TWI860149B - Fixed-focus projection lens - Google Patents

Abstract

A fixed-focus projection lens includes a first lens group, an aperture and a second lens group arranged in order from a magnified side to a minified side. The fixed-focus projection lens includes 6-9 lenses with refractive powers and meets the following conditions: (1) -9＜EFLf/EFL＜-1.5 and (2) 0.08＜IMH/OAL＜0.3, where EFLf is an effective focal length of the first lens group, EFL is an effective focal length of the fixed-focus projection lens, IMH is an image height measured at the effective focal length, and OAL is a distance along the optical axis between two outermost lens surfaces at opposite sides of the fixed-focus projection lens.

Description

Fixed focus projection lens

The present invention relates to a fixed-focus projection lens.

The current LCD projectors are limited by space and cost, and people have higher and higher requirements for miniaturization and optical performance. To meet such requirements, the projection lens generally needs to have the characteristics of low cost, large aperture, and small size. Therefore, there is an urgent need for a projection lens design that can effectively reduce the size of the projection system, have fewer lenses, and provide lower manufacturing costs and better imaging quality.

Other purposes and advantages of the present invention can be further understood from the technical features disclosed in the embodiments of the present invention.

An embodiment of the present invention provides a fixed-focus projection lens, comprising a first lens group, an aperture, and a second lens group arranged in sequence from a magnifying side to a reducing side. The first lens group includes two aspherical lenses, and one of the two aspherical lenses has a positive refractive power. The second lens group has positive refractive power, and the fixed-focus projection lens includes 6-9 lenses with refractive power and meets the following conditions: (1) -9＜EFLf/EFL＜-1.5, where EFLf is the effective focal length of the first lens group and EFL is the effective focal length of the fixed-focus projection lens; (2) 0.08＜IMH/OAL＜0.3, where IMH is the image height of the fixed-focus projection lens at the effective focal length and OAL is the distance between the two outermost lens surfaces on both sides of the fixed-focus projection lens on the optical axis of the fixed-focus projection lens.

Another embodiment of the present invention provides a fixed-focus projection lens, including a first lens group, an aperture, and a second lens group arranged in sequence from the magnification side to the reduction side. The first lens group includes two aspheric lenses, one of which has a positive refractive power, and the second lens group has a positive refractive power. The first lens of the fixed-focus projection lens from the magnification side to the reduction side is a negative refractive power lens, and the second lens is a positive refractive power lens. The fixed-focus projection lens includes 6-9 lenses with refractive power and meets the following conditions: (1) -9＜EFLf/EFL＜-1.5 and (2) 5＜EFL2/EFL＜90, wherein EFLf is the effective focal length of the first lens group, EFL is the effective focal length of the fixed-focus projection lens, and EFL2 is the effective focal length of the second lens from the magnification side to the reduction side.

According to the designs of the various embodiments of the present invention, by appropriately arranging glass and plastic lenses with spherical and aspherical surfaces, the projection lens can have a smaller lens volume and fewer lens pieces, while being able to provide a low distortion, high-resolution projection image, and the projection lens can have a lower heat transfer amount, while being able to withstand the higher temperature and temperature changes of the use environment, thereby reducing the manufacturing cost and taking into account the image quality.

In order to make the above features and advantages of the present invention more clearly understood, embodiments are specifically cited below and described in detail with reference to the accompanying drawings.

The terms "first" and "second" used in the following embodiments are used to identify the same or similar technical contents, features and effects of the present invention as mentioned above, which will be clearly presented in the detailed description of the embodiments with reference to the drawings. The directional terms mentioned in the following embodiments, such as up, down, left, right, front or back, etc., are only used to refer to the directions of the attached drawings. Therefore, the directional terms used are used to illustrate and are not used to limit the present invention. In order to show the characteristics of this embodiment, only the structure related to this embodiment is shown, and the rest of the structure is omitted.

The lens referred to in the present invention refers to a component that is partially or completely made of a transparent material and has refractive power, and is usually made of glass or plastic material.

When the lens is used in a projection system, the magnification side refers to the side on the optical path that is close to the imaging surface (such as a screen), and the reduction side refers to the side on the optical path that is close to the shutter.

A lens having a convex portion (or concave portion) located in a certain region means that the region is more "convex outward" (or "concave inward") in a direction parallel to the optical axis than the outer region radially adjacent to the region.

