TWI674436B - Projection lens - Google Patents

Abstract

A projection lens includes a first lens group, a second lens group, a third lens group, and a fourth lens group in order from a projection side to an image source side along an optical axis. The first lens group has a negative refractive power. The second lens group has a positive refractive power. The fourth lens group has a positive refractive power.

Description

Projection lens (11)

The invention relates to a projection lens.

The current development trend of projection lenses, in addition to the continuous development of miniaturization, with different application requirements, it is also necessary to simultaneously have high resolution capabilities, a large aperture to increase the number of output lumens of the projector, and resistance to environmental temperature changes. The known projection lens is no longer able to meet today's needs, and another new type of projection lens is needed to meet the needs of miniaturization, high resolution capability, large aperture, and resistance to environmental temperature changes.

In view of this, the main object of the present invention is to provide a projection lens, which has a small lens size, a large resolution, a small aperture value, and resistance to changes in ambient temperature, but still has good optical performance.

The projection lens of the present invention includes a first lens group, a second lens group, a third lens group, and a fourth lens group in order from a projection side to an image source side along an optical axis. The first lens group has a negative refractive power. The second lens group has a positive refractive power. The fourth lens group has a positive refractive power.

The first lens group includes a first lens, the first lens has a negative refractive power, the second lens group includes a second lens, the second lens has a positive refractive power, the image source side and the projection side of the second lens All are convex, the third lens group is from the projection side to the image along the optical axis The source side includes a third lens and a fourth lens in order. The third lens has a negative refractive power, the fourth lens has a positive refractive power, the fourth lens includes a convex surface, the convex surface faces the projection side, and a fourth lens group. The fifth lens includes a fifth lens including a convex surface facing the image source side. The fifth lens has a positive refractive power.

The projection lens meets the following conditions: 0.6 R ₁₂ / f 1.5; where R ₁₂ is the radius of curvature of the side of the image source of the first lens, and f is the effective focal length of the projection lens.

The projection lens meets the following conditions: 1.4 <F-number <3.5; where F-number is the aperture value of the projection lens.

The first lens is an aspheric lens and satisfies the following conditions: Vd ₁ >40; wherein Vd ₁ is the Abbe coefficient of the first lens.

The fifth lens is an aspheric lens.

The second lens, the third lens, and the fourth lens are spherical lenses and satisfy the following conditions: Nd ₂ > 1.6, Nd ₃ > 1.6, Nd ₄ > 1.6, and Vd ₃ <35; where Nd ₂ is the second lens. Refractive index, Nd ₃ is the refractive index of the third lens, Nd ₄ is the refractive index of the fourth lens, and Vd ₃ is the Abbe coefficient of the third lens.

The third lens and the fourth lens are cemented into a cemented lens.

The projection lens of the present invention may further include an aperture disposed between the second lens group and the third lens group.

The first lens group includes a first lens, the first lens has a negative refractive power, the second lens group includes a second lens, the second lens has a positive refractive power, the third lens group has a negative refractive power, and the third lens group Along the optical axis from the projection side to the image source side, a first Three lenses and a fourth lens. The fourth lens group includes a fifth lens. The fifth lens has a positive refractive power. The first lens group, the second lens group, the third lens group, and the fourth lens group are on the optical axis. The group pitch can be changed to adjust the effective focal length of the projection lens.

The projection lens satisfies the following conditions: f _T / f _W >1; where f _T is the effective focal length of the projection lens at the telephoto end, and f _W is the effective focal length of the projection lens at the wide-angle end.

The projection lens meets the following conditions: 1.4 <F-number <3.5; where F-number is the aperture value of the projection lens.

The first lens is an aspheric lens and satisfies the following conditions: Vd ₁ >40; wherein Vd ₁ is the Abbe coefficient of the first lens.

The fifth lens is an aspheric lens.

The second lens, the third lens, and the fourth lens are spherical lenses and satisfy the following conditions: Nd ₂ > 1.6, Nd ₃ > 1.6, Nd ₄ > 1.6, and Vd ₃ <35; where Nd ₂ is the second lens. Refractive index, Nd ₃ is the refractive index of the third lens, Nd ₄ is the refractive index of the fourth lens, and Vd ₃ is the Abbe coefficient of the third lens.

In order to make the above-mentioned objects, features, and advantages of the present invention more comprehensible, preferred embodiments are described in detail below in conjunction with the accompanying drawings.

