JP2006205596A - Molding method of optical element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a molding method of an optical element for molding a plastic optical element using a molten resin, especially a molding method capable of eliminating the effect on the deformation of a temporary mirror surface piece caused by the difference between the temperature of the temporary mirror surface piece at the time of molding of the optical element and the temperature at the time of the normal temperature to perform the precise molding of the optical element. <P>SOLUTION: After the molten resin is used to be subjected to injection molding treatment using the temporary mirror surface piece, the optical surface shape of the temporary mirror surface piece is measured in a temperature environment at the time of molding. The shrinkage deformation ratio to the optical surface shape of a molded product in a normal temperature environment is calculated on the basis of the optical surface shape and the optical surface shape of the optical element in the temperature environment at the time of molding is calculated based on the shrinkage deformation ratio. Then, the difference of the optical surface shape of the temporary mirror surface piece to the calculated optical surface shape is calculated and the optical surface of the temporary mirror surface piece is corrected in the temperature environment at the time of molding to form a mirror surface piece having an ideal optical surface shape. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an optical element molding method for molding a plastic optical element using a molten resin.

  Today, a molding method for molding a plastic optical element using a molten resin is used. FIG. 6 is a diagram for explaining a conventional molding method. 20 shown in the figure is used as a mirror piece of an optical element, for example, and indicates the shape of the nest attached to the mold in the molding method at room temperature. When the molten resin is filled, the molten resin becomes a high temperature (molding temperature) and expands, for example, into the shape 21 shown in FIG. In this state, a molding process is performed, and a molded product having a shape shown in 22 is generated and contracted by cooling, so that the molded product has a shape shown in 23 in FIG. However, the shrinkage rate of the molded product shown in 23 varies depending on molding conditions. Therefore, the optical surface shape of the obtained molded product is different from the ideal optical surface shape 24 shown in FIG.

In order to obtain a highly accurate optical element, a molding method described in Patent Document 1 described below has been proposed. That is, the shrinkage deformation rate of the molded product is calculated from the optical surface shape of the mirror piece having the shape 20 shown in FIG. 7 and the optical surface shape of the molded product 23, and the mirror surface piece is corrected based on this shrinkage deformation rate, and the ideal optical A mirror piece having a surface shape 24 is to be obtained.
Japanese Patent No. 2898197

  However, the above molding method has the following problems. That is, at the time of molding, the mirror surface piece is heated by a temperature adjusting mechanism installed in the mold. Specifically, the temperature of the mirror piece is about 130 ° C. In this state, the cavity is filled with resin at around 200 ° C. Therefore, the surface temperature of the mirror surface piece instantaneously becomes 130 ° C. or higher. On the other hand, the measurement environment for performing precise shape measurement is usually a room temperature of about 20 ° C. For this reason, the mirror piece is deformed due to a temperature difference from the time of molding, and the shape of the mirror piece at the time of molding cannot be grasped.

  The linear expansion coefficient of the metal used for the mirror piece is 10 × 10 −6 ° C.−1. Therefore, if there is a temperature difference of 100 ° C., a deformation of 10 μm occurs for a length of 10 mm. Such deformation becomes a problem in an optical element that requires a shape accuracy of 1 μm or less. Also, when processing the mirror piece into a shape that offsets the shape error of the molded product, if the temperature of the mirror piece is different from the temperature at the time of molding, linear expansion due to the temperature difference occurs during molding, and the mirror piece is Deform. For this reason, the target error correction shape cannot be obtained, and the shape error of the molded product cannot be offset.

  Accordingly, in view of the above problems, the present invention eliminates the influence of the deformation of the temporary mirror surface piece due to the temperature difference between the temperature of the temporary mirror surface piece at the time of molding the optical element and the normal temperature, and forms an optical element molding method that accurately molds the optical element. It is to provide.

  According to the present invention, the above-described problem is a process in which an optical element is molded using a temporary mirror surface piece, and the temperature of the temporary mirror surface piece is set to a first temperature in the temperature region of the temporary mirror surface piece at the time of molding the optical element. The step of measuring the optical surface shape of the temporary mirror surface piece, the step of measuring the first optical surface shape of the optical element in a precise measurement environment, the optical surface shape of the temporary mirror surface piece, and the optical element The step of calculating the shrinkage deformation rate of the optical element from the difference from the first optical surface shape, and using the shrinkage deformation rate, the first optical surface shape of the optical element at the first temperature of the ideal optical surface shape. And calculating the shape error amount from the difference between the optical surface shape of the temporary mirror surface piece and the second optical surface shape of the optical element, and canceling the shape error amount. Set the temperature of the temporary mirror piece to the first temperature In the state, the can be achieved by providing a process of processing correcting the provisional optical insert, the method of molding an optical element and a step of molding an optical element using the optical insert that the correction processing.

