Projection lens and projector using same

Abstract

The invention discloses a projection lens and a projector using the same, and belongs to the technical field of image display, and the projection lens comprises a first lens group and a second lens group in sequence from an object side to an image side. The first lens group is composed of a positive focal power lens, two negative focal power lenses and a positive focal power lens which are sequentially arranged from the object side to the image side. And the second lens group is composed of a positive focal power lens, a set of negative focal power balsaming lens, a negative focal power lens and a positive focal power lens which are sequentially arranged from the object side to the image side. At least one aspherical lens is used in the second lens group. The combination of the materials and the focal power of the two lens groups meets certain conditions, various aberrations can be effectively controlled, and good optical performance can be obtained. The projection lens is small in lens number, simple in structure and easy to manufacture, and the cost of the projection lens is reduced. And the transmittance is high and the aperture is large, so that the purpose of high-brightness projection is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of image display, and in particular to a projection lens and a projector using the same. Background Art

[0002] As a necessary projection equipment in various places of life such as teaching and cinema, the projection lens is the last link in the projector's optical path and is also an extremely important link. The design of the projection lens not only affects the performance of the projector, but also determines the quality of the projection effect.

[0003] Currently, the common digital projection display technology mainly uses DMD (Digital Micromirror Device) or LCOS (Liquid Crystal On Silicon) as the display device, and uses polarization spectrometers or total reflection spectrometers as lighting or imaging spectrometers. By designing a reasonable projection lens optical path, the image reflected on the display device is focused onto the projection screen.

[0004] The investigation found that the existing 0.65"DMD projection lens on the market has poor image quality. In addition, because the projection lens uses more lenses, it is not only expensive, but also makes the entire lens transmittance low, resulting in low brightness of the final projection. Summary of the invention

[0005] The object of the present invention is to provide a projection lens and a projector, which can at least solve one of the above problems.

[0006] According to one aspect of the present invention, there is provided a projection lens, comprising a first lens group with negative optical power and a second lens group with positive optical power, which are arranged in sequence from the object side to the image side;

[0007] The first lens group and the second lens group are configured to satisfy the following conditional expressions:

[0008] 1<|f1 / f2︱<2;

[0009] TTL / EFFL<7;

[0010] TTL / BFL<5;

[0011] Among them: f1 is the focal length of the first lens group, f2 is the focal length of the second lens group, TTL is the distance between the first surface of the first lens of the first lens group and the image plane, EFFL is the focal length of the wide-angle end of the lens, and BFL is the distance between the second surface of the last lens of the second lens group and the image plane.

[0012] In some embodiments, the first lens group includes a first lens, a second lens, a third lens, and a fourth lens arranged in sequence from the object side to the image side;

[0013] The first lens is a positive power lens, and its first surface is curved towards the image side;

[0014] The second lens, the third lens and the fourth lens are all meniscus lenses, and the first surface and the second surface thereof are both curved toward the image side;

[0015] The second lens and the third lens are both negative power lenses, and the fourth lens is a positive power lens.

[0016] In some embodiments, the first lens group satisfies at least the following conditional formula:

[0017] Vd11>60;

[0018] Vd21>55;

[0019] Vd31>55;

[0020] Vd41<25;

[0021] Wherein, Vd11 is the dispersion coefficient of the first lens, Vd21 is the dispersion coefficient of the second lens, Vd31 is the dispersion coefficient of the third lens, and Vd41 is the dispersion coefficient of the fourth lens.

[0022] In some embodiments, the second lens group includes a fifth lens, a sixth lens, a seventh lens, an eighth lens, and a ninth lens arranged in sequence from the object side to the image side;

[0023] The fifth lens is a positive power lens, wherein the first surface is curved toward the image side;

[0024] The sixth lens and the seventh lens are combined into a cemented lens, wherein the sixth lens is a positive power lens and the seventh lens is a negative power lens;

[0025] The eighth lens is a double concave lens with negative power;

[0026] The ninth lens is a biconvex positive power lens;

[0027] At least one surface of the ninth lens is aspherical.

