JP2006159659A - Optical element and its molding method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a molding method of an optical element of high precision such as a lens or the like made of a resin by injection molding, and the optical element. <P>SOLUTION: First, the optical element (first optical element) is molded using a temporary mirror surface piece 4 (S01). Next, the temperature of the first optical element is leveled in a high temperature tank with a temperature of 60°C (S02) and the surface shape error of the first optical element is subsequently measured (S03) to perform the correction processing of the temporary mirror surface piece 4 in the setting-off direction of the obtained surface shape error (S04). Subsequently, an optical element (second optical element) is molded using a corrected mirror surface piece 17 obtained by the correction processing of the temporary mirror surface piece 4 (S05) and the temperature of the second optical element is leveled to evaluate the second optical element (S06). In this treatment process, the temperature leveling of the second optical element is performed under the same condition as the first optical element 15 and the optical surface shape of the second optical element is measured under the same condition as the first optical element in the same way to evaluate the degree of the shape error of the second optical element. If the evaluation is good, the measurement of the optical surface shape is completed and, if bad, the measurement of the optical surface shape is again performed. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a highly accurate optical element molding method for resin lenses, prisms, and the like by injection molding, and the optical element.

  Conventionally, there are optical elements such as lenses. Traditionally, glass optical elements have been used exclusively, but glass optical elements (for example, lenses) require high technology and time for polishing to obtain an accurate curved surface, so mass production does not work. It is expensive and heavy.

  On the other hand, in recent years, plastic optics that can be mass-produced by injection molding using a mold, can be easily obtained with an aspherical curved surface, and are light in weight, and can be easily assembled into small devices. Many elements have been used.

  By the way, glass hardly deforms with respect to normal temperature changes and humidity changes, and because it is rigid, it is difficult to deform with pressure, whereas plastic is resistant to changes in temperature and humidity. There is a weak point that it is easily deformed and easily deforms against pressure. If the optical element is deformed, its function cannot be exhibited normally.

Therefore, it is considered that various modifications are made to the shape of the plastic optical element.
For example, in an optical element such as a long lens used in a laser scanning optical system, an optical element such as a large-diameter lens, the amount of deformation is large due to cooling after injection molding, and an error exceeding the design allowable range is likely to occur. In order to obtain a highly accurate optical element by incorporating the shrinkage and deformation at the time of injection molding as described above at the time of manufacture, a mirror piece of an injection mold is created.

As a method, the shape of the optical functional surface of the optical element created by a predetermined mirror piece is measured, the shape error from the optical ideal surface shape is calculated, and the optical surface shape is divided into a plurality of areas based on the calculation. A method of correcting local shrinkage and deformation that occurs during molding with an optical element by processing the shape of the specular piece into a shape that offsets the shape error of the optical element is proposed. ing. (For example, refer to Patent Document 1.)
In addition, in order to correct an error from the design accuracy caused by the deformation of the optical element due to the stress generated when the optical element is incorporated into the main unit, the optical surface shape is applied with the same force as the above stress applied to the optical element. Measure the shape error, determine the shape error, process the shape part of the specular piece into a shape that offsets the calculated shape error, and perform injection molding, so that when the optical element is incorporated into the main unit, Proposals have also been made to obtain accurate optical performance. (For example, see Patent Document 2.)
Japanese Patent No. 2898197 (Japanese Patent Laid-Open No. 07-060857) ([0006] to [0008], [0064], FIG. 1, FIG. 5, FIG. 9) Japanese Patent Application Laid-Open No. 2003-175531 ([Claim 1], [Summary], FIG. 8)

  However, in the method for measuring an optical surface shape shown by the technique described in Patent Document 1 or 2, the optical element is leveled in the environment where the measuring machine is placed. That is, there is a problem that the characteristics of the optical element are adjusted to a measurement environment when performing precise measurement.

  The environment in which precise measurement is performed is normally set to a room temperature of about 20 ° C. ± 3 ° C., and the characteristics of the optical element are stabilized within the environmental conditions. Therefore, a highly accurate optical surface shape can be obtained by handling the optical element under the environmental conditions, but the actual use environment often has a high temperature.