  In addition, the first temperature when measuring the optical surface shape of the temporary mirror surface piece is, for example, a glass transition temperature of a resin to be used, which is −10 ° C. or higher, and a temperature not higher than the resin melting temperature in the cylinder.

  According to the present invention, the above-described problems are a step of forming an optical element using a temporary mirror piece, a step of measuring a first optical surface shape of the optical element at a first temperature that is a precision measurement environment temperature, and The step of measuring the first optical surface shape of the temporary mirror surface piece at the first temperature and the second optical surface shape of the temporary mirror surface piece at the second temperature at the time of molding the optical element are calculated by simulation. A step of calculating a contraction deformation rate of the optical element from a difference between the second optical surface shape of the temporary mirror surface piece and the first optical surface shape of the optical element, and using the contraction deformation rate. Calculating the second optical surface shape of the optical element at the second temperature of the ideal optical surface shape of the optical element; the first optical surface shape of the temporary mirror surface piece; and the second optical surface shape of the optical element. A step of calculating a shape error amount from a difference from the optical surface shape, and the shape A step of calculating a third optical surface shape of the temporary mirror surface piece that cancels the difference, and a step of calculating a fourth optical surface shape of the third optical surface shape at the first temperature by simulation. And providing a method of forming an optical element having a step of correcting the temporary mirror piece into the fourth optical surface shape and a step of forming an optical element using the corrected mirror piece. Can be achieved.

  Further, the first temperature is a temperature between 20 ° C. ± 3 ° C., and the second temperature is, for example, a glass transition point temperature of a resin to be used −10 ° C. or more, and a resin melting temperature in the cylinder The temperature is as follows.

  According to the present invention, it is possible to eliminate the influence of the deformation of the temporary mirror surface piece due to the temperature difference between the temperature of the temporary mirror surface frame at the time of molding and the temperature of the temporary mirror surface frame at normal temperature, and it is possible to correct the shape error amount with higher accuracy. Thus, a highly accurate optical element can be formed.

  Further, the deformation of the temporary mirror surface piece can be obtained by simulation, and an apparatus for heating the mirror surface piece such as a thermostatic bath can be dispensed with.

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

(Embodiment 1)
FIG. 1 is a cross-sectional configuration of a molding apparatus used for explaining the molding method of the optical element of the present embodiment. The apparatus shown in FIG. 1 includes a fixed mold 1 and a movable mold 2. Furthermore, a temporary mirror piece for forming an optical element is attached to the fixed mold 1 and the movable mold 2 as a nest. The inserts 3a and 3b shown in the figure are temporary mirror surface pieces attached to the fixed mold 1 side, and the inserts 4a and 4b are temporary mirror face pieces attached to the movable mold 2 side. A cavity 5a is formed between the inserts 3a and 4a, and a cavity 5b is formed between the inserts 3b and 4b. These cavities 5a and 5b are supplied with molten resin melted in a cylinder of an injection unit (not shown) via a sprue 6 and a runner 7.

  The movable mold 2 is provided with a pin drive mechanism 9 for driving the pins 8. The pin 8 is used for protruding an optical element formed in the cavity. That is, when the resin hardens, the movable mold 2 is moved in the direction of arrow a from the parting surface (PL). Then, the pin movable mechanism 9 is driven to move the pin 8 in the arrow b direction. Thereby, a molded product protrudes from a metal mold | die (nesting), and is accommodated in the storage part not shown.

Next, a method of molding the optical element of this example will be described using the injection mold having the above configuration.
FIG. 2 is a process diagram illustrating a method for molding an optical element of this example. In this process diagram, the temporary mirror surface pieces 3a, 3b, and 4a, 4b shown in FIG. 1 described above are corrected, a mirror surface piece used for the molding process is produced, and an optical element is formed using the mirror piece. Is explained. However, in order to make it easy to understand the change in the shape of the temporary mirror surface piece, it will be described as a shape slightly different from the shapes of the temporary mirror surface pieces 3a, 3b, and 4a, 4b shown in FIG.

