OFF-AXIAL THREE-MIRROR OPTICAL SYSTEM WITH FREEFORM SURFACES

• US 20150253552A1
• Filed: 12/16/2014
• Published: 09/10/2015
• Est. Priority Date: 03/05/2014
• Status: Active Grant

• Current Assignee: Hon Hai Precision Industry Co., Ltd., Tsinghua University
• Original Assignee: Hon Hai Precision Industry Co., Ltd., Tsinghua University
• Inventors: ZHU, JUN, YANG, TONG, JIN, GUO-FAN, FAN, SHOU-SHAN
• Granted Patent: US 9,268,122 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G01J 1/0414 using plane or convex mirrors, parallel phase plates, or plane beam-splitters
• CPC Class Codes: G02B 17/0626 using three curved mirrors G02B17/0668, G02B17/0694 take precedence
• CPC Class Codes: G02B 17/0642 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

Abstract

An off-axial three-mirror optical system with freeform surfaces includes a primary mirror, a secondary mirror, a tertiary mirror, and an image sensor. The primary mirror is located on an incident light path. The secondary mirror is located on a primary mirror reflecting light path. The tertiary mirror is located on a secondary mirror reflecting light path. The image sensor is located on a tertiary mirror reflecting light path. The primary mirror, the secondary mirror, and the tertiary mirror are all xy polynomial surfaces up to the sixth order. The off-axial three-mirror optical system with freeform surfaces can achieve push-broom image with small F-number and large field angles.

Claims

1. An off-axial three-mirror optical system with freeform surfaces comprising:

a primary mirror located on an incident light path, and configured to reflect an incident light to form a first reflected light; and

a first three-dimensional rectangular coordinates system (X,Y,Z) is defined by a primary mirror vertex as a first origin;

a secondary mirror located on a first reflected light path, and configured to reflect the first reflected light to form a second reflected light;

a secondary mirror reflecting surface is a stop surface; and

a second three-dimensional rectangular coordinates system (X′

,Y′

,Z′

) is defined by a secondary mirror vertex as a second origin; and

the second three-dimensional rectangular coordinates system (X′

,Y′

,Z′

) is obtained by moving the first three-dimensional rectangular coordinates system (X,Y,Z) along a Z-axis negative direction;

a tertiary mirror located on a second reflected light path, and configured to reflect the second reflected light to form a third reflected light;

a third three-dimensional rectangular coordinates system (X″

,Y″

,Z″

) is defined by a tertiary mirror vertex as a third origin; and

the third three-dimensional rectangular coordinates system (X″

,Y″

,Z″

) is obtained by moving the second three-dimensional rectangular coordinates system (X′

,Y′

,Z′

) along a Z′

-axis positive direction; and

an image sensor is located on a third reflected light path and configured to receive the third reflected light;

wherein a primary mirror surface is an xy polynomial surface up to the sixth order;

a secondary mirror surface is an x′

y′

polynomial surface up to the sixth order; and

a tertiary mirror surface is an x″

y″

polynomial surface up to the sixth order.

2. The system as claimed in claim 1, wherein an xy polynomial surface equation is

3. The system as claimed in claim 2, wherein c=−

0.001259078, k=−

7.45441151, A₂=0.007340832, A₃=0.00011016, A₅=−

0.000509972, A₇=5.5789531E-07, A₉=−

6.1761984E-07, A₁₀=−

2.7607128E-10, A₁₂=−

3.8446170E-09, A₁₄=2.6788063E-09, A₁₆=−

4.7744225E-12, A₁₈=4.8865466E-12, A₂₀=−

1.2584172E-11, A₂₁=−

1.1562329E-14, A₂₃=2.1268750E-14, A₂₅=−

4.3909505E-16, and A₂₇=3.6354825E-14.

