JP3517592B2 - Optical element manufacturing method - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an optical element such as a lens. 2. Description of the Related Art Conventionally, as shown in FIG. 9, a lens is manufactured by a process of molding a lens blank, a rough grinding process of grinding the blank by a cup-shaped grinding wheel by a curve generator, and The process is performed by a fine grinding step of grinding the blank with a spherical grinding tool and a polishing step of grinding the blank with a spherical grinding tool. The molding of the lens blank was performed as shown in FIG. That is, the viscosity is 10
^The lower mold 104 is positioned below the glass outflow nozzle 101 that flows out of the molten glass adjusted to about ² to 10 ⁵ dPa · s, and the molten outflow glass 102 flowing out of the glass outflow nozzle 101 is connected to the glass outflow nozzle 101. It is cut by a cutting blade 103 arranged in the vicinity (FIG. 10A), and the separated vitreous mass 106 is accommodated in a lower mold 104 (FIG. 10B). As shown
The lower mold 104 is closed by the upper mold 105 and the glass mass 106 is closed.
Was formed to obtain a blank 107. In such a blank forming, in order to cut the molten outflow glass 102 using the cutting blade 103,
As shown in FIG. 10B, a cut mark 106a is formed on the glass mass 106, and when this is formed using the upper mold 105, the cut mark 106a remains on the blank 107.
As shown in FIG. 10C, a cutting mark 107a was left near the surface of the blank 107. Further, due to the temperature difference between the lower mold 104, the upper mold 105, and the glass chunk 106, and the effect of a mold release agent for mold release, defects 107b such as wrinkles and fogging remain on the surface of the blank 107. [0004] Then, when precision grinding or polishing is performed on the molded blank using a spherical processing tool, the processing tool attached to the lower shaft is rotated by a rotating mechanism, and
By mounting the lens to be processed on the upper shaft and bringing the lens into opposing contact with the processing tool on the lower shaft by a pressurizing system, the lens to be processed is processed by corotation caused by friction with the processing tool. In this type of manufacturing process, as shown in FIG. 9, in a process of forming a blank, an error from a desired radius of curvature allows a shape error width of about ± 150 μm.
This shape error is improved to ± 3 μm in the next rough grinding step, further reduced to ± 1.5 μm in the fine grinding step, and the surface roughness is finished to 0.01 μm Rt or less by the polishing step. The amount of processing removal in each step after the forming step is approximately 0.5 mm and 0.05 m for rough grinding, fine grinding, and polishing respectively.
m, about 0.01 mm. [0005] Also, there has been a proposal to omit the first rough grinding step when processing a molded blank, which has been proposed in "Optical Element Processing Technology '90", Chapter I-4, 56, published by Japan Opto-Mechatronics Association. Page. However, there is a drawback that stable processing in the precision grinding process cannot be obtained due to variations in the shape quality of the formed blank as shown in FIG. Furthermore, when the surface of the molded blank is a mirror surface, it cannot be machined with a tool in the fine grinding step, and thus cannot be put to practical use. [0006] In the prior art as described above, the processing removal amount in each step after the forming step is set to 0.5.
mm or more, a large amount of swarf is generated during processing. This swarf needs to be treated as industrial waste, which increases the cost of swarf treatment and contributes to the deterioration of the global environment. Further, since three steps are performed in one-side processing of the lens, processing costs are becoming a problem. The present invention has been made in view of the above-mentioned unsolved problems of the prior art, and has been made in consideration of the above. It is an object of the present invention to provide a method for manufacturing an optical element such as a lens, which can perform the following. [0008] In order to achieve the above object, a method of manufacturing an optical element according to the present invention comprises an optical element blank for melting a material of the optical element and molding the material into a shape close to a desired shape.
Facing the click molding step, the optical element blank to the grinding tool of the preset mounting the optical element blank is molded to the relative position of the optical element blank and machining tool spherical based on the shape of the molded optical element blank A step of performing pressure grinding and precision grinding, and placing the precision-ground optical element at a relative position between the optical element and the processing tool set in advance based on the shape of the precision-ground optical element to refine the spherical grinding tool. Grinding
Performing a polishing process by opposing and pressing the engineered optical element, wherein the optical element
In the blank molding process, the molding surface formed into the desired shape is
Using a mold unit having an upper mold and a lower mold having
Supply the molten material of the optical element to the lower mold via the supply nozzle
And after a predetermined volume of the molten material is supplied to the lower mold
The lower mold is lowered slightly to allow the molten material to
And the surface tension to make a natural cut.
