Zoom projection lens system

Information

  • Patent Grant
  • 8385001
  • Patent Number
    8,385,001
  • Date Filed
    Thursday, December 9, 2010
    14 years ago
  • Date Issued
    Tuesday, February 26, 2013
    11 years ago
Abstract
A zoom projection lens system, in order from the magnification side to the minification side thereof, includes a first lens group with negative refraction power, a second lens group with positive refraction power, a third lens group with positive refraction power, a fourth lens group with negative refraction power; and a fifth lens group with positive refraction power. The first, second, third, fourth lens group are movably positioned, and the fifth lens group is immovably positioned. The first lens group includes a first aspherical plastic lens. The second lens group includes a second aspherical plastic lens. The fourth lens group includes a third aspherical plastic lens. The system satisfies the formula: −2.4≦Fa1/Fw≦−2.1; 2.9≦Fb1/Fw≦3.2; −3.8≦Fa2/Fw≦−3.6, wherein Fa1, Fa2, Fb1 are the effective focal lengths of the first, second, third aspherical plastic lens respectively, Fw is the effective focal lengths of the system in a wide angle state.
Description
BACKGROUND

1. Technical Field


The present disclosure relates to zoom projection lens systems and, particularly, to a zoom projection lens system capable of maintaining optical performance during use.


2. Description of Related Art


Zoom projection lens systems are used in projectors to allow adjustment of effective focal length thereof and thus the projectors can be applied to different spaces, e.g., a spacious hall or a narrow room. When a projector is in use, it will produce large amounts of heat, and so glasses lenses are used in the zoom projection lens system instead of plastic lenses, because the coefficient of expansion of glass lenses is smaller than that of plastic lenses. But glass lenses are more expensive than plastic lenses, making the zoom projection lens systems more expensive to produce.


Therefore, it is desirable to provide a zoom projection lens system which can overcome the limitations described.





BRIEF DESCRIPTION OF THE DRAWINGS

Many aspects of the present disclosure can 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 disclosure. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the views.



FIG. 1 is a schematic view of a zoom projection lens system in a wide angle state according to an exemplary embodiment.



FIG. 2 is a schematic view of the zoom projection lens system of FIG. 1 in a telephoto state.



FIGS. 3-6 are graphs respectively showing spherical aberration, field curvature, distortion, and Lateral chromatic aberration occurring in the zoom projection lens system of FIG. 1 in the wide angle state.



FIG. 7-10 are graphs respectively showing spherical aberration, field curvature, distortion, and Lateral chromatic aberration occurring in the zoom projection lens system of FIG. 2 in the telephoto state.





DETAILED DESCRIPTION

Embodiments of the present disclosure will now be described in detail with reference to the drawings.


Referring to FIG. 1, a zoom projection lens system 100 in one exemplary embodiment includes, in this order from the magnification side to the minification side thereof, a first lens group 10 having negative refraction power, a second lens group 20 having positive refraction power, a third lens group 30 having positive refraction power, a fourth lens group 40 having negative refraction power, and a fifth lens group 50 having positive refraction power.


The fifth lens group 50 is immovably mounted to prevent unwanted contact between a digital micro-mirror device (DMD) and the fourth lens group 40, while the lens groups 10, 20, 30, 40 are movably mounted. Thereby, the effective focal length of the zoom projection lens system 100 can be adjusted by moving the lens groups 10, 20, 30, 40 along the optical axis thereof. In particular, the effective focal length can be reduced by moving the lens groups 10, 20, 30, 40 to any point toward the minification side of the zoom projection lens system 100 until they reach a maximum wide angle state as shown in FIG. 1. Conversely, the effective focal length can be increased by moving the lens groups 10, 20, 30, 40 to any point toward the magnification side of the zoom projection lens system 100 until they reach a maximum telephoto state as shown in FIG. 2. In the embodiment, the zoom projection lens system 100 is configured for utilization in a DLP projector. The DLP projector is typically equipped with a DMD used for modulating light signals for projection through the zoom projection lens system 100. The DMD is located at an image surface 61.


