JP2009154276A - Apparatus and method for machining lens - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To efficiently manufacture many kinds and small amount of lens with desired polishing accuracy. <P>SOLUTION: In an apparatus for machining a lens by grinding and polishing a machined material 1, a surface shape of a semi-spherical portion of the lens is machined on an inner surface. This apparatus includes a pair of metal molds 2a, 2b for sandwiching the machined material 1 therebetween; a supply nozzle 6 for dropping a polishing liquid to a gap between the pair of metal molds 2a and 2b; and means 5a, 5b for adding ultrasonic wave vibration to the pair of metal molds 2a, 2b, and the supply nozzle 6. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a lens processing apparatus and a processing method thereof, and more particularly, to a lens processing apparatus and a processing method thereof for efficiently manufacturing a large variety of small quantities of lenses.

  Conventionally, various processing methods have been used for manufacturing optical lenses. For example, mechanical processing methods such as press molding using a mold, cutting with a micro rotary tool, and polishing are known. As processing methods for spherical lenses, barrel processing machines, lapping apparatuses, double-side polishing apparatuses, and the like are known. A barrel processing machine throws a lens processed piece and an abrasive into a rotating barrel, and performs rough processing of the processed piece by collision between the processed piece and the abrasive. A wrapping apparatus arranges a work holder that holds a workpiece on a lapping machine to which abrasive grains are attached, and grinds the workpiece by rotating the lapping machine and reciprocating the work holder (for example, Patent Document 1). The double-side polishing apparatus sandwiches a workpiece between upper and lower surface plates, rotates the upper and lower surface plates while dropping the abrasive material, and performs double-side polishing of the workpiece (for example, see Patent Document 2).

  On the other hand, as a microlens processing method, there is known an ultrasonic-assisted polishing apparatus that presses a fine polisher against a surface to be processed and applies ultrasonic vibration while applying polishing abrasive grains (see, for example, Non-Patent Document 1). . Ultrasonic vibration makes it possible to reduce the size of polishing marks, and a microlens having a diameter of about 0.5 to 3 mmφ can be manufactured.

  Here, the step of manufacturing a spherical lens is a first step of cutting a cubic workpiece from the lens material (cutting), a second step of removing the corners of the cube and grinding the workpiece into a substantially spherical shape, The workpiece is divided into a substantially spherical shape and a third step of polishing the workpiece into a spherical shape with a desired accuracy. The barrel processing machine and the lapping device are mainly used in the second step, and the double-side polishing device and the ultrasonic-assisted polishing device are mainly used in the third step. In addition, the barrel processing machine, the lapping apparatus, and the double-side polishing apparatus are suitable for small-quantity mass production, while the ultrasonic-assisted polishing apparatus is suitable for production of a variety of small quantities.

JP 2003-232902 A JP 2002-326154 A Hirofumi Suzuki, “Development of Ultrasonic Assisted Micro Aspherical Polishing Method”, Journal of the Japan Society of Mechanical Engineers, Vol.108, No.1040, p.36, July 2005

  Since the grinding in the second step only needs to process the workpiece into a substantially spherical shape, the shape error of the lens surface may be about several μm to several tens of μm. On the other hand, the polishing in the third step needs to process the shape error of the lens surface to a desired accuracy or less. For example, in the case of a microlens, a polishing accuracy of about 0.1 μm is required. Therefore, in the production of the spherical lens, there is a problem that the process becomes complicated and the production cost is high because the processing is performed using a dedicated tool for each of cutting, grinding and polishing.

  The present invention has been made in view of such a problem, and an object of the present invention is to provide a lens processing apparatus and a processing method for efficiently manufacturing a small amount of various types of lenses with desired polishing accuracy. It is to provide.

  In order to achieve such an object, the present invention provides a lens processing apparatus for manufacturing a lens by grinding and polishing a workpiece, and a hemispherical surface shape of the lens. A pair of molds that are processed on the inner surface and sandwich the workpiece, a supply nozzle for dropping a polishing liquid into a gap between the pair of molds, and the pair of molds and the supply nozzle, And a means for applying ultrasonic vibration.

