CN110764221B

CN110764221B - Projection lens system

Info

Publication number: CN110764221B
Application number: CN201810822941.1A
Authority: CN
Inventors: 吴昇澈; 周昱宏; 陈宥达
Original assignee: Sun Yang Optics Development Co ltd
Current assignee: Sun Yang Optics Development Co ltd
Priority date: 2018-07-25
Filing date: 2018-07-25
Publication date: 2021-09-17
Anticipated expiration: 2038-07-25
Also published as: CN110764221A

Abstract

A projection lens system, comprising: a front group lens; an aperture located behind the front group lens, the front group lens to the aperture forms a telephoto lens, and the focal length of the telephoto lens is set at 30mm-80mm; The group lens is located behind the aperture, and the aperture to the rear group lens forms a short-focus lens, and the focal length of the short-focus lens is set at 20mm to 30mm. The invention makes the lens combination structure simple and low cost by the mutual cooperation of the telephoto lens and the short focal lens, and can also take into account the effect of the projection imaging quality.

Description

Projection lens system

Technical Field

The present invention relates to a projection lens system, and more particularly, to a projection lens system with a long focus lens and a short focus lens, which are matched with each other to make the lens assembly structure simple and the cost low.

Background

As optical technology advances, projectors are not only used in offices for bulletins, but also widely used in homes for viewing videos and programs, so that manufacturers also research and develop the reduction of the size of the lens of the projector for the convenience of using and carrying the projector.

Secondly, for the purpose of projection imaging quality, the longer the focal length of the lens, the smaller the angle of view thereof, and conversely, the shorter the focal length of the lens, the larger the angle of view thereof, so that the distortion generated by the optical principle is stronger, and the focal length of the lens affects the projection imaging quality.

However, it is an objective of the present invention to find that the focal length of the lens and the lens assembly structure both affect the projection imaging quality, and how to adjust the focal length of the lens, and the lens assembly structure of the lens is simple and low in cost, and can also achieve the projection imaging quality.

Disclosure of Invention

The main technical problem to be solved by the present invention is to overcome the above-mentioned defects in the prior art, and to provide a projection lens system, which uses the long-focus lens and the short-focus lens to cooperate with each other, so as to make the lens assembly structure simple and the cost low, and also to consider the efficacy of the projection imaging quality; the long-focus lens and the short-focus lens are matched with each other, so that a large aperture is arranged between the long-focus lens and the short-focus lens, and the effect of projection imaging quality is improved.

The technical scheme adopted by the invention for solving the technical problems is as follows:

a projection lens system, comprising: a front group lens; an aperture behind the front group lens, the front group lens forming a telephoto lens from the aperture, the focal length of the telephoto lens being set to 30mm to 80 mm; and a rear group lens located behind the diaphragm, the diaphragm to the rear group lens forming a short-focus lens, the focal length of the short-focus lens being set to 20 mm-30 mm.

According to the disclosure, the front lens group includes a first lens element, a second lens element, a third lens element and a fourth lens element, and the second lens element and the fourth lens element are plastic aspheric lens elements.

According to the aforementioned features, the plastic aspheric lens of the second lens is a meniscus lens and has a negative power, and the focal length thereof is set between-20 mm and-50 mm, or the focal length thereof is set between-25 mm and-40 mm.

According to the aforementioned characteristics, the plastic aspheric lens of the fourth lens element is a meniscus lens, and the focal length thereof is positive and greater than 300mm or negative and less than-300 mm.

According to the features disclosed above, the abbe number of the first lens is greater than 60.

According to the disclosure, the rear group lens includes at least one three cemented lens, the diopters of which are positive, negative, positive, or negative in order, and is composed of a fifth lens, a sixth lens and a seventh lens, the rear group lens includes an eighth lens located behind the three cemented lenses, and the fifth lens, the sixth lens, the seventh lens and the eighth lens are at least two glass lenses with abbe numbers greater than 60.

