Sumitomo Electric Industries, Limited

Sumitomo Electric Hardmetal Corp.

Keiji Fuse

Kenichi Watatani

Motoki Kakui

Manabu Shiozaki

Yutaka Kobayashi

Takayuki Hirai

Kenichi Kurisu

Keiji Ebata

A condensing optical system having a condensed light spot with a small size and a large focal depth without causing a problem of a decrease in intensity of the condensed light spot or discontinuity of an intensity distribution in front and rear areas of a focal position is provided. The condensing optical system that condenses a laser beam generated by a laser source at a predetermined focal length is designed to satisfy Expressions (a) to (d), thereby producing 3rd and 5th spherical aberrations:||&#x2267;0.1&#x3bb; or ||&#x2267;0.05&#x3bb;,&#x2003;&#x2003;(a)&#x2267;3 or&#x3c;1,&#x2003;&#x2003;(b)||&#x3c;1.4&#x3bb;, and&#x2003;&#x2003;(c)||&#x3c;0.5&#x3bb;,&#x2003;&#x2003;(d)where &#x3bb; is a wavelength, Zis an 8th coefficient of coefficients of the Zernike fringe polynomial of wavefront aberration corresponding to a 3rd order spherical aberration, and Zis a 15th coefficient of the coefficients of the Zernike fringe polynomial of wavefront aberration corresponding to a 5th spherical aberration.

Condensing optical system, laser processing method and apparatus, and manufacturing method of brittle material blank

The present invention relates to a laser processing method and laser processing apparatus for enabling improvement and maintenance of homogenization of a beam intensity distribution in an irradiated region. The laser processing apparatus comprises, at least, an ASE light generation section for emitting ASE light, and a homogenizer for splitting the ASE light into multiple beams. The ASE generation section for emitting the ASE light as processing laser light is provided, and whereby the deterioration of homogenization due to inter-beam interference is suppressed. The homogenization of beam intensity distribution is improved by locating a condenser lens relative to an object such that the object is shifted from a focus position of the condenser lens in the homogenizer, by intentionally deteriorating a beam quality Mof the ASE light itself emitted from the ASE light generation section to about 2 to 10, or by a combination of these, in laser processing.

Laser processing method and laser processing apparatus

Ultrashort pulse laser processing bores, welds or cuts objects (work pieces) by converging ultrashort laser pulses by a lens on the objects (work pieces) positioned at the focus and heating small spots or narrow lines on the objects (work pieces). Shortage of a focal depth of the lens prevents the ultrashort pulse laser processing from positioning the object (a work piece) and forming a deep, constant-diameter cylindrical hole. Z-parameter is defined to be Z=2fc&#x394;t/&#x394;i, where &#x394;t is a FWHM pulse width of the ultrashort pulse laser, &#x394;i is a FWHM beam diameter of the ultrashort pulse, f is a focal length of the lens and c is the light velocity in vacuum. Selection of an optical system including a diffraction-type lens which gives the Z-parameter less than 1 (Z&#x3c;1) prolongs the focal depth. Expansion of the focal depth facilitates the positioning of objects (work pieces) and enables the ultrashort pulse laser apparatus to bore a deep, constant-diameter cylindrical hole.

In a laser optical device including a beam shaping optical systemfor shaping a laser beaminto a predetermined cross-sectional intensity distribution and converging the light and an image formation optical systemfor forming an image of a shaped beamshaped and converged through the beam shaping optical system, the image formation optical systemis made up of an objective lens systemhaving a negative focal length placed ahead of a focal planeof the beam shaping optical systemand an imaging lens systemplaced behind the objective lens system

Laser optical device

A conventional diffractive optical element (DOE), which consists of repetition of a unit pattern, has an advantage of applicability of the Fast Fourier Transform algorithm to calculate diffraction beam spots intensities on lattice points on an image plane. But, the conventional DOE has a drawback of impossibility of diffracting a laser beam off the lattice points. This invention designs a DOE by giving arbitrary complex amplitude transmittance {t} to every pixel (m, n), calculating actual Fourier transform from {t} to intensity W(&#x3b1;, &#x3b2;), and obtaining intensity of a diffraction beam directing in any &#x3b1; and &#x3b2; direction. Since &#x3b1;, &#x3b2; are not necessary to be on lattice points, the FFT is of no use. Angular resolutions U and V satisfy inequalities U&#x3c;&#x3bb;/aR and V&#x3c;&#x3bb;/bS, where &#x3bb; is a wavelength, aR and bS are the size of the DOE. The DOE can produce multidiffracted beams anywhere on an image and can irradiate a plurality of arbitrary arranged points simultaneously with high precision. The DOE realizes precise multispot microprocessing on arbitrary positions, which is required for producing electronic parts. The DOE is suitable for high speed and low cost laser processing.