  According to a second aspect of the present invention, in the lens processing apparatus according to the first aspect, the polishing liquid includes abrasive grains used for grinding and an abrasive used for polishing, and the polishing liquid is used as the pair. And a plurality of tanks in which cleaning liquid for washing from the gaps of the molds is stored, and the plurality of tanks are connected to the supply nozzles via switching valves.

  According to a third aspect of the present invention, in the lens processing apparatus according to the first and second aspects, by rotating the opposing surfaces of the pair of molds so as to slide and pressing the workpiece, The apparatus further includes means for crushing the workpiece.

  According to a fourth aspect of the present invention, a first step of cutting out a plurality of quadrangular prism workpieces from a lens material, and a second step of removing the corners of the workpieces and grinding them into a substantially spherical workpiece. And a third step of polishing the substantially spherical workpiece into a spherical shape with a desired accuracy, wherein the second step includes processing the surface shape of the hemisphere of the lens into an inner surface, The pair of molds is arranged such that abrasive particles for grinding are dropped from a supply nozzle into a gap between the pair of molds sandwiching the substantially spherical workpiece, and the opposing surfaces of the pair of molds slide. Each of the two is rotated, ultrasonic vibration is applied to the pair of molds and the supply nozzle, and in the third step, an abrasive for polishing is dropped from the supply nozzle into the gap between the pair of molds. The ultrasonic vibration is applied to the pair of molds and the supply nozzle.

  In the second step, abrasive grains having a particle size of 5 to 50 μm are dropped, ultrasonic vibration having a frequency of 20 kHz and an output of 30 W to 200 W is applied, and in the third step, an abrasive having a particle size of 0.01 to 1 μm. It is desirable to add ultrasonic vibration having a frequency of 100 kHz to 3 MHz and an output of 30 W to 200 W.

  As described above, according to the present invention, it is possible to efficiently manufacture a wide variety and a small amount of lenses with a desired polishing accuracy.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the present embodiment, a lens processing apparatus and a processing method for the same that can perform grinding and polishing continuously and can efficiently manufacture a wide variety and a small amount of lenses are provided.

  FIG. 1 shows a lens processing apparatus according to an embodiment of the present invention. The workpiece 1 is sandwiched between the ultrasonic horns 2a and 2b, and a method of processing this into a spherical lens will be described. The ultrasonic horns 2a and 2b have a hemispherical bowl shape, and are molds whose inner surfaces are processed into a spherical lens surface shape. Here, if the surface error of the desired spherical lens is 0.1 μm, the surface accuracy of the inner surface of the bowl may be about several μm. The ultrasonic horns 2a and 2b are connected to the rotary crushing mechanisms 3a and 3b and rotate around the axis centers of the rotation shafts 4a and 4b. That is, the opposing surfaces of the ultrasonic horns 2a and 2b rotate so as to slide with respect to the workpiece 1 that is sandwiched. The rotary crushing mechanisms 3a and 3b grind the workpiece 1 so as to crush the workpiece 1 by pressing the ultrasonic horns 2a and 2b against the workpiece 1 with an appropriate pressure.

  Also, ultrasonic vibration generating mechanisms 5a and 5b are connected to the rotary crushing mechanisms 3a and 3b, and ultrasonic vibrations can be applied to the ultrasonic horns 2a and 2b via the rotary shafts 4a and 4b. .

  FIG. 2 shows a detailed configuration of the ultrasonic horn. As the mold material, for example, titanium alloy, stainless steel, brass steel, iron, tin, lead, and alloys thereof are used. As shown in FIG. 2A, the inner surfaces of the ultrasonic horns 2a and 2b each have the shape of a desired hemisphere of a spherical lens. Opposing surfaces of the ultrasonic horns 2 a and 2 b have a gap 21. For example, when using a cast iron horn and 0.1 mm diameter colloidal silica, the thickness is about 1 mm. This gap is adjusted according to the material of the horn and the type of polishing liquid.

  When fixed to the rotary crushing mechanisms 3a and 3b, the polishing liquid dripped from the supply nozzle 6 is supplied from the upper gaps of the ultrasonic horns 2a and 2b, and the polishing liquid is discharged from the lower gaps facing each other. (FIG. 2B). Further, spiral grooves 22 may be formed on the inner surfaces of the ultrasonic horns 2a and 2b so that the polishing liquid covers the workpiece 1 as shown in FIG.

