Projection lens

Abstract

The present invention relates to the technical field of optical lenses, and in particular to a projection lens. The projection lens comprises a lens group I, an aperture and a lens group II which are arranged in a direction from a magnification side to a reduction side, wherein the lens group I comprises two lenses, and the lens group II comprises four lenses. The projection lens in the present invention adopts few lenses, has a simple and compact structure and small occupied space, can meet miniaturization development requirements, and has low costs, good mass productivity and good imaging quality.

Description

A projection lens Technical Field

[0001] The present invention relates to the technical field of optical lenses, and in particular to a projection lens. Background Art

[0002] Projectors are increasingly used in various fields, and user demand for more diverse projector applications is growing. Consequently, projectors are trending towards smaller and lighter models. The projection lens is a crucial component of a projector, significantly impacting the quality of the projected image. Existing projection lenses are typically complex, bulky, and expensive, making them difficult to meet the demands of miniaturization. Summary of the Invention

[0003] The technical problem to be solved and the technical task proposed by the present invention are to improve the existing technology and provide a projection lens to solve the problem that the projection lens in the current technology has a complex structure, occupies a large volume, and is difficult to meet the needs of miniaturization development.

[0004] In order to solve the above technical problems, the technical solution of the present invention is:

[0005] A projection lens includes a first lens group, an aperture, and a second lens group, arranged from the magnification side to the reduction side. The first lens group includes a first lens with positive refractive power and a second lens with negative refractive power, arranged from the magnification side to the reduction side. The second lens group includes a third lens with negative refractive power, a fourth lens with positive refractive power, a fifth lens with positive refractive power, and a sixth lens with positive refractive power, arranged from the magnification side to the reduction side. The projection lens of the present invention has a simple structure and a small number of lenses, employing only six. While ensuring image quality, it is compact and occupies a small volume, meeting the needs of miniaturization.

[0006] Furthermore, the lenses of lens group 1 and lens group 2 are both spherical lenses, thereby ensuring image quality while reducing costs.

[0007] Furthermore, at least two of the fourth, fifth, and sixth lenses are made of a predetermined material, wherein the predetermined material satisfies Nd ≥ 1.6, where Nd is the refractive index. Using lenses made of high-refractive-index, low-dispersion materials effectively corrects chromatic aberration caused by increased spectral bandwidth, thereby improving imaging quality.

[0008] Furthermore, the preset material satisfies 1.50≤Vd / FLG≤5.00, where Vd is the dispersion coefficient and FLG is the focal length of the lens, thereby effectively correcting dispersion and improving imaging quality.

[0009] Furthermore, the ratio of the aperture of the projection lens to the image height of the light modulator is less than or equal to 5.0, so that the projection lens is small in both total length and aperture, effectively reducing the occupied space and achieving a compact structure with small size and low cost.

[0010] Furthermore, the projection lens satisfies 1.4≤TR≤1.8, 0.25≤EFL / TTL≤0.35, where TR is the projection ratio of the projection lens, EFL is the effective focal length of the projection lens, and TTL is the total optical length. The structure is simple and the imaging quality is good.

[0011] Furthermore, the first lens is a convex lens convex toward the magnification side, and the second lens is a meniscus lens convex toward the magnification side. The first lens can converge light and effectively correct optical distortion of light in a large field of view. The second lens further compensates for the aberrations of the first lens and appropriately diffuses the light, allowing the light passing through the aperture to fill the aperture and ensure a large amount of light transmission.

[0012] Furthermore, the fourth, fifth, and sixth lenses converge and collimate the light so that the divergence angle of the light directed toward the reduction side is less than or equal to 1.7°. While correcting chromatic aberration, the fourth, fifth, and sixth lenses converge and collimate the light, ensuring that the principal rays directed toward the light modulator are substantially parallel, thus ensuring that the projection system conforms to an image-side telecentric design.

[0013] Furthermore, the third lens and the fourth lens are connected to form a doublet lens group, thereby achieving better correction of vertical axis chromatic aberration.

[0014] Furthermore, the lenses of lens group 1 and lens group 2 are both made of glass, which can improve the sensitivity of the lens, enhance thermal stability, and solve the problem of thermal defocusing.

