Method and device for forming curved sections in a transparent material

A method of producing curved cuts in a transparent material, by generating optical breakthroughs at different locations within the material by application of pulsed laser radiation focused into the material beneath a surface of the material, wherein said laser radiation is two-dimensionally deflected in a scan pattern to produce the cut by sequential arrangement of the optical breakthroughs, comprising the steps of:

• effecting the two-dimensional deflection in the scan pattern such that the locations of optical breakthroughs are spaced apart, along a curve along which the optical breakthroughs are sequentially arranged, according to a deflection-related angular function which is non-linear and adapted to the curvature of a desired cut such that the locations of adjacent optical breakthroughs along the curve are spaced apart by substantially the same distance within a tolerance, wherein the cut is substantially spherically curved with a radius R, the laser radiation is incident in the material along a main axis of incidence and is biaxially deflected along an x-axis and a y-axis in a plane perpendicular to said main axis of incidence, wherein a step width dx between locations on the curve of adjacent optical breakthroughs is set in the plane in x-direction according to:
• dx
• =
• D
• ·
• R
• ⁢
• ⁢
• 1
• R
• ⁢
• ⁢
• 1
• 2
• -
• x
• 2
• ,
• wherein D designates the distance between centers of the optical breakthroughs and
• R
• ⁢
• ⁢
• 1
• =
• R
• ·
• cos
• ⁢
• ⁢
• (
• arc
• ⁢
• ⁢
• tan
• ⁢
• y
• R
• )
• .

An apparatus for producing curved cuts in a transparent material, said apparatus comprising:

• a pulsed laser radiation source which focuses laser radiation into the material and causes optical breakthroughs within the material,
• a deflecting unit deflecting the laser radiation two-dimensionally;
• a control unit controlling said deflecting unit to form the cut by sequential arrangement of the optical breakthroughs in the material wherein the control unit controls the deflecting unit two -dimensionally in a scan pattern according to a deflection function such that the locations of optical breakthroughs along a curve on which the optical breakthroughs are sequentially arranged within the transparent material are spaced apart according to a deflection-related angular function, which is non-linear and adapted to the curvature of the cut, such that the locations of optical breakthroughs adjacent along the curve of the cut are spaced apart by a consistent distance within a tolerance, wherein the control unit controls the deflecting unit such that the cut is substantially spherically curved with a radius R, the laser radiation is incident in the material along a main axis of incidence and the deflecting unit biaxially deflects the laser radiation along an x-axis and a y-axis in a plane perpendicular to said main axis of incidence, wherein the control unit sets a step width dx between locations on the curve of adjacent optical breakthroughs in the plane in x-direction according to:
• dx
• =
• D
• ·
• R
• ⁢
• ⁢
• 1
• R
• ⁢
• ⁢
• 1
• 2
• -
• x
• 2
• ,
• wherein D designates the distance between centers of the optical breakthroughs and
• R
• ⁢
• ⁢
• 1
• =
• R
• ·
• cos
• ⁢
• ⁢
• (
• arc
• ⁢
• ⁢
• tan
• ⁢
• y
• R
• )
• .