FIG1 is a schematic diagram of the optical structure of the fixed-focus projection lens of the first embodiment of the present invention. Referring to FIG1, in this embodiment, along the optical axis 12 of the fixed-focus projection lens 10a, the first lens group G1, the aperture (minimum light aperture) 14, and the second lens group G2 are arranged in sequence from the magnifying side IS to the shrinking side OS, wherein the shrinking side OS is the light input side of the projection lens 10a corresponding to the light valve 22, and the magnifying side IS is the light output side of the projection lens 10a corresponding to the screen. Furthermore, the flat plate 16, the prism 18, the cover plate 20, and the light valve 22 are arranged in sequence from the magnifying side IS to the shrinking side OS. The flat plate 16 can be, for example, a transmissive smooth picture (TSP) but is not limited thereto. The transmissive smooth picture can be vibrated to make the pixels of the projected image slightly blurred to improve the resolution. Referring to FIG. 1 again, in this embodiment, the first lens group G1 includes a lens L1 and a lens L2 arranged in sequence from the magnifying side IS to the retracting side OS, and the second lens group G2 includes a lens L3, a lens L4, a lens L5, and a lens L6 arranged in sequence from the magnifying side IS to the retracting side OS, and the first lens group G1 and the second lens group G2 are separated by an aperture 14. In this embodiment, the aperture (minimum clear aperture) 14 is disposed between lens L2 and lens L3, the refractive power of the first lens group G1 is negative, and the refractive power of the second lens group G2 is positive, and the refractive powers of lenses L1-L6 are negative, positive, positive, negative, positive, and positive, respectively. In this embodiment, lens L4 and lens L5 can form a combination lens such as a glued lens, that is, the adjacent two surfaces of lens L4 and lens L5 have substantially the same (the difference in curvature radius is less than 0.005 mm) or completely the same curvature radius, lenses L1 and L2 are plastic aspherical lenses, the material of the plastic lens can be PMMA or PC, but not limited, and lenses L3, L4, L5 and L6 are glass spherical lenses. Furthermore, the number of lenses in the projection lens 10a, the shape of the lenses and the optical characteristics can be designed differently according to actual needs. The enlarged side IS of each specific embodiment of the present invention is respectively arranged on the left side of each figure, and the reduced side OS is arranged on the right side of each figure, which will not be repeatedly described.

The aperture 14 referred to in the present invention refers to an aperture stop. The aperture 14 may be, for example, an independent component or may be integrated into other optical components. In the present embodiment, the aperture 14 achieves a similar effect by utilizing a mechanism to block peripheral light and retain light transmittance in the middle portion, and the aforementioned mechanism may be adjustable. The so-called adjustable refers to the adjustment of the position, shape or transparency of the mechanism. Alternatively, the aperture 14 may also be coated with an opaque light-absorbing material on the lens surface, and retain light transmittance in the central portion to achieve the effect of limiting the light path. When the aperture 14 has a larger aperture, the fixed-focus projection lens may correspond to a smaller aperture value (F-number). In each specific embodiment of the present invention, the aperture number (f-number) of the fixed-focus projection lens may be 1.6-1.7. In this embodiment, the F-number of the fixed-focus projection lens 10a is 1.7.

The lens design parameters and appearance of the fixed-focus projection lens 10a are shown in Table 1. However, the data listed below are not intended to limit the present invention. Any person with ordinary knowledge in the relevant field can make appropriate changes to the parameters or settings after referring to the present invention, but they should still fall within the scope of the present invention.

Table 1 element surface Curvature radius (mm) Distance(mm) Refractive index(mm) Abbe number (Vd) Lens L1 (aspherical) S1 -6.02 1.62 1.537 56 S2 47.87 8.87 Lens L2 (aspherical) S3 -5.47 2.05 1.537 56 S4 -6.00 -0.5 Aperture 14 S5 inf 2.84 Lens L3 (crescent) S6 -41.4 1.35 1.946 17.9 S7 -10.5 3.21 Lens L4 (double concave) S8 -40.9 0.59 2 19.3 Lens L5 (double convex) S9 9.56 2.44 1.497 81.6 S10 -9.52 0.14 Lens L6 (double convex) S11 9.99 2.41 1.497 81.6 S12 -15.6 1 Flat piece 16 S13 inf 1.5 1.523 58.5 S14 inf 0.7 Prism 18 S15 inf 9 1.713 53.8 S16 inf 0.5 Cover plate 20 S17 inf 0.7 1.51 62.9 S18 inf 0.3 Light valve 22 S19 inf

In Table 1, the radius of curvature (mm) refers to the radius of curvature of the corresponding surface, and the spacing (mm) refers to the straight line distance between two adjacent surfaces on the optical axis 12. For example, the spacing of surface S1, that is, the distance between surface S1 and surface S2, the thickness, refractive index and Abbe number corresponding to each lens and each optical element in the column, please refer to the corresponding values of each spacing, refractive index and Abbe number in the same column. Surfaces S1 and S2 are the two surfaces of lens L1. Surfaces S3 and S4 are the two surfaces of lens L2. For the parameter values of the radius of curvature, spacing, etc. of each surface, please refer to Table 1, and no repetition will be given here.

In various specific embodiments of the present invention, the fixed-focus projection lens can meet the condition of -9＜EFLf/EFL＜-1.5, preferably meet the condition of -7.7＜FLf/EFL＜-2.2, and more preferably meet the condition of -6.35＜EFLf/EFL＜-2.87, wherein EFLf is the effective focal length of the first lens group G1, and EFL is the effective focal length of the fixed-focus projection lens. When the EFLf/EFL value is limited within the above range, a better correction effect of spherical aberration, coma and astigmatism can be provided. Furthermore, in one embodiment, the effective focal length EFLf of the first lens group G1 can be between -9.9 mm and -26.5 mm.