  The abrasive grain tank 7, the abrasive material tank 8, and the water washing tank 9 are connected to the supply nozzle 6 through a switching valve to supply the polishing liquid. The abrasive grain tank 7 stores abrasive grains and dispersing material for grinding, and the abrasive material tank 8 stores abrasive material and dispersing material for polishing. The washing tank 9 stores water or pure water for washing away the polishing liquid in the gap between the ultrasonic horns 2a and 2b. In addition, ultrasonic vibration generating mechanisms 5a and 5b are also connected to the supply nozzle 6, so that ultrasonic vibration can be applied to the supplied abrasive grains and polishing material.

  Further, the lens processing apparatus includes a receiving tray 9 that receives the polishing liquid discharged from the ultrasonic horns 2a and 2b, and the recovered polishing liquid is discharged to a waste liquid tank 10 or an abrasive tank for reuse. 7 or the abrasive tank 8 can be returned. The rotary crushing mechanisms 3a and 3b, the ultrasonic vibration generating mechanisms 5a and 5b, and the switching valve are controlled by the control mechanism 11.

  First, the grinding in the second step described above will be described. The workpiece 1 is a quadrangular prism cut out from a lens material. The control mechanism 11 supplies abrasive grains for grinding from the abrasive tank 7 to the supply nozzle 6, and controls the rotary crushing mechanisms 3a and 3b to rotate the ultrasonic horns 2a and 2b. The abrasive tank 7 may be prepared according to a plurality of different types of abrasive grains, and the abrasive grains may be changed according to the progress of grinding. In the grinding process, since accuracy is not required, the grain size of the dropped abrasive grains is about 5 to 50 μm, and for example, carborundum or diamond powder of about 10 to 50 μm can be used.

  In the second step, the grinding ability is given priority. The control mechanism 11 controls the ultrasonic vibration generating mechanisms 5a and 5b to apply ultrasonic vibration having a frequency of about 20 kHz to the ultrasonic horns 2a and 2b. The frequency of the ultrasonic vibration is preferably adjusted according to the diameter of the abrasive grains, and it is desirable to increase the frequency as the particle diameter decreases. The ultrasonic horns 2a and 2b are pressed against the workpiece 1 with a pressure of 100 kPa or less, and are subjected to grinding so as to crush the workpiece 1 by applying ultrasonic vibration.

  Further, by applying ultrasonic vibration to the supply nozzle 6, ultrasonic vibration is given to the polishing liquid, and this is dropped into the gap 22 between the ultrasonic horns 2a and 2b. The polishing liquid given ultrasonic vibration easily penetrates into the gap between the ultrasonic horns 2a, 2b and the workpiece 1 and the grinding ability of the workpiece 1 can be enhanced by the impact force of the ultrasonic waves.

  Next, the polishing in the third step described above will be described. The workpiece 1 is processed into a substantially spherical shape in the second step. The control mechanism 11 switches the switching valve from the abrasive grain tank 7 to the abrasive tank 8 and supplies the abrasive for polishing to the supply nozzle 6. Further, the ultrasonic vibration generating mechanisms 5 a and 5 b are controlled to apply ultrasonic vibration to the ultrasonic horns 2 a and 2 b and the supply nozzle 6. Since accuracy is required in the polishing process, the particle size of the dropped abrasive is about 0.01 to 1 μm, for example, a colloidal abrasive of about 0.05 to 0.1 μm. Use colloidal silica.

  In the third step, the grinding accuracy is prioritized for processing, so the pressure at which the rotary crushing mechanisms 3a, 3b press the ultrasonic horns 2a, 2b against the workpiece 1 and the rotational speed of the ultrasonic horns 2a, 2b are Make it smaller than the process. The control mechanism 11 controls the ultrasonic vibration generating mechanisms 5a and 5b to apply ultrasonic vibration having a frequency of about 3 MHz to the ultrasonic horns 2a and 2b. The frequency of the ultrasonic vibration is adjusted according to the diameter of the abrasive grains, and it is desirable to increase the frequency as the particle diameter is smaller. In the third step, the frequency is 100 kHz to 3 MHz.

