Method for designing oblique camera lens

Patent metadata

Field	Value
Publication number	US-10197799-B2
Application number	US-201715691892-A
Country	US
Kind code	B2
Filing date	Aug 31, 2017
Priority date	Dec 23, 2016
Publication date	Feb 5, 2019
Grant date	Feb 5, 2019

Abstract

A method for designing a oblique camera lens comprising: step (S1), establishing an initial system, the initial system comprises a primary mirror initial structure, a secondary mirror initial structure, and a tertiary mirror initial structure; step (S2), building a new image relationship; step (S3), keeping the primary mirror initial structure and the secondary mirror initial structure unchanged; selecting a plurality of first feature rays; step (S4), keeping the secondary mirror initial structure and the tertiary mirror unchanged; selecting a plurality of fields and a plurality of second feature rays.

First claim

What is claimed is:

1. A method for designing an oblique camera lens comprising:
step (S1), establishing an initial system, the initial system comprises a primary mirror initial structure, a secondary mirror initial structure, and a tertiary mirror initial structure;
step (S2), building a new image relationship, a field focal length FFL (ω) is based on a formula of:

FFL
⁡

(
ω
)

=

p
×
H

GR
⁡

(
ω
)

×

cos
2

⁡

(

75
⁢
°

-
ω

)

wherein, ω is a field angle, p is value of a single pixel unit, H is an altitude of the oblique camera;
step (S3), keeping the primary mirror initial structure and the secondary mirror initial structure unchanged; selecting a plurality of first feature rays, the plurality of first feature rays are forward rays tracked from an object space to the image detector; and calculating a plurality of first feature data points P i (i=1, 2 . . . K) point by point based on the object-image relationship of the plurality of first feature rays, to obtain the tertiary mirror by surface fitting the plurality of first feature data points P i (i=1, 2 . . . K);
step (S4), keeping the secondary mirror initial structure and the tertiary mirror unchanged; selecting a plurality of fields and a plurality of second feature rays, the plurality of second feature rays are reverse rays tracked from the image detector to the object space; and calculating a plurality of second feature data points P i ′ (i=1, 2 . . . K) point by point based on the object-image relationship of the plurality of second feature rays, to obtain the primary mirror by surface fitting the plurality of second feature data points P i ′ (i=1, 2 . . . K).

2. The method of claim 1 , wherein the primary mirror initial structure, the secondary mirror initial structure, or the tertiary mirror initial structure is planar or spherical.

3. The method of claim 1 , wherein a field angle of the oblique camera lens is in a range from is lager than or equal to 35° and less than or equal to 65°.

4. The method of claim 1 , wherein field focal length FFL (ω) is expressed by a formula of:

FFL
⁡

(
ω
)

=

Δ
⁢

⁢
h

Δω

wherein Δ ω is a change of ω, h is a height of an object, and Δ h is a change of h.

5. The method of claim 4 , wherein after the range of FFL(ω) is obtained, the height of the object can be calculated under different field angle, and the height of the object is the new image relationship.

6. The method of claim 1 , wherein the selecting the plurality of first feature rays comprises: selecting M fields; dividing an aperture of each of the M fields into N equal parts; and P feature rays at different positions in each of the N equal parts are selected, thus, K=M×N×P different first feature rays are selected.

7. The method of claim 6 , wherein the aperture of each of the M fields is circle, the aperture of each of the M fields is divided into N angles with equal intervals, and P different positions are selected along a radial direction of each of the N angles.

8. The method of claim 1 , wherein the calculating the plurality of first feature data points comprises:
defining a first intersection of the first feature ray R 1 and the tertiary mirror initial structure as the first feature data point P 1 ;
calculating an unit normal vector {right arrow over (N)} i at the first feature data point P i (1≤i≤K−1) based on a vector form of Snell's Law after i (1≤i≤K−1) first feature data points are calculated; and
making a tangent plane at the first feature data point P i (1≤i≤K−1), thus, (K−i) intersections are obtained by the tangent plane intersecting with remaining (K−i) first feature rays; and the intersection, which is nearest to the first feature data points P 1 (1≤i≤K−1), is fixed from the (K−i) intersections as the next first feature data point P i+1 (1≤i≤K−1), until all the plurality of first feature data points P i (i=1, 2 . . . K) are calculated.

9. The method of claim 8 , wherein the first feature ray R 1 is closest to the optical axis of the off-axis three-mirror imaging system with freeform surfaces.

10. The method of claim 8 , wherein the unit normal vector is calculated as follows:

N
→

i

=

r
→

i
′

-

r
→

i

|

r
→

i
′

-

r
→

i

|

;

wherein
⁢

⁢

r
→

i

=

P
i

⁢

S
i

→

Assignees

• Univ Tsinghua
• Hon Hai Prec Ind Co Ltd

Inventors

• Hou Wei
• Zhu Jun
• Jin Guo-Fan
• Fan Shou-Shan

Classifications

• 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

• G02B17/06

  using mirrors only {, i.e. having only one curved mirror (used in non-imaging applications G02B19/00)} · CPC title

• G02B27/0012 Primary

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