  In particular, as portable imaging devices such as digital cameras (similar to mobile phones with digital cameras) become smaller and thinner, they are built in close proximity to imaging devices such as CCDs (Charge Coupled Devices) of these imaging devices. In the resin lens system used for the above, the distance between the imaging element and the lens at the shortest distance is less than 1 mm. And the image pick-up element in use generate | occur | produces the high heat | fever close to 60 to 80 degreeC. For this reason, there has been a problem that the optical surface shape of the lens fluctuates and cannot function correctly.

  An object of the present invention is to provide a method of molding an optical element such as a resin lens that functions with high accuracy in an actual use environment in view of the above-described conventional situation, and an optical element thereof.

  First, a method for molding an optical element according to a first aspect of the invention is a method for molding an optical element that is incorporated in the vicinity of an imaging element of an imaging device, and the first optical element is formed using a temporary mirror surface piece. Measuring the surface shape of the first optical element adjusted to the temperature, the step of adjusting the temperature of the first optical element to the temperature of the use temperature region of the image pickup element in the vicinity of the image pickup element A step, a step of calculating a shape error amount with respect to the ideal optical surface shape of the first optical element based on the measured surface shape data of the first optical element, and a direction to cancel the shape error amount And the step of correcting the temporary mirror surface piece and the step of forming the second optical element using the corrected temporary mirror surface piece.

  Next, a method for forming an optical element according to a second aspect of the invention includes a step of forming the first optical element using a temporary mirror surface piece, a step of bringing the first optical element to a predetermined temperature, and the predetermined A step of measuring the surface shape of the first optical element adjusted to temperature, and an ideal optical surface shape of the first optical element based on the measured surface shape data of the first optical element. A step of calculating a shape error amount, a step of creating a mirror surface piece in which the surface shape of the temporary mirror surface piece is corrected in a direction to cancel the shape error amount, and a second optical element using the corrected mirror surface piece And a step of forming.

  Furthermore, the method for molding an optical element according to the third aspect of the invention includes a step of forming the first optical element using a temporary mirror surface piece, and a first shape error amount from an ideal optical surface shape of the first optical element. A step of calculating a surface shape error amount of the ideal optical surface shape of the first optical element at a temperature of 40 ° to 80 ° C. by simulation, and the measured first shape error amount A step of calculating a second shape error amount by adding the surface shape error amount calculated from the simulation, a step of correcting the temporary mirror surface piece in a direction to offset the second shape error amount, and Forming the second optical element using the corrected temporary mirror surface piece.

Moreover, the optical element of 4th invention is shape | molded by the shaping | molding method of the optical element of the said 1st, 2nd or 3rd invention.
Furthermore, an optical element according to a fifth aspect of the present invention is a resin-made optical element that is molded into a predetermined optical surface shape by injection molding a resin material that expands by heating, and is measured at a temperature of 20 ° C. ± 3 ° C. The ideal optical surface shape of the optical element is the surface shape of the optical element at a temperature corresponding to the use environment of the optical element, which is appropriately set on the higher temperature side than the measurement atmosphere. Is configured so as to be set smaller than the ideal optical surface shape in a direction to cancel out the expansion amount corresponding to the shape error amount.

  Thus, according to the present invention, after the optical element injection-molded with the temporary mirror surface piece of the mold is brought to a temperature state close to the actual use environment, the design tolerance, that is, the optical shape error amount from the ideal optical surface shape Is calculated, and a mirror surface piece in which the surface shape of the temporary mirror surface piece is corrected in a direction that cancels the optical shape error amount is created, and injection molding is performed using the mirror surface piece, whereby a high-precision optical element such as a plastic lens is obtained. A molding method and an optical element thereof can be provided.

  Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic side cross-sectional view showing a configuration of a mold in the first embodiment.
As shown in FIG. 1, the mold 1 includes a fixed mold 2 and a movable mold 3. Furthermore, each of the fixed mold 2 and the movable mold 3 has two pairs of mirror pieces 4 for forming an optical element (in this example, this mirror piece 4 is hereinafter referred to as a temporary mirror piece 4). Is detachable.