[0028] In some embodiments, the second lens group satisfies at least the following conditional formula:

[0029] Vd22>47;

[0030] Vd23<25;

[0031] Vd25>58;

[0032] Among them, Vd22 is the dispersion coefficient of the sixth lens, Vd23 is the dispersion coefficient of the seventh lens, and Vd25 is the dispersion coefficient of the ninth lens.

[0033] In some embodiments, the projection lens further includes an aperture, which is one and located in the middle of the second lens group. Thus, the aperture is used to limit the light flux of the light passing through the first lens group entering the second lens group, and to make the light cone after passing through the first lens group more symmetrical, so that the coma of the projection lens can be corrected.

[0034] In some embodiments, the projection lens further includes a stop, which is disposed in the second lens group and between the seventh lens and the eighth lens.

[0035] In some embodiments, the position of the aperture is fixed.

[0036] In some implementations, there are only 2 groups of projection lenses.

[0037] According to another aspect of the present invention, a projector is provided, including a housing and the above-mentioned projection lens, wherein the projection lens is arranged in the housing.

[0038] Beneficial effects of the present invention:

[0039] After testing, the MTF curve (MTF, English spelling is Modulation Transfer Function, Chinese name is Modulation Transfer Function) of the projection lens of the present invention is excellent, with small distortion and small vertical axis chromatic aberration, and the aperture can reach F2.4;

[0040] The number of lenses in the entire projection lens is small, which not only reduces the cost but also makes the entire lens have high transmittance;

[0041] The projection lens of the present invention not only has good resolution capability, but also can better utilize light effects, thereby improving the brightness of the projected image when used on a projector. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 is a simplified optical structure diagram of a projection lens involved in Embodiments 1 and 2 of the present invention;

[0043] Figure 2 is a structural diagram of the wide-angle end of the projection lens involved in Embodiment 1 of the present invention;

[0044] Figure 3 is the MTF curve of the projection lens at the wide-angle end involved in Embodiment 1 of the present invention;

[0045] Figure 4 is a distortion diagram of the wide-angle end of the projection lens involved in Embodiment 1 of the present invention;

[0046] Figure 5 is a chromatic aberration diagram of the wide-angle end of the projection lens involved in Embodiment 1 of the present invention;

[0047] Figure 6 is a structural diagram of the telephoto end of a projection lens involved in Embodiment 1 of the present invention;

[0048] Figure 7 is the MTF curve of the telephoto end of the projection lens involved in Example 1 of the present invention;

[0049] Figure 8 is a distortion diagram of the telephoto end of the projection lens involved in Embodiment 1 of the present invention;

[0050] Fig. 9 is a chromatic aberration diagram of the telephoto end of the projection lens involved in Embodiment 1 of the present invention;

[0051] Fig.10 is a structural diagram of the wide-angle end of the projection lens involved in Embodiment 2 of the present invention;

[0052] Fig.11 is the MTF curve of the wide-angle end of the projection lens involved in Embodiment 2 of the present invention;

[0053] Fig.12 is a distortion diagram of the wide-angle end of the projection lens involved in Embodiment 2 of the present invention;

[0054] Fig.13 is a chromatic aberration diagram of the wide-angle end of the projection lens involved in Embodiment 2 of the present invention;

[0055] Fig.14 is a structural diagram of the telephoto end of the projection lens involved in Embodiment 2 of the present invention;

[0056] Fig.15 is the MTF curve of the telephoto end of the projection lens involved in Embodiment 2 of the present invention;

[0057] Fig.16 is a distortion diagram of the telephoto end of the projection lens involved in Embodiment 2 of the present invention;

[0058] Fig.17 3 is a chromatic aberration diagram of the projection lens at the telephoto end according to Embodiment 2 of the present invention.

[0059] Figure 1 The figure marks in the figure are: 10-first lens group; 20-second lens group; 30-aperture; 40-DMD protection glass; 50-image plane; 100-projection lens; 101-first lens; 102-second lens; 103-third lens; 104-fourth lens; 201-fifth lens; 202-sixth lens; 203-seventh lens; 204-eighth lens; 205-ninth lens. DETAILED DESCRIPTION

[0060] The present invention will be further described in detail below in conjunction with the accompanying drawings.

[0061] Figures 1 to 17 A projection lens according to the invention is schematically shown.

