JP2008238179A - Method for machining mold and apparatus for using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for machining a mold, which is not influenced by heat from a laser beam irradiated from an adjacent position and can finish a ground or cut molding part with high accuracy. <P>SOLUTION: While irradiating a laser beam 9 to one point 26 on a molding part 5 provided on a mold 4, the mold 4 is rotated for a given period of time. Thereafter, the irradiation point of the laser beam 9 is moved along the rotation radius of the mold 4 to conduct finish machining of the molding part 5. In this method, the machining level of the laser beam 9 is controlled by varying the rotating speed of the mold 4 depending upon the irradiation point of the laser beam 9. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for processing a mold used to mold an optical component such as a glass lens and a processing apparatus used therefor, and particularly to final finishing of a processed surface that has been ground or cut.

  An aspherical glass lens is used in a camera module having 1 million pixels or more mounted on a mobile phone or the like for the purpose of reducing the height and the resolution. This aspherical glass lens is a mold made of cemented carbide or the like processed based on an optically designed shape, and is formed by transferring a shape by pressing a spherical glass material while heating.

  Therefore, high mold accuracy is required for the mold to be used, and usually, as shown in FIG. 4, processing is performed using a cylindrical or abacus-shaped grindstone 1 to form a molding portion 2. FIG. 4 is a schematic diagram for explaining the state of the processing. While the mold 3 and the cylindrical grindstone 1 are rotated with respect to each other, the molding portion 2 is processed by moving the grindstone 1 along the locus of the designed shape. At this time, irregularities of a specific pattern are formed on the surface of the molding part 2 along the locus caused by the relative movement of the grindstone 1 and the mold 3, and this irregularity is transferred to the molded lens, so that the resolution and aberration are reduced. Cause. The unevenness is very minute, and therefore, the operator presses and removes the abrasive paper or the like against the molding portion 2 and finishes it manually.

As prior art document information relating to the invention of this application, for example, Patent Document 1 is known.
JP-A-7-1000075

  In the above-described conventional method, since finishing is performed manually by an operator, it is difficult to determine where to stop, and there is a problem in that shape accuracy is deteriorated by performing excessively.

  Therefore, an object of the present invention is to perform finishing without reducing the shape accuracy.

  In order to achieve the above object, the present invention rotates the mold for a certain period of time while irradiating a laser beam to a point on the molding part provided in the mold, and then sets the irradiation point of the laser beam to the mold. A processing method for finishing the molded part by moving along a rotation radius, wherein the processing amount of the laser light is changed by changing the number of rotations of the mold according to the irradiation point of the laser light. Since it is controlled, the amount of processing with laser light can be made constant according to the required processing accuracy or the rotation speed (peripheral speed) at each irradiation point, so the finished surface can be processed with high accuracy Can do.

  According to the mold processing method and the processing apparatus used therefor according to the present invention, after the mold is rotated for a certain time while irradiating the laser beam to one point on the molding portion provided in the mold, the laser beam is irradiated. The molded part is finished by moving the point along the radius of rotation of the mold. At this time, the amount of processing of the laser beam is controlled by changing the number of rotations of the mold according to the irradiation point of the laser beam at the radius of rotation, so the amount of processing per unit time according to the required processing accuracy In addition, it is possible to always keep the variation of the processing amount due to the difference in the rotation speed (peripheral speed) of the mold depending on the irradiation point, so the molded part of the mold can be finished with high accuracy. There exists an effect which can be processed.

  Also, by using laser light of ultrashort pulses such as picoseconds or femtoseconds as the laser light, and further moving the laser light from the rotation center of the mold toward the peripheral part, adjacent laser light irradiation points Since it is not affected by heat caused by the above, there is also an effect that can finish the molded part of the mold with higher accuracy at the same time.

  Embodiments of the present invention will be described below.

