JPWO2009044768A1 - Optical element manufacturing method and manufacturing apparatus - Google Patents

Abstract

Provided are an optical element manufacturing method and a manufacturing apparatus capable of ensuring high decentration accuracy when an optical element having two opposing optical surfaces is manufactured by a droplet forming method. A heating process for heating the molding die to a predetermined temperature, a dropping process for dropping molten glass droplets on the lower mold, and an optical process for pressurizing the molten glass drops by relatively moving the upper mold and the lower mold in the pressurizing direction. And a pressing step for forming the element. Based on the amount of positional deviation between the two optical surfaces of the optical element formed by the pressing step, at least one of the horizontal relative position and inclination of the upper die and the lower die in the pressing step is adjusted.

Description

  The present invention relates to an optical element manufacturing method for press-molding molten glass droplets to manufacture an optical element having two opposing optical surfaces, and an optical element manufacturing apparatus for performing the manufacturing method.

  In recent years, optical elements manufactured by pressing glass materials with molding dies are output from digital camera lenses, optical pickup lenses such as DVDs, mobile phone camera lenses, optical communication coupling lenses, and semiconductor lasers. Widely used as a beam shaping element for shaping an elliptical output beam into a circular shape.

  In addition, along with demands for miniaturization and high accuracy of optical products, the performance required for optical elements made of glass is also increasing, and the amount of deviation from the design value of the relative position of the two opposing optical surfaces ( Hereinafter, the required performance of “eccentricity” is becoming increasingly severe. In particular, in a high NA lens used as a pickup lens for a next-generation DVD or the like, the tolerance of the eccentricity is extremely small and needs to be managed within a range of 0.1 μm or less, for example.

  As one method for producing such a glass optical element, a glass gob having a predetermined mass and shape is prepared in advance, and the glass gob is heated together with the molding die to a temperature at which the glass can be deformed. (Hereinafter also referred to as “reheat press method”) is known (for example, see Patent Documents 1 and 2).

  According to the descriptions in Patent Documents 1 and 2, the outer periphery of the mold is simultaneously moved up and down from the side surfaces of the upper and lower molds separately from the method of adjusting the inclination of the molding mold in the sleeve (Patent Document 1) and the pressing operation of the upper and lower molds. It is said that the amount of eccentricity can be suppressed by the pressurizing method (Patent Document 2). However, in such a reheat press method, it is necessary to repeatedly heat and cool the mold and the glass gob every time it is molded, and there is a problem that the time required for one molding is very long.

On the other hand, as another method for producing a glass molded body, a molten glass droplet is dropped on a lower mold that has been heated to a predetermined temperature in advance, and the upper mold and the lower mold while the dropped molten glass droplet is at a deformable temperature. (Hereinafter also referred to as “droplet forming method”) is known (for example, see Patent Document 3). Since this method does not require repeated heating and cooling of a molding die or the like, and a glass molded body can be produced directly from molten glass droplets, it is attracting attention because the time required for one molding can be extremely shortened. .
JP 2005-306644 A Japanese Patent Laid-Open No. 10-182173 JP 2005-320199 A

  However, in the droplet forming method, after the molten glass droplet is dropped on the lower die in a state where the upper die is retracted from above the lower die, the upper die and the lower die are fixed to each other before the pressure molding. A process of moving the upper mold and the lower mold relative to each other so as to be in a vertical relationship is necessary. Moreover, since the dropped molten glass droplet is rapidly cooled with time, the upper mold and the lower mold must be relatively moved at a considerably high speed. Therefore, if the gap between the sleeve and the molding die is reduced in order to reduce the amount of eccentricity, an optical element having a stable performance is likely to occur when the molding die is inserted into the sleeve. There was a problem that was difficult.

  In addition, the method described in Patent Document 1 cannot cope with the eccentricity larger than the gap amount between the sleeve and the molding die, and cannot cope with the parallel displacement between the two optical surfaces. It was.

  Further, in processing the molding die, it is difficult to make the outer diameter central axis of the molding die and the axis of the molding surface completely coincide with each other. In many cases, there is a deviation. Since the method described in Patent Document 2 is a method in which the upper and lower molding dies are pressed from the side surfaces so that the outer diameter central axes coincide with each other, the outer diameter central axis of the molding dies and the axis of the molding surface do not coincide with each other. In some cases, this could not be corrected in principle.