The light signals are transmitted through the fifth lens group 50, the fourth lens group 40, the third lens group 30, the second lens group 20, and the first lens group 10 in sequence, and then projected onto a projection surface (not shown) to produce images.


The first lens group 10 includes, in this order from the magnification side to the minification side of the zoom projection lens system 100, a first spherical lens 11 and a first aspherical plastic lens 12 having negative refraction power. The second lens group 20 includes, in this order from the magnification side to the minification side of the zoom projection lens system 100, a second aspherical plastic lens 21 having positive refraction power, a second spherical lens 22, and a third spherical lens 23. The third lens group 30 includes a fourth spherical plastic lens 31. The fourth lens group 40 includes, in this order from the magnification side to the minification side of the zoom projection lens system 100, a third aspherical plastic lens 41, a fifth spherical lens 42, a sixth spherical lens 43, and a seventh spherical lens 44. The fifth lens group 50 includes an eighth spherical lens 51. The eight spherical lenses 11, 22, 23, 31, 42, 43, 44, 51 are glass lenses. The second spherical lens 22 and the third spherical lens 23 are adhered together, the fifth spherical lens 42 and the sixth spherical lens 43 are adhered together, and thus to correct the axial chromatic aberration and optimize the optical performance of the zoom projection lens system 100.


In practice, an aperture stop 70 can be interposed between the second lens group 20 and the third lens group 30 to limit the flux of light from the third lens group 30 to the second lens group 20, and thus the light cone of the light rays entering the second lens group 20 will be more symmetrical to control the coma occurring in the zoom projection lens system 100 within a correctable range. In this embodiment, the aperture stop 70 can move with the second lens group 20, and the diameter of the aperture of the aperture stop 70 is unchangeable.


The zoom projection lens system 100 further includes a prism 80, a first flat glass 91, a second flat glass 92, a third flat glass 93, a fourth flat glass 94, a fifth flat glass 95, a protective glass sheet 96 disposed between the fifth lens group 50 and the image surface 61 arranged from the magnification side to the minification side of the zoom projection lens system 100. The first flat glass 91 and the second flat glass 92 are adhered together. The third flat glass 93 and the fourth flat glass 94 are adhered together. The fifth flat glass 95, the protective glass sheet 96 and the image surface 61 are adhered together.


In particular, the light signals are transmitted through, in order, the protective glass sheet 96, the fifth flat glass 95, the fourth flat glass 94, the third flat glass 93, the second flat glass 92, the first flat glass 91, the prism 80 and then enters the five lens groups 50, 40, 30, 20, 10. Different coatings may be applied to the five glasses 91, 92, 93, 94, 95 for various purposes such as filtering.


The zoom projection lens system 100 satisfies the following formulas:

−2.4≦Fa1/Fw≦−2.1;  (1)
2.9≦Fb1/Fw≦3.2;  (2)
−3.8≦Fa2/Fw≦−3.6;  (3)


wherein, Fa1, Fa2, Fb1 are the effective focal lengths of the first, second, third aspherical plastic lens 12, 21, 41 respectively, Fw is the effective focal lengths of the zoom projection lens system 100 in a wide angle state. The formulas (1)-(3) can limit the relation between the effective focal lengths of the three aspherical plastic lenses and the effective focal length of the zoom projection lens system 100 to ensure the imaging quality of the zoom projection lens system 100 when the temperature of the projector is high. In particular, the refractive index of the first and second aspherical plastic lens 12, 21 change to increase the effective focal length of the zoom projection lens system 100, while the refractive index of the third aspherical plastic lens 31 changes to reduce the effective focal length of the zoom projection lens system 100, therefore, the effective focal length of the zoom projection lens system 100 is maintained at a desired length.


