WO2020230364A1 - Dispositif optique - Google Patents

Dispositif optique Download PDF

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Publication number
WO2020230364A1
WO2020230364A1 PCT/JP2020/000964 JP2020000964W WO2020230364A1 WO 2020230364 A1 WO2020230364 A1 WO 2020230364A1 JP 2020000964 W JP2020000964 W JP 2020000964W WO 2020230364 A1 WO2020230364 A1 WO 2020230364A1
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WO
WIPO (PCT)
Prior art keywords
light
lens
refractive index
optical device
lens unit
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PCT/JP2020/000964
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English (en)
Japanese (ja)
Inventor
佳史 村田
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株式会社村田製作所
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Publication date
Application filed by 株式会社村田製作所 filed Critical 株式会社村田製作所
Publication of WO2020230364A1 publication Critical patent/WO2020230364A1/fr

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K26/00—Working by laser beam, e.g. welding, cutting or boring
    • B23K26/02—Positioning or observing the workpiece, e.g. with respect to the point of impact; Aligning, aiming or focusing the laser beam
    • B23K26/06—Shaping the laser beam, e.g. by masks or multi-focusing
    • B23K26/064—Shaping the laser beam, e.g. by masks or multi-focusing by means of optical elements, e.g. lenses, mirrors or prisms
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B13/00—Optical objectives specially designed for the purposes specified below