1, 2, 3‧‧‧ projection lenses

LG ₁₁ 、 LG ₂₁ 、 LG ₃₁ ‧‧‧The first lens group

LG ₁₂ , LG ₂₂ , LG ₃₂ ‧‧‧Second lens group

LG ₁₃ , LG ₂₃ , LG ₃₃ ‧‧‧ third lens group

LG ₁₄ , LG ₂₄ , LG ₃₄ ‧‧‧ fourth lens group

L11, L21, L31‧‧‧First lens

L12, L22, L32‧‧‧Second lens

L13, L23, L33‧‧‧ Third lens

L14, L24, L34‧‧‧ Fourth lens

L15, L25, L35‧‧‧ fifth lens

ST1, ST2, ST3 ‧‧‧ aperture

P1, P2, P3 ‧‧‧ 稜鏡

OA1, OA2, OA3 ‧‧‧ Optical axis

IS1, IS2, IS3 ‧‧‧ image sources

CG2‧‧‧Protection glass

S11, S12, S13, S14, S15, S16, S17‧‧‧ faces

S18, S19, S110, S111, S112, S113‧‧‧ faces

S21, S22, S23, S24, S25, S26, S27

S28, S29, S210, S211, S212, S213‧‧‧ faces

S214‧‧‧face

S31, S32, S33, S34, S35, S36, S37‧‧‧ faces

S38, S39, S310, S311, S312, S313‧‧‧ faces

FIG. 1 is a schematic diagram of a lens configuration and an optical path of a first embodiment of a projection lens according to the present invention.

FIG. 2A is a field curvature diagram of the projection lens of FIG. 1.

Figure 2B is the distortion diagram of the projection lens of Figure 1.

FIG. 2C is a modulation conversion function diagram of the projection lens of FIG. 1.

Figure 2D is a graph of the defocus modulation transfer function of the projection lens of Figure 1.

Figure 2E is a light spot diagram of the projection lens of Figure 1.

Figure 2F is a light spot diagram of the projection lens of Figure 1.

Figure 2G is a light spot diagram of the projection lens of Figure 1.

FIG. 3 is a schematic diagram of a lens configuration and an optical path of a second embodiment of a projection lens according to the present invention.

FIG. 4A is a field curvature diagram of the projection lens of FIG. 3.

FIG. 4B is a distortion diagram of the projection lens of FIG. 3.

FIG. 4C is a modulation transfer function diagram of the projection lens of FIG. 3.

Figure 4D is a defocus modulation transfer function diagram of the projection lens of Figure 3.

Figure 4E is a light spot diagram of the projection lens of Figure 3.

Figure 4F is a light spot diagram of the projection lens of Figure 3.

Figure 4G is the light spot diagram of the projection lens in Figure 3.

FIG. 5 is a schematic diagram of a lens configuration and an optical path of a third embodiment of a projection lens according to the present invention.

FIG. 6A is a field curvature diagram when the projection lens of FIG. 5 is at the wide-angle end.

Figure 6B is the distortion diagram when the projection lens of Figure 5 is at the wide-angle end.

FIG. 6C is a modulation transfer function diagram when the projection lens of FIG. 5 is at the wide-angle end.

Fig. 6D is a field curvature diagram when the projection lens of Fig. 5 is at the telephoto end.

Figure 6E is the distortion diagram when the projection lens in Figure 5 is at the telephoto end.

FIG. 6F is a modulation transfer function diagram when the projection lens of FIG. 5 is at the telephoto end.

Please refer to FIG. 1. FIG. 1 is a schematic diagram of a lens configuration and an optical path of a first embodiment of a projection lens according to the present invention. The projection lens 1 includes a first lens group LG ₁₁ , a second lens group LG ₁₂ , an aperture ST1, a third lens group LG ₁₃ , and a lens lens 1 in order from a projection side to an image source side along an optical axis OA1. The fourth lens group LG ₁₄ and a pair of P1. During projection, the light from an image source IS1 is finally projected on the projection side. The first lens group LG ₁₁ has a negative refractive power. The first lens group LG ₁₁ includes a first lens L11. The first lens L11 is a convex-concave lens. The first lens group L11 has a negative refractive power and is made of glass. S12 is a concave surface, and both the object side surface S11 and the image side surface S12 are aspherical surfaces. The second lens group LG ₁₂ has a positive refractive power. The second lens group LG ₁₂ includes a second lens L12. The second lens L12 is a biconvex lens. It has a positive refractive power and is made of glass. Its object side S13 is convex and image-like. S14 is a convex surface, and both the object side surface S13 and the image side surface S14 are spherical surfaces. The third lens group LG ₁₃ includes a third lens L13 and a fourth lens L14. The third lens L13 is a biconcave lens and has a negative refractive power. The third lens L13 is made of glass. The object side S16 is concave, and the image side S17 is concave. The side surface S16 and the image side S17 are spherical surfaces. The fourth lens L14 is a biconvex lens with positive refractive power and is made of glass. The object side S18 is convex, the image side S19 is convex, and the object side S18 and the image side S19 are both Spherical surface. The fourth lens group LG ₁₄ has a positive refractive power. The fourth lens group LG ₁₄ includes a fifth lens L15. The fifth lens L15 is a biconvex lens. It has a positive refractive power and is made of glass. Its object side S110 is convex and image-like. S111 is convex, and both the object side S110 and the image side S111 are aspherical surfaces.稜鏡 P1 has both the object side S112 and the image side S113.