According to the features of the previous paragraph, the rear group of lenses includes a final lens, the last lens having an abbe number of less than 25.

According to the characteristics of the previous disclosure, the aperture is between 1.6 and 2.0.

According to the disclosure, the front lens group includes a first lens element, a second lens element, a third lens element and a fourth lens element, and the second lens element and the third lens element are plastic aspheric lens elements.

According to the aforementioned features, the plastic aspheric lens of the third lens element is a meniscus lens, and the focal length thereof is positive and greater than 300mm or negative and less than-300 mm.

The invention adopts another technical means which comprises the following steps: a projection lens system, comprising: a front group lens, including a first lens, a second lens, a third lens and a fourth lens, wherein the second lens is a plastic aspheric lens, the plastic aspheric lens of the second lens is a meniscus lens and has negative power, and the focal length of the second lens is set between-25 mm and-50 mm; an aperture between 1.6-2.0 and behind the front group of lenses, the front group of lenses forming a telephoto lens from the aperture, the focal length of the telephoto lens being set to 30 mm-80 mm; and a back group lens, including at least a three cemented lens, an eighth lens and a final lens, the diopter of the three cemented lens is positive or negative or positive or negative in order, and is composed of a fifth lens, a sixth lens and a seventh lens, and the abbe number of the fifth lens, the sixth lens, the seventh lens and the eighth lens is less than 25, and the back group lens is located behind the diaphragm, the diaphragm to the back group lens forms a short-focus lens, the focal length of the short-focus lens is set at 20 mm-30 mm.

By means of the technical means disclosed above, the long-focus lens and the short-focus lens are matched, so that the lens combination structure is simple, the cost is low, the effect of projection imaging quality can be considered, and the large aperture is arranged between the long-focus lens and the short-focus lens, so that the effect of projection imaging quality is improved.

The invention has the advantages that the long-focus lens and the short-focus lens are matched with each other, so that the lens combination framework is simple and the cost is low, and the effect of the projection imaging quality can be considered; the long-focus lens and the short-focus lens are matched with each other, so that a large aperture is arranged between the long-focus lens and the short-focus lens, and the effect of projection imaging quality is improved.

Drawings

The invention is further illustrated with reference to the following figures and examples.

FIG. 1A is a schematic view of a lens configuration according to a first embodiment of the present invention.

FIG. 1B is a cross-directional ray fan plot of an image plane exhibiting an image height of 0.0000mm in accordance with an aspect of the first embodiment of the present invention.

FIG. 1C is a cross-ray fan of light having an image plane exhibiting an image height of 5.4620mm in accordance with a first embodiment of the present invention.

FIG. 1D is a cross-ray fan plot of an image plane exhibiting an image height of 7.8030mm in accordance with an aspect of the first embodiment of the present invention.

FIG. 1E is a field curvature diagram of a first embodiment aspect of the present invention.

FIG. 1F is a distortion plot of a first embodiment aspect of the present invention.

FIG. 1G is a speckle pattern with an image plane exhibiting an image height of 0.000mm in an aspect of the first embodiment of the present invention.

FIG. 1H is a speckle pattern with an image plane exhibiting an image height of 5.462mm in accordance with an aspect of the first embodiment of the present invention.

FIG. 1I is a speckle pattern with an image plane exhibiting an image height of 7.804mm in accordance with an aspect of the first embodiment of the present invention.

FIG. 2A is a schematic view of a lens configuration according to a second embodiment of the present invention.

FIG. 2B is a cross-directional ray fan plot of an image plane exhibiting an image height of 0.0000mm in accordance with a second embodiment of the present invention.

Figure 2C is a transverse ray fan with an image plane exhibiting an image height of 5.4620mm in accordance with a second embodiment of the present invention.

Figure 2D is a transverse ray fan with an image plane exhibiting an image height of 7.8030mm in accordance with a second embodiment of the present invention.

Fig. 2E is a field curvature diagram of a second embodiment aspect of the invention.

Fig. 2F is a distortion plot of a second embodiment aspect of the present invention.

