO lens. It is a comparison figure which shows the specific Example about the concave meniscus MO lens of a single-sided aspherical surface. 3 is a flowchart illustrating an embodiment of a lens system design method according to the present invention.

  FIG. 1 is an image view when a glass sphere G is pressed with upper and lower molding dies M1 and M2 to form a biconvex lens with a flange. When a deformation stress is applied to the glass sphere G with the molds M1 and M2, the glass moves in the lateral direction (radial direction). At this time, if the space (cylindrical shape, rectangular tube shape) side portion between the molds M1 and M2 is open, the stress is dissipated, so that it does not become a biconvex lens with an edge (upper right in FIG. 1). On the other hand, if there is a cylindrical body W in the space between the molds M1 and M2, the deformation stress generated in the glass is confined in the space between the body mold W and the molds M1 and M2. It becomes a biconvex lens (lower right of FIG. 1). This embodiment proposes a rotationally symmetric aspheric shape index of an aspheric MO lens in which deformation stress is confined as shown in the lower right of FIG.

(1)式で、R,K,a,b,c,d・・・は定数であり、y,xはそれぞれレンズの半径、変位量である。
また、任意の点y_iに於けるxの値をx_iとすると、（１）式は下記（１'）式に変形される。

さらにy_iに対し、微小δ分異なる点をy_i+δ とすると、（１'）は下記（１"）式になる。

The method of predicting the molding difficulty level of an aspheric MO lens according to the present embodiment is such that the target MO lens is rotationally symmetric represented by the following formula (1) on at least one surface (at least one of the R1 surface and the R2 surface). It is assumed that it has an aspherical surface.

In Equation (1), R, K, a, b, c, d,... Are constants, and y, x are the lens radius and displacement, respectively.
If the value of x at an arbitrary point y _i is x _i , the equation (1) is transformed into the following equation (1 ′).

Further, if y _{i +} δ is a point different from y _i by minute δ, (1 ′) becomes the following equation (1 ″).

  In the present embodiment, it is assumed that aspherical data of an aspherical MO lens to be molded is received and input. The data is provided from the orderer (lens manufacturer) to the contractor (mold manufacturer), and the data is sent to the lens design program / device.

  FIG. 2A is a coordinate system showing the above lens shape. Here, in the press molding of the convex (meniscus) lens, the convex surface is molded by the lower mold, so that FIG. 2A is rewritten as shown in FIG.

従って、Ｒ１面（第１面、入射面）の傾き分布dR₁と、Ｒ２面（第２面、出射面）の傾き分布dR₂は、次の（２’）式及び（２"）式で示される。

これらの傾き分布dR₁とdR₂をy、即ち凸メニスカスレンズの半径に対してプロットした例が図３である。 From FIG. 2B, the inclination distribution dR of the lens shape is given by the following equation (2) after differentiating the equation (1 ") once.

Thus, R1 surface (first surface, the incident surface) and tilt distribution dR ₁ of, R2 surface (second surface, exit surface) gradient distribution dR ₂ of the following (2 ') and (2') below in Indicated.

FIG. 3 shows an example in which these inclination distributions dR ₁ and dR ₂ are plotted against y, that is, the radius of the convex meniscus lens.

（３）式において、y_i及びδをＲ１面、Ｒ２面で同じ値を用いれば、（３）式は（４）式となる。

In the present embodiment, in order to predict the difficulty in forming an aspherical MO lens, an inclination ratio dR _{1/2 obtained} by normalizing the inclination of the R1 surface with the inclination of the R2 surface is used. That is, the slope ratio dR _1/2 is defined by the following equation (3) obtained by dividing the equation (2 ′) by the equation (2 ″).

In equation (3), if y _i and δ are the same values on the R1 and R2 surfaces, equation (3) becomes equation (4).