Definitions

  • the present invention relates to an optical device.
  • an optical device for converting a light source light into a desired emitted light is provided.
  • a so-called thermal lens effect occurs in which the light collection performance is affected by a change in the refractive index distribution of the lens due to a change in temperature.
  • the focal position of the lens deviates from the processing point, so that the laser beam is not focused on the processing point, the beam diameter at the processing point fluctuates, and as a result, the processing accuracy deteriorates.
  • a first positive lens made of an optical material having a negative temperature coefficient of refractive index and a positive temperature coefficient of refractive index are positive.
  • a configuration in combination with a second positive lens made of a certain optical material is disclosed. In this configuration, even if the environmental temperature changes, the refractive indexes of the first positive lens and the second positive lens change in opposite directions, so that these changes are canceled out and the fluctuation of the focal position can be suppressed. it can.
  • Patent Document 2 discloses a laser irradiation device including an irradiation optical system in which at least one lens is made of a birefringent material.
  • this laser irradiation device since a plurality of focal points are formed in the optical axis direction of the laser beam by a lens made of a birefringent material, it is possible to process an object at a relatively deep depth of focus.
  • the spherical aberration of the lens can also change.
  • the temperature of the lens may rise locally because the heat of the laser beam is absorbed by a part of the lens.
  • the change in aberration characteristics may differ depending on the height of the incident light beam of the lens, but Patent Document 1 and Patent Document 2 do not consider such aberration of the lens. Therefore, when the change in the aberration characteristics due to the temperature change is remarkable, the beam diameter at the laser processing point may change significantly even if the fluctuation in the focal length is small, and the processing accuracy may deteriorate.
  • the present disclosure has been made in view of such circumstances, and an object of the present disclosure is to provide an optical device capable of maintaining a uniform beam diameter even when the temperature of a lens changes. Is.
  • the optical device is a collimating lens unit that converts light source light from a light source into parallel light, and a collection that collects parallel light emitted from the collimating lens unit and irradiates an object with irradiation light.
  • a condensing lens unit comprising an optical lens unit, the condensing lens unit includes a condensing lens made of a material having birefractive properties, and the irradiation light is a first condensing lens in which parallel light is refracted at a first refractive index.
  • the maximum value ⁇ Zmax of the amount of spherical aberration of the first ray is the focal point of the first ray and the second ray, including the second ray in which the light beam and the parallel light are refracted at the second refractive index higher than the first refractive index.
  • the focal separation amount is ⁇ f or more.
  • an optical device capable of maintaining a uniform beam diameter even when the temperature of the lens changes.
  • FIG. 1 is a diagram showing a configuration example of an optical device according to an embodiment of the present disclosure.
  • FIG. 2 is a diagram for explaining spherical aberration in a general spherical lens.
  • FIG. 3 is a diagram showing an example of an aberration curve in a lens having a positive temperature coefficient of refractive index.
  • FIG. 4 is a diagram showing an example of an aberration curve in a lens in which the temperature coefficient of the refractive index is negative.
  • FIG. 5 is a diagram showing an example of an aberration curve in a lens having birefringence.
  • FIG. 6 is a graph showing an MTF curve in the optical device according to the present embodiment and the optical device according to the comparative example.
  • FIG. 1 is a diagram showing a configuration example of an optical device according to an embodiment of the present disclosure.
  • the optical device 100 is provided in, for example, a laser processing machine or the like, and converts the light source light into a desired emitted light and outputs the light.
  • the optical device 100 may be provided in, for example, a laser processing machine that performs processing such as welding on an object such as metal or resin by laser light, but the optical device 100 is not limited thereto.
  • the optical device 100 includes, for example, a collimating lens unit 10, a condenser lens unit 20, and a lens cover 30.
  • the collimating lens unit 10 converts the light source light emitted from the light source 40 into parallel light and emits it.
  • the collimating lens unit 10 may be configured to include one or more lenses.
  • the collimating lens unit 10 in the present embodiment is configured to include three lenses 11 to 13 in order from the light source 40 side. Details of the materials and shapes of the lenses 11 to 13 will be described later.
  • the condensing lens unit 20 collects the parallel light emitted from the collimating lens unit 10 and irradiates the object 50 with the irradiation light.
  • the condenser lens unit 20 may be configured to include one or more lenses.
  • the condenser lens unit 20 in the present embodiment includes one condenser lens 21.
  • the condenser lens 21 converts parallel light so that the irradiation light is focused at the processing point of the object 50. That is, it is preferable that the focal length of the condenser lens 21 and the distance (working distance) from the condenser lens 21 to the object 50 match.
  • the focal length of the collimating lens unit 10 (that is, the distance from the principal point determined by the three lenses 11 to 13 to the focal point) is set to fa
  • the focal length of the condenser lens unit 20 (that is, the focal length of the condenser lens 21) is defined as fa.
  • the focal length fb may be longer than the focal length fa. More specifically, the focal length fb may be longer than, for example, four times the focal length fa.