  First, “1” to “4” shown in the figure are diagrams for explaining the first molding step, which is basically the same as the conventional molding process. That is, the temporary mirror surface pieces 3a3b, 4a, and 4b (hereinafter, representatively shown by the temporary mirror surface piece 3a) shown in the step “1” have shapes at room temperature. When the molding process is performed using the temporary mirror surface piece 3a having this shape, the temporary mirror surface piece 3a is heated by the filled molten resin. As a result, the shape of the temporary mirror surface piece 3a expands to the shape shown in the step “2”. In this state, in step “3”, the shape of the temporary mirror piece 3a is transferred to the molten resin. Thereafter, the optical element 10 and the temporary mirror piece 3a are cooled and contracted to have the shape shown in the step “4”. The shape shown in the step “4” is a state in which the optical element 10 and the temporary mirror surface piece 3a are both contracted.

  Next, in the process “5”, the temperature of the temporary mirror surface piece 3a is set to the temperature at the time of molding the optical element (first temperature). In this state, the optical surface shape A1 of the temporary mirror surface piece 3a is measured. That is, the temperature environment at the time of shaping | molding is implement | achieved using the thermostat etc. which are mentioned later. Then, the optical surface shape A1 is measured under this temperature environment. On the other hand, for the optical element 10 which is a finished product, the first optical surface shape B1 is measured in the precise measurement environment by the process “6”. Note that the temperature in the precision measurement environment is close to room temperature.

  Next, in step “7”, the shrinkage deformation rate of the optical element 10 is calculated from the shape difference between the optical surface shape A1 of the temporary mirror surface piece 3a and the first optical surface shape B1 of the optical element 10. That is, the optical surface shape A1 of the temporary mirror surface piece 3a is an optical surface shape measured at the molding temperature (first temperature), while the first optical surface shape B1 of the optical element 10 is substantially at room temperature. Optical surface shape. Therefore, the contraction deformation rate of the optical element 10 can be calculated by this process.

Next, using the contraction deformation rate, in step “8”, the optical surface shape of the optical element 10 at the first temperature, that is, the second optical surface shape B2 is calculated.
Next, in step “9”, the shape error amount is calculated from the difference between the optical surface shape A1 of the temporary mirror surface piece 3a and the second optical surface shape B2 of the optical element 10.

Next, in the process “10”, the temporary mirror surface piece 3a is corrected so as to cancel out the shape error amount. At this time, the temperature when the temporary mirror surface piece 3a is corrected is the first temperature described above.
Thus, the corrected temporary mirror surface piece 3a is used as the mirror surface piece 11 in the subsequent molding process of the optical element as shown in the step "11". That is, the mirror piece 11 (the corrected temporary mirror piece 3a) is incorporated in the mold, and the optical element is molded according to the molding steps “1” to “4” described above. The finished product 12 molded in this manner is an optical element having an ideal optical surface shape, with the amount of shape error canceled.

  As described above, in the present embodiment, the correction processing of the temporary mirror surface piece 3a is performed at the molding temperature (first temperature). Therefore, according to the present embodiment, it is possible to correct the shape error of the molded product caused by the cooling process after molding. In addition, the temporary mirror surface piece is deformed due to the temperature difference between the molding time and the normal temperature, and the shape error caused by such deformation can also be corrected. Therefore, a high-precision optical element very close to the ideal optical surface shape can be formed by performing the forming process using the mirror piece created by the process of this example.

In addition, the number of times the correction process is repeated can be reduced, the mold can be manufactured in a shorter period, and the start-up period of product manufacture can be shortened.
Furthermore, examples of the optical element molded by the molding method include a lens and a prism.

  FIG. 3 is a schematic view of an apparatus used for the measurement process of the optical surface shape A1 of the temporary mirror surface piece 3a performed in the step “5” and the correction processing of the temporary mirror surface piece 3a performed in the step “10”. It is. For example, FIG. 4A shows a case where the temporary mirror surface piece 3a is placed in the thermostatic chamber 15, the optical surface shape A1 is measured at the first temperature, and the temporary mirror surface piece 3a is corrected.

  FIG. 5B shows that the heater 16 is installed around the temporary mirror surface piece 3a, heated to the first temperature by a jig (not shown), the optical surface shape A1 is measured, and the temporary mirror surface piece 3a is corrected. This is an example of processing. Further, FIG. 5C shows an example in which a current is passed through the coil 18 by the high-frequency current generator 17 and the temporary mirror piece 3a is heated by induction heating.