Diffractive optical element

A single lens homogenizer for converting a wide, parallel, in-phase Gaussian beam into a narrow uniform-power beam and shooting an object with the narrow uniform-power beam is proposed. A tilt error induces beam deformation. A single lens homogenizer which can reduce the beam deformation induced by the tilt error is proposed. A suitable homogenizer is a convex/flat lens having a convex aspherical surface on the light source side and a flat surface on the object side. Another preferable homogenizer is a convex/convex lens having a convex surface on the light source side and a convex surface on the object side. At least one of the convex surfaces is an aspherical convex surface.

Tilt error reducing aspherical single lens homogenizer

A laser beam emitted from a laser source is split by a beam-splitting means such as a beam sampler, and the power Q of the split beam is measured by a first detector. In addition, the power qof light that has passed through a pinhole while a DOE is not set is measured by a second detector, and the power ratio &#x3b1;=q/Q is calculated. Then, the DOE is set and the power ratio &#x3b2;=q/Q, where qis the power of each light beam, is calculated. The power ratio &#x3b2;is evaluated on the basis of the power ratio &#x3b1;, so the optical properties of a diffractive optical element, in particular, in terms of diffraction efficiency in laser-beam diffraction and intensity uniformity of split beams can be measured with high accuracy.

Apparatus and method of measuring optical properties of diffractive optical element

The present invention provides a different optical element having superior optical characteristics. A polycrystalline substrate having crystal grains whose sizes are not more than 1 &mgr;m or an amorphous phase at the dry-etched surface thereof, or an upper film layer formed on a polycrystalline substrate being the same materials as that of the polycrystalline substrate , which has finer crystal grains than-those of the substrate. The upper film layer is dry etched, and AR coat is formed thereon.

In the design of a lens system, lens parameters are determined by minimizing a merit function which is a sum of squares of ray aberrations or wavefront errors at many sampling points. Prior methods often select the parameters which give very narrow tolerances to production errors. The small tolerance increases the difficulty of production. In order to increase the tolerances, states which allot errors &plusmn;&dgr; to some chosen parameters are considered. Merit functions corresponding the error-allotted states are made. An integrated merit function is produced by adding the error-allotted merit functions to the non-error allotted normal merit function. Parameters are determined by minimizing the integrated merit function. The optimized parameters will give wider tolerances for the error-allotted parameters. DOE (diffraction optical elements) design includes the steps of considering error-allotted states S , S , . . . in addition to a non-error state S , making merit functions E , E , . . . for S , S , . . . besides E for S , defining an integrated merit function E&equals;&Sgr;w E by multiplying the merit function with weights and summing up, minimizing the integrated merit function and determining optimum variables for the DOE.

Method for designing a refractive or reflective optical system and method for designing a diffraction optical element

A laser hole boring apparatus comprising a galvanomirror beam scanning system, a DOE beam diffraction system and a selecting device for the two systems optionally. The DOE system bores many holes simultaneously on printed circuit boards or packages by converting a laser beam into two dimensional diffraction beams and converging the diffraction beams by an f sin &thgr; lens into spots on the object (board, package). The galvanomirror system bores many holes sequentially on printed circuit boards or packages by scanning a pulse laser beam in two dimensions and converging the scanned beam by an f sin &thgr; lens into a spot on the object.

Laser hole boring apparatus

f&thgr; lens

A laser beam condensing device which can be manufactured at low cost by using reflecting mirrors which can be machined at low cost. The device is capable of condensing a laser beam to a high energy density while eliminating any optical path difference, even if the optical axis of the incident beam strays. This device includes a first and a second reflecting mirror. An incident laser beam is deflected by these mirrors in the same direction. One of the two mirrors is a toroidal mirror, while the other is a spherical, cylindrical or toroidal reflecting mirror. The mirror surfaces of the two reflecting mirrors are machined so that the second reflecting mirror can cancel out any wave front aberrations of the laser beam reflected by the first reflecting mirror.

Method and device for focusing laser beam

A unit for splitting a laser beam into a plurality of beams is provided separately from a converging unit so that both units can be manufactured easily, replaced at low cost and are less likely to be polluted or damaged during laser machining. A laser beam produced by a laser oscillator and guided into a machining head through a transmitter is split into a plurality of beams by a plane reflecting mirror. The laser beams thus split are reflected by another reflecting mirror having a single paraboloidal surface so as to be converged on focal points. The first plane reflecting mirror comprises two semicircular mirrors which can be inclined independently of each other.

Growing community of inventors

Osaka, Japan

Keiji Fuse