In addition, in order for the projection lens of the present invention to maintain good optical performance, the projection lens 1 in the first embodiment must satisfy the following seven conditions: 0.6 <R1 ₁₂ /f1<1.5 (1)

1.4 <F-number1 <3.5 (2)

Vd1 ₁ > 40 (3)

Nd1 ₂ > 1.6 (4)

Nd1 ₃ > 1.6 (5)

Nd1 ₄ > 1.6 (6)

Vd1 ₃ <35 (7)

Among them, R1 ₁₂ is the curvature radius of the image side S12 of the first lens L11, f1 is the effective focal length of the projection lens 1, F-number1 is the aperture value of the projection lens 1, Vd1 ₁ is the Abbe coefficient of the first lens L11, and Nd1 ₂ is the refractive index of the second lens L12, Nd1 ₃ is the refractive index of the third lens L13, Nd1 ₄ is the refractive index of the fourth lens L14, and Vd1 ₃ is the Abbe coefficient of the third lens L13.

Utilizing the design of the above lens and aperture ST1, the projection lens 1 can effectively reduce the volume, reduce the aperture value, effectively correct aberrations, improve the resolution of the lens, and reduce the impact of temperature changes on imaging quality.

Table 1 is a related parameter table of each lens of the projection lens 1 in the first figure. The data in Table 1 shows that the effective focal length of the projection lens 1 of the first embodiment is equal to 16.8 mm and the aperture value is 1.5.

The aspheric surface depression z of each lens in Table 1 is obtained by the following formula: z = ch ² / {1+ [1- (k + 1) c ² h ² ] ^1/2 } + Ah ⁴ + Bh ⁶ + Ch ⁸ + Dh ¹⁰ + Eh ¹² + Fh ¹⁴ + Gh ¹⁶

Where: c: curvature; h: vertical distance from any point on the lens surface to the optical axis; k: conic coefficient; A ~ G: aspheric coefficient.

Table 2 is the related parameter table of the aspheric surface of each lens in Table 1, where k Is the conic constant, and A ~ G are aspherical coefficients.

In the projection lens 1 of the first embodiment, the curvature radius R1 ₁₂ of the image side S12 of the first lens L11 is 12.66 mm, the effective focal length f1 of the projection lens 1 is 16.8 mm, and the aperture value of the projection lens 1 is F-number1 = 1.5. The Abbe coefficient Vd1 _{1 of the} first lens L11 = 70, the refractive index Nd1 _{2 of the} second lens L12 = 1.8, the refractive index Nd1 _{3 of the} third lens L13 = 1.77, the refractive index Nd1 _{4 of the} fourth lens L14 = 1.67, the first the third lens L13 Abbe Vd1 ₃ = 26, the information obtained by the _{R1 12 /f1=0.75,F-number1=1.5,Vd1 1 = 70, Nd1} 2 = 1.8, Nd1 3 = 1.77, Nd1 4 = 1.67, Vd1 ₃ = 26, which can satisfy the requirements of the above conditions (1) to (7).

In addition, the optical performance of the projection lens 1 of the first embodiment can also meet the requirements. This can be seen from Figures 2A to 2G. 2A is a Field Curvature diagram of the projection lens 1 of the first embodiment. FIG. 2B shows a distortion diagram of the projection lens 1 of the first embodiment, and FIG. 2C shows a modulation transfer function diagram of the projection lens 1 of the first embodiment. Figure 2D shows the Through Focus Modulation Transfer Function diagram of the projection lens 1 of the first embodiment, and Figure 2E shows the projection lens 1 of the first embodiment. The Spot Diagram, shown in Fig. 2F, is the Spot Diagram of the projection lens 1 of the first embodiment, and the diagram shown in Fig. 2G, is the projection lens 1 of the first embodiment. Spot Diagram.