In various specific embodiments of the present invention, the fixed-focus projection lens can meet the condition of 5<EFL2/EFL<90, preferably meet the condition of 7<EFL2/EFL<85, and more preferably meet the condition of 11<EFL2/EFL<75, where EFL2 is the effective focal length of the second lens (e.g., lens L2 in FIG. 1 ) from the magnification side IS to the reduction side OS, and EFL is the effective focal length of the fixed-focus projection lens. The EFL2/EFL value is limited within the above range to avoid the problem of poor imaging resolution caused by excessive focus drift after the projection system is heated up or cooled down.

In various specific embodiments of the present invention, the fixed-focus projection lens can satisfy the condition of 0.08＜IMH/OAL＜0.3, preferably satisfy the condition of 0.08＜IMH/OAL＜0.23, and more preferably satisfy the condition of 0.08＜IMH/OAL＜0.16, wherein IMH is the image height of the fixed-focus projection lens at the effective focal length, and OAL is the total length of the lens, that is, the distance between the two outermost lens surfaces on both sides of the fixed-focus projection lens (for example, the lens surfaces S1 and S12 in FIG. 1 ) on the optical axis of the fixed-focus projection lens. When the IMH/OAL value is limited to the above range, it can provide the optimal design value of the total length and image height of the lens. If it exceeds the lower limit of the above condition, the total length of the lens is too large, which is not conducive to miniaturization, or the image height is too small, which makes the lens difficult to manufacture and assemble; if it exceeds the upper limit of the above condition, the total length of the lens is too small, the system will be too sensitive and not conducive to tolerance design, or the image height is too large and not conducive to miniaturization. In addition, in one embodiment, the total length OAL of the lens can be between 25mm and 30mm.

In this embodiment, the maximum semi-FOV of the fixed-focus projection lens 10a is 32.4 degrees, the effective focal length EFL of the fixed-focus projection lens 10a is 4.14 mm, the maximum image height IMH of the fixed-focus projection lens 10a is 2.67 mm, the total lens length OAL is 25.02 mm, the effective focal length EFLf of the first lens group G1 is -11.95 mm, the effective focal length EFL2 of the second lens L2 is 319.79 mm, EFLf/EFL=-2.886, EFL2/EFL=77.244, and IMH/OAL=0.107.

A spherical lens is a lens whose front and rear surfaces are both parts of a spherical surface, and the curvature of the spherical surface is fixed. An aspherical lens is a lens whose front and rear surfaces have a radius of curvature that varies with the central axis, and can be used to correct aberrations. In the following design examples of the present invention, the aspherical polynomial can be expressed by the following formula: In the above formula, Z is the offset (sag) in the direction of the optical axis 12, c is the reciprocal of the radius of the osculating sphere, that is, the reciprocal of the radius of curvature close to the optical axis 12, k is the cone coefficient (conic), and r is the aspheric height, that is, the height from the center of the lens to the edge of the lens. The AF in Table 2 represents the coefficient values of the 4th, 6th, 8th, 10th, 12th, and 14th order of the aspheric polynomial. However, the data listed below are not intended to limit the present invention. Any person with ordinary knowledge in the relevant field can make appropriate changes to its parameters or settings after referring to the present invention, but it should still fall within the scope of the present invention.

Table 2 surface K A B C D E S1 -15.92 4.8E-03 -2.689E-04 1.068E-05 -2.45E-07 2.398E-09 S2 53.96 1.261E-02 -8.009E-04 5.396E-05 -1.964E-06 3.642E-08 S3 -3.99 -3.262E-03 9.032E-05 3.355E-06 -1.134E-06 5.193E-08 S4 0.7 7.294E-04 3.884E-05 -5.525E-07 7.971E-08 0

In each specific embodiment of the present invention, the total number of lenses with diopter is 6-9, but the number of lenses, the shape of the lenses and the optical characteristics can be designed differently according to actual needs without limitation. For example, in one embodiment, two adjacent single lenses with substantially the same radius of curvature can be stacked together by a mechanism to replace a thicker lens, and the two single lenses can have a high Abbe number and a low Abbe number respectively to provide a chromatic aberration correction effect, so that the resolution of the lens is better. Furthermore, in a specific embodiment of the present invention, the glass lens of the fixed-focus projection lens closest to the magnification side IS (e.g., lens L3 in FIG. 1 ) has a refractive index greater than 1.7, and all lenses with refractive power of the second lens group G2 (e.g., lenses L3, L4, L5, and L6 in FIG. 1 ) are glass spherical lenses. Furthermore, the fixed-focus projection lens may have only one glued surface, or may have two doublet lenses or one triplet lens. In addition, in a specific embodiment of the present invention, the first lens group G1 may include two aspherical lenses, and one of the two aspherical lenses has a positive refractive power, or both of the aspherical lenses have a negative refractive power.

Fig. 10 is a distortion aberration curve diagram of the fixed-focus projection lens 10a of this embodiment. The graphs shown in the optical simulation data diagram of Fig. 10 are all within the standard range, which verifies that the fixed-focus projection lens 10a of this embodiment can indeed provide good optical imaging quality.