[0062] like Figure 1-17 As shown, the projection lens 100 of the present invention includes a first lens group 10 with negative optical power and a second lens group 20 with positive optical power, which are arranged in sequence from the object side to the image side, and the first lens group 10 and the second lens group 20 are constructed in a manner that satisfies the following conditional expressions (1), (2), and (3):

[0063] 1<|f1 / f2︱<2---------------(1)

[0064] TTL / EFFL<7---------------(2)

[0065] TTL / BFL<5---------------(3)

[0066] Wherein: f1 is the focal length of the first lens group 10, f2 is the focal length of the second lens group 20, TTL is the distance between the first surface of the first lens of the first lens group 10 and the image plane 50, EFFL is the focal length of the lens at the wide-angle end, and BFL is the distance between the second surface of the last lens of the second lens group 20 and the image plane 50.

[0067] The projection lens 100 further includes an aperture 30. The aperture 30 is located in the middle of the second lens group 20 to limit the light flux of the light passing through the first lens group 10 entering the second lens group 20, and to make the light cone after passing through the first lens group 10 more symmetrical, so that the coma of the projection lens 100 can be corrected. To facilitate the design of the mechanism, the position of the aperture 30 is set to a fixed position.

[0068] In this embodiment, the first lens group 10 includes a first lens 101, a second lens 102, a third lens 103 and a fourth lens 104 arranged in sequence from the object side to the image side;

[0069] The first lens 101 is a positive power lens, and its first surface is curved towards the image side;

[0070] The second lens 102, the third lens 103 and the fourth lens 104 are all meniscus lenses, and the first surface and the second surface thereof are both curved toward the image side;

[0071] The second lens 102 and the third lens 103 are both negative power lenses, and the fourth lens 104 is a positive power lens.

[0072] The first lens group 10 is configured to satisfy at least the following conditional expressions (4), (5), (6), and (7):

[0073] Vd11>60---------------(4)

[0074] Vd21>55---------------(5)

[0075] Vd31>55---------------(6)

[0076] Vd41<25---------------(7)

[0077] Wherein, Vd11 is the dispersion coefficient of the first lens 101 , Vd21 is the dispersion coefficient of the second lens 102 , Vd31 is the dispersion coefficient of the third lens 103 , and Vd41 is the dispersion coefficient of the fourth lens 104 .

[0078] The second lens group 20 includes a fifth lens 201, a sixth lens 202, a seventh lens 203, an eighth lens 204 and a ninth lens 205 arranged in sequence from the object side to the image side;

[0079] The fifth lens 201 is a positive power lens, wherein the first surface thereof is curved toward the image side;

[0080] The sixth lens 202 and the seventh lens 203 are combined into a cemented lens, wherein the sixth lens 202 is a positive power lens, and the seventh lens 203 is a negative power lens;

[0081] The eighth lens 204 is a biconcave lens with negative power;

[0082] The ninth lens 205 is a biconvex positive power lens;

[0083] At least one surface of the ninth lens 205 is aspherical.

[0084] The second lens group 20 of this embodiment is configured to satisfy the following conditional expressions (8), (9), and (10):

[0085] Vd22>47--------------(8)

[0086] Vd23<25--------------(9)

[0087] Vd25>58-------------(10)

[0088] Wherein, Vd22 is the dispersion coefficient of the sixth lens 202 , Vd23 is the dispersion coefficient of the seventh lens 203 , and Vd25 is the dispersion coefficient of the ninth lens 205 .

[0089] Next, the operation and effects of the projection lens configured as described above will be described.

[0090] Conditions (1) to (3) define the geometric dimensions of the projection lens 100, which ensure that the length of the lens is reduced as much as possible while ensuring that the BFL is large enough. This way, the back focus has enough space to meet the functional requirements. At the same time, the shortened lens length can reduce the outer diameter of the lens, thereby achieving the purpose of reducing costs.

[0091] Conditional expressions (4) to (7) define the dispersion of the key lenses of the first lens group 10. Satisfying the conditional expressions can effectively correct the system chromatic aberration.