Since the slope ratio dR _1/2 obtained by the equation (4) is a value obtained by normalizing the slope of the R1 plane by the slope of the R2 plane, it becomes an index of the agglomeration / divergence of deformation stress or holding stress generated during press molding. I understand that. That is, for y _i, the slope ratio dR _1/2 of the outer diameter direction micro [delta] min different y _{i +} [delta] has the following relation between the deformation stress or coercive stress, the shape of the resulting surface R1 It is expected to affect stability (moldability, moldability).
a) The slope ratio dR _1/2 increases monotonously = The slope of the R1 surface increases relatively toward the outer circumference = Aggregation of stress → The shape of the R1 surface tends to be stable
b) The slope ratio dR _1/2 decreases monotonously = the slope of the R1 surface becomes relatively smaller toward the outer periphery = stress divergence → R1 surface shape tends to be unstable
c) Inclination ratio dR _1/2 has an inflection point = Stress inflection / divergence inflection point → R1 surface shape tends to be unstable. Thus, even with the same convex meniscus lens, the inclination ratio dR _{1 If / 2} is an aspherical shape that monotonously increases, a stable lens shape can be obtained, and if it has a monotonous decrease and an inflection point, the lens shape is predicted to be unstable. FIG. 4 is a list of the above relationships.

FIG. 5 shows an example of the cross-sectional shape of the convex meniscus lens of Sample 1 and Sample 2, and FIG. 6 shows the distribution shape of the slope ratio dR _1/2 of Sample 1 and Sample 2, prediction of formability, and actual molding. An example of the result is shown. Sample 1 in which the slope ratio dR _1/2 monotonously increases the actual molding result of the R1 surface, while sample 2 with an inflection point in the slope ratio dR _1/2 actually shows the R1 surface. It was confirmed that the molding result was unstable and the quality was low. In FIG. 6 (and similar figures below), the molding result is a graph in which a large number of sample lenses are molded with the same mold and the shape is examined, and is a graph of the actual molding result. In the case where the variation is small, the molding stability is good (the lens shape quality is high), and in the case where the variation is large, the molding stability is poor (the lens shape quality is poor).

Next, FIG. 7 shows the shape of the slope ratio dR _1/2 by replacing the shape of the R2 surface in the sample 2 of FIG. 6 with the R2 surface shape of the sample 1 without changing the shape of the R1 surface. For the sample 3 changed to monotonously increase, an example of the shape of each slope ratio dR _1/2 , formability prediction, and actual molding result is shown. Although the molding result of the R1 surface is a problem, it has been confirmed that the moldability is improved by changing the shape of the R2 surface (changing the shape of dR1 _{/ 2} ). That is, the R2 surface shape is closely related to the moldability of the R1 surface.

As described above, the slope ratio dR _{1 /} which is a ratio of the expression obtained by differentiating the rotationally symmetric aspheric expression of the R1 surface of the aspherical MO lens once and the expression obtained by differentiating the rotationally symmetric aspheric expression of the R2 surface once. Examination of the shape of ₂ revealed that formability can be judged. On the other hand, it has also been found that there are cases where the distribution shape of the slope ratio dR _1/2 is complicated, and there is a case where sufficient formability cannot be judged only by the shape of the slope ratio dR _1/2 . FIG. 8 shows a shape example of such a slope ratio dR _1/2 .

In such a case, the slope ratio dR _1/2 in the above equation (4) is further differentiated (the equation (1 ") is differentiated twice) to obtain d'R _1/2 in the following equation (5). The moldability can be predicted by determining the shape of the lever.

FIG. 9 shows an example of the shape of d′ R _{1/2 obtained} by redifferentiating the equation of the slope ratio dR _1/2 of FIG. This d′ R _1/2 was expected to have a clear inflection point and low molding stability, and as expected when actually molded.

FIG. 10 shows an example of the shape of d′ R _1/2 , the moldability prediction, and the actual molding result. Sample 5 in which d′ R _1/2 monotonously increases (same as the previous sample 1) has a good actual molding result on the R1 surface, whereas sample 4 having an inflection point on dR _1/2 In Sample 6 (same as Sample 2 above) and Sample 6, it was confirmed that the actual molding result of the R1 surface was unstable and the yield was poor.

  It has been confirmed that the above discussion using the aspherical convex meniscus MO lens as an example holds true regardless of biconvex, biconcave, convex meniscus, or concave meniscus. This is true not only for double-sided aspherical MO lenses but also for single-sided aspherical MO lenses. Furthermore, it does not depend on the type of press machine, whether it is glass material, center thickness, lens diameter, presence / absence of lands, presence / absence of coating, or material.

Hereinafter, for a double-sided aspherical surface and a single-sided aspherical MO lens including a specific aspherical shape formula, an example of lens cross section, dR1 _{/ 2} shape, d'R1 _{/ 2} shape, and moldability prediction will be described. . 11 to 18, “E ± a” means “× 10 ± ^a ”.