FIG2 is an optical structure diagram of a fixed-focus projection lens 10b of the second embodiment of the present invention. In this embodiment, the first lens group G1 includes lens L1 and lens L2 arranged in sequence from the magnifying side IS to the shrinking side OS, and the second lens group G2 includes lens L3, lens L4, lens L5, and lens L6. In this embodiment, the aperture 14 is disposed between lens L2 and lens L3. In this embodiment, the refractive power of the first lens group G1 is negative, the refractive power of the second lens group G2 is positive, and the refractive powers of lenses L1-L6 are negative, positive, positive, negative, positive, and positive, respectively. Lens L4 and lens L5 can form a composite lens, lenses L1 and L2 are plastic aspherical lenses, and lenses L3, L4, L5 and L6 are glass spherical lenses. In this embodiment, the aperture value (F-number) of the fixed-focus projection lens 10b is 1.7, the maximum half-field angle is 32.8 degrees, the effective focal length EFL of the fixed-focus projection lens 10b is 4.19 mm, the maximum image height IMH of the fixed-focus projection lens is 2.67 mm, the total lens length OAL is 26.45 mm, the effective focal length EFLf of the first lens group G1 is -9.98 mm, the effective focal length EFL2 of the second lens L2 is 328.86 mm, EFLf/EFL= -2.382, EFL2/EFL=78.487, and IMH/OAL=0.101. The design parameters of the lens and its peripheral components of the fixed-focus projection lens 10b are shown in Table 3, and the cone coefficient and aspheric coefficient of each aspheric surface are shown in Table 4.

Table 3 element surface Radius of curvature (mm) Distance(mm) Refractive index(mm) Abbe number (Vd) Lens L1 (aspherical) S1 -5.48 1.79 1.537 56 S2 48.16 2.34 Lens L2 (aspherical) S3 -9.87 1.74 1.537 56 S4 -9.93 7.37 Aperture 14 S5 inf 2.74 Lens L3 (crescent) S6 -157.13 1.29 1.946 17.9 S7 -14.7 3.66 Lens L4 (Crescent) S8 42.68 0.59 2 19.3 Lens L5 (double convex) S9 8.05 2.44 1.497 81.6 S10 -13.8 0.15 Lens L6 (double convex) S11 8.96 2.34 1.497 81.6 S12 -22.3 1 Flat piece 16 S13 inf 1.5 1.523 58.5 S14 inf 0.7 Prism 18 S15 inf 9 1.713 53.8 S16 inf 0.5 Cover plate 20 S17 inf 0.7 1.51 62.9 S18 inf 0.3 Light valve 22 S19 inf

Table 4 surface K A B C D S1 -10.91 5.535E-03 -4.183E-04 2.456E-05 -9.184E-07 S2 -26.02 1.262E-02 -9.103E-04 4.769E-05 7.347E-07 S3 1.41 -1.739E-03 -2.153E-04 2.866E-05 -1.675E-06 S4 1.42 -1.233E-03 -1.264E-05 9.007E-06 -5.723E-07 surface E F S1 1.955E-08 -1.76E-10 S2 -2.246E-07 9.25E-09 S3 4.493E-08 0 S4 1.641E-08 0

Fig. 11 is a distortion aberration curve diagram of the fixed-focus projection lens 10b of this embodiment. The graphs shown in the optical simulation data diagram of Fig. 11 are all within the standard range, which verifies that the fixed-focus projection lens 10b of this embodiment can indeed provide good optical imaging quality.

FIG3 is an optical structure diagram of a fixed-focus projection lens 10c of the third embodiment of the present invention. In this embodiment, the first lens group G1 includes lens L1 and lens L2 arranged in sequence from the magnifying side IS to the shrinking side OS, and the second lens group G2 includes lens L3, lens L4, lens L5, lens L6, and lens L7. In this embodiment, the aperture 14 is disposed between lens L2 and lens L3. In this embodiment, the refractive power of the first lens group G1 is negative, the refractive power of the second lens group G2 is positive, and the refractive powers of lenses L1-L7 are negative, positive, positive, negative, positive, positive, positive, respectively. Lens L4 and lens L5 can form a composite lens, lenses L1 and L2 are plastic aspherical lenses, and lenses L3, L4, L5, L6 and L7 are glass spherical lenses. In this embodiment, the aperture value (F-number) of the fixed-focus projection lens 10c is 1.7, the maximum half-field angle is 32.5 degrees, the effective focal length EFL of the fixed-focus projection lens 10c is 4.2 mm, the maximum image height IMH of the fixed-focus projection lens 10c is 2.67 mm, the total lens length OAL is 29.02 mm, the effective focal length EFLf of the first lens group G1 is -10.99 mm, the effective focal length EFL2 of the second lens L2 is 70.95 mm, EFLf/EFL= -2.617, EFL2/EFL=16.893, and IMH/OAL=0.092. The design parameters of the lens and its peripheral components of the fixed-focus projection lens 10c are shown in Table 5, and the cone coefficient and aspheric coefficient of each aspheric surface are shown in Table 6.