  • the lens cover 30 is provided to protect the condensing lens unit 20 from processing scraps and the like scattered by laser processing.
  • the optical device 100 may include, for example, a prism or the like between the collimating lens unit 10 and the condenser lens unit 20. Next, the materials and shapes of the lenses 11 to 13 and the condenser lens 21 will be described.
  • FIG. 2 is a diagram for explaining spherical aberration in a general spherical lens.
  • Spherical aberration occurs in the lenses 11 to 13 and the condenser lens 21 due to the fact that they are spherical lenses. That is, the light rays that have passed through the lens are refracted so as to intersect the optical axis.
  • the intersection with the optical axis shifts toward the lens as the passing position of the light beam moves away from the optical axis, and longitudinal aberration in the optical axis direction (hereinafter, also referred to as a vertical direction or a depth direction) occurs.
  • a light ray passing through a point at a height h from the optical axis intersects the optical axis at a position P deviated from the ideal imaging position toward the lens by the amount of aberration ⁇ Z.
  • the lenses 11 to 13 have a shorter focal length than the condenser lens 21, that is, have a stronger power, so that the amount of aberration generated is larger than that of the condenser lens 21.
  • the power of the lenses 11 to 13 is stronger in the order of proximity to the light source 40, and the amount of aberration generated is also larger.
  • the lens 11 closest to the light source 40 has a meniscus shape or a plano-convex shape (meniscus shape in FIG. 1) that is convex toward the object 50 side.
  • All of these shapes are lens shapes in which aberrations are relatively unlikely to occur, and in particular, the meniscus shape is less likely to generate aberrations than the plano-convex shape. Therefore, by forming the lens 11 having the largest amount of aberration into a meniscus shape, the influence of the aberration generated in the collimating lens unit 10 can be suppressed. This is also advantageous in reducing the amount of aberration change due to temperature change.
  • the shapes of the lenses 12 and 13 are not particularly limited, but in the present embodiment, for example, they have a plano-convex shape that is convex toward the object 50 side.
  • the lens 11 closest to the light source 40 is made of a material having a negative temperature coefficient of refractive index.
  • the material having a negative temperature coefficient of refractive index may be, for example, a crystalline material such as artificial quartz or calcium fluoride, or glass such as S-LAM73, S-LAL20 from OHARA, or N-PSK53A from Schott. It may be.
  • a lens made of such a material acts to suppress a change in beam diameter at a laser processing point when the aberration changes as the temperature of the lens rises. This point will be described with reference to FIGS. 3 and 4.
  • FIG. 3 is a diagram showing an example of an aberration curve in a lens having a positive temperature coefficient of refractive index.
  • FIG. 4 is a diagram showing an example of an aberration curve in a lens in which the temperature coefficient of the refractive index is negative.
  • the horizontal axis indicates the imaging position (mm) in the depth direction (vertical direction), and the vertical axis indicates the height of the incident light beam.
  • the beam has a core in the center, and the beam diameter is substantially reduced. Since this distribution is significantly different from the distribution before the temperature rises, the degree of deterioration of the beam diameter due to the temperature rise is greater than in the case where the focal point only moves.
  • the aberration curve changes from a convex shape to the right side (back side) to a convex shape to the left side (front side), and changes in the focusing position due to fluctuations in the height of the incident light beam. It can be read that is becoming loose.
  • the change in beam diameter becomes small. That is, the degree of change in the beam diameter due to the temperature change can be reduced.
  • the lens 11 is made of a material having a negative refractive index temperature coefficient (for example, artificial crystal), and the lenses 12 and 13 have a positive refractive index temperature coefficient.
  • the lenses 12 and 13 are also composed of a material having a negative refractive index temperature coefficient in addition to or in place of the lens 11. You may.
  • the aberration generated in the lenses 11 to 13 is as small as possible.
  • the degree of aberration generated in the collimating lens unit 10 can be further suppressed.
  • the condenser lens 21 is made of a material having birefringence.
  • the material having birefringence may be a crystalline material such as quartz, rutile, sapphire, or magnesium fluoride.
  • the condenser lens 21 will be described as being composed of artificial quartz.
  • Artificial quartz is a uniaxial crystal having an optical axis in one direction. Artificial quartz has a higher transmittance in a wide wavelength range than other materials such as glass. Even when the artificial quartz transmits light having a relatively short wavelength and strong energy (for example, deep ultraviolet light), the optical characteristics are not easily impaired and the deterioration progresses slowly. In addition, artificial quartz has excellent water resistance because it does not have deliquescent properties.
  • the condenser lens 21 is arranged so that the optical axis of the incident light is not parallel to the optical axis and is not orthogonal to the optical axis.
  • the refractive index n o ordinary ray refracted at the (first refractive index) (first light beam), refracted by the refractive index n e (second refractive index) It separates into abnormal rays (second rays) and proceeds.
  • the vibrating planes of normal and abnormal rays are orthogonal and connect two different focal points in the optical axis direction.
  • the phase velocity of light rays differs depending on the traveling direction, so that the refractive index differs depending on the vibration plane.
  • the refractive index of extraordinary ray n e towards the (second refractive index) is higher than the ordinary ray refractive index n o (first refractive index) (n o ⁇ n e).
