Apparatus and method for molding optical elements

Abstract

To provide a method that makes it possible to improve shape accuracy during molding of an optical element.SOLUTION: A method for forming an optical element with a predetermined shape by heating a pair of a first molding die and a second molding die, while moving the first and the second molding dies relative to each other to pressurize optical material housed between the first and the second molding dies, wherein distance information between the first and second molding dies is acquired in a process of a relative movement of the first and second molding dies, ands heating temperature of the first and second molding dies are controlled based on the acquired distance information and predefined reference distance information.SELECTED DRAWING: Figure 7

Description

Technical Field

[0001] The present disclosure relates to an optical element obtained by sandwiching a heat-softened optical material between a pair of molds and press-forming, as well as a molding apparatus and a molding method for the optical element.

Background Art

[0002] Of course, temperature control during molding is important in order to obtain an optical element with high precision and little distortion, but temperature control may also be performed during the cooling process.

[0003] As an example of such an optical element, glass molding for forming a glass lens will be described. Glass molding involves sandwiching a glass material between opposing molds, heating the glass material to a predetermined temperature at which it softens, applying a load to the molds to form the glass material into a lens shape, and then cooling it to a temperature at which it can be removed to form a glass lens.

[0004] Regarding temperature control and pressure (load) control during glass lens molding, for example, it is described in FIG. 6 of Patent Document 1. First, the mold is opened, the glass material is placed in the mold, and the mold is closed. The mold temperature at this time is a temperature close to room temperature. Since glass exhibits brittleness at normal temperature, no load (pressure) is applied in this state. Then, the temperature is raised to a predetermined temperature T1, the lower shaft position is adjusted so as to obtain a load P1, and pressure is applied to form the glass material into a lens shape. Further, the temperature is then lowered to the removal temperature. In a conventional example as shown in Patent Document 1 and the like, high-quality glass molding can be achieved by controlling the temperature even during the cooling process when pressing the glass.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

[0006] However, while the configuration described in Patent Document 1 controls the mold temperature to a constant level and controls the cooling curve during the cooling process, it does not measure the true temperature of the glass. Therefore, if the temperature of the temperature-controlled mold differs from the true temperature of the glass, the deformation resistance of the glass will vary with each molding. Consequently, it is difficult to manufacture glass lenses with high precision and reproducibility. Furthermore, this problem is common not only to the molding of glass lenses but also to the molding of optical elements.

[0007] This disclosure aims to solve the aforementioned conventional problems and to provide an optical element molding apparatus and molding method that can reduce variations in the shape accuracy of the optical element being molded and enable reproducible molding. [Means for solving the problem]

[0008] A method for forming an optical element according to one aspect of the present disclosure is a method for forming an optical element of a predetermined shape by heating a pair of molds, a first mold and a second mold, and moving the first mold and the second mold relative to each other, thereby pressurizing an optical material contained between the first mold and the second mold. During the process of relative movement between the first mold and the second mold, distance information between the first mold and the second mold is acquired, and the heating temperatures of the first mold and the second mold are controlled based on the acquired distance information and a preset reference distance information.

[0009] An optical element molding apparatus according to one aspect of the present disclosure comprises a pair of molding dies, a first mold and a second mold; a pressurizing device that moves the first mold and the second mold relative to each other to pressurize the optical material contained between the first mold and the second mold; a heating device that heats the first mold and the second mold; a distance sensor that acquires distance information between the first mold and the second mold; and a control device that controls the heating temperature of the first mold and the second mold by the heating device. The control device controls the heating temperature by the heating device based on preset reference distance information and distance information acquired by the distance sensor. [Effects of the Invention]

[0010] According to this disclosure, it is possible to provide an optical element molding apparatus and molding method that can reduce variations in the shape accuracy of the optical element being molded and enable reproducible molding. [Brief explanation of the drawing]

[0011] [Figure 1] This diagram shows an example of a glass lens molding apparatus that allows for production by dividing the glass lens press molding process. [Figure 2] An example of the progression of the closing time [Figure 3] Diagram explaining why the closing time varies. [Figure 4] A diagram showing the relationship between cutting time and corrected temperature (one example). [Figure 5] This diagram illustrates the flow for creating reference data for glass lenses in this embodiment. [Figure 6] This diagram illustrates the flow during mass production molding of glass lenses in this embodiment. [Figure 7] This figure illustrates a method for matching the deformation curve of the glass during pressing in this embodiment with a reference curve. [Figure 8] Main configuration of the press section of the glass lens molding apparatus in this embodiment [Figure 9] This figure illustrates an example of temperature feedback based on deformation rate in this embodiment. [Figure 10] Figure showing an example of the setting screen of the glass lens molding apparatus in the present embodiment