[0092] Conditional expressions (8) to (10) define the dispersion of the key lenses of the second lens group 20. Satisfying the conditional expressions can effectively correct the system chromatic aberration.

[0093] Next, a specific embodiment of the projection lens 100 according to the present invention will be described.

[0094] There are many possible implementations of the projection lens 100 provided by the present invention. The projection lens 100 is specifically described below using Embodiment 1 and Embodiment 2 as examples. The structures and parameters in Embodiment 1 and Embodiment 2 are merely examples of implementations of the projection lens 100 and are not intended to be limiting.

[0095] Example 1

[0096] As shown in the following Table 1, it shows the parameters of all lenses of the projection lens of this embodiment.

[0097] Table 1: Statistical table of mirror parameters of all lenses in Example 1

[0098]

[0099] In the column of surface number Si, it is indicated that the surface of the structural element closest to the object side is the first surface, and the surface numbers gradually increase along the image direction;

[0100] In the column of curvature radius Ri, the value of the curvature radius corresponding to the Si number is shown;

[0101] In the column of surface spacing Di, the lens thickness or the spacing value between lenses corresponding to the Si number is shown;

[0102] The units of the curvature radius Ri and the surface spacing Di are millimeters (mm).

[0103] The columns of refractive index Ndj and Abbe number vdj respectively show the refractive index and Abbe number of the jth (j=1 to 9) optical component from the object side with respect to d-light (wavelength 587.6 nm).

[0104] As shown in Table 2 below, it discloses the aspheric coefficients corresponding to the aspheric mirror surface in Table 1.

[0105] Table 2: Statistical table of aspheric coefficients corresponding to the aspheric mirror surfaces in Table 1

[0106] K b c d e f g h S17 9.9E-01 -1.0E-05 1.4E-06 -1.3E-09 3.7E-10 8.9E-13 -2.7E-14 -2.6E-16 S18 -6.2E+00 3.1E-05 1.0E-06 3.5E-08 -6.2E-10 1.5E-11 1.3E-14 -6.0E-16

[0107] The symbol "E" indicates that the data immediately following it is a "power exponent" with a base of 10, which means that the value represented by the exponential function with a base of 10 is multiplied by the value before "E". For example, if it is "1.0E-02", it means "1.0×10 -2 ”.

[0108] The aspheric coefficients in Table 2 are based on the center of the lens surface as the origin, the optical axis as the x-axis, and the aspheric surface type expression of the lens surface satisfies the following formula (A):

[0109]

[0110] The specific meanings of the relevant parameters in the above formula (A) are as follows:

[0111] X is the depth of the aspheric surface (mm);

[0112] Y is the distance (height) from the optical axis to the lens surface (mm);

[0113] C is the radius of curvature of the lens, C = 1 / R;

[0114] K is the cone constant;

[0115] b, c, d, e, f, g, and h are aspherical lens coefficients.

[0116] As shown in the following Table 3, it discloses four parameters of the wide-angle end of the projection lens of this embodiment.

[0117] Table 3: Statistics of the four parameters of the projection lens at the wide-angle end: focal length, aperture, viewing angle, and the distance between the first lens group and the second lens group

[0118] f(Wide angle) FNO. 2ω D1 16.9 2.4 71° 18.044

[0119] As shown in the following Table 4, it discloses four parameters of the telephoto end of the projection lens of this embodiment.

[0120] Table 4: Statistics of the four parameters of the projection lens at the telephoto end: focal length, aperture, viewing angle, and the distance between the first lens group and the second lens group

[0121] f(Telephoto end) FNO. 2ω D1 21.64 2.7 57.6° 5.033

[0122] In Table 3 and Table 4: f(wide-angle end) is the focal length of the projection lens at the wide-angle end, f(telephoto end) is the focal length of the projection lens at the telephoto end, both in units of mm, FNO. is the aperture, 2ω is the viewing angle (ω: half viewing angle), D1 is the distance between the first lens group and the second lens group, that is, the distance between the eighth surface and the ninth surface in Table 1, in units of (mm).

[0123] Example 2

[0124] The number and structure of the lenses of the projection lens of this embodiment are basically the same as those of Embodiment 1, and the only difference is that the parameters of the lenses are different. As shown in Table 5 below, it shows the parameters of all the lenses of the projection lens of this embodiment.