Abuts against the lower mold while applying pressure to form a shape close to the desired shape
Wherein the optical element blank is molded . According to the method of manufacturing an optical element of the present invention, the variation in molding quality is greatly reduced, and the relative position of the optical element blank and the processing tool corresponding to the molding quality is set in advance and the position is precisely adjusted. by grinding, to allow continuous stable processing of fine grinding process, also Ru can be omitted rough grinding step. As a result, chips of the optical element material can be significantly reduced, and the processing cost of the optical element can be significantly reduced. Embodiments of the present invention will be described with reference to the drawings. [0011] (Example) is a view for explaining the flow diagram and the processing allowance and processing quality of each step of one embodiment of a manufacturing step of the manufacturing method of the optical optical element of Figure 1 according to the present invention, FIG 2 is the invention FIG. 3 is a schematic configuration diagram of a blank forming apparatus in one embodiment of the method for manufacturing an optical element according to the present invention. FIG. 3 is a process showing a mode of cutting and separating molten glass from a molten glass supply nozzle in the blank forming apparatus shown in FIG. FIG. 4 is a diagram illustrating a working tool used in a fine grinding step and a polishing step in one embodiment of the method for manufacturing an optical element of the present invention. [0012] The method of manufacturing an optical optical element in one embodiment of the present invention, as shown in FIG. 1, the optical element to melt the material of the optical element such as a lens is molded into a shape close to a desired shape <br / > blank forming and shape step, the optical element blank molding step grinding of the loading and spherical optical element blank which is molded to the relative position of the optical element blank and machining tool preset on the basis of the shape of the optical element blank is molded by a fine grinding step of performing a fine grinding so as to face pressed against the <br/> optical element blank to the tool, it is fine grinding to the relative position of the optical element and the machining tool preset on the basis of the shape of the fine grinding is an optical element the optical element have a polishing step of performing polishing to face presses the optical element to the polishing tool mounted to a spherical shape,
The optical element blank molding step includes forming the optical element blank into a desired shape.
Unit having upper and lower dies having different molding surfaces
A nozzle for supplying the molten material of the optical element to the lower mold.
And a predetermined volume of the molten material is supplied to the lower mold.
After the lower mold is slightly lowered after being supplied, the molten material
Is naturally cut by its own weight and surface tension.
The upper mold is pressed against and brought into contact with the lower mold to form the desired shape.
It is characterized by molding an optical element blank with a shape close to
I do. First, the optical element blank forming step will be described with reference to FIGS. In FIG. 2, the mold unit A of the blank forming apparatus includes a lower mold component B and an upper mold component C. The lower mold component B is composed of a lower mold member 11 and a lower mold holder 12, and the upper mold The constituent member C is also composed of an upper mold member 21 and an upper mold holder 22. The upper and lower mold holders 12 and 22 are provided with pressure chambers 12a and 22a for supplying and distributing a fluid such as an inert gas to each of the mold members 11 and 21 in a well-balanced manner. Temperature measuring means (not shown) is embedded, and upper and lower mold members 11 and 21 are provided.
And the temperature of the fluid can be finally adjusted. Upper and lower mold members 1 as upper and lower molds
Molding surfaces 11a and 21a, which determine the shape of the optical element blank, are formed on the reference numerals 1 and 21, respectively. Further, the lower die component B and the upper die component C are provided with a drive device (not shown), are configured to be movable in the vertical and horizontal directions in FIG. 2, and supply a fluid such as an inert gas. Supply pipes 17 and 27 are rotary joints 16,
26 are connected to the pressure chambers 12a and 22a of the upper and lower mold holders 12 and 22, respectively. Next, an optical element blank (hereinafter, referred to as "blank") is used by using a blank forming apparatus shown in FIG.
U. The optical element blank forming step of forming the above (1 ) will be specifically described. The upper and lower mold members 11 and 21 have a porosity of 30%.
Forming surfaces 11a, 21a which are formed using porous carbon having a maximum pore diameter of 8 μm and determine the shape of the blank.