Mode for Carrying Out the Invention

[0012] The method for molding an optical element according to the first aspect of the present disclosure is a method for molding an optical element having a predetermined shape by pressurizing an optical material accommodated between a first molding die and a second molding die while relatively moving the first molding die and the second molding die, which are a pair of molding dies, while heating the first molding die and the second molding die. In the process of relative movement between the first molding die and the second molding die, distance information between the first molding die and the second molding die is acquired, and based on the acquired distance information and preset reference distance information, the heating temperatures of the first molding die and the second molding die are controlled.

[0013] The method for molding an optical element according to the second aspect of the present disclosure is, in the first aspect, the reference distance information is reference information indicating a temporal change in the distance between the first molding die and the second molding die in the process of relative movement between the first molding die and the second molding die, and based on the acquired distance information, the time information at which the distance information was acquired, and the reference distance information, the heating temperature is controlled.

[0014] The method for molding an optical element according to the third aspect of the present disclosure is, in the second aspect, the acquired distance information and the reference distance information are compared, and when the distance information is greater than the reference distance information, the heating temperature is increased, and when the distance information is less than the reference distance information, the heating temperature is decreased for control.

[0015] The method for molding an optical element according to the fourth aspect of the present disclosure is, in the second aspect, the moving speed in the relative movement is calculated based on the acquired distance information, the calculated moving speed and the reference speed in the reference distance information are compared, and when the moving speed is lower than the reference speed, the heating temperature is increased, and when the moving speed is higher than the reference speed, the heating temperature is decreased for control.

[0016] The molding apparatus for an optical element according to the fifth aspect of the present disclosure includes a first mold and a second mold which are a pair of molds, a pressing device that relatively moves the first mold and the second mold to press an optical material accommodated between the first mold and the second mold, a heating device that heats the first mold and the second mold, a distance sensor that acquires distance information between the first mold and the second mold, and a control device that controls the heating temperature of the first mold and the second mold by the heating device. The control device controls the heating temperature by the heating device based on preset reference distance information and the distance information acquired by the distance sensor.

[0017] The molding apparatus for an optical element according to the sixth aspect of the present disclosure is, in the fifth aspect, the control device includes a storage unit that stores the reference distance information as reference information indicating the temporal change of the distance between the first mold and the second mold in the process of the relative movement of the first mold and the second mold, and an arithmetic unit that calculates a control value for controlling the heating temperature by the heating device based on the acquired distance information, the time information at which the distance information was acquired, and the reference distance information stored in the storage unit.

[0018] The molding apparatus for an optical element according to the seventh aspect of the present disclosure is, in the sixth aspect, the arithmetic unit compares the acquired distance information with the reference distance information, and calculates the control value so as to increase the heating temperature when the distance information is greater than the reference distance information and decrease the heating temperature when the distance information is less than the reference distance information.

[0019] The molding apparatus for an optical element according to the eighth aspect of the present disclosure is, in the sixth aspect, the arithmetic unit calculates the moving speed in the relative movement based on the acquired distance information, compares the calculated moving speed with the reference speed in the reference distance information, and calculates the control value so as to increase the heating temperature when the moving speed is lower than the reference speed and decrease the heating temperature when the moving speed is higher than the reference speed.

[0020] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings.

[0021] (Embodiment) As an example of an optical element molding apparatus according to the embodiments of this disclosure, Figure 1 shows a glass lens molding apparatus 50 for molding glass lenses as optical elements. The glass lens molding apparatus 50 shown in Figure 1 is a glass lens molding apparatus that divides the glass lens molding process into multiple stages and increases productivity by using multiple molds 1. The glass lens molding apparatus 50 is an apparatus that uses, for example, an air cylinder as the pressurizing source of the pressurizing device.