FIG. 2G is a speckle pattern with an image plane exhibiting an image height of 0.000mm in an aspect of the second embodiment of the present invention.

FIG. 2H is a speckle pattern with an image plane exhibiting an image height of 5.462mm in accordance with an aspect of the second embodiment of the present invention.

Fig. 2I is a speckle pattern with an image plane exhibiting an image height of 7.804mm in accordance with an aspect of the second embodiment of the present invention.

FIG. 3A is a schematic view of a lens configuration according to a third embodiment of the present invention.

FIG. 3B is a cross-directional ray fan plot with an image plane exhibiting an image height of 0.0000mm in accordance with a third embodiment of the present invention.

Figure 3C is a transverse ray fan with an image plane exhibiting an image height of 5.4620mm in accordance with a third embodiment of the present invention.

Figure 3D is a transverse ray fan with an image plane exhibiting an image height of 7.8030mm in accordance with a third embodiment of the present invention.

Fig. 3E is a field curvature diagram of a third embodiment aspect of the present invention.

Fig. 3F is a distortion plot of a third embodiment aspect of the present invention.

FIG. 3G is a speckle pattern with an image plane exhibiting an image height of 0.000mm in an aspect of the third embodiment of the present invention.

Fig. 3H is a speckle pattern with an image plane exhibiting an image height of 5.463mm in accordance with an aspect of the third embodiment of the present invention.

Fig. 3I is a speckle pattern with an image plane exhibiting an image height of 7.804mm in accordance with an aspect of the third embodiment of the present invention.

The reference numbers in the figures illustrate:

10 telephoto lens

20 short focal length lens

30A, 30B, 30C projection lens system

C triple cemented lens

E optical element

G glass cover plate

G₁Front group lens

G₂Rear group lens

L₁First lens

L₂Second lens

L₃Third lens

L₄Fourth lens

L₅Fifth lens element

L₆Sixth lens element

L₇Seventh lens element

L₈Eighth lens element

L₉Last lens

P-penetration type image smoothing device

S aperture

λ₁A first wavelength

λ₂A second wavelength

λ₃A third wavelength

IMA imaging surface

1R₁、1R₂、2R₁、2R₂、3R₁、3R₂、4R₁、4R₂、5R₁、6R₁、7R₁、7R₂、8R₁、8R₂、9R₁、9R₂Surface of

Detailed Description

First, referring to fig. 1A to 1I, fig. 2A to 2I, and fig. 3A to 3I, a

projection lens system

30A, 30B, and 30C according to a preferred embodiment of the present invention includes: a front group lens G₁In this embodiment, the front group lens G₁Includes a first lens L₁A second lens element L₂A third lens element L₃And a fourth lens L₄In this embodiment, the second lens element L₂The plastic aspherical lens of (1) is a meniscus lens and has a negative power (power) and a focal length set between-20 mm and-50 mm, and in another preferred embodiment, the focal length is set between-25 mm and-40 mm, but is not limited thereto.

A Stop (Stop) S between 1.6 and 2.0 and located in the front group lens G₁Rear of the front group lens G₁ A telephoto lens 10 is formed to the aperture A, and the focal length of the telephoto lens 10 is set to be 30mm to 80mm, also near the screen end.

A rear group lens G₂Comprises at least a tri-cemented lens C and an eighth lens L₈And a final lens L₉The diopter of the three cemented lens C is positive, negative, positive or negative in sequence, and is composed of a fifth lens L₅A toSixth lens L₆And a seventh lens element L₇And the fifth lens L₅The sixth lens element L₆The seventh lens element L₇And the eighth lens L₈At least two glass lenses with Abbe number greater than 60 and the final lens L₉Is less than 25, and the rear group lens G₂Behind the aperture S to the rear group lens G₂A short-focus lens 20 is formed, and the focal length of the short-focus lens 20 is set to be 20mm to 30 mm.