In this embodiment, Fa1=−41.48 mm, Fb1=56.88 mm, Fa2=−70.37 mm, Fw=18.68 mm, Fa1/Fw=−2.22, Fb1/Fw=3.05, Fa2/Fw=−3.76.


The aspherical surfaces of the aspherical plastic lenses 12, 21, 41 are shaped according to the formula:







x
=



ch
2


1
+


1
-


(

k
+
1

)



c
2



h
2






+







Aih
i




,





wherein h is a height from the optical axis of the zoom projection lens system 100 to the aspherical surface, c is a vertex curvature, k is a conic constant, and Ai is i-th order correction coefficients of the aspheric surfaces.


In this embodiment, the following symbols are used:


F: effective focal length of the zoom projection lens system 100;


D4: the distance between the first lens group 10 and the second lens group 20 along the optical axis of the zoom projection lens system 100 (i.e. the distance between the minification side surface of the first aspherical plastic lens 12 and the magnification side surface of the second aspherical plastic lens 21 along the optical axis of the zoom projection lens system 100);


D10: the distance between the second lens group 20 and the third lens group 30 along the optical axis of the zoom projection lens system 100 (i.e. the distance between the minification side surface of the third spherical lens 23 and the magnification side surface of the fourth spherical lens 31 along the optical axis of the zoom projection lens system 100);


D12: the distance between the third lens group 30 and the fourth lens group 40 along the optical axis of the zoom projection lens system 100 (the distance between the minification side surface of the fourth spherical lens 31 and the magnification side surface of the third aspherical plastic lens 41 along the optical axis of the zoom projection lens system 100);


D19: the distance between the fourth lens group 40 and the fifth lens group 50 along the optical axis of the zoom projection lens system 100 (the distance between the minification side surface of the seventh spherical lens 44 and the magnification side surface of the eighth spherical lens 51 along the optical axis of the zoom projection lens system 100);


F/No: F number;


2ω: field angle;


R: radius of curvature;


D: distance between surfaces on the optical axis of the zoom projection lens system 100;


Nd: refractive index of lens of d light (wavelength: 587.6 nm); and


Vd: Abbe number of d light (wavelength: 587.6 nm).


The zoom projection lens system 100 of the exemplary embodiment satisfies the tables 1-3.













TABLE 1






R
D




Surface
(mm)
(mm)
Nd
Vd



















Magnification side surface of the
30.027
1.494
1.487
70.441


first lens 11


Minification side surface of the
14.42
9.644


first lens 11


Magnification side surface of the
−75.209
1.9056
1.531
55.753


first aspherical plastic lens 12


Minification side surface of the
31.65
D4 


first aspherical plastic lens 12


Magnification side surface of the
67.429
3.967
1.632
23.239


second aspherical plastic lens 21


Minification side surface of the
−76.91
0.1309


second aspherical plastic lens 21


Magnification side surface of the
51.84
4.702
1.7432
49.221


second spherical lens 22


Minification side surface of the
−36.46
1.099


second spherical lens 22


(Magnification side surface


of the third spherical lens 23)


Minification side surface of the
−155.83
2.935
1.846
23.784


third spherical lens 23


Aperture stop 70
infinity
D10


Magnification side surface of the
35.026
3.44
1.487
70.44


fourth spherical lens 30


Minification side surface of the
−95.85
D12


fourth spherical lens 30


Magnification side surface of the
80.265
0.872
1.632
23.23


third aspherical plastic lens 41


Minification side surface of the
28.68
5.95


third aspherical plastic lens 41


Magnification side surface of the
−12.351
1.097
1.846
23.78


fifth spherical lens 42


Minification side surface of the
36.053
6.42
1.487
70.441


fifth spherical plastic lens 42


(Magnification side surface of


the sixth spherical lens 43)


