Variable-step-distance micro-milling repair cutter path generating method for damage points on surface of optical crystal

Patent metadata

Field	Value
Publication number	US-12194657-B2
Application number	US-202117524762-A
Country	US
Kind code	B2
Filing date	Nov 12, 2021
Priority date	Nov 13, 2020
Publication date	Jan 14, 2025
Grant date	Jan 14, 2025

Abstract

A variable-step-distance micro-milling repair cutter path generating method for damage points on a surface of an optical crystal related to a field of optical material and optical element surface repair and includes steps of establishing a mathematical model of a repair profile; determining discrete contact points between a cutter and the repair profile to obtain a cutter contact control point set by a GPR path generating method to control a movement trend of a pseudo-random path; interpolating the cutter position control point set into a spatial curve by a NURBS modeling method; creating a UG curve in a UG software according to the mathematical model, and using the UG curve as the repair path to perform a machining process simulation. The method has good elimination effects on cutter marks with constant period and improves the ability of the KDP crystal to resist strong laser damage.

First claim

What is claimed is:

1. A variable-step-distance micro-milling repair cutter path generating method for damage points on a surface of an optical crystal, comprising:
step 1: designing a damage repair profile with suitable depth and width according to a laser damage degree of a surface of a potassium dihydrogen phosphate (KDP) crystal and morphological characteristics of damage points; establishing a mathematical model of the damage repair profile; determining a conical repair profile as a laser-friendly repair profile;
establishing a mathematical model of the conical repair profile, and a control equation is as follows:

z
=

f
⁡

(

x
,
y

)

=

-

D

2
⁢
h

⁢

x
2

+

y
2

+
h

(
1
)

wherein x, y, and z respectively represent a Cartesian coordinate value of any point on the conical repair profile; D is a width of the conical repair profile; h is a depth of the conical repair profile;
since the mathematical model of the conical repair profile is a revolving model, if ρ 2 =x 2 +y 2 , coordinates of any point P on the conical repair profile is P=(x,y,z); the point P is expressed in polar coordinates as P=(ρ, θ) and satisfies:

{

x
=

ρ
⁢
cos
⁢
θ

y
=

ρ
⁢
sin
⁢
θ

z
=

f
⁡

(

x
,
y

)

(
2
)

step 2: determining Gaussian pseudo-random (GPR) path generation parameters according to a processing requirement; determining discrete contact points between a cutter and the conical repair profile when the cutter is milling the conical repair profile to obtain a cutter contact control point set by a GPR path generating method;
wherein the cutter contact control point set is configured to control a movement trend of a pseudo-random path; a process is as follow:
adopting a spiral repair path with a cutting depth and a step distance; generating pseudo-random cutter contact control points by adjusting polar angles and polar diameters under a GPR strategy; when establishing a GPR path, a first cutter contact control point is initialized, and the first cutter contact control point is initialized to a point on an edge of the conical repair profile where a polar angle is 0, wherein
P CC 0 =( D/ 2,0)  (3)

other cutter contact control points are generated by a polar diameter and polar angle control equation as follow:

{

θ
i

⁢

=

θ

i
-
1

+

K

lg
⁡

(

ρ

i
-
1

)

Assignees

• Harbin Inst Technology

Inventors

• Cheng Jian
• Chen Mingjun
• Wu Wenqiang
• Liu Qi
• Yang Hao
• Zhao Linjie
• Tan Chao
• Cheng Xumeng
• Liu Henan
• Wang Tingzhang

Classifications

• G06F17/16

  Matrix or vector computation {, e.g. matrix-matrix or matrix-vector multiplication, matrix factorization (matrix transposition G06F7/78)} · CPC title

• G06F17/11

  for solving equations {, e.g. nonlinear equations, general mathematical optimization problems (optimization specially adapted for a specific administrative, business or logistic context G06Q10/04)} · CPC title

• B28D5/0064 Primary

  Devices for the automatic drive or the program control of the machines · CPC title

• B23C2265/08

  Conical · CPC title

• B23C2260/56

  Lasers · CPC title