After the surface is processed into a desired shape, the porous molded surface is finished smoothly so that there is no defect such as protruding. The mold members 11 and 21 thus processed are mounted on upper and lower mold holders 12 and 22, respectively, of the blank forming apparatus shown in FIG. A nitrogen gas is used as a fluid to be supplied to the upper and lower mold members 11 and 21 in order to prevent oxidation of the mold members 11 and 21. On the other hand, a glass material as a material of an optical element is:
The molten glass 32 is melted in a glass melting furnace (not shown), defoamed, and homogenized to prepare a homogenized molten glass 32 in a softened state. As shown in FIG. Is supplied to a molten glass supply nozzle 31 provided in the nozzle. The supply nozzle 31 is set at a temperature of 1200 ° C., and moves the lower die component B to just below the supply nozzle 31. Then, as shown in FIG. 3A, the molten glass 32 is caused to flow out of the supply nozzle 31 and
A predetermined volume of molten glass is caused to flow down on the molding surface 11a of the lower mold member 11. Then, as shown in FIG.
The lower mold component B is slightly lowered downward as indicated by the arrow, and the crack portion 3 is formed between the molten glass 32 on the supply nozzle 31 side and the molten glass block 32b received on the molding surface 11a of the lower mold member 11.
2c, and waits until the crack portion 32c separates and cuts due to the glass's own weight and surface tension.
As shown in FIG. 3C, the soft cutting of the molten glass lump 32b is obtained on the molding surface 11a of the lower mold member 11 by the natural cutting of the crack 32c. As described above, in the step of separating and cutting the molten glass 32, the lower die component member B is slightly moved downward and then temporarily stopped, whereby the molten glass crack portion 32c is formed.
Is cooled, and the glass can be cut naturally by its own weight and surface tension. Therefore, no cut marks remain on the cut portion as in the past, and the surface of the molten glass block 32b is harmful. It is possible to eliminate the occurrence of a serious defect. The temperature of the fluid (nitrogen gas) at this time is set to a temperature near the transition point of the glass when the molten glass is received on the molding surface 11a, and immediately thereafter, the temperature is set to be higher by about 50 to 100 ° C. The temperature of 13 is adjusted, and the flow rate of the nitrogen gas is controlled by a device (not shown) so that the flow rate is 20 liters per minute until immediately before the molten glass 32 is received on the molding surface 11a, and thereafter 5 liters per minute. By doing so, the tip of the molten glass 32 is slightly solidified before the molten glass 32 reaches the molding surface 11a of the lower mold member 11, and
Since the flow rate of the nitrogen gas is also increased, the tip of the molten glass 32 does not come into contact with the molding surface 11a at all, and in combination with the above-described cutting method using its own weight and surface tension, there is no defect on the surface. A glass mass 32b is obtained. Next, the lower mold component B is moved to a position immediately below the upper mold component C, and the speed of 5 mm per second is applied until the center thickness of the molten glass block 32b becomes 0.1 to 0.5 mm thicker than desired. Then, the upper mold component C is lowered so as to close the mold unit A. At this time, the molding surface of the molten glass lump 32 b 1
The viscosity near the lower surface received at 1a is 10 ⁶ to ^7.5 d
Pa · s, other viscosity near the surface is 10 ³ to ⁶ dPa
S, and while the vicinity of the center is sufficiently soft, the flow rate of nitrogen gas ejected from the molding surfaces 11a and 21a is set to 20 per minute.
The liter and the temperature were set so as to be a temperature corresponding to 10 ^6.5 dPa · s in terms of glass viscosity. Next, the temperature and the flow rate of the nitrogen gas are adjusted by adjusting the viscosity of the glass so that the film thickness of the gas becomes about 20 μm.
^The temperature is set to ^7.6 dPa · s and 10 liters per minute, and the pressure is applied to the upper mold component C of the mold unit A so that the center thickness of the molded blank becomes a desired value. Close A. Thereafter, the molten glass block 32b is moved to the mold unit A.
The molten glass mass 32b has a viscosity of 10 ¹⁴ dP
By cooling to a temperature equal to or higher than a · s and then taking out from the mold unit A, a blank having a desired shape as shown in FIG. 1 could be obtained. The shape error width ± 20 μm of the blank formed as described above is finished to ± 1.5 μm in the next fine grinding step. On the other hand, as for the surface roughness, 0.5 μmRt at the end of the fine grinding step is finished to a mirror surface of 0.01 μmRt or less in the polishing step. The machining removal allowance in each step in the present embodiment is set to 0.1 mm in each of the fine grinding step and the polishing step.