FIGS. 11, 12, 13, and 14 are specific examples of a double-sided aspherical MO lens that is a biconvex lens, a biconcave lens, a convex meniscus lens, and a concave meniscus lens.
FIG. 11 shows aspherical data of three double-sided aspherical biconvex MO lenses. Each parameter (R, k, a, b, c, d) of the aspheric surface on the R1 surface is set to the same value, and each parameter (R, k, a, b, c, d) of the aspheric surface on the R2 surface is shown in FIG. Designed as shown in
In FIG. 11, the example on the left side has no inflection points in both dR _1/2 and d′ R _1/2 , and is an example that is predicted to be easily molded in the first and second derivatives. In addition, in the figure, the middle example was predicted to be easy to form without an inflection point at dR _1/2 , and the inflection point was confirmed for the first time at d'R _1/2 , and it was predicted to be difficult to form. This is an example. In addition, in the example on the right side, the inflection point was confirmed at dR _1/2 , so it was predicted that molding was difficult, but d'R _1/2 was also evaluated and the inflection point was confirmed. It is.

FIG. 12 shows aspherical data of three double-sided aspherical biconcave MO lenses. Each parameter (R, k, a, b, c, d) of the aspheric surface on the R1 surface is set to the same value, and each parameter (R, k, a, b, c, d) of the aspheric surface on the R2 surface is shown in FIG. Designed as shown in
In FIG. 12, the example on the left side has no inflection points in both dR _1/2 and d′ R _1/2 , and is an example that is predicted to be easily molded in the first and second derivatives. In addition, in the figure, the middle example was predicted to be easy to form without an inflection point at dR _1/2 , and the inflection point was confirmed for the first time at d'R _1/2 , and it was predicted to be difficult to form. This is an example. In addition, in the example on the right side, the inflection point was confirmed at dR _1/2 , so it was predicted that molding was difficult, but d'R _1/2 was also evaluated and the inflection point was confirmed. It is.

FIG. 13 shows aspherical data of three double-sided aspherical convex meniscus MO lenses. Each parameter (R, k, a, b, c, d) of the aspheric surface on the R1 surface is set to the same value, and each parameter (R, k, a, b, c, d) of the aspheric surface on the R2 surface is shown in FIG. Designed as shown in
In FIG. 13, the example on the left side has no inflection points in both dR _1/2 and d′ R _1/2 , and is an example that is predicted to be easily molded in the first and second derivatives. In addition, in the figure, the middle example was predicted to be easy to form without an inflection point at dR _1/2 , and the inflection point was confirmed for the first time at d'R _1/2 , and it was predicted to be difficult to form. This is an example. In addition, in the example on the right side, the inflection point was confirmed at dR _1/2 , so it was predicted that molding was difficult, but d'R _1/2 was also evaluated and the inflection point was confirmed. It is.

FIG. 14 shows aspheric data of three double-sided aspheric concave meniscus MO lenses. Each parameter (R, k, a, b, c, d) of the aspheric surface on the R1 surface is set to the same value, and each parameter (R, k, a, b, c, d) of the aspheric surface on the R2 surface is shown in FIG. Designed as shown in
In FIG. 14, the example on the left side has no inflection points in both dR _1/2 and d′ R _1/2 , and is an example that is predicted to be easily molded in the first and second derivatives. In addition, in the figure, the middle example was predicted to be easy to form without an inflection point at dR _1/2 , and the inflection point was confirmed for the first time at d'R _1/2 , and it was predicted to be difficult to form. This is an example. In addition, in the example on the right side, the inflection point was confirmed at dR _1/2 , so it was predicted that molding was difficult, but d'R _1/2 was also evaluated and the inflection point was confirmed. It is.