  The present invention has been made in view of the technical problems as described above, and an object of the present invention is to provide high eccentricity accuracy when manufacturing an optical element having two optical surfaces facing each other by a droplet forming method. It is providing the manufacturing method of the optical element which can be ensured. Another object of the present invention is to provide an optical element manufacturing apparatus for carrying out the manufacturing method.

  In order to solve the above problems, the present invention has the following features.

1. In a method for manufacturing an optical element, wherein a molten glass droplet is pressure-formed by a molding die having an upper mold and a lower mold, and an optical element having two optical surfaces facing each other is manufactured.
A heating step of heating the molding die to a predetermined temperature;
A dropping step of dropping the molten glass droplet on the lower mold;
A pressurizing step of molding the optical element by relatively moving the upper mold and the lower mold in the vertical direction to pressurize the molten glass droplets;
Based on the amount of positional deviation between the two optical surfaces of the optical element formed by the pressing step, at least one of the horizontal relative position and inclination of the upper die and the lower die in the pressing step is adjusted. A method for manufacturing an optical element.

2. The relative position in the horizontal direction of the upper mold and the lower mold is different between the dropping process and the pressing process,
Between the dropping step and the pressurizing step, there is a moving step of moving at least one of the upper mold and the lower mold in the horizontal direction,
The adjustment of the relative position in the horizontal direction between the upper die and the lower die in the pressurizing step is performed by changing the stop position of at least one of the upper die and the lower die moving in the moving step. The method for producing an optical element according to 1 above.

3. The horizontal position of the lower mold is different between the dropping step and the pressing step,
Between the dropping step and the pressurizing step, a moving step of moving the lower mold in the horizontal direction,
3. The horizontal position adjustment of the upper die and the lower die in the pressurizing step is performed by changing a stop position of the lower die that moves in the moving step. A method for manufacturing an optical element.

  4). 4. The method of manufacturing an optical element as described in 3 above, wherein in the pressurizing step, pressurization is performed by lowering the upper mold.

  5. 4. The method of manufacturing an optical element according to item 3, wherein the inclination of the upper mold and the lower mold in the pressurizing step is adjusted by changing the angle of the upper mold.

  6). 6. The method of manufacturing an optical element according to any one of 1 to 5, wherein the positional deviation amount between the two optical surfaces is obtained by measuring a transmitted wavefront aberration of the optical element.

  7. At least one of the upper mold and the lower mold includes a mark transfer portion for transferring a mark for identifying a position with respect to the optical element. The manufacturing method of the optical element of description.

8). The mark transfer part consists of a recess,
The concave portion has a depth D of 0.5 μm or more and 20 μm or less,
8. The method for manufacturing an optical element according to 7, wherein the width W is 3 μm or more and 200 μm or less.

  9. 9. The method of manufacturing an optical element according to 8, wherein the length of the mark is 5% or more and 30% or less of the effective diameter of the optical surface on which the mark is formed.

10. In an optical element manufacturing apparatus for press-molding molten glass droplets and manufacturing an optical element having two opposing optical surfaces,
A molding die having an upper mold and a lower mold;
Heating means for heating the molding die to a predetermined temperature;
Dropping means for dropping the molten glass droplet on the lower mold;
A pressurizing means for relatively moving the upper mold and the lower mold in the vertical direction to pressurize the molten glass droplets;
A horizontal position adjusting means for adjusting a horizontal relative position of the upper mold and the lower mold when the molten glass droplet is pressurized;
An apparatus for manufacturing an optical element, comprising: an inclination adjusting means for adjusting an inclination of at least one of the upper mold and the lower mold when the molten glass droplet is pressurized.

  According to the present invention, based on the positional deviation amount of the two optical surfaces calculated from the characteristics of the optical element manufactured in advance, at least the horizontal relative position and inclination of the upper mold and the lower mold in the pressurizing step. Since one of them is adjusted, the amount of positional deviation between the two optical surfaces of the optical element to be manufactured can be minimized. Therefore, when manufacturing an optical element having two optical surfaces facing each other by the droplet forming method, even if the outer diameter central axis of the molding die does not coincide with the axis of the molding surface, high eccentricity accuracy is achieved. Can be secured.