  FIG. 1 shows an example of a mold to be processed using the mold processing apparatus of the present invention. Fig.1 (a) is an external appearance perspective view of the metal mold | die 4 used for mold shaping | molding, such as a glass lens, FIG.1 (b) is AAA sectional drawing of Fig.1 (a). The mold 4 is made of a material such as carbide, and the top surface portion 4a has a spherical or aspherical molding portion 5 for molding a glass lens, and the other bottom surface portion 4b has a top surface portion. A flange 6 having a diameter different from that of 4a is provided. The pair of molds 4 is inserted into a cylindrical sleeve having both ends opened, and the shape is transferred to the glass material by heating and pressing while sandwiching the glass material with the molding portion 5. When forming a convex lens, as shown in FIG.1 (b), the concave-shaped shaping | molding part 5 is formed, and when forming a concave lens, the convex-shaped shaping | molding part 5 is formed.

  When forming the molding part 5 in the mold 4, the following two main processes are performed. This is a first process mainly for processing the lens shape and a second process for finishing the surface of the molded part 5 processed in the first process into a mirror surface. The first processing is to contact a tool such as a tool that is shaped diamond, or a fixed whetstone that is shaped after sintering fine diamond grains with metal, ceramic, resin, etc. while moving relative to the mold. By doing so, the molded part 5 having a spherical or aspherical shape is processed.

  In the second step, the unevenness remaining on the surface of the molded part 5 in the first step is removed to finish the mirror surface. In the first step, minute irregularities are formed on the surface of the forming portion 5 in a geometric pattern such as a cross stitch due to fluctuations in the number of rotations of the tool and the feed pitch. If the glass lens is molded with the minute unevenness remaining, the unevenness is transferred to the surface of the lens, and light is scattered or abnormally refracted, resulting in a decrease in resolution and aberration. For this reason, in particular, in a lens used in an image sensor with a high pixel of 1 million pixels or more, it is necessary to remove the minute irregularities from the molding unit 5 to make a mirror surface. The present embodiment is a processing method for removing minute irregularities remaining on the ground or cut surface of the molded part 5 and a processing apparatus used therefor.

  FIG. 2 is an external perspective view of the mold processing apparatus according to the embodiment of the present invention. The mold processing apparatus in the present embodiment includes a multi-axis stage 8 that holds and moves a mold 4 on a vibration isolation table 7, and a laser that irradiates a laser beam 9 to a molding portion 5 of the mold 4. The light generation unit 10 is mainly provided.

  The laser light generation unit 10 sends the excitation light 12 emitted from an excitation light source 11 such as an LD to the outside as a laser light 9 having a certain pulse width via an oscillator 13, a regenerative amplifier 14, and a power adjustment unit 15. By reflecting with a plurality of mirrors 16 and 17, the optical path is guided to the molding part 5 of the mold 4 held by the multi-axis stage 8, condensed by the condenser lens 18, and irradiated to the molding part 5. is there.

The oscillator 13 causes a crystal such as YLF (lithium yttrium fluoride: LiYF ₄ ) to emit light by irradiating the excitation light 12 from the excitation light source 11 and irradiates the semiconductor supersaturated mirror with the emitted light. An ultrashort pulse laser beam 9 such as picosecond or femtosecond is oscillated.

  Further, the laser beam 9 from the oscillator 13 is incident on the regenerative amplifier 14 to be amplified or polarized, and then the wavelength of the laser beam 9 is converted to a second harmonic by an SHG unit or the like as occasion demands. The power adjustment unit 15 adjusts the output to a constant level.

  The mold 4 is held and fixed to the multi-axis stage 8 by a holder 19 with the molding portion 5 exposed. The multi-axis stage 8 includes an x-axis, a y-axis, and a z-axis orthogonal three axes 20, a rotating shaft 21 that rotates on a horizontal plane composed of two of the orthogonal three axes 20, and a holder 19 at a constant rotation speed. And a rotating shaft 22 including a rotating air spindle and a high-frequency spindle. The rotating shaft 22 and the rotating shaft 21 are arranged so as to be orthogonal to each other, and the rotating shaft 21 adjusts the perpendicularity between the molding unit 5 and the optical path of the laser light 9. Then, the irradiation point of the laser beam 9 is moved along a substantially circular locus on the molding unit 5 by continuously rotating the rotating shaft 22 for a certain time while irradiating the laser beam 9 to one point on the molding unit 5. And finish processing.