[0022] As shown in Figure 1, in the glass lens molding apparatus 50, the mold 1 is transported from right to left, and multiple processes are sequentially performed on the mold 1. Specifically, in the glass lens molding apparatus 50, the molding process is carried out by sequentially performing the lens insertion process, heating process, press molding process, cooling 1 process, cooling 2 process, and lens removal process at each transport position of the mold 1 from right to left in the figure. In the following explanation, the position within the molding apparatus 50 where each process is performed will be referred to as the "~ section" (for example, the heating section for the heating process). Although not shown in the figure, the glass lens molding apparatus 50 is equipped with a mechanism (mold transport mechanism, shown as 56 in Figure 3) that sequentially transports the mold 1 at regular cycle times (for example, every 10 minutes). The mold 1 is composed of a pair of molds, and includes an upper mold (upper punch (corresponding to the first mold)) 2 and a lower mold (lower punch (corresponding to the second mold)) 3.

[0023] In the lens loading process, the upper mold 2 is removed from the mold 1 and placed on the lower mold 3, which is the optical material, the glass material 5a. Then, the upper mold 2 is inserted into the barrel mold 4, and the glass material 5a is sandwiched between the lower mold 3 and the upper mold 2, so that the glass material 5a is housed in the pair of molds 1. After a certain period of time, the loading shutter 11a opens, and the mold 1 is transported into the processing chamber 55 as if sliding sideways by the feeding mechanism, and the mold 1 is positioned near the center of the heater block 7 in the heating section. The processing chamber 55 is kept under vacuum or in an inert gas atmosphere such as nitrogen to prevent oxidation of the mold 1.

[0024] The heater block 7 of the heating section has, for example, multiple rod-shaped cartridge heaters 6 inserted into it, and a heater plate 8 with a hardness is mounted on top of them and controlled to maintain a predetermined temperature. Immediately after the mold 1 is placed on the heater plate 8 of the heating section, the temperature is lower than the set temperature of the heater plate 8 of the heating section, so in this process, almost no load is applied to the mold 1 by the press shaft 10. This is because if a load is applied when the temperature of the glass material 5a is low, the glass material 5a may crack, or the contact surfaces of the upper mold 2 and lower mold 3 with the glass material 5a may be damaged. The upper mold 2 also needs to be heated to a predetermined temperature in a predetermined time, so the upper heater plate 8 is provided so as to be in contact with the upper mold 2. In the latter half of this heating process, the glass material 5a reaches a temperature at which it can be sufficiently thermally deformed. After a predetermined time has elapsed, the mold 1 is transported to the molding section by sliding sideways on the heater plate 8 and heated in the press molding section.

[0025] When mold 1 is placed on the heater plate 8 of the press molding section, the press shaft 10 descends to push down the upper mold 2, crushing the glass material 5a and transferring the mold shape to the glass material 5a. After a predetermined time has elapsed, mold 1 is transported to the cooling section 1, and the next mold 1 is placed in the press molding section, and the press molding process is performed on the next mold 1.

[0026] When mold 1 is placed on the heater plate 8 of cooling section 1, the press shaft 10 descends, and the glass material 5b, which has been deformed into a lens shape, is held between the upper mold 2 and the lower mold 3. The set temperature of the heater plate 8 in cooling section 1 is set slightly lower than the temperature of the heater plate 8 in the molding section. As a result, the glass material 5b shrinks as the temperature drops, and this shrinkage completely transfers the shape by the upper mold 2 and the lower mold 3. After a predetermined time has elapsed, mold 1 is transported to cooling section 2, and the next mold 1 is transported from the press molding section to cooling section 1.

[0027] When the mold 1 is placed on the heater plate 8 of the cooling section 2, the press shaft 10 descends, and, similar to the cooling section 1, the glass material 5b, which has been deformed into a lens shape, is held between the upper mold 2 and the lower mold 3. The set temperature of the heater plate 8 of the cooling section 2 is set to the mold 1 removal temperature, and the mold temperature drops rapidly. After a predetermined time has elapsed, the removal section shutter 11b opens, and the mold 1 is transported to the removal section outside the processing chamber 55, and the next mold 1 is transported from the cooling section 1 to the cooling section 2.

[0028] When mold 1 moves to the removal section, the upper mold 2 is removed, and the molded glass material 5b, i.e., the molded lens 5b, is removed from the lower mold 3. Then mold 1 moves to the lens insertion section, where the next new glass material 5a is placed, and the same process is repeated.

[0029] Figure 1 illustrates the process overview in the glass lens molding apparatus 50. However, depending on the process time (cycle time), the heating process may be divided into two stages, or the cooling process may be further divided into multiple stages. It goes without saying that the set temperature (heating temperature) of the heater plate 8 differs for each process, but generally the temperatures in the heating process and the molding process are higher than those in the other processes. Specifically, in the molding process, it goes without saying that the set temperature of the heater plate 8 differs depending on the characteristics of the glass material 5a to be molded, but since a temperature above the glass transition temperature and near the flexing point is required, it may reach around 600°C. The set temperature in the first cooling process following the molding process is lower than that of the molding process, and the set temperature in the second cooling process is the removal temperature, so it is lower than that of the first cooling process.