It is the figure which showed typically the manufacturing apparatus 10 of the optical element of this invention (state in the dripping process). It is the figure which showed typically the manufacturing apparatus 10 of the optical element of this invention (state in a pressurization process). It is a perspective view of the lower mold 12 vicinity. 2 is a cross-sectional view of the upper mold base 16 taken along the line AA. FIG. It is a flowchart which shows the basic process for manufacturing an optical element. It is a flowchart which shows the process of adjusting the horizontal relative position and inclination of the upper mold | type 11 and the lower mold | type 12. 4 is a flowchart illustrating a process of calculating a positional deviation amount between two optical surfaces of the optical element 25. It is a schematic diagram which shows the optical element 25 manufactured by the manufacturing method of this invention. It is a figure which shows the lower mold | type 12 which has the recessed part 18 as a mark transcription | transfer part. It is a schematic diagram for demonstrating inclination amount ((alpha)) and inclination direction ((theta)).

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Optical element manufacturing apparatus 11 Upper mold | type 12 Lower mold | type 13 Molding die 14x, 14y, 14z Ball screw 15x, 15y, 15z Servo motor 16 Upper mold | type base 17 Lower mold | type base 18 Recessed part 19 Reinforcement screw 20 Molten glass droplet 25 Optical element 26 Mark 27a, 27b Optical surface 31, 32 Heater 33a, 33b Axis of symmetry S11 Heating process S13 Dropping process S14 Moving process S15 Pressurizing process

  Hereinafter, embodiments of the present invention will be described in detail with reference to FIGS.

(Optical element manufacturing equipment)
First, the structure of the optical element manufacturing apparatus 10 of the present invention will be described with reference to FIGS. 1 and 2 are diagrams schematically showing an optical element manufacturing apparatus 10 according to the present invention. FIG. 1 shows a state in a dropping step, and FIG. 2 shows a state in a pressurizing step. 3 is a perspective view of the vicinity of the lower mold 12, and FIG. 4 is a cross-sectional view of the upper mold base 16 taken along the line AA.

  A molding die 13 for press-molding the molten glass droplet 20 has an upper die 11 and a lower die 12. The upper die 11 is on the lower surface of the upper die base 16, and the lower die 12 is a lower die base 17. Are supported on the upper surface of each. The upper mold base 16 is configured to be movable in the vertical direction (z direction) by a servo motor 15z and a ball screw 14z which are pressurizing means of the present invention.

  In the present embodiment, only the upper mold 11 is moved in the vertical direction by the pressing means, but the present invention is not limited to this, and only the lower mold 12 may be moved. It is good also as a structure which moves both the upper mold | type 11 and the lower mold | type 12 to an up-down direction. Further, the pressurizing means is not limited to the servo motor 15z and the ball screw 14z, and known means such as a stepping motor, a hydraulic cylinder, a pneumatic cylinder, etc. can be appropriately selected and used.

  The lower mold base 17 is configured to be movable by a servo motor 15x and a ball screw 14x, whereby the lower mold 12 receives a dropped molten glass droplet 20 (dropping position P1), and the upper mold 11 And a position for pressurizing the molten glass droplet 20 (pressing position P2). The moving means is not limited as long as it can move the upper mold 11 and the lower mold 12 in the horizontal direction, and may be configured to move only the lower mold 12 as in the present embodiment, or only the upper mold 11 or the upper mold. The structure which moves both 11 and the lower mold | type 12 may be sufficient. However, if the lower mold is moved between the dropping process and the pressurizing process, and the dropping position P1 and the pressing position P2 are different, the lower mold is dropped with another lower mold while the lower mold is in the pressing process. Since it becomes possible to receive, it is preferable. And since the mechanism is complicated to move the lower mold having the moving means in the horizontal direction also in the vertical direction, the upper and lower relative movements of the upper mold and the lower mold in the pressurizing process move the upper mold. It is preferable to carry out.

