Method for designing a freeform surface reflective imaging system

Patent metadata

Field	Value
Publication number	US-11025841-B2
Application number	US-202016910370-A
Country	US
Kind code	B2
Filing date	Jun 24, 2020
Priority date	Aug 1, 2019
Publication date	Jun 1, 2021
Grant date	Jun 1, 2021

Abstract

The present invention relates to a method for designing a freeform surface reflective imaging system, comprising: selecting an initial system, wherein an FOV of the initial system is X0×Y0; selecting an FOV sequence as [X0, Y0], [X1, Y1], [X2, Y2], . . . , [Xn, Yn], while the FOV of the system to be designed is Xn×Yn, and X0<X1<X2< . . . <Xn, Y0<Y1<Y2< . . . <Yn; using point-by-point methods to construct all freeform surfaces of the initial system in the FOV of X1×Y1; setting the system obtained in the last step as a second initial system for system construction in the FOV of X2×Y2; repeating the last step to execute system construction in the order of the FOV sequence until the final FOV Xn×Yn is obtained.

First claim

What is claimed is:

1. A method for designing a freeform surface reflective imaging system, comprising:
(i) selecting an initial system, wherein an FOV of the initial system is X 0 ×Y 0 ;
(ii) selecting the FOV sequence as [X 0 , Y 0 ], [X 1 , Y 1 ], [X 2 , Y 2 ], . . . [X n , Y n ], while the FOV of the system to be designed is X n ×Y n , and X 0 <X 1 <X 2 < . . . <X n , Y 0 <Y 1 <Y 2 < . . . <Y n ;
(iii) using point-by-point methods to construct all freeform surfaces of the initial system in the FOV of X 1 ×Y 1 ;
(iv) setting the system obtained in step (iii) as a second initial system for system construction in the FOV of X 2 ×Y 2 ; and
(v) repeating step (iv) to execute system construction in the order of the FOV sequence until the final FOV X n ×Y n is obtained.

2. The method of claim 1 , wherein the initial system is a freeform surface system and comprises a plurality of freeform surfaces.

3. The method of claim 1 , wherein the FOV sequence is selected by using an equal step length.

4. The method of claim 3 , wherein the differences between adjacent values in X 0 , X 1 , X 2 , . . . , X n are equal, and the differences between adjacent values in Y 0 , Y 1 , Y 2 , . . . , Y n are equal.

5. The method of claim 1 , wherein the FOV sequence is selected by using an unequal step length with a step length during the first few constructions larger than that when approaching the final FOV.

6. The method of claim 3 , wherein the initial system comprises L initial surfaces, and the L initial surfaces are defined as L j (j=1, 2, . . . L), and the initial freeform surface L j (j=i=1, 2 . . . L) is constructed sequentially into freeform surface N j (j=i=1, 2 . . . L) using the point-by-point method.

7. The method of claim 6 , wherein constructing the initial freeform surface L 1 into the freeform surface N 1 comprises:
selecting K feature rays R i (i=1, 2 . . . K);
obtaining a plurality of intersection points of the K feature rays and the freeform surface N 1 based on the object-image relationships and the law of reflections, and calculating a plurality of feature data points P i (i=1, 2 . . . K) on the freeform surface N 1 ; and
surface fitting the plurality of feature data points to obtain an equation of the freeform surface N 1 .

8. The method of claim 7 , wherein the step of selecting K feature rays comprises selecting M feature fields within the FOV of X 1 ×Y 1 ; and selecting K feature rays in the M feature fields.

9. The method of claim 8 , wherein if a center FOV of the initial system is (0, y 0 ), the feature fields are selected in the following manner:

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10. The method of claim 8 , wherein the step of selecting the K feature rays in the M feature fields comprises: an aperture of each of the M feature fields is divided into N equal parts; and, P feature rays at different aperture positions in each of the N equal parts are selected; as such, K=M×N×P different feature rays correspond to different aperture positions and different fields are selected.

11. The method of claim 7 , wherein the step of calculating a plurality of feature data points P i (i=1, 2 . . . K) on the freeform surface N 1 further comprises:
(a) defining a first intersection of a first feature ray R 1 and the freeform surface N 1 as a feature data point P 1 ;
(b) when i (1≤i≤K−1) first feature data points P i (1≤i≤K−1) have been obtained, a unit normal vector {right arrow over (N)} i (1≤i≤K−1) at each of the i (1≤i≤K−1) first feature data points P i (1≤i≤K−1) can be calculated based on a vector form of Snell's Law;
(c) making a first tangent plane at the i (1≤i≤K−1) first feature data points P i (1≤i≤K−1) respectively; thus i first tangent planes are obtained, and i×(K−i) second intersections are obtained by the i first tangent planes intersecting with remaining (K−i) feature rays; and a second intersection, which is nearest to the i (1≤i≤K−1) first feature data points P i , is fixed from the i×(K−i) second intersections as a next feature data point P i+1 (1≤i≤K−1); and
(d) repeating steps (b) and (c), until a

Assignees

• Univ Tsinghua
• Hon Hai Prec Ind Co Ltd

Inventors

• Wu Wei-Chen
• Zhu Jun
• Jin Guo-Fan
• Fan Shou-Shan

Classifications

• H04N25/41 Primary

  Extracting pixel data from a plurality of image sensors simultaneously picking up an image, e.g. for increasing the field of view by combining the outputs of a plurality of sensors · CPC title

• G02B27/0012 Primary

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

• G02B17/0626 Primary

  using three curved mirrors (G02B17/0668, G02B17/0694 take precedence) · CPC title

• G02B17/0642

  off-axis or unobscured systems in which not all of the mirrors share a common axis of rotational symmetry, e.g. at least one of the mirrors is warped, tilted or decentered with respect to the other elements · CPC title

• G02B27/0025

  for optical correction, e.g. distorsion, aberration · CPC title