It can be seen from FIG. 2A that the projection lens 1 of the first embodiment has a pair of rays having a wavelength of 0.470 μm, 0.486 μm, 0.550 μm, 0.588 μm, 0.620 μm, and 0.656 μm in the direction of the meridian (Tangential) and the sagittal (Sagittal) The field curvature in the direction of) is between -0.07mm and 0.14mm. From Figure 2B (the 6 lines in the figure are almost superimposed so that only one line appears), it can be seen that the pair of projection lenses of the first embodiment has a wavelength of 0.470 μm, 0.486 μm, 0.550 μm, 0.588 μm, 0.620 The distortion caused by the light of μm and 0.656μm is between -0.9% and 0%. As can be seen from Figure 2C, the projection lens 1 of the first embodiment has a pair of rays with a wavelength ranging from 0.470 μm to 0.656 μm, respectively in the Tangential direction and the Sagittal direction, and the field heights are 0.0000. mm, -2.8350mm, -6.6150mm, -8.8050mm, -9.4500mm, the spatial frequency is between 0lp / mm and 37lp / mm, and its modulation conversion function value is between 0.67 and 1.0. It can be seen from the 2D diagram that the projection lens 1 of the first embodiment has a pair of rays with a wavelength range of 0.470 μm to 0.656 μm, respectively in the Tangential direction and the Sagittal direction, and the field heights are 0.0000. mm, -2.8350mm, -6.6150mm, -8.8050mm, -9.4500mm, and the spatial frequency equals 37.0000lp / mm, when the focus shift is between -0.028mm to 0.031mm The value of its modulation transfer function is greater than 0.2. Figures 2E, 2F, and 2G show the projection lens 1 of the first embodiment for a pair of light having a wavelength of 0.470 μm, 0.486 μm, 0.550 μm, 0.588 μm, 0.620 μm, 0.656 μm, respectively, at an image height of 0.000 mm. ,-2.835mm, -9.450mm, the Root Mean Square radii of the corresponding light points are 4.545um, 6.848um, 8.445um, and the geometrical radii of the corresponding light points are respectively It is 10.829um, 18.240um, 26.934um. It is obvious that the field curvature and distortion of the projection lens 1 of the first embodiment can be effectively corrected, and the lens resolution and focal depth can also meet the requirements, thereby obtaining better optical performance.

Please refer to FIG. 3, which is a schematic diagram of a lens configuration and an optical path of a second embodiment of a projection lens according to the present invention. The projection lens 2 includes a first lens group LG ₂₁ , a second lens group LG ₂₂ , an aperture ST2, a third lens group LG ₂₃ , and a first lens group LG ₂₁ , a second lens group LG ₂₂ in order, along an optical axis OA2. The fourth lens group LG ₂₄ , a pair of P2, and a protective glass CG2. During projection, the light from an image source IS2 is finally projected on the projection side. The first lens group LG ₂₁ has a negative refractive power. The first lens group LG ₂₁ includes a first lens L21. The first lens L21 is a convex-concave lens. It has a negative refractive power and is made of a plastic material. S22 is a concave surface, and both the object side surface S21 and the image side surface S22 are aspherical surfaces. The second lens group LG ₂₂ has a positive refractive power. The second lens group LG ₂₂ includes a second lens L22. This second lens L22 is a biconvex lens. It has a positive refractive power and is made of glass. Its object side S23 is convex and image-like. S24 is a convex surface, and both the object side surface S23 and the image side surface S24 are spherical surfaces. The third lens group LG ₂₃ includes a third lens L23 and a fourth lens L24. The third lens L23 and the fourth lens L24 are glued to form a cemented lens. The third lens L23 is a biconcave lens and has negative refractive power and is made of glass material. The object side S26 is concave, the image side S27 is concave, and the object side S26 and the image side S27 are spherical surfaces. This fourth lens L24 is a biconvex lens with positive refractive power and is made of glass. The object side S27 is convex. The image side surface S28 is a convex surface, and the object side surface S27 and the image side surface S28 are both spherical surfaces. The fourth lens group LG ₂₄ has a positive refractive power. The fourth lens group LG ₂₄ includes a fifth lens L25. The fifth lens L25 is a biconvex lens with a positive refractive power and is made of a plastic material. The object side S29 is a convex surface and the image side. S210 is convex, and both the object side S29 and the image side S210 are aspherical surfaces.稜鏡 P2 has both the object side S211 and the image side S212 as planes. The cover glass CG2 has both an object side surface S213 and an image side surface S214 that are flat.