  The temporary mirror surface piece 4 is a pair of two, and forms a facing surface corresponding to the optical surface shape of the injection-molded product around the pressing surface 5 of the fixed mold 2 and the movable mold 3, and injection is performed between the facing surfaces. A cavity (cavity) 6 into which a molding resin material is injected is formed.

  A sprue (spout) 7 into which an injection molding resin material is injected from the outside is formed at the center of the fixed mold 2. The runner (runner: runner) that conducts to the sprue 7, extends to the pressing surface 5 of the fixed mold 2 and the movable mold 3, and branches left and right (up and down in the drawing) along the pressing surface 5. 8 is formed. The branched runners 8 are electrically connected to the cavity 6 while forming thinner gates 8a.

  The movable mold 3 is inserted into the movable mold 3 and extends to a branch point at the pressing surface 5 between the fixed mold 2 and the movable mold 3 of the runner 8 (eject-pin: Extrusion rod) 9 is provided.

  Said temporary mirror surface piece 4 is formed in the surface shape which considered the shrinkage | contraction rate of resin with respect to the ideal optical surface shape of an optical element. That is, the opposing surface of the temporary mirror surface piece 4 is formed so that the shape after cooling of the optical element injection-molded by the temporary mirror surface piece 4 forms an ideal optical surface shape in which a manufacturing error is within the design allowable range. Is formed.

  FIG. 2 is a flowchart for explaining a process of manufacturing the optical element of this example in the configuration of the mold 1 described above. The process of manufacturing the optical element of this example will be described below with reference to FIGS.

In FIG. 2, first, an optical element using the temporary mirror surface piece 4 is molded (S01).
In this processing step, in FIG. 1, first, molten resin is injected from an injection molding unit (not shown) and injected into the sprue 7. The molten resin injected into the sprue 7 is cooled after being filled into the cavity 6 formed by the temporary mirror surface piece 4 via the runner 8 and the gate 8a.

  The molded product in the cavity 6 is cooled, and when the shape is sufficiently solidified and stabilized, the movable mold 3 moves to the left in FIG. 1, and the fixed mold 2 and the pressing surface 5 of the movable mold 3 are moved. And the eject pin 9 extends from the moving mold 3 side, and the molded product (optical element) solidified in the mold 1 and the runner 8 that is an excess resin portion are taken out.

  Subsequently, the portion remaining on the runner 8 and the portion of the molded product are separated, and the resin at the injection port 8a portion remaining continuously in the portion of the molded product is removed (deburring), and the temporary mirror surface piece The molding of the optical element using 4 is completed. In this example, the optical element obtained here is referred to as a “first optical element”.

Subsequently to the above, in FIG. 2, the optical element taken out from the mold 1 as described above is subjected to a temperature adjustment at 60 ° C. (S02).
In this processing step, the optical element (first optical element) is placed in a constant temperature bath at a temperature of 60 ° C. and is left until the optical element is completely at a temperature of 60 ° C.

  FIG. 3 is a diagram showing the relationship between the temperature state of the optical element and time until the temperature of the optical element is adjusted to 60 ° C. under the above conditions. In the figure, the horizontal axis represents time, and the vertical axis represents the temperature of the optical element.

The time Tx on the horizontal axis indicates the time until the temperature of the optical element is adjusted to 60 ° C. on the vertical axis and the temperature is balanced.
The standing time is preferably about 24 hours regardless of the type of resin used as the material of the optical element. Of course, it varies somewhat depending on the size and thickness of the optical element.

After the above, as shown in FIG. 2, the surface shape error is measured (S03).
In this processing step, the optical element that is completely at a temperature of 60 ° C. as described above is taken out of the thermostatic bath, and the surface shape error is measured with a measuring instrument. The measuring device is a contact type measuring device or a non-contact measuring device. As such a measuring machine, there is, for example, a foam Talysurf manufactured by Taylor Hobson or an ultra-high precision three-dimensional measuring machine UA3P manufactured by Matsushita Electric Industrial Co., Ltd.