  The servo motor 15x and the ball screw 14x also function as a horizontal position adjusting means for adjusting the relative position in the x direction of the upper mold 11 and the lower mold 12 when the molten glass droplet 20 is pressurized. Similarly, a servo motor 15y and a ball screw 14y shown in FIG. 3 are provided as horizontal position adjusting means for adjusting the relative position in the y direction.

  Further, as an inclination adjusting means for adjusting the inclination of the upper mold 11 and the lower mold 12, the upper mold base 16 is provided with a tilt screw 19. As shown in FIG. 4, the three tilting screws 19 are arranged at intervals of 120 ° (circularly divided into three equal parts), and the upper die is adjusted by adjusting the protruding amount of the tilting screw 19 from the upper mold base 16. The angle with respect to the upper mold base 16 can be adjusted.

  The materials of the upper mold 11 and the lower mold 12 are heat-resistant alloys (such as stainless steel), super hard materials mainly composed of tungsten carbide, various ceramics (such as silicon carbide, silicon nitride, and aluminum nitride), composite materials containing carbon, etc. As a molding die for pressure-molding a glass optical element, it can be appropriately selected from known materials. Moreover, what formed protective films, such as various metals, ceramics, and carbon, on the surface of these materials can also be used. The upper mold 11 and the lower mold 12 may be made of the same material, or may be made of different materials.

  Moreover, the upper mold | type 11 and the lower mold | type 12 are comprised so that each can be heated to predetermined temperature with the heaters 31 and 32 which are heating means. As the heating means, known heating means can be appropriately selected and used. For example, a cartridge heater that is used by being embedded inside the member to be heated, a sheet heater that is used while being in contact with the outside of the member to be heated, an infrared heating device, a high-frequency induction heating device, or the like can be used.

  The optical element manufacturing apparatus 10 further includes a melting tank 21 for storing molten glass 22 and a nozzle 23 provided therebelow as dropping means for dropping the molten glass droplet 20 onto the lower mold 12. I have.

(Manufacturing method of glass molding)
Next, the manufacturing method of the optical element of this invention is demonstrated using FIGS. FIG. 5 is a flowchart showing a basic process for manufacturing an optical element. FIG. 6 is a flowchart showing a process of adjusting the horizontal relative position and inclination of the upper mold 11 and the lower mold 12, and FIG. 7 is a flowchart showing a process of calculating the amount of positional deviation between the two optical surfaces of the optical element 25. It is.

  First, the steps of the method for manufacturing an optical element of the present invention will be described step by step using the flowchart shown in FIG.

  First, the molding die 13 is heated to a predetermined temperature (heating step S11). The predetermined temperature may be a temperature at which two good optical surfaces can be formed on the optical element 25. In general, if the temperature of the upper mold 11 and the lower mold 12 is too low, it becomes difficult to form a good optical surface. On the other hand, it is not preferable to raise the temperature more than necessary because fusion with glass tends to occur or the life of the upper mold 11 and the lower mold 12 may be shortened. Normally, the glass transition temperature of the glass is set to a temperature of about Tg-100 ° C. to Tg + 100 ° C. In practice, however, the type of glass, the shape and size of the glass molded body, the material of the upper mold 11 and the lower mold 12 Since an appropriate temperature varies depending on various conditions such as the type of the protective film, it is preferable to obtain an appropriate temperature experimentally. The heating temperature of the upper mold 11 and the lower mold 12 may be the same temperature or different temperatures.

  In the present invention, since the molten glass droplet 20 is dropped onto the molding die 13 heated to a predetermined temperature and pressure-molded, a series of steps are performed while the heating temperature of the molding die 13 is kept constant. Can do. Furthermore, a plurality of optical elements 25 can be repeatedly manufactured while keeping the heating temperature of the molding die 13 constant. Therefore, it is not necessary to repeat the temperature rise and cooling of the molding die 13 every time one optical element 25 is manufactured, so that the optical element can be manufactured efficiently in an extremely short time.

  Here, keeping the heating temperature of the molding die 13 constant means that the target set temperature in the temperature control for heating the upper die 11 and the lower die 12 is kept constant. Therefore, it is not intended to prevent temperature fluctuation due to contact with the molten glass droplet 20 during each process, and such temperature fluctuation is allowed.