In addition, in order for the projection lens of the present invention to maintain good optical performance, the projection lens 2 in the second embodiment must satisfy the following seven conditions: 0.6 <R2 ₁₂ /f2<1.5 (8)

1.4 <F-number2 <3.5 (9)

Vd2 ₁ > 40 (10)

Nd2 ₂ > 1.6 (11)

Nd2 ₃ > 1.6 (12)

Nd2 ₄ > 1.6 (13)

Vd2 ₃ <35 (14)

Among them, R2 ₁₂ is the curvature radius of the image side S22 of the first lens L21, f2 is the effective focal length of the projection lens 2, F-number2 is the aperture value of the projection lens 2, Vd2 ₁ is the Abbe coefficient of the first lens L21, and Nd2 ₂ is the refractive index of the second lens L22, Nd2 ₃ is the refractive index of the third lens L23, Nd2 ₄ is the refractive index of the fourth lens L24, and Vd2 ₃ is the Abbe coefficient of the third lens L23.

Utilizing the design of the above lens and aperture ST2, the projection lens 2 can be effectively used Reduce the volume, reduce the aperture value, effectively correct aberrations, improve the lens resolution, and reduce the impact of temperature changes on imaging quality.

Table 3 is a related parameter table of each lens of the projection lens 3 in the third figure. The data in Table 3 shows that the effective focal length of the projection lens 2 of the second embodiment is equal to 16.8 mm and the aperture value is equal to 1.5.

The aspheric surface depression z of each lens in Table 3 is obtained by the following formula: z = ch ² / {1+ [1- (k + 1) c ² h ² ] ^1/2 } + Ah ⁴ + Bh ⁶ + Ch ⁸ + Dh ¹⁰ + Eh ¹² + Fh ¹⁴ + Gh ¹⁶

Where: c: curvature; h: vertical distance from any point on the lens surface to the optical axis; k: conic coefficient; A ~ G: aspheric coefficient.

Table 4 is a table of related parameters of the aspheric surface of each lens in Table 3, where k is the Conic Constant and A ~ G are aspheric coefficients.

The projection lens 2 of the second embodiment has a curvature radius R2 ₁₂ of the image side S22 of the first lens L21 = 12.35mm, an effective focal length f2 of the projection lens 2 = 16.8mm, and an aperture value F-number2 = 1.5 of the projection lens 2. The Abbe coefficient Vd2 _{1 of the} first lens L21 = 56, the refractive index Nd2 _{2 of the} second lens L22 = 1.8, the refractive index Nd2 _{3 of the} third lens L23 = 1.77, the refractive index Nd2 _{4 of the} fourth lens L24 = 1.64, the first Abbe three lens L23 of Vd2 ₃ = 26, the information obtained by the _{R2 12 /f2=0.74,F-number2=1.5,Vd2 1 = 56, Nd2} 2 = 1.8, Nd2 3 = 1.77, Nd2 4 = 1.64, Vd2 ₃ = 26, which can satisfy the requirements of the above conditions (8) to (14).

In addition, the optical performance of the projection lens 2 of the second embodiment can also meet the requirements, which can be seen from FIGS. 4A to 4G. FIG. 4A is a Field Curvature diagram of the projection lens 2 of the second embodiment. FIG. 4B is a distortion diagram of the projection lens 2 of the second embodiment, and FIG. 4C is a modulation transfer function diagram of the projection lens 2 of the second embodiment. As shown in FIG. 4D, it is the Through Focus Modulation Transfer function of the projection lens 2 of the second embodiment. Function) diagram, shown in FIG. 4E, is a spot diagram of the projection lens 2 of the second embodiment (Spot Diagram), and FIG. 4F is a diagram of the light spot of the projection lens 2 of the second embodiment ( Spot Diagram), shown in FIG. 4G, is a Spot Diagram of the projection lens 2 of the second embodiment.