  The control mechanism 11 applies ultrasonic vibration of about 3 MHz to the ultrasonic horns 2a and 2b and the supply nozzle 6, thereby applying ultrasonic vibration to the abrasive and dropping it into the gap 22 between the ultrasonic horns 2a and 2b. To do. When the abrasive material subjected to ultrasonic vibration comes into contact with the workpiece 1, the workpiece 1 is polished by a mechanochemical reaction. By adjusting the polishing time or the like, a surface shape error of 50 nm can be secured. Therefore, it can be seen that the accuracy of the molds of the ultrasonic horns 2a and 2b may be about several μm with respect to the surface error of the desired spherical lens of 0.1 μm.

According to the present embodiment, grinding and polishing can be continuously performed with one lens processing apparatus, and a large variety of small quantities of spherical lenses can be efficiently manufactured. Needless to say, the lens processing apparatus according to the present embodiment can be applied not only to processing a spherical lens but also to processing an aspherical lens by changing the inner surface shape of the ultrasonic horn. Hereinafter, an example in which the present embodiment is applied to manufacture of a lens using a KTaO ₃ crystal will be described. In addition, a present Example is an illustration, Comprising: A various change or modification can be performed in the range which does not deviate from the mind of this invention.

A step of manufacturing a spherical lens includes a first step of cutting a quadrangular prism or a substantially cubic workpiece from a KTaO ₃ crystal, and a second step of grinding the workpiece to a substantially spherical shape by removing the corners of the quadrangular prism or the substantially cube. The steps and the third step of polishing the workpiece ground into a substantially spherical shape into a spherical shape with a desired accuracy will be described in order.

  In the first step, a widely used inner edge type crystal cutting device is used. The inner peripheral type crystal cutting device sprinkles water or oil on a portion of a workpiece to be cut and rotates the blade to cut the crystal. In this embodiment, an inner peripheral blade having a blade thickness of 0.5 mm and water containing a surfactant are used.

About 40 mm square cubic KTaO ₃ crystal is fixed to a ceramic base of an inner peripheral type crystal cutting apparatus with an adhesive, and is cut into 2 mm-thick wafers and 20 sheets. The wafer is removed together with the ceramic table, the wafers are stacked and bonded, rotated 90 degrees, and further cut. Thereby, a strip-like crystal having a length of 2 mm and a length of 40 mm can be obtained. Remove the strip-shaped crystals from the ceramic table and place them horizontally and fix them to the ceramic table again. By cutting this, approximately 8000 KTaO ₃ crystals of approximately 2 mm square are obtained. The roughness of the cut surface depends on the diamond diameter of the inner peripheral blade and the cutting speed, and is in the range of 20 to 80 μm under the conditions in this example.

In the second step, the approximately 2 mm square KTaO ₃ crystal is ground using the lens processing apparatus shown in FIG. One KTaO ₃ crystal is sandwiched between the ultrasonic horns 2a and 2b. A polishing liquid in which CG abrasive grains having an average particle size of 30 μm are dispersed in water is supplied from the supply nozzle 6 from the abrasive grain tank 7. Ultrasonic vibration with a frequency of about 20 kHz is applied to the ultrasonic horns 2a and 2b, and the rotary crushing mechanisms 3a and 3b are controlled to rotate the ultrasonic horns 2a and 2b in opposite directions at 10 rpm.

By grinding for 15 minutes, a substantially spherical or spherical KTaO ₃ crystal with rounded corners can be obtained. The outputs of the ultrasonic vibration generating mechanisms 5a and 5b are adjusted according to the shape of the workpiece 1 within the initial machining range of 30W to 200W. The pressure with respect to the workpiece 1 of the ultrasonic horns 2a and 2b is adjusted to a pressure of 100 kPa or less. Abrasive grains can be recovered from the tray 9 to the abrasive tank 7 and reused. However, since the grinding ability is reduced by long-term use, the abrasive grains are appropriately replaced so that the desired grinding ability can be maintained. When the grinding process is completed, the polishing liquid is switched to the water from the washing tank 9, and the ultrasonic vibration and rotation are stopped after 3 minutes.