  Next, the lower mold 12 is moved to the dropping position P1 (S12), and the molten glass droplet 20 is dropped on the lower mold 12 (dropping step S13) (see FIG. 1).

  The melting tank 21 is heated by a heater (not shown), and a molten glass 22 is stored therein. A nozzle 23 is provided in the lower part of the melting tank 21, and the molten glass 22 passes through a flow path provided in the nozzle 23 by its own weight, and accumulates at the tip portion by surface tension. When a certain amount of molten glass accumulates at the tip of the nozzle 23, it naturally separates from the tip of the nozzle 23, and a certain amount of molten glass droplet 20 drops downward.

  The mass of the molten glass droplet 20 to be dropped can be adjusted by the outer diameter of the tip portion of the nozzle 23, and depending on the type of glass or the like, about 0.1 to 2 g of the molten glass droplet 20 can be dropped. Further, the dropping interval of the glass droplets can be adjusted by the inner diameter, length, heating temperature, and the like of the nozzle 23. Therefore, by appropriately setting these conditions, it is possible to drop molten glass droplets having a predetermined mass at predetermined intervals.

  Further, the molten glass droplet 20 is not directly dropped onto the lower mold 12 from the nozzle 23, but the molten glass droplet 20 dropped from the nozzle 23 is caused to collide with a member provided with through-holes, A part of the droplets may be dropped on the lower mold 12 through the through pores as fine droplets. Thereby, it is possible to manufacture a micro optical element such as 0.001 g to 0.3 g. Also, it is preferable to change the diameter of the through-holes because the volume of the molten glass droplet can be adjusted without replacing the nozzle 23, and various types of glass molded bodies can be produced efficiently. This method is described in detail in JP-A No. 2002-154834.

  There is no restriction | limiting in particular in the kind of glass which can be used, A well-known glass can be selected and used according to a use. Examples thereof include optical glasses such as borosilicate glass, silicate glass, phosphate glass, and lanthanum glass.

  Next, the lower mold 12 is moved to a position (pressing position P2) for pressing the molten glass droplet 20 so as to face the upper mold 11 (moving step S14). At least one of the horizontal relative position and inclination of the upper mold 11 and the lower mold 12 at the pressing position P2 is calculated from the characteristics of the optical element 25 manufactured prior to the manufacturing of the optical element 25 to be manufactured. Adjustment is made based on the amount of positional deviation between the two optical surfaces. Therefore, even when the central axis of the outer diameter of the upper mold 11 or the lower mold 12 does not coincide with the axis of the molding surface, the amount of positional deviation between the two optical surfaces of the optical element 25 to be manufactured can be minimized. And high eccentricity accuracy can be secured.

  Adjustment of the horizontal relative positions of the upper die 11 and the lower die 12 at the pressing position P2 is performed by adjusting the servo motor 15x and ball screw 14x as adjusting means in the x direction and the servo motor 15y and ball screw 14y as adjusting means in the y direction. And do by. Further, the tilt is adjusted by the tilt screw 19. Details of the process of adjusting the relative position and inclination in the horizontal direction will be described later.

  After the lower mold 12 is moved to the pressurization position P2, the upper mold 11 is moved downward by the pressurizing means to pressurize the molten glass droplet 20 (pressurizing step S15) (see FIG. 2).

  During the pressing step S <b> 15, the molten glass droplet 20 is rapidly cooled mainly by heat radiation from the contact surface with the molding die 13, and solidifies to become the optical element 25. The release of the pressurization is preferably performed after cooling to a temperature at which the shape of the formed optical surface does not collapse even if the pressurization by the pressurizing unit is released. Although it depends on the type of glass, the size and shape of the optical element 25, the required accuracy, etc., it is usually sufficient that the glass is cooled to a temperature near the Tg of the glass. Moreover, the magnitude | size of the load to load should just be suitably set according to the size etc. of the optical element 25 to manufacture.

  Finally, the optical element 25 obtained by moving the upper mold 11 upward and retracting is recovered (S16), and the manufacturing of the optical element 25 is completed. Thereafter, when the optical element 25 is subsequently manufactured, the lower mold 12 is moved again to the dropping position P1 (S12), and the subsequent steps may be repeated.