Table 5 element surface Curvature radius (mm) Distance(mm) Refractive index(mm) Abbe number (Vd) Lens L1 (aspherical) S1 -12.5 0.9 1.537 56 S2 7.28 2.62 Lens L2 (aspherical) S3 -26.9 3.8 1.537 56 S4 -16.6 8.01 Aperture 14 S5 inf 2.24 Lens L3 (double convex) S6 54.72 1.62 1.946 18 S7 -14.5 2.71 Lens L4 (double concave) S8 -18.7 0.59 2 19.3 Lens L5 (double convex) S9 9.39 2.25 1.497 81.6 S10 -12.9 0.14 Lens L6 (double convex) S11 49.9 1.56 1.497 81.6 S12 -22.0 0.14 Lens L7 (double convex) S13 11.57 2.44 1.593 68.6 S14 -24.7 1.1 Flat piece 16 S15 inf 1.5 1.509 56.2 S16 inf 0.7 Prism 18 S17 inf 9 1.713 53.9 S18 inf 0.5 Cover plate 20 S19 inf 0.7 1.51 62.9 S20 inf 0.3 Light valve 22 S21

Table 6 surface K A B C D E S1 0.84 4.709E-03 -1.999E-04 6.95E-06 -1.431E-07 1.696E-09 S2 2.21 7.339E-04 1.103E-04 -1.95E-05 8.358E-07 -2.008E-08 S3 -99 -4.634E-03 2.774E-04 -1.98E-05 6.369E-07 1.492E-09 S4 -10 -1.273E-03 1.199E-04 -7.935E-06 3.816E-07 -5.341E-09

FIG4 is an optical structure diagram of a fixed-focus projection lens 10d according to a fourth embodiment of the present invention. In this embodiment, the first lens group G1 includes lens L1 and lens L2 arranged in sequence from the magnifying side IS to the shrinking side OS, and the second lens group G2 includes lens L3, lens L4, lens L5, lens L6, and lens L7. In this embodiment, the aperture 14 is disposed between lens L2 and lens L3. In this embodiment, the refractive power of the first lens group G1 is negative, the refractive power of the second lens group G2 is positive, and the refractive powers of lenses L1-L7 are negative, positive, negative, positive, negative, positive, and positive, respectively. Lens L3 and lens L4 can form a laminated lens, lens L5 and lens L6 can form another laminated lens, lenses L1 and L2 are plastic aspherical lenses, and lenses L3, L4, L5, L6 and L7 are glass spherical lenses. In this embodiment, the aperture value (F-number) of the fixed-focus projection lens 10d is 1.7, the maximum half field of view angle is 32.4 degrees, the effective focal length EFL of the fixed-focus projection lens 10d is 4.16 mm, the maximum image height IMH of the fixed-focus projection lens is 2.67 mm, the total lens length OAL is 26.45 mm, the effective focal length EFLf of the first lens group G1 is -26.46 mm, the effective focal length EFL2 of the second lens L2 is 47.53 mm, EFLf/EFL=-6.361, EFL2/EFL=11.425, and IMH/OAL=0.101.

The design parameters of the lens and its peripheral components of the fixed-focus projection lens 10d are shown in Table 7, and the cone coefficient and aspheric coefficient of each aspheric surface are shown in Table 8.

Table 7 element surface Radius of curvature (mm) Distance(mm) Refractive index(mm) Abbe number (Vd) Lens L1 (aspherical) S1 -3.94 1.36 1.537 56 S2 -13.02 8.28 Lens L2 (aspherical) S3 -5.36 2.15 1.537 56 S4 -5.06 0.3 Aperture 14 S5 inf 1.46 Lens L3 (double concave) S6 -20.4 0.60 1.749 35.3 Lens L4 (biconvex) S7 8.99 3.99 1.923 20.9 S8 -12.7 1.64 Lens L5 (double concave) S9 -34.5 0.60 2 19.3 Lens L6 (double convex) S10 8.00 2.75 1.497 81.6 S11 -9.0 0.10 Lens L7 (double convex) S12 10.36 3.22 1.497 81.6 S13 -12.5 1.10 Flat piece 16 S14 inf 1.5 1.509 56.2 S15 inf 0.7 Prism 18 S16 inf 9 1.713 53.9 S17 inf 0.5 Cover plate 20 S18 inf 0.7 1.51 62.9 S19 inf 0.3 Light valve 22 S20

Table 8 surface K A B C D E S1 -8.300 6.086E-03 -3.586E-04 1.449E-05 -3.27E-07 3.078E-09 S2 -98.99 1.137E-02 -4.392E-04 6.722E-06 8.952E-07 -3.049E-08 S3 -6.02 -5.186E-03 3.512E-04 -2.963E-05 1.598E-06 -2.354E-08 S4 -0.03 5.25E-04 3.673E-05 -2.332E-06 1.971E-07 0

FIG5, FIG6, FIG7, FIG8 and FIG9 are optical structure diagrams of fixed-focus projection lenses 10e, 10f, 10g, 10h and 10i, respectively. The design parameters of the lens and its peripheral components of the fixed-focus projection lens 10e are shown in Table 9, and the cone coefficient and the aspheric coefficient of each aspheric surface are shown in Table 10. The design parameters of the lens and its peripheral components of the fixed-focus projection lens 10f are shown in Table 11, and the cone coefficient and the aspheric coefficient of each aspheric surface are shown in Table 12. The design parameters of the lens and its peripheral components of the fixed-focus projection lens 10g are shown in Table 13, and the cone coefficient and the aspheric coefficient of each aspheric surface are shown in Table 14. The design parameters of the lens and its peripheral components of the fixed-focus projection lens 10h are shown in Table 15, and the cone coefficient and the aspheric coefficient of each aspheric surface are shown in Table 16. The design parameters of the lens and its peripheral components of the fixed-focus projection lens 10i are shown in Table 17, and the cone coefficient and the aspheric coefficient of each aspheric surface are shown in Table 18.