In addition, a transmission Smooth image device (transmission Smooth image adjuster) P, which is a glass plate device capable of rotating a little and quickly, is disposed behind the final lens L9, and the resolution is increased by image shift synthesis, so that the 1080P resolution can be increased to 4K2K resolution; an optical element E disposed behind the transmission-type smooth image Device P, in this embodiment, the optical element E may be a prism, and a Cover Glass (Cover Glass) G and an image plane IMA of a Digital micro-mirror Device (DMD) are sequentially arranged behind the prism, but not limited thereto. The present invention has three embodiments, and the first embodiment, the second embodiment and the third embodiment all have the common technical features mentioned above, and have unity.

Referring to FIG. 1A, a first embodiment of the projection lens system 30A is shown with the first lens element L₁The second lens L₂The third lens element L₃The fourth lens element L₄The fifth lens element L₅The sixth lens element L₆The seventh lens element L₇The eighth lens element L₈And the final lens L₉Radius (Radius), Thickness (Thickness), refractive index (Nd), and abbe number (Vd) according to:

watch 1

Further, the 1R₁、1R₂Respectively the first lens L₁The projection side surface, the image source side surface of (a); the 2R₁、2R₂Respectively the second lens L₂The projection side surface, the image source side surface of (a); the 3R₁、3R₂Respectively the third lens L₃The projection side surface, the image source side surface of (a); the 4R₁、4R₂Respectively the fourth lens L₄The projection side surface, the image source side surface of (a); the 5R₁Is the fifth lens L₅The projection side surface of (a); the 6R₁Respectively the sixth lens L₆The projection side surface of (a); the 7R₁、7R₂Are the seventh lens L respectively₇The projection side surface, the image source side surface of (a); the 8R₁、8R₂Respectively the eighth lens L₈The projection side surface, the image source side surface of (a); the 9R₁、9R₂Respectively the final lens L₉The projection side surface, the image source side surface.

In the second table, the 2R is listed in the plastic aspheric lens (ASPH)₁、2R₂The projection side surface and the image source side surface of the plastic aspheric lens are respectively arranged and are respectively listed as the consi, 4TH, 6TH, 8TH, 10TH and 12TH of the plastic aspheric lens; in accordance with table three, the 4R is listed in the plastic aspheric lens (ASPH)₁、4R₂The projection side surface and the image source side surface of the plastic aspheric lens are respectively arranged and configured as common, 4TH, 6TH, 8TH, 10TH and 12TH of the plastic aspheric lens.

Watch two

ASPH	2R₁	2R₂
			Radius	15.81	8.29
Conic	--	-0.83
			4TH	-1.57E-04	-2.03E-04
6TH	5.84E-07	7.29E-07
			8TH	-3.41E-09	-4.44E-09
10TH	1.08E-11	1.33E-11
			12TH	-2.20E-14	-1.55E-14

Watch III

In this embodiment, the fourth lens element L₄The plastic aspheric lens is a meniscus lens, and the focal length of the plastic aspheric lens can be positive and is more than 300mm or negative and is less than-300 mm; the first lens L₁The Abbe number of (2) is more than 60, but not limited thereto.

Thus, the projection lens system 30A has a first wavelength λ₁A second wavelength lambda₂And a third wavelength lambda₃0.460um, 0.545um and 0.620um respectively, and can simulate different transverse ray fan diagrams of fig. 1B, 1C and 1D respectively, and different image heights of 0.0000mm, 5.4620mmm and 7.8030mm are presented on the same imaging plane IMA respectively, and the symbols ey, py, ex and px respectively represent y-axis transverse aberration, y-axis pupil height, x-axis transverse aberration and x-axis pupil height, the y-axis transverse aberration and the x-axis transverse aberration have a maximum scale of ± 20.000um, and the y-axis pupil height and the x-axis pupil height are normalized ratios; the Field Curvature (Field) plot of FIG. 1E and the Distortion (Distortion) plot of FIG. 1F, with a Maximum Field of view (Maximum Field) of 31.786 degrees; in the Spot (Spot) diagrams of fig. 1G, 1H, and 1I, the same image plane IMA respectively shows different image heights of 0.000mm, 5.462mm, and 7.804mm, when the image plane is at 0.000mm, the root mean square Radius (RMS Radius) is 2.578um, the distribution Radius (GEO Radius) is 5.051um, when the image plane is at 5.462mm, the root mean square Radius (RMS Radius) is 2.636um, the distribution Radius (GEO Radius) is 12.865um, and when the image plane is at 7.804mm, the root mean square Radius (RMS Radius) is 4.563um, the distribution Radius (GEO Radius) is 22.942 um.

