Optical tracking system, and optical element therefore with quartic phase plate

• US 20050146790A1
• Filed: 10/29/2004
• Published: 07/07/2005
• Est. Priority Date: 10/31/2003
• Status: Abandoned Application

• Current Assignee: The National Research Council (The National Academies of Science)
• Original Assignee: The National Research Council (The National Academies of Science)
• Inventors: Cai, Xianyang, Liu, Xinping
• Application Number:
  US10/975,347
• Publication Number:
  US 20050146790A1
• Time in Patent Office: Days
• US Class Current: 359/586
• CPC Class Codes: G02B 5/3083 Birefringent or phase retarding elements G02B5/3008, G02B5/3016 take precedence; systems for polarisation control G02B27/286; manufacturing phase modulating patterns by lithographic processes G03F7/001

Abstract

A phase plate having a phase-retardation function with a quartic term is located in an imaging system to increase the depth of field or depth of focus of a tracking system, such as a telescope of microscope tracking system.

Claims

1. An optical element comprising a phase plate having a phase-retardation function with a quartic term.

2. The optical element of claim 1, wherein said phase-retardation function also has a quadratic term.

3. The optical element of claim 2, wherein said phase retardation function is described by φ

(ρ

)=−

π

·

(α

₁·

ρ

⁴/ρ

₀⁴−

α

₂·

ρ

²/ρ

₀²)

where ρ

is the radial coordinate of the phase plate, ρ

₀ is the effective radius of the phase plate, and α

₁ and α

₂ constants.

4. The optical element of claim 3, wherein the value of α

₁ lies in the range −

50 to +50 and the value of α

₂ lies in the range −

80 to +80.

5. The optical element of claim 1, wherein said phase plate is derived from a logarithmic aspheric lens.

6. An optical imaging system comprising:

a plurality of lenses; and

a phase plate having a phase-retardation function with a quartic term disposed in said imaging system to increase the depth of field or depth of focus.

7. The optical imaging system of claim 6, wherein said phase plate is located in or near a pupil plane of said imaging system.

8. The optical imaging system of claim 6, wherein said phase plate is located in or near an aperture stop plane of said imaging system

9. The optical imaging system of claim 6, wherein said phase-retardation function also has a quadratic term.

10. The optical imaging system of claim 9, wherein said phase retardation function is described by φ

(ρ

)=−

π

·

(α

₁·

ρ

⁴/ρ

₀⁴−

α

₂·

ρ

²/ρ

₀²)

where ρ

is the radial coordinate of the phase plate, ρ

₀ is the effective radius of the phase plate, and α

₁ and α

₂ constants.

11. The optical imaging system of claim 10, wherein the value of α

₁ lies in the range −

50 to +50 and the value of 0;

2 lies in the range −

80 to +80.

12. The optical imaging system of claim 11, having an effective focal length of about 27 mm, an F-number of 1.6, a field of view of 20 degrees, and a wavelength range of 0.5˜

0.75 μ

m, an effective semi-diameter of 6.3 mm, and where the phase plate is described by z=6.2×

10<sup>−

6</sup>×

ρ

⁴.

13. An optical tracking system comprising:

an optical sensor array;

an optical imaging system for imaging a distant object onto said sensor array; and

a phase plate having a phase-retardation function with a quartic term located in said imaging system to increase the depth of field or depth of focus thereof.

14. The optical tracking system of claim 13, wherein said phase plate is located in or near an aperture stop plane of said imaging system.

15. The optical tracking system of claim 13, wherein said phase plate is located in or near a pupil plane of said imaging system.

16. The optical tracking system of claim 13, wherein said phase-retardation function also has a quadratic term.

17. The optical tracking system of claim 16, wherein said phase retardation function is described by φ

(ρ

)=−

π

·

(α

₁·

ρ

⁴/ρ

₀⁴−

α

₂·

ρ

²/ρ

₀²)

where ρ

is the radial coordinate of the phase plate, ρ

₀ is the effective radius of the phase plate, and α

₁ and α

₂ constants.

18. The optical tracking system of claim 17, wherein the value of α

₁ lies in the range −

50 to +50 and the value of α

₂ lies in the range −

80 to +80.

19. The optical tracking system of claim 13, wherein said optical imaging system is a microscope objective and said phase plate increases the depth of field of said microscope objective.

20. The optical tracking system of claim 13, wherein said optical imaging system is a telescope objective and said imaging system increases the depth of focus of said telescope objective.

21. A method of enhancing the tracking capability of an imaging system comprising inserting a phase plate having a phase-retardation function with a quartic term in said imaging system.

22. The method of claim 21, wherein said phase-retardation function also has a quadratic term.

23. The method of claim 22, wherein said phase retardation function is described by φ

(ρ

)=−

π

·

(α

₁·

ρ

⁴/ρ

₀⁴−

α

₂·

ρ

²/ρ

₀²)

where ρ

is the radial coordinate of the phase plate, ρ

₀ is the effective radius of the phase plate, and α

₁ and α

₂ constants.

24. The method of claim 23, wherein the value of al lies in the range −

50 to +50 and the value of α

₂ lies in the range −

80 to +80.