Zoom projection lens having a lens correction unit

• US 6,417,971 B1
• Filed: 02/04/2000
• Issued: 07/09/2002
• Est. Priority Date: 08/05/1997
• Status: Expired due to Term

• Current Assignee: Regents of The University of Minnesota (University of Minnesota)
• Original Assignee: US Precision Lens, Inc.
• Inventors: Moskovich, Jacob
• Primary Examiner(s): SCHWARTZ, JORDAN MARC
• Application Number:
  US09/485,278
• Time in Patent Office: 886 Days
• Field of Search: 359/649, 359/650, 359/651, 359/676, 359/684, 359/686, 359/689, 359/680-682
• US Class Current: 359/649
• CPC Class Codes: G02B 15/142 having two groups only
• CPC Class Codes: G02B 15/1425 the first group being negative

Abstract

A zoom projection lens for use with LCD or DMD panels is provided. The lens has two units U1 and U2, which are moved relative to one another for zooming. It also has a corrector unit (CR) at a fixed distance from the LCD or DMD panel (PP). The corrector unit, which may be a color correcting doublet, is at the object (panel) end of the lens and has a weak power. This unit allows for a high level of distortion and lateral color correction, without unduly increasing the complexity or cost of the lens.

Claims

1. A projection lens for forming an image of an object, said lens having a zoom range between a minimum effective focal length f_min and a maximum effective focal length f_max, said lens comprising in order from its image end to its object end:

(A) a first lens unit;

(B) a second lens unit separated from the first lens unit by an axial space, said first and second lens units being moved relative to the object during zooming and/or focusing of the lens; and

(C) a corrector lens unit having at least one aspherical surface and a focal length f_CR which satisfies the relationship;

2. The projection lens of claim 1 wherein:

3. The projection lens of claim 1 where the lens satisfies the relationship:

4. The projection lens of claim 1 wherein the first lens unit has a negative optical power.

5. The projection lens of claim 1 wherein the second lens unit has a positive optical power.

6. The projection lens of claim 1 wherein the first lens unit has a negative optical power and the second lens unit has a positive optical power.

7. The projection lens of claim 1 wherein the corrector lens unit comprises color correcting means.

8. The projection lens of claim 1 further comprising a third lens unit on the image side of the first lens unit.

9. The projection lens of claim 8 wherein the third lens unit is separated from the object by a fixed axial distance.

10. The projection lens of claim 8 wherein the third lens unit has a positive power.

11. The projection lens of claim 1 wherein the distortion of the projection lens over the zoom range is less than or equal to 2.5 percent.

12. The projection lens of claim 1 wherein the object is a pixelized panel and the lateral color blur of the lens over the zoom range is less than a pixel for wavelengths in the range from 465 nanometers to 608 nanometers.

13. The projection lens of claim 1 wherein the lens'"'"' back focal length changes by less than 0.2 percent as the lens is heated from room temperature to its operating temperature.

14. A projection lens system for forming an image of an object, said system comprising:

(A) an illumination system comprising a light source and illumination optics which forms an image of the light source;

(B) a pixelized panel which comprises the object; and

(C) a projection lens for forming an image of the object, said lens having a zoom range between a minimum effective focal length f_min and a maximum effective focal length f_max, said lens comprising in order from its image end to its object end;

(a) a first lens unit;

(b) a second lens unit separated from the first lens unit by an axial space, said first and second lens units being moved relative to the object during zooming and/or focusing of the lens; and

(c) a corrector lens unit having at least one aspherical surface and a focal length f_CR which satisfies the relationship;

15. The projection lens system of claim 14 wherein said projection lens has an entrance pupil whose location substantially corresponds to the location of the output of the illumination system.