Referring to FIG. 2A, a second embodiment of the projection lens system 30B, in accordance with the fourth embodiment, includes the first lens element L₁The second lens L₂The third lens element L₃The fourth lens element L₄The fifth lens element L₅The sixth lens element L₆The seventh oneLens L₇The eighth lens element L₈And the final lens L₉Radius (Radius), Thickness (Thickness), refractive index (Nd), and abbe number (Vd) according to:

watch four

Surface of	Radius (mm)	Thickness (mm)	Refractive index	Abbe number
					1R₁	51.46	1.70	1.61	63.3
1R₂	16.79
					2R₁	20.83	3.00	1.53	56.3
2R₂	9.82
					3R₁	59.89	6.84	1.83	42.7
3R₂	-54.01
					4R₁	18.24	6.90	1.53	56.3
4R₂	15.65
					S	Infinity
5R₁	566.05	3.79	1.49	81.6
					6R₁	-15.24	6.00	1.80	25.4
7R₁	32.82	4.87	1.49	81.6
					7R₂	-25.83
8R₁	41.17	4.09	1.49	81.6
					8R₂	-50.52
9R₁	32.84	4.24	1.92	18.90
					9R₂	118.74

In Table V, the 2R is listed in the plastic aspheric lens (ASPH)₁、2R₂The projection side surface and the image source side surface of the plastic aspheric lens are respectively arranged and are respectively listed as the consic, 4TH, 6TH, 8TH, 10TH, 12TH and 14TH of the plastic aspheric lens; in accordance with the sixth embodiment, the 4R is listed in the plastic aspheric lens (ASPH)₁、4R₂The projection side surface and the image source side surface of the plastic aspheric lens are respectively arranged and configured as common, 4TH, 6TH, 8TH, 10TH and 12TH of the plastic aspheric lens.

Watch five

ASPH	2R₁	2R₂
			Radius	20.83	9.82
Conic	-6.57	-0.89
			4TH	-1.12E-05	-1.31E-04
6TH	3.08E-07	1.04E-06
			8TH	-2.31E-09	-8.61E-09
10TH	8.54E-12	3.90E-11
			12TH	-1.13E-14	-7.84E-14
14TH	-6.40E-18	0.00E+00

Watch six

ASPH	4R₁	4R₂
			Radius	18.24	15.65
Conic	0.39	1.19
			4TH	-1.67E-05	-5.36E-05
6TH	-1.97E-08	-5.14E-08
			8TH	-9.33E-10	-1.13E-08
10TH	6.06E-12	1.42E-10
			12TH	-2.67E-14	-1.10E-12

In this embodiment, the fourth lens element L₄The plastic aspheric lens is a meniscus lens, and the focal length of the plastic aspheric lens can be positive and is more than 300mm or negative and is less than-300 mm; the first lens L₁Has an Abbe number of greater than 60; the rear group lens G₂Includes at least one tri-cemented lens C with positive and negative refractive powers in sequence, but is not limited thereto.