  It should be noted that a monitor camera unit 23 for monitoring the state of the finishing process, and a centering camera unit 24 for correcting the machine origin by obtaining the rotation center of the mold 4 held by the holder 19, It is provided in parallel with the optical path of the laser beam 9.

  The above-described centering camera unit 24, monitor camera unit 23, multi-axis stage 8, oscillator 13 and the like are connected to the controller 25 via an input / output port. The mold 4 is rotated for a certain period of time while irradiating one point on the molding unit 5 with the laser beam 9, and then the multi-axis stage 8 is moved so that the laser beam 9 is constant along the rotation radius of the mold 4. Move at a pitch of. Then, by rotating again for a predetermined time and repeating these steps a plurality of times, the entire surface or a part of the molded part 5 is finished into a substantially circular shape. At this time, the processing amount per unit time is adjusted according to the peripheral speed and the required processing accuracy by changing the number of rotations of the rotating shaft 22 according to the irradiation point of the laser light 9 by the controller 25. It is.

  The mold processing apparatus described above is for adjusting the position of the laser beam 9 applied to the molding unit 5 by the multi-axis stage 8, but moving a part of the plurality of mirrors 16 and 17 for adjusting the optical path. Thus, the position of the laser light 9 can be adjusted. Thus, when the multi-axis stage 8 is configured, the accumulated error due to the incorporation of each axis can be reduced, and the laser beam 9 can be positioned with high accuracy.

  Next, an embodiment of a processing method using the mold processing apparatus will be described with reference to FIG.

  First, the energy distribution of the laser beam 9 is measured. Since the laser beam 9 has a Gaussian distribution centered on the optical path and the energy decreases, an effective diameter that actually contributes to processing is determined in advance.

  Next, the mold 4 is fixed to the holder 19, and the first point 26 on the molding part 5 is irradiated with the laser beam 9. At the first point 26, adjustment is performed by the rotating shaft 21 of the multi-axis stage 8 so that the laser light 9 is incident on the forming portion 5 substantially perpendicularly. Then, by rotating the mold 4 continuously by the rotating shaft 22 for a certain period of time while irradiating the laser beam 9, the irradiation point of the laser beam 9 on the molding portion 5 is moved, so that the effective diameter is substantially reduced. A first finishing process 27 that is circular is performed. Then, the multi-axis stage 8 is moved at a constant pitch, the irradiation point of the laser light 9 is moved along the rotation radius of the mold 4 to the second point 28, and then rotated again for a certain time. Then, the second finishing process 29 is performed on the molding portion 5 adjacent to the first finishing process 27. By repeating the above steps, a finishing process is performed on a part or the entire surface of the molded part 5.

  At this time, finishing is performed by varying the number of rotations of the mold 4 for each irradiation point of the laser light 9 in accordance with the required processing accuracy or the difference in rotational speed (peripheral speed) of the mold 4. Specifically, the amount of processing by the laser beam 9 is proportional to the amount of heat input to the irradiation point, and therefore the amount of processing is proportional to the product of the input energy of the laser beam 9 and the rotational speed of the mold 4. Therefore, by changing the number of rotations of the mold 4 for each irradiation point of the laser light 9, the amount of processing per unit time is adjusted according to the required processing accuracy.

  Further, when the mold 4 is rotated at the same rotational speed, the rotational speed (peripheral speed) of the mold 4 is different for each irradiation point (for example, 26, 28), so that the processing amount is different for each irradiation point. Become. Therefore, by making the number of rotations of the mold 4 variable for each irradiation point, the processing amount does not depend on the irradiation point and can always be constant.

  Further, by lowering the rotational speed of the mold 4, the processing mode of the laser light 9 can be mainly removed by heat, while by increasing the rotational speed, ablation or heat treatment is mainly used. be able to. Thus, by making the rotation speed of the mold 4 variable, the processing mode of the laser light 9 can be arbitrarily changed.