[0125] Table 5: Parameter statistics of the mirror surfaces of all lenses in Example 2

[0126]

[0127] As shown in Table 6 below, it discloses the aspheric coefficients corresponding to the aspheric mirror surface in Table 5.

[0128] Table 6: Statistical table of aspheric coefficients corresponding to the aspheric mirror surfaces in Table 5

[0129] K b c d e f g h S17 7.0E-01 -1.9E-05 9.8E-07 1.4E-08 -1.6E-10 5.3E-12 -4.6E-14 8.0E-17 S18 -1.3E+01 4.7E-05 1.3E-06 4.6E-08 -1.2E-09 2.4E-11 3.2E-14 -1.8E-15

[0130] As shown in Table 7 below, it discloses four parameters of the wide-angle end of the projection lens of this embodiment.

[0131] Table 7: Statistics of the four parameters of the projection lens at the wide-angle end: focal length, aperture, viewing angle, and the distance between the first lens group and the second lens group

[0132] f(Wide angle) FNO. 2ω D 1 16.9 2.4 70° 27.679

[0133] As shown in the following Table 8, it discloses four parameters of the telephoto end of the projection lens of this embodiment.

[0134] Table 8: Statistics of the four parameters of the projection lens at the telephoto end: focal length, aperture, viewing angle, and the distance between the first lens group and the second lens group

[0135] f(Telephoto end) FNO. 2ω D 1 21.6 2.7 56.6° 12.863

[0136] Furthermore, as shown in Table 9 below, conditional expressions and specific numerical values ​​of Examples 1 and 2 of the present invention are described.

[0137] Table 9: Statistical table of conditional expressions and specific values ​​of Examples 1 and 2

[0138] Conditional expression Example 1 Example 2 <h2 style=";text-align:left;direction:ltr">1<| f1 / f2 |<2<h2 style=";text-align:left;direction:ltr"> 1.27 1.13 TTL / EFFL<7 6.29 6.8 TTL / BFL<5 4.5 4.86 Vdll>60 70.4 70.4 Vd21>55 55.5 55.5 Vd31>55 55.5 55.5 Vd41<25 23.8 23.8 Vd22>47 47.9 68.3 Vd23<25 23.8 25 Vd25>58 64 59.5

[0139] The following is a further description of the specific data of the above embodiments in conjunction with the accompanying drawings:

[0140] from Figure 3 , Figure 7 , Fig.11 , Fig.15 From the MTF curve, we can see that the optical transfer function MTF>50% at a spatial frequency of 67lp / mm for the full field of view.

[0141] from Figure 4 , Figure 8 , Fig.12 , Fig.16 It can be seen from the distortion diagram that the maximum distortion of the entire field of view is less than 2%.

[0142] from Figure 5 , Fig. 9 , Fig.13 , Fig.17 From the chromatic aberration diagram, we can see that the maximum vertical chromatic aberration in the entire field of view is about 3.5μm.

[0143] From the imaging results and parameters of the projection lens 100 obtained in the above Examples 1 and 2, it can be seen that the projection lens 100 of the present invention has excellent MTF performance, small distortion, small vertical axis chromatic aberration, and the aperture can reach F2.4. In addition, due to the small number of lenses, the transmittance of the entire lens is high. Such a lens can not only have a good resolution capability, but also make better use of light effects, thereby improving the brightness of the projected image when used on a projector.

[0144] In summary, the present invention is a two-group projection lens 100 with large aperture, high image quality, low cost and compact structure. It includes, from the object side to the image side, a first lens group 10 with negative optical power and a second lens group 20 with positive optical power. The first lens group 10 is composed of a positive optical power lens, two negative optical power lenses and a positive optical power lens arranged in sequence from the object side to the image side. The second lens group 20 is composed of a positive optical power lens, a set of negative optical power cemented lenses, a negative optical power lens and a positive optical power lens arranged in sequence from the object side to the image side. At least one aspherical lens is used in the second lens group 20. The material and optical power combination of the two lens groups meet certain conditions, which can effectively control various aberrations and obtain good optical performance. The projection lens 100 has a small number of lenses, a simple structure, and is easy to manufacture, so that the cost of the projection lens 100 is reduced. The small number of lenses of the entire lens makes the transmittance of the entire lens high, and the large aperture achieves the purpose of high brightness projection.