[0015] Furthermore, it also includes a prism and a light modulation device arranged on the reduction side of the lens group 2 from the magnification side to the reduction side.

[0016] A projection lens includes a first lens group, an aperture, and a second lens group, arranged from the magnification side to the reduction side. The first lens group includes a first lens with positive refractive power and a second lens with negative refractive power, arranged from the magnification side to the reduction side. The second lens group includes a third lens with negative refractive power, a fourth lens with positive refractive power, a fifth lens with positive refractive power, and a sixth lens with positive refractive power, arranged from the magnification side to the reduction side. The first lens satisfies at least one of the following conditions: 0.15 < |R1 / R2| < 0.5, where R1 is the radius of curvature of the surface facing the magnification side and R2 is the radius of curvature of the surface facing the reduction side; and 25 < |R2| - |R1| - CT1 < 130, where R1 is the radius of curvature of the surface facing the magnification side and R2 is the radius of curvature of the surface facing the reduction side, and CT1 is the center thickness of the first lens. The arrangement of the first lens achieves the goal of projecting a large image while ensuring the workability of the lens.

[0017] Furthermore, at least two of the fourth lens, the fifth lens and the sixth lens are made of a preset material, and the preset material satisfies Nd≥1.55, where Nd is a refractive index.

[0018] Furthermore, the ratio of the aperture of the projection lens to the image height of the light modulation device is less than or equal to 7.5.

[0019] Furthermore, the projection lens satisfies 1.4≤TR≤2.4, 0.2≤EFL / TTL≤0.5, where TR is a throw ratio of the projection lens, EFL is an effective focal length of the projection lens, and TTL is a total optical length.

[0020] Furthermore, the first lens is a positive lens convex toward the magnification side, the second lens is a meniscus lens convex toward the magnification side, and the sixth lens is convex on both the magnification side and the reduction side.

[0021] Furthermore, the fourth lens, the fifth lens and the sixth lens converge the collimated light so that the divergence angle of the light emitted to the reduction side is less than or equal to 3.0°.

[0022] Furthermore, the lenses of lens group 1 and lens group 2 are both made of glass.

[0023] Furthermore, the third lens and the fourth lens are connected to form a doublet lens group.

[0024] Furthermore, it also includes a prism and a light modulation device arranged on the reduction side of the lens group 2 from the magnification side to the reduction side.

[0025] Compared with the prior art, the present invention has the following advantages:

[0026] The projection lens of the present invention adopts a small number of lenses, has a simple and compact structure, occupies a small space, meets the demand for miniaturization development, has low cost, good mass production, and good imaging quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] FIG1 is a schematic diagram of a projection lens according to the present invention;

[0028] FIG2 is a diagram of field curvature of the projection lens of the present invention;

[0029] FIG3 is a distortion diagram of the projection lens of the present invention;

[0030] FIG. 4 is a schematic diagram of another projection lens according to the present invention.

[0031] In the picture:

[0032] Lens group 1 10 , aperture 7 , lens group 2 20 , first lens 1 , second lens 2 , third lens 3 , fourth lens 4 , fifth lens 5 , sixth lens 6 , prism 8 , protection glass 9 , light modulator 11 . DETAILED DESCRIPTION

[0033] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0034] The projection lens disclosed in the embodiment of the present invention has a small number of lenses, a simple and compact structure, occupies a small space, and has a low cost, thus meeting the demand for miniaturization development.

[0035] As shown in FIG1 , a projection lens mainly includes a lens group 10, an aperture 7, and a lens group 20, which are arranged from the magnification side to the reduction side. The lens group 10 includes two lenses, and the lens group 20 includes four lenses. Specifically, the lens group 10 includes a first lens 1 with positive refractive power and a second lens 2 with negative refractive power, which are arranged from the magnification side to the reduction side. The lens group 20 includes a third lens 3 with negative refractive power, a fourth lens 4 with positive refractive power, a fifth lens 5 with positive refractive power, and a sixth lens 6 with positive refractive power, which are arranged from the magnification side to the reduction side.

[0036] Preferably, the lenses of lens group 1 10 and lens group 2 20 are all spherical lenses, that is, the first lens 1 to the sixth lens 6 are all spherical lenses. The projection lens described in this embodiment uses only spherical lenses, which has a simple structure, relatively low requirements for lens processing performance, easy manufacturing, high mass production, and low production cost. It achieves high-quality, low-distortion imaging without using aspherical lenses.