Table 9 element surface Curvature radius (mm) Distance(mm) Refractive index(mm) Abbe number (Vd) Lens L1 (aspherical) S1 -4.71 1.02 1.537 56 S2 -12.3 2.35 Lens L2 (aspherical) S3 -7.25 0.78 1.537 56 S4 14.72 0.44 Lens L3 (crescent) S5 6.87 1.18 1.946 17.9 S6 21.69 1.83 Aperture 14 S7 inf 2.52 Lens L4 (double concave) S8 -21.1 0.6 2 25.5 Lens L5 (double convex) S9 10.14 2.39 1.497 81.6 S10 -6.67 0.1 Lens L6 (double convex) S11 50.45 1.93 1.497 81.6 S12 -10.4 0.1 Lens L7 (double convex) S13 13.86 2.23 1.603 65.4 S14 -16.4 1.1 Flat piece 16 S15 inf 1.5 1.523 58.5 S16 inf 0.7 Prism 18 S17 inf 9 1.713 53.8 S18 inf 0.5 Cover plate 20 S19 inf 0.7 1.51 62.9 S20 inf 0.30 Light valve 22 S21 inf

Table 10 surface K A B C D E S1 -13.89 1.532E-02 -1.522E-03 1.188E-04 -5.251E-06 1.022E-07 S2 -0.64 3.191E-02 -3.233E-03 3.059E-04 -1.216E-05 7.456E-08 S3 -37.12 1.360E-03 -7.620E-04 8.885E-05 -6.584E-06 0 S4 28.35 8.139E-03 -2.077E-03 2.677E-04 -1.819E-05 0

Table 11 element surface Radius of curvature (mm) Distance(mm) Refractive index(mm) Abbe number (Vd) Lens L1 (aspherical) S1 -6.52 1.09 1.537 56 S2 -55.5 6.16 Lens L2 (aspherical) S3 -5.45 0.6 1.537 56 S4 -180.6 0.29 Aperture 14 S5 inf 0.1 Lens L3 (double convex) S6 656.9 1.23 1.946 17.9 S7 -8.65 3.46 Lens L4 (double concave) S8 -37.8 0.6 1.946 17.9 Lens L5 (double convex) S9 8.03 2.65 1.497 81.6 S10 -7.30 0.1 Lens L6 (double convex) S11 12.15 2.18 1.804 46.5 S12 -17.2 1 Flat piece 16 S13 inf 1.5 1.523 58.5 S14 inf 0.7 Prism 18 S15 inf 9 1.713 53.8 S16 inf 0.5 Cover plate 20 S17 inf 0.7 1.51 62.9 S18 inf 0.30 Light valve 22 S19 inf

Table 12 surface K A B C D E S1 -19.01 9.951E-03 -7.376E-04 4.477E-05 -1.559E-06 2.292E-08 S2 98.48 1.963E-02 -1.529E-03 1.403E-04 -6.034E-06 1.211E-07 S3 -4.34 -9.124E-04 -3.905E-04 4.181E-05 -1.117E-05 1.130E-06 S4 46.86 2.169E-03 -5.413E-04 6.729E-05 -9.256E-06 6.942E-07

Table 13 element surface Curvature radius (mm) Distance(mm) Refractive index(mm) Abbe number (Vd) Lens L1 (aspherical) S1 -4.74 0.79 1.537 56 S2 -17.8 2.26 Lens L2 (aspherical) S3 -5.79 0.71 1.537 56 S4 9.95 0.36 Lens L3 (double convex) S5 7.01 2.5 1.808 22.8 S6 -11.7 0.49 Aperture 14 S7 inf 1.69 Lens L4 (double concave) S8 -7.65 0.7 2 25.5 Lens L5 (double convex) S9 6.40 1.76 1.734 51.5 S10 -20.5 0.1 Lens L6 (double convex) S11 57.74 1.89 1.497 81.6 S12 -8.35 0.1 Lens L7 (double convex) S13 21.29 2.26 1.497 81.6 S14 -10.8 0.09 Lens L8 (aspherical) S15 47.16 1.61 1.669 55 S16 -14.1 1.02 Flat piece 16 S17 inf 1.5 1.523 58.5 S18 inf 0.7 Prism 18 S19 inf 9 1.713 53.8 S20 inf 0.5 Cover plate 20 S21 inf 0.7 1.51 62.9 S22 inf 0.30 Light valve 22 S23 inf

Table 14 surface K A B C D E S1 -14.42 2.007E-02 -2.686E-03 2.677E-04 -1.482E-05 3.613E-07 S2 0 3.752E-02 -4.934E-03 4.974E-04 -1.952E-05 0 S3 0 5.154E-03 -3.379E-03 8.699E-04 -1.162E-04 5.962E-06 S4 0 4.101E-03 -2.234E-03 6.561E-04 -9.050E-05 4.897E-06 S15 0 -7.149E-05 -6.355E-06 7.705E-07 -1.854E-08 0 S16 0 2.813E-04 -7.602E-06 7.812E-07 -1.893E-08 0