FIGS. 15, 16, 17 and 18 are specific examples of single-sided aspherical MO lenses, which are biconvex lenses, biconcave lenses, convex meniscus lenses and concave meniscus lenses.
FIG. 15 shows aspherical data of three single-sided aspherical biconvex MO lenses. The R2 surface is formed into a spherical surface having a certain curvature, and the parameters (R, k, a, b, c, d) of the aspheric surface on the R1 surface are designed as shown in FIG.
In FIG. 15, the example on the left side has no inflection points in both dR _1/2 and d′ R _1/2 , and is an example that is predicted to be easy to form in the first and second derivatives. Further, in FIG. 15, the middle example was predicted to have no inflection point at dR _1/2 and easy to form, and the inflection point was confirmed for the first time at d'R _1/2 and predicted to be difficult to form. This is an example. In addition, in the example on the right side in FIG. 15, since the inflection point was confirmed at dR _1/2 , it was predicted that molding was difficult, but d'R _1/2 was also evaluated and the inflection point was confirmed. It is.

FIG. 16 shows aspherical data of three single-sided aspherical biconcave MO lenses. The R2 surface is formed into a spherical surface having a certain curvature, and the parameters (R, k, a, b, c, d) of the aspheric surface on the R1 surface are designed as shown in FIG.
In FIG. 16, the example on the left side has no inflection points in both dR _1/2 and d′ R _1/2 , and is an example that is predicted to be easily molded in the first and second derivatives. Further, in FIG. 16, the middle example was predicted to be easy to form without an inflection point at dR _1/2 , and the inflection point was confirmed for the first time at d'R _1/2 , and it was predicted to be difficult to form. This is an example. Further, in the example on the right side in FIG. 16, the inflection point was confirmed at dR _1/2 , and thus it was predicted that molding was difficult, but d'R _1/2 was also evaluated and the inflection point was confirmed. It is.

FIG. 17 shows aspherical data of three single-sided aspherical convex meniscus MO lenses. The R2 surface is formed into a spherical surface having a certain curvature, and the parameters (R, k, a, b, c, d) of the aspheric surface on the R1 surface are designed as shown in FIG.
In FIG. 17, the example on the left side has no inflection points in both dR _1/2 and d′ R _1/2 , and is an example that is predicted to be easy to form in the first and second derivatives. In FIG. 17, in the middle example, it was predicted that there was no inflection point at dR _{1/2 and} that molding was easy, and the inflection point was confirmed for the first time at d'R _1/2 , and it was predicted that molding was difficult. This is an example. In addition, in the example on the right side in FIG. 17, since the inflection point was confirmed at dR _1/2 , it was predicted that molding was difficult, but d'R _1/2 was also evaluated and the inflection point was confirmed. It is.

FIG. 18 shows aspheric data of three single-sided aspheric concave meniscus MO lenses. The R2 surface is formed into a spherical surface having a certain curvature, and the aspherical parameters (R, k, a, b, c, d) on the R1 surface are designed as shown in FIG.
In FIG. 18, the example on the left side has no inflection points in both dR _1/2 and d′ R _1/2 , and is an example that is predicted to be easily molded in the first and second derivatives. Further, in FIG. 18, the middle example was predicted to be easy to form without an inflection point at dR _1/2 , and the inflection point was confirmed for the first time at d′ R _1/2 , and it was predicted to be difficult to form. This is an example. In addition, in the example on the right side in FIG. 18, since the inflection point was confirmed at dR _1/2 , it was predicted that molding was difficult. However, d'R _1/2 was also evaluated and the inflection point was confirmed. It is.

In the embodiments of FIGS. 11 to 18, “whether there is an inflection point” is the only criterion for both dR _1/2 and d′ R _1/2 . From these examples, it is possible to formability of primary judgment alone whether there is an inflection point dR _1/2, to d'R _1/2 be whether there is an inflection point In addition, more accurate moldability can be predicted by using the judgment material. In particular, it was confirmed that the presence or absence of an inflection point in the two-derivative equation has universality that can determine whether the moldability is good or bad regardless of the lens shape. Furthermore, if the presence or absence of an inflection point is not clear in the two-fold differential equation, the presence or absence of an inflection point in the three or more differential equations may be examined.

  According to the method of predicting the molding difficulty level according to the present embodiment, based on the prediction result (prediction result that molding is difficult), the basis of the request from the manufacturing site to the design department to change the aspherical shape. In addition to making proposals, the quality assurance department can contribute to the examination of molded lens sorting methods and advance arrangements for null lenses, etc., and the sales department can contribute to sales price negotiations in view of low yield and sorting costs. it can. As a result, production with high yield, delivery at an appropriate price, and production without confusion or delay in delivery are possible.

