Lens systems for projection televisions

• US 7,133,084 B2
• Filed: 12/22/2005
• Issued: 11/07/2006
• Est. Priority Date: 11/09/2000
• Status: Expired due to Fees

• Current Assignee: 3M Innovative Properties Company (3M Company)
• Original Assignee: 3M Innovative Properties Company (3M Company)
• Inventors: Moskovich, Jacob, Larson, Michael B., Wessling, Richard J.
• Primary Examiner(s): HSIA, SHERRIE Y
• Application Number:
  US11/315,725
• Publication Number:
  US 20060098125A1
• Time in Patent Office: 320 Days
• Field of Search: 348/779, 348/781, 348/744, 348/776, 348/778, 359/649, 359/650, 359/772, 359/780, 359/708, 359/771, 353/100
• US Class Current: 348/779
• CPC Class Codes: G02B 13/06 Panoramic objectives; So-called "sky lenses" including panoramic objectives having reflecting surfaces
• CPC Class Codes: G02B 13/16 for use in conjunction with image converters or intensifiers , or for use with projectors, e.g. objectives for projection TV
• CPC Class Codes: H04N 5/7408 Direct viewing projectors, e.g. an image displayed on a video CRT or LCD display being projected on a screen
• CPC Class Codes: H04N 9/18 using separate electron beams for the primary colour signals H04N9/27 takes precedence
• CPC Class Codes: H04N 9/28 Arrangements for convergence or focusing
• CPC Class Codes: H04N 9/31 Projection devices for colour picture display , e.g. using electronic spatial light modulators [ESLM]

Abstract

Projection lens systems for use with cathode ray tube (CRT) projection televisions are provided which have positive first lens units (U1) and negative second lens units (U2) where the negative second lens units are customized in terms of at least one optical property for at least two of the colors of light produced by the CRTs with which the units are used. The at least one optical property is not spectral transmission, although the second lens units can also be customized for spectral transmission. As illustrated in FIGS. 1B–1F and FIGS. 8B–8F, such customization of a non-transmissive property provides an effective and cost effective approach for improving the color performance of CRT projection lens systems. Constructions for the positive first lens unit which improve image contrast and reduce manufacturing costs are also provided.

Claims

1. A projection lens system for use in a projection television which has a screen and a first cathode ray tube which produces light of primarily a first color, a second cathode ray tube which produces light of primarily a second color, and a third cathode ray tube which produces light of primarily a third color, said projection lens system comprising three projection lenses, one projection lens being associated with each of the cathode ray tubes during use of the system for forming an image of the light produced by that tube on the screen, each projection lens consisting of:

(A) a first lens unit on the long conjugate side of the lens, said first lens unit having a positive power; and

(B) a second lens unit which (i) is associated with a cathode ray tube during use of the lens, (ii) has a strong negative power when so associated, and (iii) provides most of the correction of the lens'"'"' field curvature;

wherein;

(a) the first color is green and the second color is red;

(b) the first lens units of the first and second projection lenses are identical to within manufacturing tolerances;

(c) the second lens unit of the second projection lens differs from the second lens unit of the first projection lens in at least one optical property, said difference being based on said first and second colors; and

(d) the MTF/OTF performance of the second projection lens is improved compared to the MTF/OTF performance of the first projection lens refocused for use with red light.

2. A projection lens system for use in a projection television which has a screen and a first cathode ray tube which produces light of primarily a first color, a second cathode ray tube which produces light of primarily a second color, and a third cathode ray tube which produces light of primarily a third color, said projection lens system comprising three projection lenses, one projection lens being associated with each of the cathode ray tubes during use of the system for forming an image of the light produced by that tube on the screen, each projection lens consisting of:

(A) a first lens unit on the long conjugate side of the lens, said first lens unit having a positive power; and

(B) a second lens unit which (i) is associated with a cathode ray tube during use of the lens, (ii) has a strong negative power when so associated, and (iii) provides most of the correction of the lens'"'"' field curvature;

wherein;

(a) the first color is green and the second color is blue;

(b) the first lens units of the first and second projection lenses are identical to within manufacturing tolerances;

(c) the second lens unit of the second projection lens differs from the second lens unit of the first projection lens in at least one optical property, said difference being based on said first and second colors; and

(d) the MTF/OTF performance of the second projection lens is improved compared to the MTF/OTF performance of the first projection lens refocused for use with blue light.

3. A projection lens system for use in a projection television which has a screen and a first cathode ray tube which produces light of primarily a first color, a second cathode ray tube which produces light of primarily a second color, and a third cathode ray tube which produces light of primarily a third color, said projection lens system comprising three projection lenses, one projection lens being associated with each of the cathode ray tubes during use of the system for forming an image of the light produced by that tube on the screen, each projection lens consisting of:

(A) a first lens unit on the long conjugate side of the lens, said first lens unit having a positive power; and

(B) a second lens unit which (i) is associated with a cathode ray tube during use of the lens, (ii) has a strong negative power when so associated, and (iii) provides most of the correction of the lens'"'"' field curvature;

wherein;

(a) the first color is green, the second color is red, and the third color is blue;

(b) the first lens units of the first, second, and third projection lenses are identical to within manufacturing tolerances;

(c) the second lens units of the first, second, and third projection lenses differ from one another in at least one optical property, said differences being based on said first, second, and third colors;

(d) the MTF/OTF performance of the second projection lens is improved compared to the MTF/OTF performance of the first projection lens refocused for use with red light; and

(e) the MTF/OTF performance of the third projection lens is improved compared to the MTF/OTF performance of the first projection lens refocused for use with blue light.