05 mm and 0.01 mm. FIG. 4 is a chart for explaining actual working tools in the fine grinding step and the polishing step.
Finishing is performed in a processing time of 20 seconds or less using a diamond tool obtained by sintering (at a temperature of about 800 ° C. or more) diamond powder having an average particle diameter of 8 μm with metal powder. In the polishing step, polishing is performed with a polishing liquid in which abrasive grains having a particle size of 0.1 to 2 μm are suspended in water and a polishing tool having a foamed polyurethane sheet formed into a spherical shape in a processing time of 1 minute or less. FIG. 5 shows the result that the processing quality of the fine grinding process is affected by the shape of the formed blank. In a blank shape having a desired radius of curvature (半径 in FIG. 5), the processing quality is stable even after processing 200 pieces. However, the radius of curvature deviated from the desired radius of curvature, and in the case of a blank shape (△ or □ in FIG. 5) having an error from the desired shape, the processing quality also changed with the number of processes, and stable processing was not possible. In addition, whether or not the stable processing is possible is related to a blank position with respect to a tool position determined by an individual blank shape, and a blank position at which stable processing can be performed with respect to a desired formed blank quality is referred to as a reference position. [0024] Figure 6, by changing the position of the molded blank quality and the blank and the processing tool is a representation of the results of the continuous processing, ○ it is of molded having a desired radius of curvature
It is an example of continuously processing the blank at the reference position,
200 or more stable workings were obtained, indicating that many more stable workings are possible. On the other hand, △
For molded blank radius of curvature is large, the blank position is moved by an amount preset into the outer peripheral side of the grinding tool from the reference position shows the results of processed, it was possible to obtain a stable processing. Also, the □ in FIG. 6, for the radius of curvature of the blank which is molded is small, the blank position is moved by an amount set in advance in the center of the grinding tool shows the results of machining, to obtain as stable machining Was completed. Also in the polishing step, the stability of the polishing quality is affected by the shape of the lens after the fine grinding step, as in the fine grinding step. In the polishing process, there is a lens position with respect to a tool position determined by an individual lens shape. FIG. 7 shows the result of polishing a lens having a stable shape by continuous processing in the fine grinding step at a reference position. As described above, by performing polishing at a reference position or a relative position set in advance according to the precisely ground lens shape, the processing can be stabilized. As described above, according to the present embodiment, a large amount of chips generated in the conventional rough grinding process can be reduced to about one tenth of the conventional size, and the rough grinding process can be eliminated. Therefore, the cost can be reduced by the processing cost of both sides in the rough grinding process. [0027] (Reference Example) FIG. 8 is a flow diagram and diagram for explaining the processing quality and processing allowance for each manufacturing step of a reference example of the method for manufacturing an optical optical element. [0028] In the embodiments described above, but are processed molded blank by directly grinding process, the glass material is can not be directly processed by the processing tool precision grinding process. Therefore, in the present reference example, for the glass material of this type, the surface of the molded blank is once roughened so that the next fine grinding step or polishing step can be performed efficiently. Things. In FIG. 8, the blank having a shape error of ± 20 μm and a surface roughness of 0.05 μm Rt or less were formed in the same manner as in the above-described embodiment, and the surface roughness was reduced to 1 to 1.5 μm Rt in the next roughening step. The surface is roughened. After that, in the fine grinding step, the shape is finished to a shape error width of ± 1.5 μm and the surface roughness is also improved. The surface roughness of 0.5 μmRt at the end of the fine grinding step is finished to a mirror surface of 0.01 μmRt or less in the polishing step. The machining removal allowance in each step in this embodiment is 0.03 mm, 0.05 mm, and 0.01 mm, respectively, for the roughening step, the fine grinding step, and the polishing step. The roughening of the shaped blank surface, the molded blanks are arranged through the jig, the abrasive grains of the abrasive grain size # 2500 from the top (the average particle diameter of 4 [mu] m), sprayed on the blank surface Do it. By this blast, the shape error width of the blank does not change, and the surface roughness is 1 to 1.5 μm.