It is also possible to incorporate the molding difficulty prediction method according to the present invention into the lens design program. In lens design generally performed by an automatic design program, the designer inputs the focal length, the number of lenses, the allowable aberration, whether or not an aspheric surface can be introduced, the number of locations, etc. before starting the automatic design. As a result of the automatic design, the slope ratio dR _1/2 and d'R _1/2 are calculated using the aspheric data on the front and back of the resulting aspheric MO lens, and the molding difficulty is predicted and displayed. For example, a warning that there is a difficulty in formability can be issued to the designer, and the designer can change the design based on the warning. Alternatively, undesired slope ratios dR _1/2 and d'R _1/2 do not occur in the automatic design program (so that the preferred slope ratios dR _1/2 and d'R _1/2 are combined). A subroutine for determining the aspheric shape can also be included.

FIG. 19 is a flowchart showing an example of a lens design method according to the present invention.
First, in the course of designing the lens system, lens data including rotationally symmetric aspheric data of the R1 and R2 surfaces is input (step S11).
Next, the slope of the R1 surface and the R2 surface is calculated by differentiating the input aspheric data of the R1 surface and the R2 surface once, and either one of the slope of the R1 surface or the slope of the R2 surface is divided by the other. Then, an equation dR _{1/2 of the} slope ratio is obtained (step S12).
Next, the slope ratio formula dR _1/2 obtained in step S12 is further differentiated once to obtain a slope formula d′ R _1/2 (step S13).
When there is no inflection point in either the slope ratio equation dR _1/2 obtained in step S12 or the slope equation d′ R _1/2 obtained in step S13 (step S14: NO, step S15: NO) Then, it is determined that the molding difficulty level of the aspherical lens is low (easy molding) (step S16), and the process is terminated.
On the other hand, if there is an inflection point in either the slope ratio formula dR _1/2 obtained in step S12 or the slope formula d′ R _1/2 obtained in step S13 (step S14: YES, step S15: YES), a warning that the degree of difficulty in molding the aspherical lens is high is issued (step S17), and the aspherical data is redesigned (step S18).
If there is a design solution in the aspheric data redesigned in step S18 (step S19: YES), the aspheric data already input is replaced with the redesigned aspheric data, and the processing from step S12 to step S19 is performed. repeat. In other words, as long as there is a design solution in the redesigned aspheric data (step S19: YES), until aspheric data without inflection points in the slope ratios dR _1/2 and d′ R _1/2 is obtained (step S19). S14: NO, step S15: NO), the lens system of the lens system including the aspherical lens having a low molding difficulty (easily molded) is repeated.
If there is no design solution in the aspherical data redesigned in step S18 (no design solution having no inflection points in the slope ratios dR _1/2 and d′ R _1/2 ) (step S19: NO), the null lens One or more of the following methods are determined (step S20), and the process is terminated.

In the above embodiment, the slope ratio dR _1/2 obtained by dividing the slope of the R1 plane by the slope of the R2 plane is used. Can be judged. Moreover, in each Example of FIGS. 11-14, although the value of R1 surface was unified about three Examples and the example which changed the value of R2 surface was shown, it is not limited to this. Further, in the above-described embodiment, an example in which dR _1/2 is increased and it is predicted that molding is easy, but is not limited thereto, and the present invention can be applied even when it is decreased.

  In the above embodiment, the rotationally symmetric aspheric surface data is provided from the lens maker to the mold maker, but may be provided from the camera manufacturer's design department to the manufacturing department. In addition, the provision of data includes the case where aspherical data moves within the lens design program / device.

The glass material used to mold the glass lens described in the above embodiment is prepared by mixing glass raw materials at a predetermined ratio, obtaining a melting, homogenous, clarification process, and supplying molten glass to a mold. By cooling and cooling, the molten glass supplied on the mold is molded into a predetermined shape (spherical preform, flat gob, approximate shape preform approximated to the shape of the aspheric lens to be obtained), and a glass material Got.
Then, a glass material was precision press-molded with a press mold having a precision-molded molding surface, whereby the surface shape of the molding surface was transferred to the molding material to produce a lens. At this time, precision press molding is performed by heating the glass material to a temperature exhibiting a viscosity of about 10 ⁶ to 10 ¹² dPa · s, cooling to a temperature exhibiting a viscosity of 10 ¹² dPa · s or more, and then precision press molding. The product was removed from the press mold.