  FIG. 4 is a diagram schematically illustrating the measurement operation of the contact-type measuring machine. This figure shows a measuring object 11 (for example, a lens) and a probe 12 of a measuring machine. The probe 12 moves while following the surface shape of the surface 14 to be measured as indicated by a double-pointed arrow a with the probe end 13 in contact with the surface 14 to be measured of the object 11 to be measured.

  In this measurement, the measurement is performed while moving along a cross section including the optical axis of the optical element. In the case of an aspherical lens, the measurement is performed by moving while following the surface shape of the entire effective diameter (surface effectively functioning as an optical element) in the three-dimensional surface shape.

  Normally, the environment where the measuring machine is used for precision measurement is set at a temperature of about 20 ° C ± 3 ° C. Therefore, if the measurement is carried out for a long time, the temperature will be raised to 60 ° C from the thermostatic chamber. Since the taken-out optical element may be adjusted to a temperature of the measurement environment of 20 ° C. ± 3 ° C., it is preferable to complete the measurement of the surface shape of the optical element within about 30 minutes at the longest. . If it is 30 or less, the optical element can be measured while the temperature does not fall below 50 ° C., and there is little influence on the temperature state of the optical element at a temperature of 60 ° C.

  The measurement of the optical element is the most ideal measurement method under the same conditions as in the thermostatic bath. However, if the measuring machine is placed in a high temperature environment such as a temperature of 60 ° C., the temperature is high. For this reason, not only does the measurement accuracy be adversely affected, but the measuring machine itself may deteriorate at an early stage due to high temperatures and break down, and thus is not practical.

  Subsequently, the surface shape of the temporary mirror surface piece 4 is measured to obtain the shape data of the temporary mirror surface piece 4. From the surface shape data of the optical element obtained by the measurement by the measuring instrument and the ideal optical surface shape, the surface shape error when the temperature of the optical element reaches 60 ° C. is found. Then, processing data for processing the temporary mirror surface piece 4 is calculated in a direction in which the surface shape error of the optical element thus found is offset with respect to the shape data of the temporary mirror surface piece 4.

Then, as shown in FIG. 2, the temporary mirror surface piece 4 is corrected in a direction to cancel the surface shape error (S04).
FIGS. 5A to 5D are diagrams schematically showing the processing steps up to the correction processing of the temporary mirror surface piece 4 described above. FIG. 5 (a) shows the temporary mirror surface piece 4 shown in FIG. 1 (however, only one of the movable and fixed pieces is shown and the other piece is not shown, the same applies hereinafter) and the temporary mirror surface piece. 4 shows the optical element (first optical element) 15 created as described in the processing step S01 of FIG.

  Next, FIG. 5B shows the first optical element 15 that has finished the temperature adjustment together with the temporary mirror surface piece 4. The portion shown by hatching of the first optical element 15 in FIG. 5B is obtained by the temperature leveling of 60 ° C. described in the processing step S02 of FIG. 2 and the measurement described in the processing step S03 of FIG. The obtained surface shape error is 16. Note that the surface shape error 16 figure shown in FIG. 5B does not indicate the thickness of the optical surface shape error, but represents the degree (size) of the error for easy understanding. Is.

  FIG. 5C shows a state in which the temporary mirror surface piece 4 is corrected in a direction that cancels the surface shape error 16. In this correction processing, the surface of the temporary mirror surface piece 4 shown in FIG. 5A is corrected in a direction to cancel the surface shape error obtained by the above measurement.

  In this example, the first optical element 15 after the temperature adjustment shown in FIG. 5 (b) is deformed (expanded) by an amount corresponding to the temperature. Therefore, the surface shape error 16 measured by the expansion is changed. The amount of offset is processed so that the surface of the temporary mirror surface piece 4 is scraped off.