  In addition, the manufacturing method of the optical element of this invention may include another process other than having demonstrated here. For example, a step of inspecting the shape of the optical element 25 before collecting the optical element 25, a step of cleaning the upper mold 11 and the lower mold 12 after collecting the optical element 25, and the like may be provided.

  Next, the process of adjusting the horizontal relative position and inclination of the upper mold | type 11 and the lower mold | type 12 is demonstrated using the flowchart shown in FIG.

  In the present invention, the horizontal relative positions of the upper mold 11 and the lower mold 12 in the pressurizing step S15 based on the positional deviation amounts of the two optical surfaces calculated from the characteristics of the optical element 25 manufactured in advance. By adjusting at least one of the inclinations, the optical element 25 having high eccentricity accuracy can be manufactured. Further, by adjusting both the horizontal relative position and the inclination, it is possible to ensure higher eccentricity accuracy. Here, a case where both the horizontal relative position and the inclination are adjusted will be described as an example.

  When adjusting both the relative position and the inclination in the horizontal direction, the parameters to be adjusted are the x coordinate (x), the y coordinate (y), the inclination amount (α), and the inclination direction (θ) of the pressing position P2. One.

  FIG. 10 is a schematic diagram for explaining the tilt amount (α) and the tilt direction (θ). FIG. 10A is a view of the optical element 25 as viewed from one optical surface 27a side, and FIG. 10B is a cross-sectional view of the optical element 25 taken along the line BB.

  In the optical element 25, both optical surfaces 27a and 27b are rotationally symmetric aspherical surfaces. When both surfaces of the optical element are rotationally symmetric aspheric surfaces, the positional deviation between the two optical surfaces appears as a deviation of the symmetry axis of each rotationally symmetric aspheric surface.

  Here, as shown in FIG. 10, the angle between the symmetry axis 33a of one optical surface 27a and the symmetry axis 33b of the other optical surface 27b is defined as an inclination amount (α). This inclination amount (α) needs to be suppressed within a certain allowable range. In addition, the rotation angle from an arbitrary reference position 34 to the direction of the symmetric axis 33a of the optical surface 27a in the plane perpendicular to the symmetric axis 33b of the optical surface 27b is defined as a tilt direction (θ). Usually, there is no particular limitation on the tilt direction (θ) itself, but it is a parameter necessary for performing adjustment to reduce the tilt amount (α).

  First, the above four parameters are set to arbitrary initial values (x = x0, y = y0, α = α0, θ = θ0) (S21), and the optical element is processed by the steps S11 to S16 shown in FIG. 25 is manufactured (S22).

  Next, the shift amounts (dx, dy, dα, dθ) of the symmetry axes of the two optical surfaces are calculated from the characteristics of the manufactured optical element 25 (S23). There is no particular limitation on the method for obtaining the symmetry axis deviation amount of the two optical surfaces from the characteristics of the optical element 25, and the symmetry axis deviation amount may be obtained from the transmitted wavefront aberration of the optical element 25, or the reflection of the optical element 25. The symmetry axis deviation amount may be obtained from the measurement result of eccentricity or transmission eccentricity. Further, the symmetry axis deviation amount may be obtained from the shape measurement results of the two optical surfaces of the optical element 25. Among them, the method of calculating the symmetry axis deviation amount from the transmitted wavefront aberration is preferable because it does not require a special measuring apparatus and can be calculated with high accuracy.

  Thereafter, it is determined whether dx and dy are within an allowable range among the calculated symmetry axis deviation amounts (S24). If it is out of the allowable range, the calculated dx and dy are added to the x-coordinate and y-coordinate of the pressurization position P2, respectively, to change the coordinate of the pressurization position P2 (S25). As for the coordinates of the pressure position P2 after the change, the x coordinate is x + dx, and the y coordinate is y + dy.

  After changing the pressure position P2, the steps S22 to S24 are performed again. If dx and dy are within the allowable range, it is next determined whether dα is within the allowable range (S26). If dα is not within the allowable range, the tilt screw 19 is operated to change the pressure position P2 (S27), and the optical element 25 is manufactured again. By repeating this several times, dx, dy, and dα can all be within the allowable range.