[0030] Furthermore, the process of removing the upper mold 2 from the mold 1 and taking out the molded glass lens 5b, as well as the process of inserting new glass material 5a and assembling it, may also be automated. This can increase productivity.

[0031] In the press section of the glass lens molding apparatus shown in Figure 1, the press shaft 10 descends, pressing the upper die 2 against the lower die 3, and the heated and softened glass material 5a is molded into a lens shape. The upper die 2 is prevented from descending further by hitting, for example, a stopper, and a predetermined space corresponding to the lens shape is formed between the upper die 2 and the lower die 3. Figure 2 shows the time required from the start of pressing the glass material until the upper die hits the stopper (this state is called "cut-off") (referred to as "cut-off time"). Figure 2 shows an example of the change in cut-off time during continuous production of glass lenses in a glass lens molding apparatus according to a comparative example of this embodiment. The vertical axis shows the cut-off time (sec), and the horizontal axis shows the number of glass lenses produced during continuous production (N). The cut-off time is approximately 272 seconds, but it can be seen that there is a variation of nearly 30 seconds even in data of only a little over 60 units. Furthermore, since there is a large change even among adjacent data, it is not possible to read a trend over time. The glass lens molding apparatus in this comparative example has a similar apparatus configuration to the glass lens molding apparatus 50 of this embodiment, but it does not employ heating temperature control using a deformation curve, which will be described later as a reference.

[0032] A glass lens molding apparatus is a device that molds glass lenses with high productivity using multiple molds. Specifically, the molds move with each cycle time, and each process is carried out sequentially. For example, in the press section, multiple molds are transported sequentially to perform the pressing process, so the installation state differs for each mold, resulting in the problem that the heat transfer state to the mold changes. To explain this specifically using Figure 3, mold 1 moves and is transported as if sliding sideways along the press axis, but even if the heater plate 8 is at a predetermined temperature, the contact state between the bottom surface of the lower mold 3 and the heater plate 8 is different each time. That is, due to the sideways sliding of mold 1, dust is generated and the contact surface of the heater plate 8 wears down. As a result, the heat transfer state from the heater plate 8 to the lower mold 3 differs, and the problem arises that mold 1 and the glass material 5a contained in mold 1 are not at the same temperature each time.

[0033] Next, to verify the above problem, we changed the set temperature of the press section (press molding section) and evaluated how much the pressing time increased or decreased as a result. The results are shown in Figure 4. In Figure 4, the vertical axis shows the increase or decrease in the set temperature of the press section as the correction temperature (°C), and the horizontal axis shows the increase or decrease in pressing time (sec). Since a single experiment would result in large variations, multiple experiments were conducted. In the case of this glass lens, it was found that a change of ±2°C in the set temperature (standard set temperature: 605°C) resulted in an increase or decrease of approximately 30 seconds in the pressing time, compared to the standard pressing time of 272 seconds. From this, it can be concluded that the reason why the pressing time changes during normal production is due to variations in the actual temperature of the glass material contained in the mold, as mentioned above. It goes without saying that the relationship between these specific molding temperatures (set temperature of the press section) and lens shape will vary depending on the design shape of the lens, the type of glass material, or the molding conditions, but it is an important control point when mass-producing molded lenses.

[0034] Considering the mass production challenges described above, stabilizing the pressing time in the press molding process is crucial for producing high-precision lens shapes with good yield. Therefore, first, test molding is performed to establish the molding conditions for glass lenses, thereby establishing reference test conditions. Then, by mass-producing while reproducibly repeating the established reference test conditions, high-precision lens shapes can be produced with good yield. The basic process flow of the glass lens molding apparatus and molding method of this embodiment will be explained using the flowcharts in Figures 5 and 6.

[0035] Figure 5 shows a flowchart for creating reference data for glass lens molding in this embodiment. First, the mold and other equipment for glass lens molding are prepared, and initial conditions are created based on the glass material type and lens shape. Data such as deformation profile and pressing time are collected during actual glass lens molding (Step S1). Then, the shape of the molded lens is measured to determine its quality (Step S2). While sequentially reviewing the molding conditions (Step S3), these Steps S1 to S3 are repeated to determine the optimal conditions, taking into account lens performance and productivity. With these optimal conditions, reproducibility is confirmed (by the required number of experiments) (Step S4), reference conditions are determined, and the deformation curve and pressing time of the glass material obtained at that time are used as reference data (Step S5).