  As a result, as shown in FIG. 5D, a corrected mirror surface piece 17 formed by correcting the temporary mirror surface piece 4 in the direction to cancel the surface shape error 16 is completed. In addition, you may create the mirror surface piece which has the surface shape which corrected the surface shape of the temporary mirror surface piece from the separate mirror surface piece material.

Subsequently, as shown in FIG. 2, an optical element is formed using the modified mirror piece 17 obtained by modifying the temporary mirror piece 4 (S05).
As a result, the second optical element 18 is obtained as shown in FIG. Finally, the second optical element 18 obtained as described above is evaluated after temperature adjustment (S06).

  In this processing step, the temperature of the second optical element 18 is adjusted under the same conditions as in the case of the first optical element 15, and then the optical conditions are the same as in the case of the first optical element 15. The surface shape is measured to evaluate the degree of shape error.

  In this evaluation process, when the degree of the shape error is larger than a predetermined allowable range, the corrected mirror surface piece 17 is regarded as the first temporary mirror surface piece 4 and steps S01 to S06 in FIG. 2 are repeated.

  Then, in the evaluation step of S06, if the degree of the shape error is within a predetermined allowable range, that is, if the evaluation is good, the second optical element 18 is used as a sample of the final product. That is, the modified mirror surface piece 17 on which the second optical element 18 is created is used as a main mirror surface piece to start mass production of optical elements.

  In this way, an optical element which is the final product of this example is produced. Since the optical element of this final product is created so that its optical surface shape forms an optical ideal surface shape when the temperature is 60 ° C., the optical surface shape when the temperature is 20 ° C. ± 3 ° C. is optical. Compared to a conventional product that is formed into an ideal surface shape, that is, a shape that has been measured and measured in a normal state, it is not greatly deformed by temperature.

FIG. 6 (a) is a diagram schematically showing an example of deformation due to temperature of the optical element of the final product of this example, and FIG. 6 (b) is a diagram schematically showing an example of deformation due to temperature of the conventional product. It is.
As shown in FIG. 6 (a), in the final product optical element showing a normal optical surface shape at a temperature of 60 ° C., even when the temperature is as low as 20 ° C., the difference from the normal value is 40% below. Therefore, the deformation is small, and even when the temperature is as high as 80 ° C., the difference from the normal value is 20 ° C., so the deformation is small. That is, the degree of deformation is small in a wide temperature range of 20 ° C. to 80 ° C. Therefore, even if the optical element of this final product is incorporated in the main body device and used in a practical stage, the function does not change greatly.

  On the other hand, as shown in FIG. 5 (b), in the conventional optical element showing a normal optical surface shape at a temperature of 20 ° C., the difference from the normal value is 40 ° C. at a temperature of 60 ° C. Therefore, the deformation becomes large, and when the temperature further reaches 80 ° C., the difference from the normal value becomes 60 ° C., so the deformation becomes further large. That is, the degree of deformation is large in the temperature range of 20 ° C. to 80 ° C. as a whole. Therefore, when such an optical element is incorporated in the main unit, when it is placed in the vicinity of the CCD and placed in a high temperature environment of 80 ° C. generated from the CCD in use, for example. Normal function cannot be demonstrated.

FIG. 7 is a flowchart for explaining the steps of the optical element molding method according to the second embodiment.
FIGS. 8A to 8D are diagrams schematically showing the steps of the molding method of the optical element in an easy-to-understand manner. A method for molding an optical element according to the second embodiment will be described with reference to FIGS. 7 and 8A to 8D.

First, in FIG.7 and FIG.8 (a), the optical element using the temporary mirror surface piece 4 is shape | molded (S101). This processing step is the same as the processing step S01 in FIG.
FIG. 8 (a) shows the temporary mirror surface piece 4 shown in FIG. 1 (however, only one of movable and fixed pieces is shown and the other piece is not shown, the same applies hereinafter) and its temporary mirror surface piece. 4 shows the optical element (first optical element) 15 created as described in the processing step S101 of FIG.