  Here, the adjustment for suppressing dx and dy is performed before the determination (S26) of the inclination amount (dα), and it is difficult to accurately calculate dα while dx and dy remain large. Because there are cases. In addition, when dα and dθ are changed (S27), it is preferable to perform the determination of dx and dy (S24) again. This is because the values of dx and dy are also changed by changing dα and dθ.

  Next, with reference to the flowchart shown in FIG. 7, the process of calculating the symmetric axis deviation amount (dx, dy, dα, dθ) from the transmitted wavefront aberration of the optical element 25 will be described.

  First, the transmitted wavefront aberration of the optical element 25 is measured using an interferometer (S31). Next, the transmitted wavefront aberration measured in S31 is developed into a Zernike polynomial (S32) using commercially available analysis software (eg, MetroPro, manufactured by Zygo Corporation), etc. (S32). A Zernike coefficient corresponding to the deviation is extracted (S33).

  On the other hand, from the optical design value of the optical element 25, the amount of change in the Zernike coefficient when a certain amount of symmetry axis deviation occurs is calculated in advance (S34). By comparing the change amount of the Zernike coefficient obtained in this calculation with the value of the Zernike coefficient extracted in S33, it is possible to calculate the symmetrical axis deviation amount of the two optical surfaces existing in the optical element 25 (S35). .

  In the above description, the case where the two optical surfaces of the optical element are rotationally symmetric aspherical surfaces has been described. In the case of not a rotationally symmetric aspherical surface, for example, in the case of a spherical surface or a free-form surface, it does not have an axis of symmetry, but the present invention can be applied by measuring a horizontal displacement.

  In addition, in order to calculate the symmetry axis deviation amount of the two optical surfaces of the optical element 25 by such a method and determine the coordinates of the pressing position P2 from the calculated symmetry axis deviation amount, the optical element 25 is It is necessary to accurately grasp the positional relationship of the optical element 25 with respect to the upper mold 11 and the lower mold 12 when pressed by the mold 11 and the lower mold 12. Therefore, the optical element 25 preferably has a mark indicating a positional relationship with respect to the upper mold 11 or the lower mold 12. In order to form such a mark, it is preferable that at least one of the upper die 11 and the lower die 12 has a mark transfer portion for transferring the mark. By transferring the mark to the optical element 25, the mark can be applied to the optical element 25 accurately and stably.

  FIG. 8 is a schematic view showing an optical element 25 manufactured by the manufacturing method of the present invention. The position of the mark is not particularly limited, but it is preferably provided at a position that has little influence on optical performance and does not become an obstacle during assembly. For example, the mark 26 may be provided on the flat portion 28 outside the optical surface 27a as shown in FIG. 8 (a), and the influence on the optical performance of the optical surface 27a as shown in FIG. 8 (b). The mark 26 may be provided on the outer peripheral portion having a small diameter. Further, the mark 26 may be provided on the side surface portion 29 of the optical element 25.

  When the mark 26 is formed by transfer, from the viewpoint that the processing of the molding die 13 (at least one of the upper die 11 and the lower die 12) is easy, the molding die 13 is provided with a mark transfer portion formed of a recess. Is preferred. In this case, the mark 26 formed on the optical element 25 by the transfer has a convex shape.

  Moreover, it is preferable to provide a mark transfer part in the one where the curvature radius is larger among the upper mold 11 and the lower mold 12. This is because visual confirmation and automatic detection of the formed mark 26 are facilitated.

  FIG. 9 is a diagram showing the lower mold 12 having the concave portion 18 as a mark transfer portion for transferring the mark 26. 9A is a view of the lower mold 12 as viewed from above, and FIG. 9B is a partially enlarged view of the AA cross section. As shown in FIG. 9A, the lower mold 12 has a concave portion 18 as a mark transfer portion on a flat surface 12s provided outside the molding surface 12c for forming the optical surface of the optical element 25. Yes.