  When the irradiation point of the laser beam 9 is moved along the rotation radius of the mold 4 at a constant pitch, the pitch is at least equal to or larger than the spot diameter of the laser beam 9. Further, as indicated by an arrow B, the moving direction is moved from the rotation center of the mold 4 toward the peripheral portion. By doing so, the molded part 5 can be finished with high accuracy without being affected by the heat from the adjacent finished part.

  When performing the above-described finishing process, the pulse width of the laser beam 9 was set to an ultrashort pulse of about several tens of picoseconds. By setting it as such an ultrashort pulse, the influence of the heat by the adjacent laser beam 9 can further be reduced. In the present embodiment, the above-mentioned ultrashort pulse is used to set the energy to several mJ, so that ablation is generated at the irradiation point irradiated with the laser light 9 and minute irregularities are removed.

  In addition, carbon easily segregates on the uneven protrusions by grinding or cutting, and it is possible to remove only the protrusions depending on the irradiation condition of the laser light 9.

  According to the mold processing method and the processing apparatus used therefor according to the present invention, after the mold is rotated for a certain time while irradiating the laser beam to one point on the molding portion provided in the mold, the laser beam is irradiated. The molded part is finished by moving the point along the radius of rotation of the mold. At this time, the amount of processing of the laser beam is controlled by changing the number of rotations of the mold according to the irradiation point of the laser beam at the radius of rotation, so the amount of processing per unit time according to the required processing accuracy In addition, it is possible to always keep the variation of the processing amount due to the difference in the rotation speed (peripheral speed) of the mold depending on the irradiation point, so the molded part of the mold can be finished with high accuracy. There exists an effect which can be processed.

  Also, by using laser light of ultrashort pulses such as picoseconds or femtoseconds as the laser light, and further moving the laser light from the rotation center of the mold toward the peripheral part, adjacent laser light irradiation points Because it is not affected by the heat caused by heat, it also has the effect of being able to finish the molded part of the mold with higher accuracy, so the processing method of the mold used to mold optical parts such as glass lenses and so on It is useful for the finishing machine of the processing apparatus used for it, especially the grinding | polishing or the cutting processed surface.

(A) Appearance perspective view for explaining an example of a mold to be processed using the mold processing apparatus of the present invention, (b) A-AA sectional view of FIG. The whole perspective view explaining one embodiment of the metallic mold processing device of the present invention Schematic diagram illustrating the mold processing method of the present invention Schematic diagram explaining the conventional mold processing method

Explanation of symbols

4 Mold 5 Molding unit 7 Vibration isolation table 8 Multi-axis stage 9 Laser beam 10 Laser beam generator 11 Excitation light source 13 Oscillator 26 First point 27 First finishing 28 Second point 29 Second finishing

Claims (6)

While rotating the mold for a certain time while irradiating one point on the molding part provided in the mold, by moving the irradiation point of the laser light along the rotation radius of the mold, A processing method for finishing a molded part, wherein a mold for finishing a molded part by controlling the processing amount of the laser light by changing the rotational speed of the mold according to the irradiation point of the laser light. Processing method. The mold processing method according to claim 1, wherein the laser beam is an ultrashort pulse laser beam. The mold processing method according to claim 2, wherein the irradiation point of the laser beam is moved from the rotation center of the mold toward the peripheral portion. A vibration isolator, a multi-stage stage having at least a holder for holding a mold having a molding unit on the anti-vibration table, a rotating shaft for continuously rotating the holder, and the molding unit are irradiated with laser light. And a laser beam generator comprising an optical system such as an excitation light source, an oscillator, a mirror and a lens, and rotating the mold for a certain period of time by irradiating a laser beam to one point on the molding unit Then, the laser beam irradiation point is moved along the radius of rotation of the mold, thereby finishing the molding part. A mold processing apparatus for controlling the processing amount of the laser beam and finishing the molded portion by changing the irradiation point according to the irradiation point. The mold processing apparatus according to claim 4, wherein the laser unit is a generator of ultrashort pulse laser light. The mold processing apparatus according to claim 5, wherein the irradiation point of the laser beam is moved from the rotation center of the mold toward the peripheral edge.

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