Thus, the projection lens system 30B has a first wavelength λ₁A second wavelength lambda₂And a third wavelength lambda₃0.460um, 0.545um and 0.620um respectively,and can simulate different transverse ray fan diagrams of fig. 2B, fig. 2C and fig. 2D, respectively, and the same image plane IMA presents different image heights of 0.0000mm, 5.4620mmm, 7.8030mm, respectively, and the symbols ey, py, ex, px represent y-axis transverse aberration, y-axis pupil height, x-axis transverse aberration, x-axis pupil height, respectively, the y-axis transverse aberration, the x-axis transverse aberration, its maximum scale ± 20.000um, and the y-axis pupil height, the x-axis pupil height, which is a normalized ratio; the Field Curvature (Field) plot of FIG. 2E and the Distortion (Distortion) plot of FIG. 2F, with a Maximum Field of view (Maximum Field) of 31.800 degrees; fig. 2G, 2H, and 2I show Spot (shot) images with different image heights of 0.000mm, 5.462mmm, and 7.804mm on the same imaging plane (IMA), respectively, where the root mean square Radius (RMS Radius) is 2.864um and the distribution Radius (GEO Radius) is 7.106um when the imaging plane is 0.000mm, 4.134um and the distribution Radius (GEO Radius) is 24.451um when the imaging plane is 5.462mm, and 8.510um and the distribution Radius (GEO Radius) is 42.360um when the imaging plane is 7.804mm, and the simulation curves and data show that the projection lens system 30B can perform projection with a simple lens assembly structure and low cost, and still maintain good projection imaging quality.

Referring to FIG. 3A, a third embodiment of the projection lens system 30C is provided, together with TABLE VII, the first lens L₁The second lens L₂The third lens element L₃The fourth lens element L₄The fifth lens element L₅The sixth lens element L₆The seventh lens element L₇The eighth lens element L₈And the final lens L₉Radius (Radius), Thickness (Thickness), refractive index (Nd), and abbe number (Vd) according to:

watch seven

In the eighth table, the 2R is listed in the plastic aspheric lens (ASPH)₁、2R₂The projection side surface and the image source side surface of the plastic aspheric lens are respectively arranged and are respectively listed as the consic, 4TH, 6TH, 8TH, 10TH, 12TH and 14TH of the plastic aspheric lens; in accordance with the ninth embodiment, the 3R is listed in the plastic aspheric lens (ASPH)₁、3R₂The projection side surface and the image source side surface of the plastic aspheric lens are respectively arranged and configured as common, 4TH, 6TH, 8TH, 10TH and 12TH of the plastic aspheric lens.

Table eight

Watch nine

ASPH	3R₁	3R₂
			Radius	-23.93	-24.64
Conic	-7.46	-2.70
			4TH	-4.31E-05	-9.59E-06
6TH	3.88E-07	3.24E-08
			8TH	-8.10E-10	4.01E-10
10TH	8.20E-12	-1.33E-12
			12TH	-2.51E-14	5.23E-15

In this embodiment, the third lens element L₃The plastic aspheric lens is a meniscus lens, and the focal length of the plastic aspheric lens can be positive and is more than 300mm or negative and is less than-300 mm; the rear group lens G₂Includes at least one cemented lens C with positive and negative refractive powers, but is not limited thereto.

Thus, the projection lens system 30C has a first wavelength λ₁A second wavelength lambda₂And a third wavelength lambda₃0.460um, 0.545um and 0.620um respectively, and can simulate different transverse ray fan diagrams of fig. 3B, 3C and 3D respectively, and different image heights of 0.0000mm, 5.4620mmm and 7.8030mm are presented on the same imaging plane IMA respectively, and the symbols ey, py, ex and px respectively represent y-axis transverse aberration, y-axis pupil height, x-axis transverse aberration and x-axis pupil height, the y-axis transverse aberration and the x-axis transverse aberration have a maximum scale of ± 20.000um, and the y-axis pupil height and the x-axis pupil height are normalized ratios; the Field Curvature (Field) plot of FIG. 3E and the Distortion (Distortion) plot of FIG. 3F, with a Maximum Field of view (Maximum Field) of 31.710 degrees; fig. 3G, 3H, and 3I show Spot (Spot) images, where the same imaging plane IMA respectively shows different image heights of 0.000mm, 5.463mmm, and 7.804mm, when the imaging plane is at 0.000mm, the root mean square Radius (RMS Radius) is 2.073um, the distribution Radius (GEO Radius) is 3.928um, when the imaging plane is at 5.462mm, the root mean square Radius (RMS Radius) is 2.216um, the distribution Radius (GEO Radius) is 8.737um, and when the imaging plane is at 7.804mm, the root mean square Radius (RMS Radius) is 3.343um, the distribution Radius (GEO Radius) is 14.738 um.