Minification side surface of the
−16.605
0.1309


sixth spherical lens 43


Magnification side surface of the
222.485
4.526
1.846
23.78


seventh spherical lens 44


Minification side surface of the
−32.524
D19


seventh spherical lens 44


Magnification side surface of the
116.62
4.19
1.6204
60.343


eighth spherical lens 50


Minification side surface of the
−51.458
3.85


eighth spherical lens 50


Magnification side surface of the
infinity
21
1.5168
64.16


prism 80


Minification side surface of the
infinity
1.24


prism 80


Magnification side surface of the
infinity
0.55
1.458
67.82


first flat glass 91


Minification side surface of the
infinity
0.215
1.51
68


first flat glass 91 (Magnification


side surface of the second flat


glass 92)


Minification side surface of the
infinity
1.9


second flat glass 92


Magnification side surface of the
infinity
0.5
1.458
67.82


third flat glass 93


Minification side surface of the
infinity
0.2
1.51
68


third flat glass 93(Magnification


side surface of the fourth flat


glass 94)


Minification side surface of the
infinity
3.087


fourth flat glass 94


Magnification side surface of the
infinity
0.7
1.458
67.82


fifth flat glass 95


Minification side surface of the
infinity
1.2
1.51
68


fifth flat glass 95(Magnification


side surface of the protective


glass sheet 96)


Minification side surface of the
infinity



protective glass sheet 96 (The


image surface 61)

















TABLE 2





Surface
Aspherical coefficient







Magnification side surface of the first
K = 0; A4 = 2.47728E−08; A6 = −2.40190E−08;


aspherical plastic lens 12
A8 = 1.32518E−10; A10 = −9.73536E−13; A12 = 0


Minification side surface of the first
K = −7.971; A4 = 7.25628E−06; A6 = −1.13482E−07;


aspherical plastic lens 12
A8 = 2.28143E−10; A10 = −1.24683E−12; A12 = 0


Magnification side surface of the
K = 0; A4 = −4.37631E−06; A6 = −9.87470E−09;


second aspherical plastic lens 21
A8 = 1.13300E−10; A10 = 0; A12 = 0


Minification side surface of the
K = 0; A4 = −1.89894E−06; A6 = −1.33585E−08;


second aspherical plastic lens 21
A8 = 1.15711E−10; A10 = 0; A12 = 0


Magnification side surface of the third
K = −0.569381; A4 = 2.10814E−04; A6 = −3.90837E−06;


aspherical plastic lens 41
A8 = 6.82785E−08; A10 = −6.68693E−10;



A12 = 3.27002E−12


Minification side surface of the third
K = 8.9571; A4 = 1.68745E−04; A6 = −4.51479E−06;


aspherical plastic lens 41
A8 = 6.82208E−08; A10 = −6.82592E−10;



A12 = 2.59674E−12






















TABLE 3







F(mm)
D4
D10
D12
D19





















Wide angle state
18.68
17.975
14.55
0.25993
0.25993


Telephoto state
24.28
10.509
10.414
6.259
5.247









As illustrated in FIG. 3, the curves are respective spherical aberration characteristic curves of light of wavelength 460 nm, light of wavelength 550 nm, light of wavelength 610 nm, occurring in the zoom projection lens system 100 in the wide angle state. Obviously, spherical aberration of visible light (400-700 nm) occurring in the zoom projection lens system 100 of this embodiment is in a range of: −0.1 mm˜0.1 mm. In FIG. 4, the curves T and S are the tangential field curvature curve and the sagittal field curvature curve, respectively. Clearly, field curvature occurring in the zoom projection lens system 100 in the wide angle state is limited to a range of: −0.02 mm˜0.02 mm. In FIG. 5, distortion occurring in the zoom projection lens system 100 of this embodiment is limited within the range of: −1.5%˜0. In FIG. 6, the lateral chromatic aberration of visible light (400-700 nm) occurring in the zoom projection lens system 100 is limited within the range of: −10 μm˜10 μm.