Further, the contact type 3 is used for the measurement of the optical surface shape A1 of the temporary mirror surface piece 3a performed in the above-described step “5” and the measurement of the second optical surface shape B1 in the precise measurement environment performed in the step “6”. A dimensional shape measuring device or a non-contact type three-dimensional shape measuring device is used.

(Embodiment 2)
Next, Embodiment 2 of the present invention will be described.

FIG. 4 is a process diagram for explaining the optical element molding method according to the second embodiment. However, in this example, the first temperature is a temperature under a precision measurement environment, and the second temperature is a temperature at the time of molding.
First, similarly to the above-described first embodiment, the optical element is molded using the temporary mirror surface pieces 3a, 3b, and 4a, 4b (steps “1” to “4” shown in FIG. 4 described above). Thus, the optical element 10 shape | molded in this way measures 1st optical surface shape D1 in 1st temperature in process <1>. In the step <2>, the first optical surface shape C1 of the temporary mirror surface piece 3a is measured at the first temperature.

Next, based on the first optical surface shape C1 of the temporary mirror surface piece 3a, the second optical surface shape C2 of the temporary mirror surface piece 3a at the second temperature is calculated by simulation.
Next, in step <4>, the contraction deformation rate of the optical element 10 is calculated from the difference between the optical surface shape C2 of the temporary mirror surface piece 3a and the optical surface shape D1 of the optical element 10. That is, the second optical surface shape C2 of the temporary mirror surface piece 3a is an optical surface shape obtained by simulating the temperature at the time of molding, while the first optical surface shape D1 of the optical element 10 is optical at normal temperature. The surface shape. Therefore, the contraction deformation rate of the optical element 10 can be calculated by this process.

  Next, the second optical surface shape D2 of the optical element 10 at the second temperature is calculated in step <5> using the shrinkage deformation rate. This process is the same as the process of the above-mentioned process “8”.

  Next, in step <6>, the shape error amount is calculated in the same manner as in step “9” described above. In step <7>, the third optical surface shape C3 of the temporary mirror surface piece 3a is calculated. The third optical surface shape C3 is a surface shape that cancels out the shape error amount. Further, in step <8>, the optical surface shape C4 at the first temperature corresponding to the third optical surface shape C3 is calculated by simulation.

  In step <9>, the simulated temporary mirror face piece 3a is subjected to correction processing at room temperature. That is, in this case, the temporary mirror surface piece 3a can be corrected without using equipment such as the thermostatic chamber 15 or the like.

  The temporary mirror surface piece 3a thus corrected is used as the mirror surface piece 11 for the subsequent molding process of the optical element. That is, as described above, an optical element very close to the ideal optical surface shape can be obtained by incorporating the mirror piece 11 into a mold and performing a molding process.

  As described above, also by the molding method of the optical element of this example, the shape error caused by the deformation of the temporary mirror surface piece can be corrected, and a highly accurate molded product extremely close to the ideal optical surface shape can be molded. .

  In addition, according to this example, the temperature environment in which the correction processing of the temporary mirror surface piece 3a is performed is almost normal temperature, and the correction processing work of the temporary mirror surface piece 3a becomes easy. In addition, a highly accurate molded product can be molded by a cheaper apparatus without requiring the equipment such as the constant temperature bath 15 as described above.

Furthermore, examples of the optical element molded by the molding method include a lens and a prism as described above.
In this example as well, a contact-type three-dimensional shape measurement device or a non-contact-type three-dimensional shape measurement device is used to measure the optical surface shape of the temporary mirror piece 3a and the optical surface shape of the optical element. .

  In addition, the 1st temperature in the said Embodiment 1 and the 2nd temperature in Embodiment 2 are the glass transition point temperature of the resin to be used -10 degreeC or more, for example, are the temperature below the resin melting temperature in a cylinder. . The reason for setting such a temperature is that the temperature of the mirror piece immediately before the molded product is released from the mirror piece is a glass transition temperature of the resin of the molded product of −10 ° C. or higher. Immediately after the mold release, the mirror piece is rapidly cooled by the surrounding air and becomes lower than the glass transition temperature of the resin −10 ° C., and the optical surface of the mirror piece is deformed. It does not match and is inappropriate.

  Further, the mirror surface temperature at the time of molding does not become higher than the resin melting temperature in the cylinder. A temperature higher than the resin melting temperature in the cylinder is not suitable because the optical surface shape of the mirror piece does not match the optical surface shape at the time of molding.

  Further, the second temperature in the second embodiment is, for example, a temperature between 20 ° C. ± 3 ° C., and the operation of the measuring device cannot be guaranteed outside the temperature range, and precise measurement can be performed. Can not.