The above description is only a preferred embodiment of the present invention, and is not intended to limit the present invention in any way, and all simple modifications, equivalent variations and modifications made to the above embodiment according to the technical spirit of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. a projection lens system, is characterized in that, comprises:

a front group lens, the front group lens includes a first lens, a second lens, a third lens and a fourth lens, the second lens and the fourth lens are plastic aspherical lenses;

an aperture, located behind the front group lens, the front group lens to the aperture form a telephoto lens, and the focal length of the telephoto lens is set at 30mm˜80mm; and

A rear group lens is located behind the aperture, the aperture and the rear group lens form a short-focus lens, the focal length of the short-focus lens is set at 20mm to 30mm, and the rear group lens includes at least one triplet lens, Its diopter is positive, negative, positive or negative, and is composed of a fifth lens, a sixth lens and a seventh lens, and the rear group lens includes an eighth lens, which is located at the position of the triplet lens. At the rear, the fifth lens, the sixth lens, the seventh lens and the eighth lens are at least two glass lenses whose Abbe number is greater than 60.

2 . The projection lens system according to claim 1 , wherein the plastic aspherical lens of the second lens is a meniscus lens with negative power, and its focal length is set between -20mm and -50mm. 3 . between.

3 . The projection lens system according to claim 1 , wherein the plastic aspherical lens of the second lens is a meniscus lens with negative power, and its focal length is set between -25mm and -40mm. 4 . between.

4 . The projection lens system according to claim 1 , wherein the plastic aspherical lens of the fourth lens is a meniscus lens, and its focal length is positive when its focal length is greater than 300 mm or its focal length is negative. 5 . , while the focal length is less than -300mm.

5 . The projection lens system according to claim 1 , wherein the Abbe number of the first lens is greater than 60. 6 .

6 . The projection lens system of claim 1 , wherein the rear group lens comprises a last lens, and the Abbe number of the last lens is less than 25. 7 .

7 . The projection lens system according to claim 1 , wherein the aperture is between 1.6 and 2.0. 8 .

8. A projection lens system, characterized in that, comprising:

a front group lens, the front group lens includes a first lens, a second lens, a third lens and a fourth lens, the second lens and the third lens are plastic aspherical lenses;

9 . The projection lens system according to claim 8 , wherein the plastic aspherical lens of the third lens is a meniscus lens, and its focal length is positive when its focal length is greater than 300 mm or its focal length is negative. 10 . , while the focal length is less than -300mm.

10. A projection lens system, comprising:

A front group lens includes a first lens, a second lens, a third lens and a fourth lens, the second lens is a plastic aspherical lens, and the plastic aspherical lens of the second lens is a meniscus lens , and has negative power, and the focal length of the second lens is set between -25mm and -50mm;

an aperture, ranging from 1.6 to 2.0, located behind the front group lens, the front group lens to the aperture forms a telephoto lens, and the focal length of the telephoto lens is set at 30mm to 80mm; and

A rear group lens includes at least a triplet lens, an eighth lens and a final lens. The dioptric power of the triplet lens is positive or negative in sequence, or negative and positive, and consists of a fifth lens, a sixth lens and a final lens. A seventh lens is formed, and the fifth lens, the sixth lens, the seventh lens and the eighth lens have at least two glass lenses whose Abbe number is greater than 60 and the Abbe number of the last lens is less than 25, and The rear group lens is located behind the aperture, the aperture and the rear group lens form a short-focus lens, and the focal length of the short-focus lens is set at 20mm˜30mm.