mRt. In this surface state, processing in the next fine grinding step is performed, and the shape error width is greatly improved by the fine grinding tool, and the surface roughness is set to 0.5 μmRt. In this fine grinding step, similarly to the above-described embodiment, there is a blank position with respect to a tool position determined by an individual blank shape, and processing is performed based on a reference position or a relative position that is a position where stable processing can be performed. The shape error width of the blank in the process and the surface roughening process was greatly improved, and the error width was finished to ± 1.5 μm. As a means for roughening, in addition to the above-mentioned blasting method, chemical treatment such as acid treatment,
It can be carried out similarly by the method of a sand barrel. [0032] As described above, also in the present embodiment, the molding
Using a blank that has been roughened, the precision grinding process can be performed at a preset machining reference position or relative position according to the blank shape that has undergone the roughening process to stabilize the process and eliminate the rough grinding process. it can. As a result, the amount of chips generated in a large amount in the conventional rough grinding process can be reduced to about one-ninth of the conventional amount, and the blasting can perform a large amount of processing at a time. Processing can be performed at about one half of the processing cost of grinding, resulting in cost reduction. [0033] As has been described in the foregoing, according to the manufacturing method of the optical optical element of the present invention, along with greatly reduced the variations in the quality of the molded optical element blank, in fine grinding step and the polishing step by performing the processing at the processing position set in advance based on the shape of the optical element such as a lens, to allow continuous stable machining, also, Ru can be omitted rough grinding step. As a result, chips of the optical element material can be significantly reduced, and the processing cost of an optical element such as a lens can be significantly reduced.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a flow chart of a manufacturing process of an embodiment of a method for manufacturing an optical element of the present invention, and a diagram for explaining a processing quality and a machining allowance of each process. FIG. 2 is a schematic configuration diagram of a blank forming apparatus in an embodiment of a method for manufacturing an optical element of the present invention. FIG. 3 is a process explanatory view showing a mode of cutting and separating molten glass from a molten glass supply nozzle in the blank forming apparatus shown in FIG. 2 in the order of processes. FIG. 4 is a diagram illustrating a working tool used in a fine grinding step and a polishing step in one embodiment of the method for manufacturing an optical element of the present invention. FIG. 5 is a table showing that the processing quality of the precision grinding process is affected by the shape of a formed optical element blank. FIG. 6 is a chart illustrating an example of continuous stable processing in the fine grinding step. FIG. 7 is a table illustrating an example of continuous and stable processing in a polishing step. 8 is a diagram for explaining the processing quality and processing allowance of the flow diagrams and respective steps of the manufacturing process of the reference example of the method for manufacturing an optical optical element. FIG. 9 is a flow chart of manufacturing steps in a conventional method for manufacturing an optical element, and a diagram for explaining processing quality and processing allowance in each step. FIG. 10 is a process explanatory view showing a conventional blank forming method in the order of processes. DESCRIPTION OF SYMBOLS A Mold unit B of blank forming apparatus Lower mold component C Upper mold component 11 Lower mold member 11a Molding surface 12 Lower mold holder 12a Pressure chamber 13 Heater 17 Supply pipe 21 Upper mold member 21a Molding surface 22 Mold holder 22a Pressure chamber 23 Heater 27 Supply pipe 31 Molten glass supply nozzle 32 Molten glass 32b Molten glass block 32c Crack

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Kazuo Mizunaga 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Hiroshi Koibuchi 3-30-2 Shimomaruko, Ota-ku, Tokyo Ki Within Canon Inc. (72) Inventor Takashi Kosakai 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. Within (72) Inventor Isamu 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (56) References JP-A-9-253977 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B24B 13/00 B24B 13/02

Claims (1)

(57) [Claims 1] An optical element blank molding step of melting a material of an optical element and molding it into a shape close to a desired shape, and setting in advance based on the shape of the molded optical element blank wherein the optical element blank is molded to the relative position of the optical element blank and machining tool for grinding tools mounted to spherical optical element
A step of performing precision grinding by opposing pressure contact of a blank , and placing a precision-ground optical element at a relative position between an optical element and a processing tool set in advance based on the shape of the precisely ground optical element and polishing the spherical shape. A step of polishing the optical element which has been finely ground to the tool by opposing pressure contact .
The manufacturing method, wherein the optical element blank forming step includes forming the optical element blank into a desired shape.
Unit having upper and lower dies having different molding surfaces
A nozzle for supplying the molten material of the optical element to the lower mold.
And a predetermined volume of the molten material is supplied to the lower mold.
After the lower mold is slightly lowered after being supplied, the molten material
Is naturally cut by its own weight and surface tension.
The upper mold is pressed against and brought into contact with the lower mold to form the desired shape.
A method for producing an optical element, comprising: forming an optical element blank having a shape close to a shape .