In the third step, the KTaO ₃ crystal ground in the second step is polished with a desired polishing accuracy using the lens processing apparatus shown in FIG. One ground KTaO ₃ crystal is sandwiched between the ultrasonic horns 2a and 2b. A polishing liquid in which colloidal silica having an average particle size of 0.1 μm is dispersed in water is supplied from a supply nozzle 6 from an abrasive tank 8. Ultrasonic vibration with a frequency of about 100 to 500 kHz is applied to the ultrasonic horns 2a and 2b, and the rotary crushing mechanisms 3a and 3b are controlled to rotate the ultrasonic horns 2a and 2b in the opposite directions at 20 rpm, respectively.

A spherical KTaO ₃ crystal can be obtained by polishing for 20 minutes. The outputs of the ultrasonic vibration generating mechanisms 5a and 5b are adjusted according to the shape of the workpiece 1 within the initial machining range of 30W to 200W. The colloidal silica can be recovered from the tray 9 to the abrasive tank 8 and reused. However, since the pH changes and the polishing ability decreases with long-term use, the colloidal silica is changed as necessary so that the desired polishing ability can be maintained. To do. When the polishing process is completed, the polishing liquid is switched to water from the washing tank 9, and the ultrasonic vibration and rotation are stopped after 3 minutes.

When the spherical KTaO ₃ crystal is observed with a microscope, no scratch is observed, and a surface shape error of 50 nm can be secured.

  The polishing liquid is selected from the desired surface shape error, economy, and productivity. Other polishing liquids are used as long as the performance of the lens processing apparatus of the present embodiment and the influence of mechanical damage are not affected. be able to. It is also clear that the ultrasonic horn can be ground and polished more uniformly by moving the ultrasonic horn with respect to the workpiece. Further, if a plurality of ultrasonic horns are driven simultaneously, a plurality of lenses can be processed simultaneously.

It is a block diagram which shows the processing apparatus of the lens concerning one Embodiment of this invention. It is a figure which shows the detailed structure of an ultrasonic horn.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Work material 2 Ultrasonic horn 3 Rotating mechanism 4 Rotating shaft 5 Ultrasonic vibration generating mechanism 6 Supply nozzle 7 Abrasive grain tank 8 Abrasive material tank 9 Flushing tank 10 Waste liquid tank 11 Control mechanism

Claims (6)

In a lens processing apparatus for manufacturing a lens by grinding and polishing a workpiece,
A pair of molds in which the surface shape of the hemisphere of the lens is processed on the inner surface, and sandwiches the workpiece;
A supply nozzle for dripping the polishing liquid into the gap between the pair of molds;
A lens processing apparatus, comprising: means for applying ultrasonic vibration to the pair of molds and the supply nozzle. The polishing liquid includes abrasive grains used for grinding and an abrasive used for polishing,
A plurality of tanks storing cleaning liquid for washing the polishing liquid from the gap between the pair of molds;
The lens processing apparatus according to claim 1, wherein the plurality of tanks are connected to the supply nozzle via a switching valve.   3. The apparatus according to claim 1, further comprising means for crushing the workpiece by rotating the opposing surfaces of the pair of molds so as to slide and pressing the workpiece. The lens processing apparatus described in 1. A first step of cutting out a plurality of quadrangular prism workpieces from a lens material; a second step of removing corners of the workpieces to grind into a substantially spherical workpiece; and the substantially spherical workpieces. A lens processing method including a third step of polishing into a spherical shape with a desired accuracy;
The second step includes
The surface shape of the hemisphere of the lens is processed on the inner surface, and abrasive grains for grinding are dropped from a supply nozzle into a gap between a pair of molds sandwiching the substantially spherical workpiece,
Rotate each of the pair of molds so that the opposing surfaces of the pair of molds slide,
Apply ultrasonic vibration to the pair of molds and the supply nozzle,
The third step includes
An abrasive for polishing is dropped from the supply nozzle into the gap between the pair of molds,
A lens processing method, wherein ultrasonic vibration is applied to the pair of molds and the supply nozzle.   5. The lens processing method according to claim 4, wherein in the second step, abrasive grains having a particle diameter of 5 to 50 μm are dropped, and ultrasonic vibration having a frequency of 20 kHz and an output of 30 W to 200 W is applied.   6. The lens according to claim 4, wherein in the third step, an abrasive having a particle size of 0.01 to 1 μm is dropped, and ultrasonic vibration with a frequency of 100 kHz to 3 MHz and an output of 30 W to 200 W is applied. Processing method.

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