It can be seen from FIG. 4A that the projection lens 2 of the second embodiment has a pair of rays with a wavelength of 0.470 μm, 0.486 μm, 0.550 μm, 0.588 μm, 0.620 μm, and 0.656 μm in the Tangential direction and the sagittal direction. The field curvature in the direction of) is between -0.05mm and 0.15mm. From Figure 4B (the 6 lines in the figure are almost superimposed so that only one line appears), it can be seen that the projection lens 2 of the second embodiment has a wavelength of 0.470 μm, 0.486 μm, 0.550 μm, 0.588 μm, 0.620 The distortion caused by the light of μm and 0.656μm is between -0.9% and 0%. As can be seen from Figure 4C, the projection lens 4 of the second embodiment has a pair of rays with a wavelength ranging from 0.470 μm to 0.656 μm, respectively in the Tangential direction and the Sagittal direction, and the field heights are 0.0000. mm, -2.8350mm, -6.6150mm, -8.8050mm, -9.4500mm, the spatial frequency is between 0lp / mm and 37lp / mm, and its modulation conversion function value is between 0.57 and 1.0. As can be seen from the 4D diagram, the projection lens 2 of the second embodiment has a pair of rays with a wavelength ranging from 0.470 μm to 0.656 μm in the Tangential direction and the Sagittal direction, respectively, and the field heights are 0.0000 mm, -2.8350mm, -6.6150mm, -8.8050mm, -9.4500mm, when the spatial frequency is equal to 37lp / mm, when the focus shift is between -0.026mm and 0.032mm, its modulation conversion function value is greater than 0.2. Figures 4E, 4F, and 4G show the projection lens 2 of the second embodiment of the pair of light having a wavelength of 0.470 μm, 0.486 μm, 0.550 μm, 0.588 μm, 0.620 μm, 0.656 μm, and the image height is 0.000 mm ,-2.835mm,-9.450mm, the corresponding Root Mean Square radii of the light spots are 5.533um, 8.145um, 9.088um, the geometrical radii of the corresponding light spots are 7.738um, 24.387um, 29.781um, respectively. It is obvious that the field curvature and distortion of the projection lens 2 of the second embodiment can be effectively corrected, and the lens resolution and focal depth can also meet the requirements, thereby obtaining better optical performance.

Please refer to FIG. 5, which is a schematic diagram of a lens configuration and an optical path of a third embodiment of a projection lens according to the present invention. The projection lens 3 includes a first lens group LG ₃₁ , a second lens group LG ₃₂ , an aperture ST3, a third lens group LG ₃₃ , a The fourth lens group LG ₃₄ and a pair of P3. During projection, the light from an image source IS3 is finally projected on the projection side. The projection lens 3 can adjust the effective focal length of the projection lens 3 by changing the group distance on the optical axis OA3 of the first lens group LG ₃₁ , the second lens group LG ₃₂ , the third lens group LG _33, and the fourth lens group LG _34. , So that the projection lens 3 has a zoom function. The first lens group LG ₃₁ has a negative refractive power. The first lens group LG ₃₁ includes a first lens L31. The first lens L31 is a convex-concave lens. The negative lens has a negative refractive power and is made of glass. The object side S31 is convex and image-like. S32 is a concave surface, and both the object side surface S31 and the image side surface S32 are aspherical surfaces. The second lens group LG ₃₂ has a positive refractive power. The second lens group LG ₃₂ includes a second lens L32. This second lens L32 is a biconvex lens. It has a positive refractive power and is made of glass. Its object side S33 is convex and image-like. S34 is a convex surface, and both the object side surface S33 and the image side surface S34 are spherical surfaces. The third lens group LG ₃₃ has a negative refractive power. The third lens group LG ₃₃ includes a third lens L33 and a fourth lens L34. The third lens L33 is a biconcave lens. It has a negative refractive power and is made of glass. S36 is concave, the image side S37 is concave, the object side S36 and the image side S37 are spherical surfaces. This fourth lens L34 is a biconvex lens with positive refractive power and is made of glass. The convex surface, the object side surface S38 and the image side surface S39 are all spherical surfaces. The fourth lens group LG ₃₄ has a positive refractive power. The fourth lens group LG ₃₄ includes a fifth lens L35. This fifth lens L35 is a biconvex lens. It has a positive refractive power and is made of glass. Its object side S310 is convex and image-like. S311 is a convex surface, and both the object side surface S310 and the image side surface S311 are aspherical surfaces. The object side S312 and the image side S313 of the P3 are both flat.

In addition, in order for the projection lens of the present invention to maintain good optical performance, the projection lens 3 in the third embodiment must satisfy the following seven conditions: f _T / f _W > 1 (15)

1.4 <F-number3 <3.5 (16)

Vd3 ₁ > 40 (17)

Nd3 ₂ > 1.6 (18)

Nd3 ₃ > 1.6 (19)

Nd3 ₄ > 1.6 (20)

Vd3 ₃ <35 (21)

Among them, f _T is the effective focal length of the projection lens 3 at the telephoto end, f _W is the effective focal length of the projection lens 3 at the wide-angle end, F-number3 is the aperture value of the projection lens 3, and Vd3 ₁ is the Abbe coefficient of the first lens L31 , Nd3 ₂ is the refractive index of the second lens L32, Nd3 ₃ is the refractive index of the third lens L33, Nd3 ₄ is the refractive index of the fourth lens L34, Vd3 ₃ is the Abbe number of the third lens L33.