  The example shown in FIG. 5 shows an example of the glass transition point temperature (Tg point temperature) and the cylinder internal temperature of the resin used in this example.

It is a figure which shows the cross-sectional structure of the injection molding apparatus used in order to demonstrate the shaping | molding method of the optical element of this embodiment. It is process drawing explaining the shaping | molding method of the optical element of 1st Embodiment. (A) is a figure which shows the example which puts a temporary mirror surface piece in a thermostat, performs the measurement of an optical surface shape, and correction processing of a temporary mirror surface piece.

(B) is a figure which shows the example which heats the circumference | surroundings of a temporary mirror surface piece with the jig | tool not shown which installed the heater, performs an optical surface shape measurement, and correction processing of a temporary mirror surface piece.
(C) shows an example in which a current is passed through a coil by a high-frequency current generator, the temporary mirror surface piece is set to the first temperature by induction heating, the optical surface shape is measured, and the temporary mirror surface piece is corrected. FIG.
It is process drawing explaining the shaping | molding method of the optical element of 2nd Embodiment. It is a figure which shows an example of the glass transition point temperature (Tg point temperature) and cylinder temperature of resin used by this embodiment. It is process drawing explaining the shaping | molding method of the conventional optical element. It is process drawing explaining the shaping | molding method of the conventional optical element.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Fixed mold 2 ... Movable mold 3a, 3b, 4a, 4b ... Temporary mirror surface piece 5a, 5b ... Cavity 6 ... Sprue 7 ... Runner 8 ... Pin 9 ... Pin movable mechanism 10 ... Mold resin 11 ... Specular piece 15 ... Constant temperature bath 16 ... Heater 17 ... High frequency current generator 18 ... Coil

Claims (6)

Forming an optical element using a temporary mirror surface piece;
Measuring the optical surface shape of the temporary mirror surface piece in a state where the temperature of the temporary mirror surface piece is set to the first temperature in the temperature region of the temporary mirror surface piece at the time of molding the optical element;
Measuring a first optical surface shape of the optical element in a precision measurement environment;
Calculating the shrinkage deformation rate of the optical element from the difference between the optical surface shape of the temporary mirror surface piece and the first optical surface shape of the optical element;
Calculating the second optical surface shape of the optical element at the first temperature of the ideal optical surface shape of the optical element using the shrinkage deformation rate;
Calculating a shape error amount from the difference between the optical surface shape of the temporary mirror surface piece and the second optical surface shape of the optical element;
Correcting the temporary mirror piece in a state in which the temperature of the temporary mirror piece is set to the first temperature in a direction to cancel the shape error amount;
Forming an optical element using the corrected mirror piece;
A method for molding an optical element, comprising:   The first temperature at the time of measuring the optical surface shape of the temporary mirror surface piece is a glass transition temperature of a resin to be used, which is −10 ° C. or higher and a temperature not higher than a resin melting temperature in the cylinder. The method for molding an optical element according to claim 1. Forming an optical element using a temporary mirror surface piece;
Measuring a first optical surface shape of the optical element at a first temperature which is a precision measurement environment temperature;
Measuring the first optical surface shape of the temporary mirror surface piece at the first temperature;
Calculating a second optical surface shape of the temporary mirror surface piece at a second temperature at the time of molding the optical element by simulation;
Calculating the contraction deformation rate of the optical element from the difference between the second optical surface shape of the temporary mirror surface piece and the first optical surface shape of the optical element;
Calculating the second optical surface shape of the optical element at the second temperature of the ideal optical surface shape of the optical element using the shrinkage deformation rate;
Calculating a shape error amount from the difference between the first optical surface shape of the temporary mirror surface piece and the second optical surface shape of the optical element;
Calculating a third optical surface shape of the temporary mirror surface piece to offset the shape error amount;
Calculating a fourth optical surface shape of the third optical surface shape at the first temperature by simulation;
Correcting the temporary mirror piece into the fourth optical surface shape;
Forming an optical element using the corrected mirror piece;
A method for molding an optical element, comprising:   The method for molding an optical element according to claim 3, wherein the first temperature is a temperature between 20 ° C. ± 3 ° C. 5.   The optical element molding according to claim 3 or 4, wherein the second temperature is a glass transition temperature of a resin to be used, which is not lower than -10 ° C and not higher than a resin melting temperature in the cylinder. Method.   An optical element formed by the method according to any one of claims 1 to 5.