  • FIG. 5 is a diagram showing an example of an aberration curve in a lens having birefringence.
  • the horizontal axis indicates the position in the depth direction
  • the vertical axis indicates the height of the incident light beam.
  • FIG. 5 shows an image of the aberration curves of the normal light ray and the abnormal light ray divided into two by the condenser lens 21.
  • the artificial quartz since lower than the refractive index n e of the extraordinary ray direction of the refractive index n o of the ordinary ray, is longer than the focal length f e of the extraordinary ray direction of the focal length f o of the ordinary ray.
  • the distance between the focal point Fo of the normal light beam arranged on the back side and the focal point Fe of the abnormal light ray arranged on the front side is defined as the separation amount ⁇ f between the focal points.
  • the normal light is blurred so that a part of the normal light covers the optical path of the abnormal light, so that the two focal points Fo and Fe are smoothly connected and in the depth direction. A uniform beam diameter can be obtained.
  • the maximum value ⁇ Zmax of the aberration amount ⁇ Z of ordinary light rays is equal to or greater than the separation amount ⁇ f between focal points ( ⁇ Zmax ⁇ ⁇ f).
  • the condition is expressed in a mathematical formula as follows.
  • the amount of aberration ⁇ Z generated in the spherical lens is generally expressed by the following equation (1).
  • h is the height of the incident light beam from the optical axis.
  • f (h) is the distance between the principal point of the lens and the intersection of the light ray passing through the incident light ray height h and the optical axis.
  • f 0 is the focal length.
  • the coefficient K is a value represented by the following equation (2).
  • n is the refractive index.
  • q is a so-called shape factor.
  • the shape factor is a value represented by the following equation (3) when the radius of curvature on the object side of the lens is r 1 and the radius of curvature on the image side is r 2 .
  • p is a so-called position factor.
  • the position factor p is a value represented by the following equation (4) when the object distance is S and the image distance is S'(both are positive values).
  • the separation amount ⁇ f of the two focal points Fo and Fe is obtained.
  • the focal length f 0 of a lens having a refractive index n is expressed by the following equation (5) if the thickness of the lens is small.
  • the separation amount ⁇ f of the focal point of the normal light ray and the abnormal light ray in the present embodiment is expressed by the following formula (6).
  • n l is the lower refractive index of the two refractive index n o, n e. ⁇ n two refractive index n o, an absolute value of the difference between n e. f is the focal length when the refractive index is n l .
  • the amount of aberration ⁇ Z becomes maximum when, for example, a light ray passes through the maximum periphery of the lens (that is, the effective diameter of the lens).
  • a ratio of the focal length f of the lens to the effective diameter that is, corresponding to 2h
  • a general lens having a focal length f of 200 mm and an effective diameter of 48 mm for example, A. Laskin et al. " Beam shapping of focal length of multimode lasers ”, High-Power Laser Materials Processing: Applications, Diameters, Diseases ..
  • the condenser lens 21 preferably has a lens shape such that the shape factor q satisfies 1.3 ⁇ q.
  • the condenser lens 21 may be, for example, a lens having a positive meniscus shape convex toward the light source 40 side.
  • the upper limit of the shape factor q is preferably about 9 (1.3 ⁇ q ⁇ 9).
  • the condenser lens 21 is made of a crystal
  • the temperature coefficient of the refractive index of the crystal is negative. Therefore, as with the lens 11, the aberration characteristics are steep according to the height of the incident light even when the temperature rises. The degree of change in beam diameter due to temperature change can be reduced without changing to.
  • the condenser lens 21 is made of a material having birefringence, and the maximum value ⁇ Zmax of the aberration amount in the light ray having the lower refractive index is the separation amount ⁇ f between the focal points. That is all.
  • the maximum value ⁇ Zmax of the aberration amount in the light ray having the lower refractive index is the separation amount ⁇ f between the focal points. That is all.
  • the lens 11 closest to the light source 40 is made of a material having a negative temperature coefficient of refractive index.
  • FIG. 6 is a graph showing MTF curves in the optical device according to the present embodiment and the optical device according to the comparative example in order to show the degree of light collection in a specific diameter.
  • the vertical axis indicates MTF (Modulation Transfer Function), and the horizontal axis indicates the position in the depth direction.
  • the lens 11 shown in FIG. 1 is made of a glass material having a positive temperature coefficient of refractive index
  • the condenser lens 21 is a synthetic quartz (SiO 2 ) material having no birefringence. It is an aspect composed of.
  • the spatial frequency was set to 10 LP / mm (LP: Line Pairs).
  • the MTF is highest at the point where the depth direction is zero, but the MTF drops sharply as it deviates from that point. That is, a sharp edge can be processed at the condensing position, but it can be said that the processing accuracy is significantly deteriorated when the condensing position fluctuates due to a temperature change or the like.
  • the MTF value at the point where the depth direction is zero is not as high as in the comparative example, but the MTF is uniformly maintained over a wide range including the zero point. From this, it can be said that in the present embodiment, uniform processing is maintained even if the light collection position fluctuates as compared with the comparative example.
  • the optical device 100 is used in a laser processing machine that converts laser light, but the light converted by the optical device 100 is not limited to the laser light and may be other light. There may be.
  • Optical device 10 ... Collimating lens unit, 11-13 ... Lens, 20 ... Condensing lens unit, 21 ... Condensing lens, 30 ... Lens cover, 40 ... Light source, 50 ... Object