Utilizing the design of the above lens and aperture ST3, the projection lens 3 can effectively reduce the volume, reduce the aperture value, effectively correct aberrations, improve the lens resolution, and reduce the impact of temperature changes on the imaging quality.

Table 5 is the relevant parameter table of each lens of the projection lens 3 in Figure 5, the table Five data show that the effective focal length of the projection lens 3 of the third embodiment at the wide-angle end is equal to 16.7mm, the effective focal length at the telephoto end is equal to 17mm, and the aperture value is equal to 2.0.

The aspheric surface depression z of each lens in Table 5 is obtained by the following formula: z = ch ² / {1+ [1- (k + 1) c ² h ² ] ^1/2 } + Ah ⁴ + Bh ⁶ + Ch ⁸ + Dh ¹⁰ + Eh ¹² + Fh ¹⁴ + Gh ¹⁶

Where: c: curvature; h: vertical distance from any point on the lens surface to the optical axis; k: conic coefficient; A ~ G: aspheric coefficient.

Table 6 is a table of related parameters of the aspheric surface of each lens in Table 5, where k is Conic Constant and A ~ G are aspheric coefficients.

The effective focal length f _{T of the} third embodiment of the projection lens 3 at the telephoto end = 17 mm, the effective focal length f _W at the wide-angle end of f = 16.1 mm, the aperture value of the projection lens 3 F-number 3 = 2.0, Abbe coefficient Vd3 ₁ = 70, refractive index Nd3 _{2 of the} second lens L32 = 1.8, refractive index Nd3 _{3 of the} third lens L33 = 1.77, refractive index Nd3 _{4 of the} fourth lens L34 = 1.67, and refractive index of the third lens L33 The coefficient is Vd3 ₃ = 26. From the above data, f _T / f _W = 1.06, F-number3 = 2.0, Vd3 ₁ = 70, Nd3 ₂ = 1.8, Nd3 ₃ = 1.77, Nd3 ₄ = 1.67, Vd3 ₃ = 26 , Can meet the requirements of the above conditions (15) to (21).

In addition, the optical performance of the projection lens 3 of the third embodiment can also meet the requirements, which can be seen from FIGS. 6A to 6F. FIG. 6A is a Field Curvature diagram when the projection lens 3 of the third embodiment is at the wide-angle end. Figure 6B shows the distortion when the projection lens 3 of the third embodiment is at the wide-angle end. Figure 6C shows the distortion when the projection lens 3 of the third embodiment is at the wide-angle end. Modulation Transfer Function chart, shown in Figure 6D, is the projection mirror of the third embodiment Field Curvature diagram with head 3 at the telephoto end. Fig. 6E shows the distortion when the projection lens 3 of the third embodiment is at the telephoto end, and Fig. 6F shows the adjustment when the projection lens 3 of the third embodiment is at the telephoto end. Diagram of Modulation Transfer Function.