[0036] In the next stage, mass production of glass lenses is started. Figure 6 shows the flowchart for mass production of glass lenses in this embodiment. First, the reference data (deformation curve during press molding) obtained in the flowchart of Figure 5 is input (Step S11: the specific method will be described later). Next, mass production of glass lenses is started under the conditions obtained in Figure 5 (Step S12). In the press molding process, the deformation curve is compared with the reference curve each time it is pressed, and if the deformation curve deviates from the reference curve, the heating temperature is fed back to the heating device such as the heater plate 8 of the glass lens molding apparatus 50 to control the deformation curve so that it does not deviate from the reference curve as much as possible (Step S13). This reduces the variation in pressing time. The reproducibility of the lens shape of the molded lenses produced in this way is high, enabling high-quality production.

[0037] This section describes in detail a method for matching the deformation curve of the glass material during the press molding process in the glass lens molding apparatus 50 of this embodiment with a reference curve. Figure 7 is a graph of the process state from the start of pressing (before pressing) to the completion of cutting (after pressing) in the press section of the glass lens molding apparatus 50, with process time on the horizontal axis. The top row shows the press pressure (MPa), the middle row shows the temperature of the heater plate 8, and the bottom row shows the deformation curve (change in the position of the press axis 10).

[0038] The deformation curve shown in the lower part of Figure 7 illustrates how the distance between the upper die 2 and the lower die 3 changes over process time, using the height position information of the press axis 10 as the distance between the upper die 2 and the lower die 3. In this disclosure, reference distance information is used as reference information that shows the temporal change in distance, specifically how the distance between the upper die 2 and the lower die 3 changes during the relative movement process between the upper die 2 and the lower die 3. An example of such reference distance information is the reference curve (reference) shown in Figure 7.

[0039] The glass lens molding apparatus 50 of this embodiment is of the type that applies the load during molding using an air cylinder as the pressure source for the pressurizing device, and a constant pressure (load) is applied to the mold 1 as shown in Figure 7. However, such an air cylinder is just one example, and the load may be varied using an electro-pneumatic regulator or the like as the pressurizing device. Also, the deformation curve shown in the lower part of Figure 7 is set so that the press axis position (height position of the press axis 10) moves from a positive (+) position to a negative (-) position and becomes zero (0) at the cut-off position.

[0040] In the glass lens molding apparatus described in the comparative example above, the pressure and heating device temperature are constant. As the pressure in the air cylinder increases, the press shaft descends, and the upper die comes into contact with the glass material (press shaft position: Z0mm). Subsequently, over time, the press shaft descends to the cut-off position (press shaft position: 0mm). At this time, as explained in Figure 2, the cut-off time changes, so the time it takes for the press shaft to reach 0mm will differ for each molding operation.

[0041] In the glass lens molding apparatus 50 of the present embodiment, a deformation curve serving as a reference is pre-input according to the flow described in FIG. 6. When the pressing process is started, the deformation curve serving as a reference and the deformation curve of the glass material 5a being currently pressed are compared and calculated in real time starting from the position (press axis position: Z0) where the upper mold 2 and the glass material 5a come into contact. Specifically, with the press axis position: Z0 as time zero, when the press axis position Zn of the current deformation curve is smaller than the press axis position Zrn of the reference deformation curve at a certain time tn (Zrn > Zn), it can be seen that the glass material 5a being currently pressed is more deformed. When comparing with the temperature of the actual glass material, it can be estimated that the temperature of the actual glass material 5a is higher than that of the glass material during reference molding. In this case, control is performed so that the temperature (pressing temperature) of the heater plate 8 is set lower by Δt than the set value tr. Then, the actual temperature of the glass material 5a during deformation decreases, and the deformation resistance increases, thereby changing the deformation curve. As a result, by operating so that the deformation curve serving as a reference and the deformation curve of the glass material 5a during pressing are aligned, it becomes possible to match or approximate the cutting-off time when the press axis position becomes zero with the reference. When the cutting-off times match, an effect of reducing the variation in shape accuracy can be obtained. On the contrary, at time tn, if Zrn < Zn, it is considered that the actual temperature of the glass material 5a during molding is lower compared to that at the reference time. Therefore, it can be understood that the set temperature of the heater plate 8 may be controlled to be higher by Δt. The default values for the timings of these controls may be at a predetermined time interval, for example, at an interval of 1 second, and the temperature may be on the order of 0.1 °C units. As a control method, PID control or the like may be adopted.