As illustrated in FIG. 7, the spherical aberration of visible light (400-700 nm) occurring in the zoom projection lens system 100 in the telephoto state is in a range of: −0.1 mm˜0.1 mm. In FIG. 8, the field curvature occurring in the zoom projection lens system 100 in the telephoto state is limited to a range of: −0.2 mm˜0.2 mm. In FIG. 9, distortion occurring in the zoom projection lens system 100 in the telephoto state is limited within the range of: 0˜0.2%. In FIG. 10, the lateral chromatic aberration of visible light (400-700 nm) occurring in the zoom projection lens system 100 is limited within the range of: −10 μm˜10 μm.


It will be understood that the above particular embodiments 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.

Claims
  • 1. A zoom projection lens system, in order from the magnification side to the minification side thereof, comprising: a first lens group with negative refraction power, the first lens group comprising a first aspherical plastic lens;a second lens group with positive refraction power, the second lens group comprising a second aspherical plastic lens;a third lens group with positive refraction power;a fourth lens group with negative refraction power, the fourth lens group comprising a third aspherical plastic lens; anda fifth lens group with positive refraction power;the first lens group, the second lens group, the third lens group, and the fourth lens group being movably positioned, the fifth lens group being immovably positioned, the zoom projection lens system satisfying the formula: −2.4≦Fa1/Fw≦−2.12.9≦Fb1/Fw≦3.2−3.8≦Fa2/Fw≦−3.6wherein Fa1, Fa2, Fb1 are the effective focal lengths of the first, second, third aspherical plastic lenses respectively, Fw is the effective focal lengths of the zoom projection lens system in a wide angle state.
  • 2. The zoom projection lens system of claim 1, wherein the first lens group further comprises a first spherical lens positioned on the magnification side of the first aspherical plastic lens, the second lens group further comprises a second spherical lens and a third spherical lens positioned on the minification side of the second aspherical plastic lens, the third lens group further comprises a fourth spherical lens, the fourth lens group further comprises a fifth spherical lens, a sixth spherical lens, and a seventh spherical lens positioned on the minification side of the third aspherical plastic lens and arranged from the magnification side to the minification side of the zoom projection lens system, the fifth lens group comprises an eighth spherical lens.
  • 3. The zoom projection lens system of claim 2, wherein the second spherical lens and the third spherical lens are adhered together to form a compound lens, the fifth spherical lens and the sixth spherical lens are adhered together to form a compound lens.
  • 4. The zoom projection lens system of claim 2, wherein the first, second, third, fourth, fifth, sixth, seventh, eighth spherical lenses are glass lenses.
  • 5. The zoom projection lens system of claim 1, wherein the zoom projection lens system further comprises an aperture stop positioned between the second lens group and the third lens group.
  • 6. The zoom projection lens system of claim 5, wherein the aperture stop is capable of moving with the second lens group, the diameter of the aperture stop is unchanged.
  • 7. The zoom projection lens system of claim 1, wherein the zoom projection lens system further comprises an image surface positioned on the minification side of the fifth lens group.
  • 8. The zoom projection lens system of claim 7, wherein the zoom projection lens system further comprises a prism positioned between the fifth lens group and the image surface.
  • 9. The zoom projection lens system of claim 8, wherein the zoom projection lens system further comprises a first flat glass, a second flat glass, a third flat glass, a fourth flat glass, a fifth flat glass, a protective glass sheet immovably positioned between the prism and the image surface arranged from the magnification side to the minification side of the zoom projection lens system.
  • 10. The zoom projection lens system of claim 9, wherein the first flat glass and the second flat glass are adhered together, the third flat glass and the fourth flat glass are adhered together, the fifth flat glass, the protective glass sheet and the image surface are adhered together.
Priority Claims (1)
Number Date Country Kind
2010 1 0533430 Nov 2010 CN national
US Referenced Citations (3)
Number Name Date Kind
6515803 Hirose Feb 2003 B2
7009776 Wada Mar 2006 B2
8072690 Nagatoshi Dec 2011 B2
Related Publications (1)
Number Date Country
20120113526 A1 May 2012 US