Claims (10)

A method for predicting the molding difficulty of an aspheric glass mold lens in which at least one of the R1 surface and the R2 surface is a rotationally symmetric aspheric surface expressed by the following aspheric expression (1):
Inputting lens data including the rotationally symmetric aspheric data of the R1 and R2 surfaces;
Calculating the slopes of the R1 and R2 surfaces by differentiating the aspherical expression (1) of the R1 and R2 surfaces once;
Dividing either one of the inclination of the R1 surface and the inclination of the R2 surface by the other to obtain an expression of an inclination ratio that is an index of molding difficulty;
A method for predicting the difficulty of molding an aspheric glass mold lens, comprising:

2. The method for predicting the difficulty of molding an aspheric glass mold lens according to claim 1, wherein whether or not an inflection point is included in the equation of the inclination ratio of the R1 surface and the R2 surface is an index of the difficulty of molding. A method for predicting the degree of difficulty of molding an aspheric glass mold lens that predicts that molding is difficult when there is a point and that molding is easy when there is no inflection point. 2. The method for predicting the molding difficulty level of an aspheric glass mold lens according to claim 1, further comprising differentiating the formula of the slope ratio between the R1 surface and the R2 surface one or more times, and using the differential formula as an index of the molding difficulty level. A method for predicting the difficulty of molding an aspheric glass mold lens. 4. The method of predicting the difficulty of molding an aspheric glass mold lens according to claim 3, wherein it is difficult to mold whether or not an inflection point is included in an expression obtained by further differentiating the expression of the slope ratio of the R1 surface and the R2 surface at least once. A method of predicting the degree of difficulty of molding an aspheric glass mold lens, which uses the degree of degree as an index, and predicts that molding is difficult when there is an inflection point and molding is easy when there is no inflection point. A design method of a lens system including an aspheric glass mold lens in which at least one of the R1 surface and the R2 surface is a rotationally symmetric aspheric surface expressed by the following aspheric expression (1):
Inputting lens data including the rotationally symmetric aspheric surface data of the R1 and R2 surfaces in the middle of the design;
Calculating the slopes of the R1 and R2 surfaces by differentiating the aspherical expression (1) of the R1 and R2 surfaces once;
Dividing one of the inclination of the R1 surface and the inclination of the R2 surface by the other to obtain an equation of the inclination ratio;
Using the slope ratio equation as an index of the difficulty of molding the aspheric glass mold lens;
A design method for a lens system including an aspheric glass mold lens.

6. The method of designing a lens system including an aspherical glass mold lens according to claim 5, wherein whether or not an inflection point is included in the equation of the inclination ratio between the R1 surface and the R2 surface is used as an index of the molding difficulty. A lens system design method including an aspheric glass mold lens that predicts that molding is difficult when there is a bending point and molding is easy when there is no inflection point. 6. The method of designing a lens system including an aspheric glass mold lens according to claim 5, further comprising differentiating the slope ratio equation of the R1 surface and the R2 surface one or more times, and using the differential equation as an index of molding difficulty. A method for designing a lens system including an aspheric glass mold lens that predicts that molding is difficult when there is an inflection point and molding is easy when there is no inflection point. The method for designing a lens system including an aspherical glass mold lens according to any one of claims 5 to 7, further comprising a step of giving a warning when it is determined that molding is difficult in the step of determining the molding difficulty. A lens system design method including an aspheric glass mold lens. 9. A method of designing a lens system including an aspheric glass mold lens according to claim 5, wherein an inclination ratio of the R1 surface and the R2 surface or an equation of the inclination ratio is determined at the stage of determining the molding difficulty level. If the inflection point is included in the expression that is further differentiated one or more times, the slope ratio of the R1 surface and the R2 surface, or the same slope, as long as there is a redesign solution by redesigning the aspheric data A design method for a lens system including an aspherical glass mold lens in which the design is continued until the inflection point is eliminated by further differentiating the ratio formula once more. 10. The method of designing a lens system including an aspheric glass mold lens according to claim 9, wherein if there is no redesign solution even if the aspheric data is redesigned, a null lens is produced, a multistage press is employed, a press die A design method of a lens system including an aspherical glass mold lens, which decides to adopt one or more methods of application of a side contact sleeve to a lens and modified polishing of a molded lens.

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