[0042] We have explained how to control the temperature of the heater plate 8 in real time from the difference between the deformation curve of the reference and the deformation curve currently being pressed. However, it goes without saying that the response characteristics of temperature control will change depending on the shape of the lens, the type of glass material, and the mold size. Therefore, using the mass production flow shown in Figure 6 again, if the variation in the pressing time does not improve as much as expected even when trying to control the temperature with default values, it is necessary to optimize the temperature control. Specifically, in the flowchart of Figure 6, it is determined whether the variation in the pressing time exceeds a threshold (step S14). If it is determined that the variation is greater than the threshold, the temperature control is optimized, for example, by reviewing the control timing, control unit, or PID values ​​(step S15). If the variation in the pressing time is less than the threshold, the shape of the molded lens is measured (step S16), and the yield of shape accuracy is determined (step S17). If the yield is determined to be poor, the molding conditions are reviewed (step S18), and the reference data may be recreated if necessary (step S19).

[0043] Figure 8 shows the main configuration of the press section of the glass lens molding apparatus 50 in this embodiment, which can realize the glass lens molding process shown in Figure 7. Figure 8(a) shows the state before pressing, and Figure 8(b) shows the state after pressing.

[0044] The mold 1 comprises an upper mold 2, a lower mold 3, and a body mold 4, with the glass material 5a sandwiched between the upper mold 2 and the lower mold 3. The heating device comprises a heater block 7 containing multiple cartridge heaters 6, and a heater plate 8 positioned between the heater block 7 and the upper mold 2 and lower mold 3 to transfer heat from the heater block 7 to each mold 1. A temperature sensor 21 is positioned between the heater block 7 and the heater plate 8. An insulating material 9 is placed on the device side of the heater block 7 to prevent heat generated in the heater block 7 from being transferred to the device body. The mold 1 is installed in the central part of the surface of the heater plate 8 in this heating device, and heating devices of the same structure are symmetrically installed above and below it. The upper heating device is provided with a press shaft 10 that penetrates the wall (upper wall) of the processing chamber 52 in the vertical direction, and an air cylinder 22 that serves as a pressurizing source is provided on the upper end side of the press shaft 10. As shown in Figure 8(b), when a predetermined air pressure is supplied to the air cylinder 22, the press shaft 10 descends and pressurizes the die 1, specifically the upper die 2. A distance sensor 23 is fixed to the main body of the apparatus, for example, the processing chamber 52. The distance sensor 23 measures the operating distance (downward distance) of the press shaft 10 by measuring the distance between the press shaft 10, which is driven by the air cylinder 22, and a sensor target 24 attached to the shaft. In other words, the distance sensor 23 functions as a sensor that acquires distance information between the upper die 2 and the lower die 3, which changes due to the pressurization by the press shaft 10.

[0045] The glass lens molding apparatus 50 (see Figures 8 and 1) is operated by a control device 30 that controls the operation of each component of the glass lens molding apparatus 50, but the operation of the entire apparatus will not be described in detail. The main operation of this embodiment will be described below. The control device 30 comprises a calculation unit 31, a heater control unit 32, an amplifier 33, and a storage unit 34. The signal from the distance sensor 23 for measuring the operating distance of the press shaft 10 is input to the calculation unit 31 via the amplifier 33. The heater control unit 32 for temperature control drives the cartridge heater 6 based on commands from the calculation unit 31 and the temperature from the temperature sensor 21, and controls the heating temperature of the heating device. The storage unit 34 stores the reference described above.

[0046] The arithmetic unit 31 and the heater control unit 32 include a general-purpose processor such as a CPU or MPU that performs predetermined functions by executing a program. The arithmetic unit 31 and the heater control unit 32 perform temperature control of the heating device by calling and executing a control program stored in memory. The arithmetic unit 31 and the heater control unit 32 are not limited to those that perform predetermined functions through the cooperation of hardware and software, but may also be hardware circuits specifically designed to perform predetermined functions. For example, they can be implemented with various processors such as CPUs, MPUs, GPUs, FPGAs, DSPs, and ASICs.