Table 15 element surface Radius of curvature (mm) Distance(mm) Refractive index(mm) Abbe number (Vd) Lens L1 (aspherical) S1 -4.4 0.7 1.537 56 S2 -40.08 1.38 Lens L2 (aspherical) S3 -12.3 0.7 1.537 56 S4 7.77 0.23 Lens L3 (crescent) S5 4.70 1.81 1.873 19.9 S6 87.1 1.21 Aperture 14 S7 inf 0.34 Lens L4 (double concave) S8 -7.59 0.7 1.949 21.6 Lens L5 (double convex) S9 6.27 2.37 1.496 81.6 S10 -5.74 0.1 Lens L6 (Crescent) S11 -14.0 1.73 1.496 81.6 S12 -7.81 0.2 Lens L7 (Crescent) S13 -16.2 1.89 1.496 81.6 S14 -8.37 0.09 Lens L8 (double convex) S15 52.97 1.84 1.697 56.5 S16 -24.5 0.1 Lens L9 (double convex) S17 49.12 2.03 1.729 54.7 S18 -18.5 1.01 Flat piece 16 S19 inf 1.5 1.523 58.6 S20 inf 0.7 Prism 18 S21 inf 9 1.713 53.8 S22 inf 0.5 Cover plate 20 S23 inf 0.7 1.510 62.9 S24 inf 0.30 Light valve 22 S25 inf 0

Table 16 surface K A B C D E S1 -17.28 2.301E-02 -3.483E-03 4.153E-04 -2.779E-05 9.131E-07 S2 0 4.354E-02 -7.317E-03 8.259E-04 -2.873E-05 0 S3 0 -8.334E-03 -4.903E-04 6.509E-04 -1.280E-04 7.976E-06 S4 0 -4.548E-03 9.332E-04 3.538E-04 -9.563E-05 7.430E-06

Table 17 element surface Curvature radius (mm) Distance(mm) Refractive index(mm) Abbe number (Vd) Lens L1 (aspherical) S1 -8.3 0.9 1.537 56 S2 9.34 1.43 Lens L2 (aspherical) S3 5.12 1.30 1.537 56 S4 5.25 0.46 Lens L3 (biconvex) S5 8.63 1.60 1.785 25.7 S6 -187.5 4.33 Aperture 14 S7 inf 1.79 Lens L4 (double concave) S8 -6.0 0.8 2 29.1 Lens L5 (double convex) S9 21.8 2.18 1.497 81.6 S10 -6.9 0.09 Lens L6 (plano-convex) S11 infinity 2.81 1.497 81.6 S12 -7.4 0.09 Lens L7 (double convex) S13 67.9 1.59 1.729 54.7 S14 -30.8 0.09 Lens L8 (Crescent) S15 14.5 1.87 1.729 54.7 S16 91.4 1.26 Flat piece 16 S17 inf 1.5 1.523 58.6 S18 inf 0.7 Prism 18 S19 inf 10.6 1.713 54 S20 inf 0.7 Cover plate 20 S21 inf 1.1 1.51. 62 S22 inf 0.30 Light valve 22 S23 inf

Table 18 surface K A B C D S1 -20.78 2.740E-03 -9.224E-05 2.164E-06 -2.542E-09 S2 -0.01 7.743E-04 8.044E-05 -5.189E-06 -8.556E-08 S3 0 -1.102E-02 3.315E-04 -2.992E-07 -3.488E-07 S4 0 -7.266E-03 1.995E-04 1.073E-05 -1.070E-06 surface E F S1 -7.304E-10 1.065E-11 S2 2.318E-08 -5.771E-10 S3 5.611E-09 0 S4 2.447E-08 0

According to the designs of the various embodiments of the present invention, by appropriately arranging glass and plastic lenses with spherical and aspherical surfaces, the projection lens can have a smaller lens volume and fewer lens pieces, while being able to provide a low distortion, high-resolution projection image, and the projection lens can have a lower heat transfer amount, while being able to withstand the higher temperature and temperature changes of the use environment, thereby reducing the manufacturing cost and taking into account the image quality.

Although the present invention has been disclosed as above by the embodiments, they are not intended to limit the present invention. Any person with ordinary knowledge in the relevant technical field can make some changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention shall be defined by the scope of the attached patent application.

10a-10i: Fixed focus projection lens 12: Optical axis 14: Aperture 16: Flat plate 18: Prism 20: Cover plate 22: Shutter G1: First lens group G2: Second lens group L1-L9: Lens S1-S25: Surface IS: Magnification side OS: Reduction side

FIG. 1 is a schematic diagram of the optical structure of a fixed-focus projection lens of an embodiment of the present invention. FIG. 2 is a schematic diagram of the optical structure of a fixed-focus projection lens of another embodiment of the present invention. FIG. 3 is a schematic diagram of the optical structure of a fixed-focus projection lens of another embodiment of the present invention. FIG. 4 is a schematic diagram of the optical structure of a fixed-focus projection lens of another embodiment of the present invention. FIG. 5 is a schematic diagram of the optical structure of a fixed-focus projection lens of another embodiment of the present invention. FIG. 6 is a schematic diagram of the optical structure of a fixed-focus projection lens of another embodiment of the present invention. FIG. 7 is a schematic diagram of the optical structure of a fixed-focus projection lens of another embodiment of the present invention. FIG. 8 is a schematic diagram of the optical structure of a fixed-focus projection lens of another embodiment of the present invention. FIG. 9 is a schematic diagram of the optical structure of a fixed-focus projection lens of another embodiment of the present invention. FIG10 is a distortion aberration curve diagram of the fixed-focus projection lens of FIG1. FIG11 is a distortion aberration curve diagram of the fixed-focus projection lens of FIG2.

