Method for designing hybrid surface optical system

Patent metadata

Field	Value
Publication number	US-11386246-B2
Application number	US-201715841311-A
Country	US
Kind code	B2
Filing date	Dec 14, 2017
Priority date	Jan 24, 2017
Publication date	Jul 12, 2022
Grant date	Jul 12, 2022

Abstract

A method for designing a hybrid surface optical system comprises establishing a first initial system; keeping the first initial system unchanged and calculating a plurality of first feature data points, and fitting the first feature data points to obtain a spherical surface; repeating such steps until all spherical surfaces are obtained; calculating a plurality of second feature data points, and fitting the plurality of second feature data points to obtain an aspheric surface; repeating such steps until all aspheric surfaces are obtained; calculating a plurality of third feature data points, and fitting the plurality of third feature data points to obtain a freeform surface; repeating such steps until all freeform surfaces are obtained.

First claim

What is claimed is:

1. A method for making an off-axis hybrid surface optical system, comprising:
step (S 1 ), establishing a first initial system, wherein the first initial system comprises a plurality of initial surfaces, and each of the plurality of initial surfaces corresponds to a surface of the off-axis hybrid surface optical system; and selecting a plurality of feature rays R i (i=1, 2 . . . K) from different fields and different aperture positions;
step (S 2 ), step (S 2 a ), defining a spherical surface of the off-axis hybrid surface optical system to be calculated as a spherical surface “a”, keeping the plurality of initial surfaces unchanged and calculating a plurality of first feature data points (P 1 , P 2 , . . . P m ) point by point, wherein m is less than K, and the plurality of first feature data points (P 1 , P 2 , . . . P m ) are m first intersection points of the spherical surface “a” and m of the plurality of feature rays R i (i=1, 2 . . . K); and surface fitting the plurality of first feature data points (P 1 , P 2 , . . . P m ) to obtain an initial spherical surface A m ; step (S 2 b ), calculating a (m+1)th first feature data point P m+1 based on the initial spherical surface A m , wherein a global coordinate system is defined by a primary mirror location, a beam propagation direction is defined as a Z-axis, and a plane perpendicular to the Z-axis is defined as an xy plane; a tangent plane T m at a first feature data point P m is calculated, the tangent plane T m intersects with the initial spherical surface A m at an intersection line L m ; and in the global coordinate system, a first feature data point located on the intersection line L m whose x coordinate is the same as an x coordinate of the first feature data point P m is defined as a intermediate point G m , and surface fitting the (m+1) first feature data points (P 1 , P 2 , . . . P m , P m+1 ) to obtain a spherical surface A m+1 using the intermediate point G m ; step (S 2 c ), repeating steps from step (S 2 a ) to step (S 2 b ) until a Kth first feature data point P K is obtained, and surface fitting the first feature data points (P 1 , P 2 , . . . P K ) to obtain a spherical surface A K , wherein the spherical surface A K is the spherical surface “a”; step (S 2 d ), repeating steps from step (S 2 a ) to step (S 2 c ) until all spherical surfaces of the off-axis hybrid surface optical system are obtained, and a spherical surface optical system is obtained;
step (S 3 ), step (S 3 a ), defining an aspheric surface of the off-axis hybrid optical system to be calculated as an aspheric surface “b”, the spherical surface optical system being a second initial system, keeping all spherical surfaces of the spherical optical system unchanged and calculating a plurality of second feature data points (P′ 1 , P′ 2 , . . . P′ K ), wherein the plurality of second feature data points (P′ 1 , P′ 2 , . . . P′ K ) are K second intersection points of the spherical surface “a” and the plurality of feature rays R i (i=1, 2 . . . K); and step (S 3 b ), surface fitting the plurality of second feature data points (P′ 1 , P′ 2 , . . . P′ K ) to obtain the aspheric surface “b”; repeating steps from step (S 3 a ) to step (S 3 b ) until all aspheric surfaces of the off-axis hybrid surface optical system are obtained, and a first hybrid surface optical system is obtained;
step (S 4 ), step (S 4 a ), defining a freeform surface of the off-axis hybrid optical system as a freeform surface “c”, the first hybrid surface optical system being a third initial system, and keeping all aspheric surfaces of the first hybrid surface optical system unchanged and calculating a plurality of third feature data points (P″ 1 , P″ 2 , . . . P″ K ), wherein the plurality of third feature data points (P″ 1 , P″ 2 , . . . P″ K ) are K third intersection points of the aspheric surface “b” and the plurality of feature rays R i (i=1, 2 . . . K); and step (S 4 b ), surface fitting the plurality of third feature data points (P″ 1 , P″ 2 , . . . P″ K ) to obtain the freeform surface “c”; repeating steps from step (S 4 a ) to step (S 4 b ) until all freeform surfaces of the off-axis hybrid surface optical system are obtained; and
step (S 5 ), making a hybrid surface optical system comprising a primary mirror, a secondary mirror and a tertiary mirror based on the spherical surfaces obtained in step (S 2 ), the aspheric surfaces obtained in step (S 3 ) and the freeform surfaces obtained in step (S 4 ).