Next, a surface shape error is measured (S102). This processing step is the processing step S0 in FIG.
3 is the same.
However, in this example, the surface shape error of the optical element molded using the temporary mirror surface piece 4 is measured as it is without adjusting the temperature. Then, the shape error thus obtained is set as a first shape error as shown in FIG. This is essentially a surface shape error of the temporary mirror piece 4 in a normal environment.

  Subsequently, a shape error when the temperature is adjusted near the image sensor is calculated by simulation (S103). For example, Japanese Patent Application Laid-Open No. 2004-012249 discloses a technique for simulating the change in characteristics of a resin optical element over time.

  If this is applied to a temperature calculation shape calculation simulation, for example, a. A three-dimensional shape generation step of the optical element; b. A finite element method analysis model generation step; and c. This is performed in the deformation amount calculation step.

  a. The above-described processing steps S101 and S102 correspond to the optical element three-dimensional shape generation step. b. The finite element method analysis model generation step includes a diffusion constant calculation step of measuring and inputting the diffusion constant of each optical material. The diffusion constant calculation uses a value obtained when the temperature is adjusted to 20 ° C. ± 3 ° C. And c. In the deformation amount calculation step, the deformation amount after the temperature adjustment of the optical element is calculated.

  Subsequently to the above, an error from the simulation is added to the already obtained first shape error (S104). In this processing step, first, an error from the optical ideal surface shape is calculated from the deformation amount of the optical element obtained by the simulation as described above. As a result, for example, as shown in FIG. 8C, an error amount between the shape calculated by the simulation and the optical ideal surface shape is obtained.

  Then, as shown in FIGS. 8B and 8C, this error amount is added to the first shape error. This addition result is taken as a second shape error (corresponding to the surface shape error 16 in FIG. 5 (b)) as shown in FIG. 8 (d).

  Subsequently, as shown in FIG. 7, the temporary mirror surface piece 4 is corrected in a direction to cancel the surface shape error (second shape error) (S105). This processing step corresponds to the processing step S04 in FIG. 2 and the diagram in FIG.

  Then, an optical element is formed using the corrected mirror piece obtained by correcting the temporary mirror piece 4 (S106). This processing step corresponds to the processing step S05 in FIG. 2 and the diagram in FIG. Thereby, also in this case, the second optical element 18 is obtained.

  Finally, as shown in FIG. 7, the second optical element 18 obtained as described above is evaluated under a temperature-conditioning condition (S107). This processing step is the same as the processing step S06 in FIG.

  In this evaluation process, when the degree of the shape error is larger than the predetermined allowable range, the above-described corrected mirror surface piece is regarded as the first temporary mirror surface piece 4, and the processing steps S101 to S107 in FIG. 7 are repeated.

  In the evaluation step of S107, if the degree of the shape error is within a predetermined allowable range, that is, if the evaluation is good, the second optical element 18 is used as a sample of the final product. That is, the modified mirror surface piece on which the second optical element 18 is created is used as the main mirror surface piece, and mass production of the optical element is started.

  In this way, an optical element which is the final product of this example is produced. Since the optical element of the final product is created so that the optical surface shape forms the optical ideal surface shape based on the simulation showing the shape at a temperature of 60 ° C., the temperature is 20 ° C. ± 3 ° C. Compared with the conventional product in which the optical surface shape is formed in the optical ideal surface shape in the state of time, as already explained in FIG.

  In addition, in Example 1 or 2, although demonstrated using the lens shape which consists of two pairs of mirror surface pieces 4, not only this but an optical element may be a prism shape which has a some optical function surface, Further, the optical functional surface may be a spherical surface, an aspherical surface, or a free curved surface shape having no rotational symmetry axis such as a Fresnel surface (DOE).