[0047] The memory unit 34 is a recording medium for recording various types of information. The memory unit 34 can be implemented as, for example, flash memory, an SSD (Solid State Device), a hard disk, other storage devices, or a combination thereof as appropriate.

[0048] Here, we will explain again using Figure 8. The state before pressing, as shown in Figure 8(a), is when the mold 1 has been laterally fed from the heating section to the pressing section of the glass lens molding apparatus 50. Next, based on the control sequence of the entire glass lens molding apparatus 50, when air is supplied to the air cylinder 22, the press shaft 10 descends and the upper heater plate 8 comes into contact with the upper mold 2 of the mold 1. The distance measured by the distance sensor 23 at this time is Z0 (see Figure 7). In addition to the pressing load, heat is transferred from the heater plate 8 to the glass material 5a via the mold 1, so the glass material 5a softens and begins to deform. The amount of deformation of the glass material 5a is input to the calculation unit 31 as the measured value of the distance sensor 23. In the calculation unit 31, the deformation curve of the reference data stored in the storage unit 34 is compared with the measured value of the distance sensor 23. This comparison is performed based on the time information when the measurement was taken by the distance sensor 23, and the time information is acquired using a time measurement means such as a timer (not shown). The calculation unit 31 determines whether the production process is lagging or leading the reference deformation curve based on this comparison, and calculates a control value to control the heating device according to the difference from the reference. The heater control unit 32 changes the heating amount of the heating device based on this control value. As a result, the deformation curve of the mass-produced glass material 5a operates as if it were aligned with the deformation curve of the reference, thus reducing the variation in cutting time.

[0049] Figures 7 and 8 illustrate an example of temperature control by comparing a reference deformation curve with the actual deformation curve during molding, but the molding method of this disclosure is not limited to such cases. Figure 9 illustrates a modified example of this embodiment in which temperature feedback control is performed based on the deformation speed of the glass material (i.e., the movement speed of the press axis 10). The deformation speed Vn of the glass material is given by Vn = (Zn - Zn) as shown in Figure 9. +1) It can be obtained in real time as d / dt. Since the reference data can be calculated in the same way, the deformation speed of the reference and the real-time deformation speed can be compared. As described in FIG. 7, when the actual temperature of the glass material is high, the deformation speed Vn at the press axis position Zn corresponds to the deformation speed Vrn at the reference deformation position (press axis position) Zrn. When these are compared by the deformation speed, Vrn < Vn. Since the reference and the real deformation curves will deviate, in order to control the temperature of the heater to make the deformation curves coincide or approach each other, it is necessary to temporarily create a relationship of Vrn > Vn. After a certain time m has elapsed, when Zrn + m = Zn + m, by controlling so that Vrn + m = Vn + m, the reference and the real-time deformation curves can be made to coincide again.

[0050] An example of the setting screen of the glass lens molding apparatus 50 in the present embodiment is shown in FIG. 10. In order to realize the present embodiment, it is necessary to create and hold data that serves as a reference. It is desirable that the data can be changed according to the model of the glass lens to be produced. For this purpose, the control device 30 of the glass lens molding apparatus 50 shown in FIG. 8 may be provided with an interface function for storing and calling the reference data. For example, an interface as shown in FIG. 10 is convenient. With the interface of FIG. 10, the reference curve used in production can be selected from a plurality of types of reference curves stored in advance. Also, as a control method used in production, either control of the press axis position or speed control can be selected.

[0051] The glass lens molding apparatus 50 of this embodiment comprises a mold 1, a pressurizing device, a heating device, a distance sensor 23, and a control device 30. The mold 1 comprises a pair of molds, an upper mold 2 and a lower mold 3. The pressurizing device includes a press shaft 10 and an air cylinder 22, and pressurizes the glass material contained between the upper mold 2 and the lower mold 3 by moving the upper mold 2 and the lower mold 3 relative to each other. The heating device comprises a cartridge heater 6, a heater block 7, and a heater plate 8, and heats the upper mold 2 and the lower mold 3. The distance sensor 23 acquires distance information between itself and a sensor target 24 fixed to the press shaft 10 as distance information between the upper mold 2 and the lower mold 3. The control device 30 controls the heating temperature of the upper mold 2 and the lower mold 3 by the heating device. The control device 30 controls the heating temperature by the heating device based on a reference, which is a preset reference distance information, and the distance information acquired by the distance sensor 23.