2. The method as claimed in claim 1 , wherein a method for calculating the plurality of first feature data points (P 1 , P 2 , . . . P m ) comprises:
Step (a): defining the first intersection point of a first feature ray R 1 and the spherical surface “a” as a first feature data point P 1 ;
Step (b): an ith (1≤i≤m−1) first feature data point P i (1≤i≤m−1) has been obtained, a unit normal vector {right arrow over (N)} i at the ith (1≤i≤m−1) first feature data point P i (1≤i≤m−1) is calculated based on a vector form of Snell's Law;
Step (c): making a first tangent plane through the ith (1≤i≤m−1) first feature data point P i (1≤i≤m−1); and (m−i) fourth intersection points are obtained by the first tangent plane intersects with remaining (m−i) feature rays; a fourth intersection point Q i+1 , which is nearest to the ith (1≤i≤m−1) feature data point P i (1≤i≤m−1), is fixed; and a feature ray corresponding to the fourth intersection point Q i+1 is defined as R i+1 , a shortest distance between the fourth intersection point Q i+1 and the ith (1≤i≤m−1) first feature data point P i (1≤i≤m−1) is defined as d i ;
Step (d): making a second tangent plane at each of the (i−1) first feature data points that are obtained before the ith first feature data point P i (1≤i≤m−1) respectively; thus, (i−1) second tangent planes are obtained, and (i−1) fifth intersection points are obtained by the (i−1) second tangent planes intersecting with a feature ray R i+1 ; in each of the (i−1) second tangent planes, each of the fifth intersection points and its corresponding feature data point form an intersection pair; the intersection pair, which has the shortest distance between a fifth intersection point and its corresponding feature data point, is fixed; and the fifth intersection point and the shortest distance is defined as and d′, respectively;
Step (e): comparing d i and d′ i if d i ≤d′ i , Q i+1 is taken as the next first feature data point P i+1 (1≤i≤m−1); otherwise, Q′ i+1 is taken as the next first feature data point P i+1 (1≤i≤m−1); and
Step (f): repeating steps from step (b) to step (e), until the plurality of first feature data points P i (i=1, 2 . . . m) are all calculated.

3. The method as claimed in claim 1 , wherein a method for calculating a (m+1)th first feature data point P m+1 comprises:
finding a feature ray R m+1 corresponding to the (m+1)th first feature data point P m+1 , wherein a feature ray R m+1 is nearest to the intermediate point G m in remaining K−m characteristic rays;
finding a first feature data point closest to the first feature data point P m+1 from the plurality of first feature data points (P 1 , P 2 , . . . P m ); and
calculating a sixth intersection point between the feature ray R m+1 and a tangent plane of the first feature data point closest to the first feature data point P m+1 , wherein the sixth intersection point is the (m+1)th first feature data point P m+1 .

4. The method as claimed in claim 3 , wherein a method for finding the feature ray R m+1 corresponding to the (m+1)th feature data point P m+1 comprises: a normal vector n m and a tangent plane of the intermediate point G m at the initial spherical surface A m are obtained according to an spherical surface expression; (K−m) intersection points are obtained by a tangent plane of

Assignees

• Univ Tsinghua
• Hon Hai Prec Ind Co Ltd

Inventors

• Zhu Jun
• Gong tong-tong
• Jin Guo-Fan
• Fan Shou-Shan

Classifications

• G06F30/23

  using finite element methods [FEM] or finite difference methods [FDM] · CPC title

• G02B27/0012 Primary

  Optical design, e.g. procedures, algorithms, optimisation routines · CPC title

• G02B5/10

  with curved faces · CPC title

• G06F30/20 Primary

  Design optimisation, verification or simulation (optimisation, verification or simulation of circuit designs G06F30/30) · CPC title