It can be seen from FIG. 6A that when the projection lens 3 of the third embodiment is at the wide-angle end, the light with a wavelength of 0.470 μm, 0.486 μm, 0.550 μm, 0.588 μm, 0.620 μm, 0.656 μm is in the direction of the meridian (Tangential) The field curvature from the Sagittal direction is between -0.09mm and 0.09mm. From Figure 6B (the six lines in the figure are almost superimposed so that there appears to be only one line), it can be seen that when the projection lens 3 of the third embodiment is at the wide-angle end, the wavelengths are 0.470 μm, 0.486 μm, 0.550 μm , 0.588μm, 0.620μm, 0.656μm light distortion caused by light between -0.8% to 0%. It can be seen from FIG. 6C that when the projection lens 3 of the third embodiment is at the wide-angle end, light rays with a wavelength range of 0.470 μm to 0.656 μm are respectively in the Tangential direction and the Sagittal direction. The field height is 0.0000mm, -2.8350mm, -6.6150mm, -8.8050mm, -9.4500mm, the spatial frequency is between 0lp / mm and 37lp / mm, and its modulation transfer function value is between 0.67 and 1.0. It can be seen from FIG. 6D that when the projection lens 3 of the third embodiment is at the telephoto end, the light with a wavelength of 0.470 μm, 0.486 μm, 0.550 μm, 0.588 μm, 0.620 μm, 0.656 μm is in the direction of the meridian (Tangential) The field curvature in the Sagittal direction is between -0.09mm and 0.11mm. It can be seen from FIG. 6E that when the projection lens 3 of the third embodiment is at the telephoto end, the distortion caused by light with a wavelength of 0.470 μm, 0.486 μm, 0.550 μm, 0.588 μm, 0.620 μm, 0.656 μm is between − Between 0.025% and 0.015%. It can be seen from FIG. 6F that when the projection lens 3 of the third embodiment is at the telephoto end, the wavelength range is from 0.470 μm to 0.656. The light of μm is in the Tangential direction and the Sagittal direction, the field height is 0.0000mm, -2.8350mm, -6.6150mm, -8.8050mm, -9.4500mm, and the spatial frequency is between 0lp / mm. To 37lp / mm, its modulation transfer function value is between 0.57 and 1.0. It is obvious that the field curvature and distortion of the projection lens 3 of the third embodiment can be effectively corrected, and the lens resolution can also meet the requirements, thereby obtaining better optical performance.

Claims (10)

A projection lens, along an optical axis, sequentially from a projection side to an image source side includes: a first lens group having a negative refractive power; a second lens group having a positive lens group Refractive power, both the image source side and the projection side of the second lens group are convex; a third lens group, the third lens group has a convex surface facing the projection side; and a fourth lens group, the fourth lens group With positive refractive power, the fourth lens group has a convex surface facing the image source side; wherein the projection lens satisfies the following conditions: 1.4<F-number<3.5 where F-number is the aperture value of the projection lens; wherein the first lens The group spacing of the group, the second lens group, the third lens group, and the fourth lens group on the optical axis can be changed to adjust the effective focal length of the projection lens. The projection lens as described in item 1 of the patent application scope, wherein the first lens group includes a first lens having a negative refractive power, and the second lens group includes a second lens having a positive lens Refractive power, the third lens group includes a third lens and a fourth lens in sequence from the projection side to the image source side along the optical axis, the third lens has negative refractive power, and the fourth lens has positive refractive power, The fourth lens group includes a fifth lens having positive refractive power. The projection lens as described in item 2 of the patent application scope, wherein the projection lens satisfies the following conditions: 0.6

R ₁₂ /f

1.5 where R _{12 is} the radius of curvature of the side of the image source of the first lens, and f is the effective focal length of the projection lens. The projection lens as described in item 2 of the patent application scope, wherein the first lens is an aspheric lens and satisfies the following condition: Vd ₁ >40, where Vd _{1 is} the Abbe coefficient of the first lens. The projection lens as described in item 2 of the patent application scope, wherein the fifth lens is an aspheric lens. The projection lens as described in item 2 of the patent application scope, wherein the second lens, the third lens and the fourth lens are spherical lenses and satisfy the following conditions: Nd ₂ >1.6 Nd ₃ >1.6 Nd ₄ >1.6 Vd ₃ <35 where Nd _{2 is} the refractive index of the second lens, Nd _{3 is} the refractive index of the third lens, Nd _{4 is} the refractive index of the fourth lens, and Vd _{3 is} the Abbe coefficient of the third lens. The projection lens as described in Item 2 of the patent application scope further includes an aperture disposed between the second lens and the fourth lens, and the third lens and the fourth lens are cemented into a cemented lens. The projection lens as described in item 1 or 2 of the patent application scope, wherein the third lens group has negative refractive power. The projection lens as described in item 8 of the patent application scope, wherein the projection lens satisfies the following conditions: f _T /f _W >1 where f _{T is} the effective focal length of the projection lens at the telephoto end, and f _{W is} the projection lens at Effective focal length at the wide-angle end. The projection lens as described in item 8 of the patent application range, wherein the first lens is an aspheric lens, the second lens, the third lens, and the fourth lens are spherical lenses and satisfy the following conditions: Vd ₁ >40 Nd ₂ >1.6 Nd ₃ >1.6 Nd ₄ >1.6 Vd ₃ <35 where Nd _{2 is} the refractive index of the second lens, Nd _{3 is} the refractive index of the third lens, and Nd _{4 is} the refractive index of the fourth lens , Vd _{3 is} the Abbe coefficient of the third lens, and Vd _{1 is} the Abbe coefficient of the first lens.