[0052] The control device 30 comprises a storage unit 34 and a calculation unit 31. The storage unit 34 stores a reference as reference information indicating the temporal change in the distance between the upper mold 2 and the lower mold 3 during the relative movement of the upper mold 2 and the lower mold 3. The calculation unit 31 calculates a control value for controlling the heating temperature by the heating device based on the acquired distance information, the time information at which this distance information was acquired, and the reference stored in the storage unit 34.

[0053] The distance information between the upper type 2 and the lower type 3 may be used as velocity information, which is the temporal change in distance.

[0054] In the above explanation, the example of forming a lens as an optical element was used, but the object to be formed is not limited to lenses; other optical elements may also be formed. Furthermore, while glass was used as an example of the optical material, other materials may be used as long as they can be molded.

[0055] Furthermore, the distance sensor only needs to be capable of detecting the distance between the upper type 2 and the lower type 3, and for example, an optical distance sensor may be used.

[0056] Furthermore, while the example given was one where the press shaft 10 is lowered to push the upper die 2 down relative to the lower die 3, a configuration in which the lower die 3 is pushed up relative to the upper die 2 is also acceptable. Any configuration in which the upper die 2 and lower die 3 move relative to each other is acceptable.

[0057] Furthermore, although the example given was that reference data is pre-stored in the storage unit 34 of the control device 30, it is also possible that the reference data is obtained from a source other than the control device 30, such as a server.

[0058] Furthermore, while the example given was that the reference is curve data such as a deformation curve, this is not the only case. For example, the reference may be information on the press axis position at multiple points in time. The reference can be any reference distance information that shows changes over time.

[0059] Furthermore, by appropriately combining any of the above various embodiments, the effects of each can be achieved. [Industrial applicability]

[0060] The optical element molding apparatus and molding method disclosed herein can stabilize the cutting time during optical element molding, thereby improving shape accuracy and reproducibility. Furthermore, it can also be applied to the reheat molding of resin parts. [Explanation of Symbols]

[0061] 1. Mold 2. Upper mold (upper punch) 3. Lower type (lower punch) 4. Torso shape 5. Glass (5a Glass material, 5b Molded lens) 6. Cartridge heater 7. Heater Block (HB) 8. Heater Plate 9. Insulation 10. Press shaft (load shaft) 11. Shutters (11a Entrance, 11b Exit) 21. Temperature sensor (e.g., thermocouple) 22. Air Cylinder 23. Distance Sensor 24. Sensor Target 30. Control device 31. Arithmetic section 32. Heater Control Unit 33. Distance Sensor Amplifier 34.Memory part 50. Glass lens molding apparatus (overall) 51. Bass 52. Processing room 55. Processing chamber 56. Mold feeding mechanism

Claims

1. A method for forming an optical element of a predetermined shape by heating a pair of molds, a first mold and a second mold, and moving the first mold and the second mold relative to each other, thereby pressurizing the optical material contained between the first mold and the second mold, Reference distance information indicating the temporal change in the distance between the first mold and the second mold during the relative movement process between the first mold and the second mold is set in advance. During the relative movement between the first mold and the second mold, distance information between the first mold and the second mold is acquired. During the relative movement between the first mold and the second mold, the heating temperatures of the first mold and the second mold are controlled based on a comparison of the distance information at a certain time with the reference distance information at that time. In controlling the heating temperature, If the distance information at a given time is greater than the reference distance information at that time, the heating temperature is increased. A method for molding an optical element, wherein the heating temperature is controlled to be lowered if the distance information at a certain time is smaller than the reference distance information at that time.

2. A pair of molding dies, namely the first mold and the second mold, A pressurizing device that moves the first mold and the second mold relative to each other to pressurize the optical material contained between the first mold and the second mold, A heating device for heating the first mold and the second mold, A distance sensor that acquires distance information between the first mold and the second mold, The system includes a control device for controlling the heating temperatures of the first mold and the second mold by the heating device, The control device is A storage unit that pre-stores reference distance information indicating the temporal change in the distance between the first mold and the second mold during the relative movement process between the first mold and the second mold, The heating device comprises a calculation unit that calculates a control value for controlling the heating temperature based on a comparison of distance information at a certain time with reference distance information at that time stored in the storage unit during the relative movement process between the first mold and the second mold, An optical element molding apparatus, wherein the calculation unit calculates the control value such that if the distance information at a certain time is greater than the reference distance information at that time, the heating temperature is increased, and if the distance information at a certain time is less than the reference distance information at that time, the heating temperature is decreased.

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