  It is more preferable that the recess 18 provided in the molding die 13 has a depth D of 0.5 μm or more and 20 μm or less, and a width W of 3 μm or more and 200 μm or less. The droplet forming method is a method in which high-temperature molten glass droplets 20 are pressure-molded while being cooled by a relatively low-temperature molding die 13, so that the vicinity of the contact surface of the molten glass droplets 20 with the molding die 13 is It is rapidly cooled to become a high viscosity state. Therefore, when the depth D of the recess 18 is less than 0.5 μm or the width W is less than 3 μm, the molten glass droplet 20 is difficult to enter the recess 18 and it is difficult to form the mark 26 by transfer. There is a case. On the contrary, if the depth D is larger than 20 μm, the mark 26 formed by the transfer is likely to be chipped. On the other hand, if the width W is larger than 200 μm, the detection accuracy in the rotational direction may be lowered.

  Furthermore, the length of the mark 26 is not less than 5% and not more than 30% of the effective diameter (diameter) of the optical surface in order to facilitate automatic recognition by image processing and to minimize deterioration in appearance quality. It is preferable.

Claims (10)

In a method for manufacturing an optical element, wherein a molten glass droplet is pressure-formed by a molding die having an upper mold and a lower mold, and an optical element having two optical surfaces facing each other is manufactured.
A heating step of heating the molding die to a predetermined temperature;
A dropping step of dropping the molten glass droplet on the lower mold;
A pressurizing step of molding the optical element by relatively moving the upper mold and the lower mold in the vertical direction to pressurize the molten glass droplets;
Based on the amount of positional deviation between the two optical surfaces of the optical element formed by the pressing step, at least one of the horizontal relative position and inclination of the upper die and the lower die in the pressing step is adjusted. A method for manufacturing an optical element. The relative position in the horizontal direction of the upper mold and the lower mold is different between the dropping process and the pressing process,
Between the dropping step and the pressurizing step, there is a moving step of moving at least one of the upper mold and the lower mold in the horizontal direction,
The adjustment of the relative position in the horizontal direction between the upper die and the lower die in the pressurizing step is performed by changing the stop position of at least one of the upper die and the lower die moving in the moving step. A method for manufacturing an optical element according to claim 1. The horizontal position of the lower mold is different between the dropping step and the pressing step,
Between the dropping step and the pressurizing step, a moving step of moving the lower mold in the horizontal direction,
3. The horizontal relative position adjustment of the upper die and the lower die in the pressurizing step is performed by changing a stop position of the lower die moving in the moving step. The manufacturing method of the optical element of description.   4. The method of manufacturing an optical element according to claim 3, wherein in the pressurizing step, pressurization is performed by lowering the upper mold.   The method for manufacturing an optical element according to claim 3, wherein the inclination of the upper mold and the lower mold in the pressurizing step is adjusted by changing the angle of the upper mold.   6. The optical according to claim 1, wherein the amount of positional deviation between the two optical surfaces is obtained by measuring a transmitted wavefront aberration of the optical element. Device manufacturing method.   7. At least one of the upper mold and the lower mold has a mark transfer portion for transferring a mark for identifying a position with respect to the optical element. The manufacturing method of the optical element of any one of these. The mark transfer part consists of a recess,
The concave portion has a depth D of 0.5 μm or more and 20 μm or less,
8. The method of manufacturing an optical element according to claim 7, wherein the width W is 3 μm or more and 200 μm or less.   9. The method of manufacturing an optical element according to claim 8, wherein the length of the mark is 5% or more and 30% or less of the effective diameter of the optical surface on which the mark is formed. In an optical element manufacturing apparatus for press-molding molten glass droplets and manufacturing an optical element having two opposing optical surfaces,
A molding die having an upper mold and a lower mold;
Heating means for heating the molding die to a predetermined temperature;
Dropping means for dropping the molten glass droplet on the lower mold;
A pressurizing means for relatively moving the upper mold and the lower mold in the vertical direction to pressurize the molten glass droplets;
A horizontal position adjusting means for adjusting a horizontal relative position of the upper mold and the lower mold when the molten glass droplet is pressurized;
An apparatus for manufacturing an optical element, comprising: an inclination adjusting means for adjusting an inclination of at least one of the upper mold and the lower mold when the molten glass droplet is pressurized.