Patent Grant
8139293
1. Technical Field
The disclosure relates to lenses and, particularly, to a projection lens having a high resolution and a reduced length.
2. Description of Related Art
To obtain a sharp projection image and reduced size of projectors, projection lenses with high resolution but short overall length are needed. However, factors affecting both the resolution and the overall length of the projection lens, such as the number, position, and refractive power distribution of lenses employed, complicate any attempt at increasing resolution and shortening overall length of projection lenses.
Therefore, it is desirable to provide a projection lens, which can overcome the problems mentioned above.
Many aspects of the present projection lens should be better understood with reference to the following drawings. The components in the drawings are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the present projection lens. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views.
Embodiments of the present projection lens will now be described in detail with reference to the drawings.
Referring to
The projection lens 100 includes, in this order from a screen-side to the SLM-side, a negative lens group 10 and a positive lens group 20.
The lens groups 10 and 20 can slide along the optical axis of the projection lens 100. Depending on the user needs, these lens groups can slide towards (telephoto
The projection lens 100 satisfies the formulas of: (1) −2<Φ1/Φ2<−0.5, (2) −2<EFL1/EFL(W)<−1.5, (3) 1.5<EFL2/EFL(W)<1.75, (4) −1.2<EFL1/EFL(T)<−1, (5) 0.8<EFL2/EFL(T)<1.2, (6) 0.5<EFL(W)/BFL(W)<0.6, (7) 0.68<EFL(T)/BFL(T)<0.75, (8) 6.2<TTL(W)/EFL(W)<6.5, and (9) 3.5<TTL(T)/EFL(T)<3.6; where Φ1 and Φ2 represent refractive powers of the negative lens group 10 and the positive lens group 20 respectively, EFL(W) and EFL(T) represent effective focal lengths of the projection lens 100 when the projection lens 100 is in the wide-angle state and in the telephoto state respectively, EFL1 and EFL2 represent effective focal lengths of the negative lens group 10 and the positive lens group 20 respectively, TTL(W) and TTL(T) represent overall lengths (i.e., a distance from the screen-side surface of the projection lens 100 to the screen 99) of the projection lens 100 when the projection lens 100 is in the wide-angle state and in the telephoto state respectively, and BFL(W) and BFL(T) represent rear focal lengths of the projection lens 100 when the projection lens 100 is in the wide-angle state and in the telephoto state respectively.
The formula (1) is configured to obtain a high zoom ratio of the projection lens 100. The formulas (2) and (3) are adapted to obtaining a wide field angle of the projection lens 100. The formulas (4) and (5) are configured for increasing a size of a projection image on the screen when the projection lens 100 is in the telephoto state. The formulas (6) and (7) are adapted for correcting aberrations occurring in the projection lens 100. The formula (8) is for limiting the overall length of the projection lens within an acceptable range.
Specifically, the negative lens group 10 includes, in this order from the screen-side to the SLM-side of the projection lens 100, a positive first lens 11, a negative second lens 12, a negative third lens 13, and a positive fourth lens 14.
The positive lens group 20 includes, in this order from the screen-side to the SLM-side of the projection lens 100, a positive fifth lens 21, a positive sixth lens 22, a negative seventh lens 23, a positive eighth lens 24, and a positive ninth lens 25, a positive tenth lens 26, and a positive eleventh lens 27, wherein the eighth lens 24 and the ninth lens 25 are combined.
More specifically, the projection lens 100 further includes an aperture stop 97. The aperture stop 97 is interposed between the seventh lens 23 and the eighth lens 24 to block off-axis light rays from the eighth lens 24 entering the seventh lens 23, and thereby prevents too much distortion occurring in the projection lens 100. In this embodiment, aperture stop 97 is an opaque layer deposited on the eighth lens 24.
Detailed examples of the projection lens 100 are given below in company with
Table 1 shows the lens data of Example 1, where EFL(W)=15.9 (millimeter, mm), EFL(T)=25.44 mm, FNo=2.6(W)˜3.4(T) (representing that FN0 is about 2.6 when the projection lens 100 is in the wide-angle state and is about 3.4 when the projection lens 100 is in the telephoto state), EFL1=−28.88 mm, EFL2=25.67 mm, (Φ1=−0.035, Φ2=0.039, BFL(W)=27.16 mm, BFL(T)=35.84 mm, TTI(W)=100 mm, and TTI(T)=91.25 mm. As such, Φ1/Φ2=−0.88, EFL1/EFL(W)=−1.82, EFL2/EFL(W)=1.61, EFL1/EFL(T)=−1.14, EFL2/EFL(T)=1.00, EFL(W)/BFL(W)=0.585, EFL(T)/BFL(T)=0.70, TTI(W)/EFL(W)=6.28, and TTI(T)/EFL(T)=3.59.
In
Table 2 shows the lens data of Example 2, where EFL(W)=16 mm, EFL(T)=25.6 mm, FNo=2.64(W)˜3.44(T), EFL1=−28.43 mm, EFL2=26.53 mm, Φ1=−0.035, Φ2=0.037, BFL(W)=27.16 mm, BFL(T)=36.28 mm, TTI(W)=100 mm, and TTI(T)=91.44 mm. As such, Φ1/Φ2=−0.93, EFL1/EFL(W)=−1.78, EFL2/EFL(W)=1.66, EFL1/EFL(T)=−1.11, EFL2/EFL(T)=1.04, EFL(W)/BFL(W)=0.59, EFL(T)/BFL(T)=0.71, TTI(W)/EFL(W)=6.25, and TTI(T)/EFL(T)=3.57.
As illustrated in
Table 3 shows the lens data of Example 3, where EFL(W)=15.9 mm, EFL(T)=25.44 mm, FNo=2.42(W)˜3.05(T), EFL1=−28.89 mm, EFL2=25.67 mm, Φ1=−0.063, (Φ2=0.039, BFL(w)=27.16 mm, BFL(T)=35.84 mm, TTI(W)=100 mm, and TTI(T)=91.25 mm. As such, Φ1=−1.6, EFL1/EFL(W)=−1.82, EFL2/EFL(W)=1.61, EFL1/EFL(T)=−1.14, EFL2/EFL(T)=1.01, EFL(W)/BFL(W)=0.585, EFL(T)/BFL(T)=0.709, TTI(W)/EFL(w)=6.29, TTI(T)/EFL(T)=3.59.
As illustrated in
In all, in Examples 1˜3, though the overall length of the projection lens 100 is reduced, the resolution of the projection lens 100 is maintained, even improved, since aberrations occurring in the projection lens 100 are controlled to be in an acceptable range.
It will be understood that the above particular embodiments and methods are shown and described by way of illustration only. The principles and the features of the present disclosure may be employed in various and numerous embodiment thereof without departing from the scope of the disclosure as claimed. The above-described embodiments illustrate the scope of the disclosure but do not restrict the scope of the disclosure.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2010 1 0300312 | Jan 2010 | CN | national |
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| Number | Date | Country | |
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| 20110170201 A1 | Jul 2011 | US |