[0145] In addition, the present invention is not limited to the above-mentioned embodiments, and various modifications are possible. For example, the values ​​of the radius of curvature, surface spacing, and refractive index of each lens component are not limited to the values ​​shown in the above-mentioned numerical embodiments, and other values ​​may be used. These changes made according to the spirit of the present invention are all included in the protection scope required by the present invention.

[0146] The above are only some embodiments of the present invention. For those skilled in the art, several modifications and improvements can be made without departing from the creative concept of the present invention, which all belong to the protection scope of the present invention.

Claims

1. A projection lens, characterized in that: It comprises a first lens group (10) with negative optical power and a second lens group (20) with positive optical power, which are arranged in sequence from the object side to the image side; The first lens group (10) and the second lens group (20) are constructed in a manner that satisfies the following conditional expression: 1<|f1 / f2︱<2; TTL / EFFL<7; TTL / BFL<5; Wherein: f1 is the focal length of the first lens group (10), f2 is the focal length of the second lens group (20), TTL is the distance between the first surface of the first lens of the first lens group (10) and the image plane (50), EFFL is the focal length of the wide-angle end of the projection lens (100), and BFL is the distance between the second surface of the last lens of the second lens group (20) and the image plane (50).

2. The projection lens according to claim 1, characterized in that: The first lens group (10) comprises a first lens (101), a second lens (102), a third lens (103) and a fourth lens (104) which are arranged in sequence from the object side to the image side; The first lens (101) is a positive power lens, and its first surface is curved toward the image side; The second lens (102), the third lens (103) and the fourth lens (104) are all meniscus lenses, and the first surface and the second surface thereof are both curved toward the image side; The second lens (102) and the third lens (103) are both negative power lenses, and the fourth lens (104) is a positive power lens.

3. The projection lens according to claim 2, characterized in that: The first lens group (10) at least satisfies the following conditional formula: Vd11>60; Vd21>55; Vd31>55; Vd41<25; Wherein, Vd11 is the dispersion coefficient of the first lens (101), Vd21 is the dispersion coefficient of the second lens (102), Vd31 is the dispersion coefficient of the third lens (103), and Vd41 is the dispersion coefficient of the fourth lens (104).

4. The projection lens according to claim 1, wherein: The second lens group (20) comprises a fifth lens (201), a sixth lens (202), a seventh lens (203), an eighth lens (204) and a ninth lens (205) which are arranged in sequence from the object side to the image side; The fifth lens (201) is a positive power lens, wherein the first surface thereof is curved toward the image side; The sixth lens (202) and the seventh lens (203) are combined into a cemented lens, wherein the sixth lens (202) is a positive power lens, and the seventh lens (203) is a negative power lens; The eighth lens (204) is a biconcave lens with negative focal power; The ninth lens (205) is a biconvex positive power lens; At least one surface of the ninth lens (205) is an aspherical surface.

5. The projection lens according to claim 4, characterized in that: The second lens group (20) at least satisfies the following conditional formula: Vd22>47; Vd23<25; Vd25>58; Wherein, Vd22 is the dispersion coefficient of the sixth lens (202), Vd23 is the dispersion coefficient of the seventh lens (203), and Vd25 is the dispersion coefficient of the ninth lens (205).

6. The projection lens according to claim 1, wherein: It also includes an aperture (30), which is one and is located in the middle of the second lens group (20).

7. The projection lens according to claim 4, characterized in that: It also includes a stop (30), which is arranged in the second lens group (20) and located between the seventh lens (203) and the eighth lens (204).

8. The projection lens according to claim 6 or 7, characterized in that: The position of the aperture (30) is fixed.

9. The projection lens according to any one of claims 1 to 7, characterized in that: The projection lens (100) has only two groups.

10. A projector, comprising a housing, characterized in that: It also comprises a projection lens (100) as claimed in any one of claims 1 to 9, wherein the projection lens (100) is arranged on the housing.

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