[0037] More specifically, the first lens 1 is a convex lens convex to the magnifying side, which can converge the light and correct the optical distortion of the light of a large field of view at the same time, which is beneficial to improving the field of view angle of the system and correcting the off-axis aberration and system distortion. The second lens 2 is a meniscus lens convex to the magnifying side, which further compensates for the aberration of the first lens 1 and properly diffuses the light so that the light passing through the aperture 7 can fill the aperture 7, ensuring a large amount of light passing through. The third lens 3 is a concave-flat lens with a negative refractive power, which has a divergent effect on the light so that the subsequent lenses can better correct the aberration of the light. The fourth lens 4, the fifth lens 5 and the sixth lens 6 are all lenses with positive refractive power, which can converge and collimate, so that the main light rays of each field of view on the reduction side of the projection lens are as parallel as possible, and the divergence angle of the light rays directed to the reduction side is less than or equal to 1.7°, so that the optical system conforms to the image-side telecentric design.

[0038] More specifically, at least two of the fourth lens element 4, the fifth lens element 5, and the sixth lens element 6 are made of a predetermined material having a high refractive index and low dispersion. Specifically, the predetermined material satisfies Nd ≥ 1.6, where Nd is the refractive index. Preferably, the predetermined material satisfies 1.50 ≤ Vd / FLG ≤ 5.00, where Vd is the dispersion coefficient and FLG is the focal length of the lens. This effectively corrects chromatic aberration of light and compensates for thermal defocus of the entire optical system, thereby improving imaging quality.

[0039] Furthermore, the ratio of the aperture of the projection lens to the image height of the light modulator is less than or equal to 5.0. The aperture of the projection lens is specifically determined by the largest lens in the projection lens. The image height of the light modulator specifically refers to the distance from the light-emitting point on the light modulator 11 farthest from the origin, with the optical axis as the origin. The light modulator 11 can specifically be a DMD chip, an LCD screen, etc. The projection lens is compact in both overall length and aperture, effectively reducing the space occupied by the projection lens and achieving a compact structure with small size and low cost. The projection lens also includes a prism 8, a protective glass 9, and a light modulator 11, arranged on the reduction side of lens group 2 from the magnification side to the reduction side. The illumination beam is irradiated by the light modulator 11 and modulated by the light modulator 11 to produce an image beam. The image beam then passes through the protective glass 9 and prism 8 in sequence before exiting the projection lens. Ultimately, the image beam is projected onto the screen through the projection lens to form a projection image.

[0040] Furthermore, the aperture 7 adopts an aperture 7 structure with adjustable aperture size, and the aperture size of the aperture 7 is adjusted by driving the blades of the aperture 7 through the driving motor, so as to flexibly adapt to work in different scenes and improve the projection display effect.

[0041] Preferably, the lenses of both lens group 1 and lens group 2 are made of glass, which can improve the sensitivity of the lens, enhance thermal stability, and solve the problem of thermal defocusing. The above-mentioned projection lens is suitable for use in environments such as vehicles, which are often exposed to high temperatures. Therefore, the use of glass for the first lens 1 to the sixth lens 6 can effectively ensure the thermal stability of the entire projection lens, avoid thermal defocusing, ensure accurate and reliable projection, and ensure the stability of the projected image. In addition, the projection lens has a small aperture and a short overall length, so the overall projection lens is small in size, making it suitable for installation environments with limited space.

[0042] The projection lens of the above embodiment satisfies 1.4≤TR≤1.8, 0.25≤EFL / TTL≤0.35, where TR is the projection ratio of the projection lens, EFL is the effective focal length of the projection lens, and TTL is the total optical length, which refers to the total length from the vertex of the magnification side of the first lens 1 to the light modulator 11. The field curvature diagram of the projection lens for different wavelengths is shown in Figure 2, and the distortion diagram of the projection lens for different wavelengths is shown in Figure 3. By optimizing the curvature, material properties, and spacing of each lens included in the optical system, high performance, low distortion, small aberration, and high resolution are achieved. The projection lens has good MTF performance at the spatial limit frequency of 66lp / mm and in the visible light range of 460nm to 625nm, with small distortion, simple structure, and good imaging quality.