4. The system as claimed in claim 1, wherein an x′

y′

polynomial surface equation is

5. The system as claimed in claim 4, wherein c′

=0.003876139, k′

=−

0.34802184, A₂′

=−

0.199697292, A₃′

=−

0.003296752, A₅′

=−

0.006989087, A₇′

=−

1.9538487E-06, A₉′

=−

2.8779308E-05, A₁₀′

=−

9.4487860E-08, A₁₂′

=−

2.4621298E-07, A₁₄′

=2.7636424E-07, A₁₆′

=−

7.4539496E-10, A₁₈′

=−

2.7376614E-09, A₂₀′

=1.1386414E-08, A₂₁′

=−

9.1533262E-12, A₂₃′

=−

3.4125882E-11, A₂₅′

=4.5002836E-12, and A₂₇′

=2.5113825E-10.

6. The system as claimed in claim 1, wherein an x″

y″

polynomial surface equation is

7. The system as claimed in claim 6, wherein c″

=0.002586059, k″

=−

19.29884842, A₂″

=−

0.084234843, A₃″

=−

0.004737493, A₅″

=−

0.004749666, A₇″

=−

1.2831834E-06, A₉″

=−

3.4279386E-06, A₁₀″

=−

1.9965925E-08, A₁₂″

=−

2.8581720E-08, A₁₄″

=1.5682997E-07, A₁₆″

=−

3.1135397E-11, A₁₈″

=−

2.3756684E-10, A₂₀″

=1.1136538E-09, A₂₁″

=−

4.3993354E-12, A₂₃″

=−

1.0892720E-11, A₂₅″

=−

5.9049331E-12, and A₂₇″

=1.0527961E-11.

8. The system as claimed in claim 1, wherein a distance between the first origin and the second origin is about 139.873 mm.

9. The system as claimed in claim 1, wherein a distance between the second origin and the third origin is about 84.992 mm.

10. The system as claimed in claim 1, wherein a distance between the image sensor and a Y″

X″

plane is about 85.414 mm.

11. The system as claimed in claim 1, wherein an off-axial three-mirror optical system with freeform surfaces effective entrance pupil diameter is about 72 mm.

12. The system as claimed in claim 1, wherein an off-axial three-mirror optical system with freeform surfaces field angle is about 24°

×

0.07°

.

13. The system as claimed in claim 12, wherein an angle along a X-axis direction is in a range from about −

12°

to about 12°

.

14. The system as claimed in claim 12, wherein an angle along a Y-axis direction is in a range from about −

9.965°

to about −

10.035°

.

15. The system as claimed in claim 1, wherein an off-axial three-mirror optical system with freeform surfaces wavelength is in a range from about 350 nm to about 770 nm.

16. The system as claimed in claim 1, wherein an off-axial three-mirror optical system with freeform surfaces effective focal length is about 94.09 mm.

17. The system as claimed in claim 1, wherein an off-axial three-mirror optical system with freeform surfaces relative aperture is about 0.769.

18. The system as claimed in claim 1, wherein an off-axial three-mirror optical system with freeform surfaces F-number is about 1.3.

19. A freeform surface reflective scanning system comprising:

a primary mirror, a secondary mirror, a tertiary mirror, and an image sensor;

wherein the primary mirror is located on an incident light path, the secondary mirror is located on a primary mirror reflective light path, the tertiary mirror is located on a secondary mirror reflective light path, and the image sensor is located on a tertiary mirror reflecting light path; and

a primary mirror surface, a secondary mirror surface, and a tertiary mirror surface are all polynomial surfaces up to the sixth order.

20. The system as claimed in claim 19, wherein an off-axial three-mirror system light path is defined as follows:

when an incident light reaches the primary mirror, the incident light is reflected by the primary mirror, and forms a first reflected light;

when the first reflected light reaches the secondary mirror, the first reflected light is reflected by the secondary mirror, and forms a second reflected light; and

when the second reflected light reaches the tertiary mirror, the second reflected light is reflected by the tertiary mirror, and forms a third reflected light; and

the third reflected light is finally received by the image sensor.