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  • Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Engineering & Computer Science (AREA)
  • General Physics & Mathematics (AREA)
  • Plasma & Fusion (AREA)
  • Mechanical Engineering (AREA)
  • Lenses (AREA)

Abstract

L'invention concerne un dispositif optique (100) comprenant : une unité de lentille de collimateur (10) qui convertit la lumière de source de lumière provenant d'une source de lumière en lumière parallèle ; et une unité de lentille de condensation (20) qui condense la lumière parallèle émise par l'unité de lentille de collimateur et irradie un objet avec une lumière d'irradiation, l'unité de lentille de condensation comprenant une lentille de condensation (21) constituée d'un matériau ayant une biréfringence, la lumière d'irradiation comprenant un premier rayon résultant de la réfraction de la lumière parallèle avec un premier indice de réfraction dans la lentille de condensation, et un second rayon résultant de la lumière parallèle étant réfracté avec un second indice de réfraction supérieur au premier indice de réfraction, et la valeur maximale ΔZmax de la quantité d'aberration sphérique du premier rayon est égale ou supérieure à la quantité de séparation δf du point focal du premier rayon et du point focal du second rayon.
PCT/JP2020/000964 2019-05-13 2020-01-15 Dispositif optique WO2020230364A1 (fr)

Applications Claiming Priority (2)

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JP2019090386 2019-05-13
JP2019-090386 2019-05-13

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WO2020230364A1 true WO2020230364A1 (fr) 2020-11-19

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Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2002169083A (ja) * 2000-11-30 2002-06-14 Nikon Corp 対物光学系、収差測定装置、投影露光装置、対物光学系の製造方法、収差測定装置の製造方法、投影露光装置の製造方法及びマイクロデバイスの製造方法
JP2003088984A (ja) * 2001-09-14 2003-03-25 Kawasaki Heavy Ind Ltd 薄板のレーザ溶接用出力ヘッド
JP2005169395A (ja) * 2003-12-05 2005-06-30 Toyota Motor Corp 固体レーザ加工装置およびレーザ溶接方法
WO2008069099A1 (fr) * 2006-11-30 2008-06-12 Sumitomo Electric Industries, Ltd. Système optique de condensation de lumière, procédé et appareil de traitement laser, et procédé de fabrication de matériau fragile
JP2011005537A (ja) * 2009-06-29 2011-01-13 Seishin Shoji Kk レーザー照射装置及びレーザー加工方法
JP2015198182A (ja) * 2014-04-02 2015-11-09 株式会社ディスコ 光デバイスウェーハの加工方法
WO2019078092A1 (fr) * 2017-10-17 2019-04-25 三菱電機株式会社 Dispositif d'usinage laser

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2002169083A (ja) * 2000-11-30 2002-06-14 Nikon Corp 対物光学系、収差測定装置、投影露光装置、対物光学系の製造方法、収差測定装置の製造方法、投影露光装置の製造方法及びマイクロデバイスの製造方法
JP2003088984A (ja) * 2001-09-14 2003-03-25 Kawasaki Heavy Ind Ltd 薄板のレーザ溶接用出力ヘッド
JP2005169395A (ja) * 2003-12-05 2005-06-30 Toyota Motor Corp 固体レーザ加工装置およびレーザ溶接方法
WO2008069099A1 (fr) * 2006-11-30 2008-06-12 Sumitomo Electric Industries, Ltd. Système optique de condensation de lumière, procédé et appareil de traitement laser, et procédé de fabrication de matériau fragile
JP2011005537A (ja) * 2009-06-29 2011-01-13 Seishin Shoji Kk レーザー照射装置及びレーザー加工方法
JP2015198182A (ja) * 2014-04-02 2015-11-09 株式会社ディスコ 光デバイスウェーハの加工方法
WO2019078092A1 (fr) * 2017-10-17 2019-04-25 三菱電機株式会社 Dispositif d'usinage laser

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