It is a typical sectional side view which shows the structure of the metal mold | die in one Embodiment. It is a flowchart explaining the process of manufacturing the optical element of this example in the structure of the metal mold | die of this example. It is a figure which shows the relationship between the temperature state of an optical element and time until the optical element left to put in the thermostat of 60 degreeC will be completely set to the temperature of 60 degreeC. It is a figure which shows typically the measurement operation | movement of a contact-type measuring device. (a)-(d) is a figure which shows typically the processing process until it corrects a temporary mirror surface piece. (a) is a figure which shows typically the example of the deformation | transformation by the temperature of the optical element of the final product of this example, (b) is a figure which shows typically the example of the deformation | transformation by the temperature of a conventional product. It is a flowchart explaining the process of the shaping | molding method of the optical element in 2nd Embodiment. (a)-(d) is a figure which shows typically the process of the shaping | molding method of the optical element in 2nd Embodiment intelligibly.

Explanation of symbols

1 Mold 2 Fixed mold 3 Movable mold 4 Mirror face piece (temporary mirror face piece)
5 Pressing surface 6 Cavity
7 sprue
8 runners (runner)
9 Eject-pin (extruded rod)
DESCRIPTION OF SYMBOLS 11 Measurement object 12 Probe 13 Exploration end 14 Surface to be measured 15 Optical element (1st optical element)
16 Surface shape error 17 Corrected mirror piece 18 Second optical element

Claims (10)

A method of molding an optical element that is used in the vicinity of an imaging element of an imaging apparatus,
Forming a first optical element using a temporary mirror surface piece;
Leveling the first optical element to a temperature in a use temperature range at a position close to the imaging element;
Measuring the surface shape of the first optical element at the temperature; and
Calculating a shape error amount from the ideal optical surface shape of the first optical element based on the measured surface shape data of the first optical element;
Creating a mirror piece that corrects the surface shape of the temporary mirror piece in a direction to offset the shape error amount; and
Forming a second optical element using the corrected mirror piece;
A method for forming an optical element, comprising: Forming a first optical element using a temporary mirror surface piece;
The step of bringing the first optical element to a predetermined temperature;
Measuring the surface shape of the first optical element at the predetermined temperature;
Calculating a shape error amount from the ideal optical surface shape of the first optical element based on the measured surface shape data of the first optical element;
Creating a mirror piece that corrects the surface shape of the temporary mirror piece in a direction to offset the shape error amount; and
Forming a second optical element using the corrected mirror piece;
A method for forming an optical element, comprising:   The method for molding an optical element according to claim 1, wherein the temperature at which the first optical element is leveled is a temperature set between 40C and 80C.   The method of molding an optical element according to claim 1, wherein the step of adjusting the temperature of the first optical element is performed by a thermostatic bath.   The method for molding an optical element according to claim 1, wherein the step of measuring the surface shape of the first optical element is performed in a measurement atmosphere at a temperature of 20 ° C ± 3 ° C.   5. The method for molding an optical element according to claim 4, wherein a measurement elapsed time until the measurement is completed in the measurement atmosphere is within 30 minutes. Forming a first optical element using a temporary mirror surface piece;
Measuring a first shape error amount from an ideal optical surface shape of the first optical element;
Calculating a surface shape error amount from the ideal optical surface shape of the first optical element at a temperature of 40 ° to 80 ° C. by simulation;
Calculating the second shape error amount by adding the measured first shape error amount and the surface shape error amount calculated from the simulation;
Correcting the temporary mirror piece in a direction to cancel the second shape error amount; and
Forming a second optical element using the corrected temporary mirror surface piece;
A method for forming an optical element, comprising:   The method for molding an optical element according to claim 7, wherein the environment for measuring the first shape error is a measurement environment at a temperature of 20 ° C. ± 3 ° C.   An optical element formed by the method according to claim 1, 2, or 7. A resinous optical element formed into a predetermined optical surface shape by injection molding a resin material that expands by heating,
The surface shape of the optical element measured in a measurement atmosphere at a temperature of 20 ° C. ± 3 ° C., the surface shape of the optical element at a temperature corresponding to the use environment of the optical element appropriately set on the higher temperature side than the measurement atmosphere An optical element characterized in that the optical element is set to be smaller than the ideal optical surface shape in a direction to cancel out an expansion amount corresponding to a shape error amount from the ideal optical surface shape of the optical element.

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