10a: Fixed focus projection lens

12: Light axis

14: Aperture

16: Flat pieces

18: Prism

20: Cover plate

22: Light valve

G1: First lens group

G2: Second lens group

L1-L6: Lens

S1-S19: Surface

IS: Enlarged side

OS: Zoom out

Claims (10)

A fixed-focus projection lens comprises: A first lens group, an aperture and a second lens group arranged in sequence from a magnification side to a reduction side; The first lens group comprises two aspheric lenses, and one of the two aspheric lenses has positive refractive power; and The second lens group has positive refractive power; The fixed-focus projection lens comprises 6-9 lenses with refractive power and meets the following conditions: (1) -9＜EFLf/EFL＜-1.5, where EFLf is the effective focal length of the first lens group and EFL is the effective focal length of the fixed-focus projection lens; and (2) 0.08＜IMH/OAL＜0.3, where IMH is the image height of the fixed-focus projection lens at the effective focal length, and OAL is the distance between the two outermost lens surfaces on both sides of the fixed-focus projection lens on the optical axis of the fixed-focus projection lens. A fixed-focus projection lens comprises: A first lens group, an aperture and a second lens group arranged in sequence from a magnification side to a reduction side; The first lens group comprises two aspheric lenses, and one of the two aspheric lenses has a positive refractive power; and The second lens group has a positive refractive power; The first lens of the fixed-focus projection lens from the magnification side to the reduction side is a negative refractive power lens, and the second lens is a positive refractive power lens. The fixed-focus projection lens includes 6-9 lenses with refractive power, and EFLf is the effective focal length of the first lens group, EFL is the effective focal length of the fixed-focus projection lens, and EFL2 is the effective focal length of the second lens from the magnification side to the reduction side. The fixed-focus projection lens meets the following conditions: (1) -9＜EFLf/EFL＜-1.5; and (2) 5＜EFL2/EFL＜90. The fixed-focus projection lens as described in claim 2 further satisfies the condition of 0.08＜IMH/OAL＜0.3, wherein IMH is the image height of the fixed-focus projection lens at the effective focal length, and OAL is the distance between the two outermost lens surfaces on both sides of the fixed-focus projection lens on the optical axis of the fixed-focus projection lens. A fixed-focus projection lens as described in claim 1 or 2, wherein the fixed-focus projection lens satisfies one of the following conditions: (1) the second lens group includes a laminated lens, which is composed of a negative lens close to the magnification side and a positive lens close to the reduction side, and the refractive index of the negative lens is greater than 1.7; (2) the refractive index of a glass lens of the fixed-focus projection lens closest to the magnification side is greater than 1.7. A fixed-focus projection lens as described in claim 1 or 2, wherein all lenses with refractive power in the second lens group are glass spherical lenses. A fixed-focus projection lens as described in claim 1 or 2, wherein the fixed-focus projection lens satisfies one of the following conditions: (1) the fixed-focus projection lens has only one glued surface; (2) the second lens group has two doublet lenses or one triplet lens. A fixed-focus projection lens as claimed in claim 1 or 2, wherein the f-number of the fixed-focus projection lens is 1.6-1.7. A fixed-focus projection lens as described in claim 1 or 2, wherein the effective focal length of the first lens group is between -9.9 mm and -26.5 mm. A fixed-focus projection lens as described in claim 1 or 3, wherein the distance between the two outermost lens surfaces on both sides of the fixed-focus projection lens on the optical axis of the fixed-focus projection lens is between 25 mm and 30 mm. A fixed-focus projection lens comprises: A first lens group, an aperture and a second lens group arranged in sequence from a magnifying side to a reducing side; The first lens group comprises two aspherical lenses; and The second lens group has a positive refractive power; The first lens of the fixed-focus projection lens from the magnification side to the reduction side is a negative diopter lens, the fixed-focus projection lens comprises 6-9 lenses with diopter, and EFLf is the effective focal length of the first lens group, EFL is the effective focal length of the fixed-focus projection lens, EFL2 is the effective focal length of the second lens from the magnification side to the reduction side, IMH is the image height of the fixed-focus projection lens at the effective focal length, OAL is the distance between the two outermost lens surfaces on both sides of the fixed-focus projection lens on the optical axis of the fixed-focus projection lens, and the fixed-focus projection lens meets the following conditions: (1) -9＜EFLf/EFL＜-1.5; (2) 5＜EFL2/EFL＜90; and (3)0.08＜IMH/OAL＜0.3.

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