[0043] The optical parameters of each component of a projection system are shown in Table 1.

[0044] Table 1

[0045] In an embodiment as shown in Figure 4, the third lens 3 and the fourth lens 4 are connected to form a doublet lens group, which can better correct chromatic aberration and achieve better correction of vertical axis chromatic aberration. Preferably, the third lens 3 and the fourth lens 4 are matched with high and low refractive indices. Specifically, the refractive index of the fourth lens 4 is greater than the refractive index of the third lens 3, and the Abbe number of the fourth lens 4 is less than the Abbe number of the third lens 3. That is, the third lens 3 is made of a material with a low refractive index and a high Abbe number, and the fourth lens 4 is made of a material with a high refractive index and a low Abbe number, which can better correct chromatic aberration and improve the quality of the projection image.

[0046] The optical parameters of each component of a projection system are shown in Table 2.

[0047] Table 2

[0048] As shown in FIG1 , a projection lens includes a lens group 1, an aperture, and a lens group 2, arranged from the magnification side to the reduction side. The lens group 1 includes a first lens with positive refractive power and a second lens with negative refractive power, arranged from the magnification side to the reduction side. The lens group 2 includes a third lens with negative refractive power, a fourth lens with positive refractive power, a fifth lens with positive refractive power, and a sixth lens with positive refractive power, arranged from the magnification side to the reduction side. The first lens satisfies at least one of the following conditions: 0.15 < |R1 / R2| < 0.5, where R1 is the radius of curvature of the surface facing the magnification side and R2 is the radius of curvature of the surface facing the reduction side; and 25 < |R2| - |R1| - CT1 < 130, where R1 is the radius of curvature of the surface facing the magnification side and R2 is the radius of curvature of the surface facing the reduction side, and CT1 is the center thickness of the first lens. The arrangement of the first lens achieves the goal of projecting a large image while ensuring the workability of the lens.

[0049] Furthermore, at least two of the fourth, fifth, and sixth lenses are made of a preset material, wherein the preset material satisfies Nd ≥ 1.55, where Nd is the refractive index. Lenses made of high-refractive-index, low-dispersion materials are used to effectively correct chromatic aberration caused by the increased spectral bandwidth, thereby improving imaging quality. Furthermore, the ratio of the aperture of the projection lens to the image height of the optical modulator is less than or equal to 7.5, enabling the projection lens to be small in both overall length and aperture, effectively reducing the occupied space and achieving a compact structure with small size and low cost. The projection lens satisfies 1.4 ≤ TR ≤ 2.4, 0.2 ≤ EFL / TTL ≤ 0.5, where TR is the projection lens's throw ratio, EFL is the effective focal length of the projection lens, and TTL is the total optical length. The structure is simple and the imaging quality is good. The first lens is a positive lens convex toward the magnification side, the second lens is a meniscus lens convex toward the magnification side, and the sixth lens is convex on both the magnification and reduction sides. The first lens converges light, effectively correcting optical distortion for wide-field light. The second lens further compensates for the aberrations of the first lens and appropriately diffuses light, ensuring that light passing through the aperture fills the entire aperture and ensuring a high light throughput. The fourth, fifth, and sixth lenses converge and collimate light, ensuring that the divergence angle of light directed toward the reduction side is less than or equal to 3.0°. The fourth, fifth, and sixth lenses simultaneously converge and collimate light, ensuring that the principal rays directed toward the light modulator are substantially parallel, ensuring that the projection system conforms to an image-side telecentric design. Both lens groups 1 and 2 are made of glass, ensuring image quality while minimizing the effects of high-temperature environments. This improves lens sensitivity, enhances thermal stability, and addresses thermal defocusing issues. Also included are prisms and a light modulator positioned on the reduction side of lens group 2, from the magnification side to the reduction side. Specifically, at least two of the fourth, fifth, and sixth lenses are made of a preset material, wherein the preset material satisfies Nd of 1.55 or 1.6, where Nd is the refractive index; the ratio of the aperture of the projection lens to the image height of the light modulator is 3, 5, or 7.5, thereby achieving a small size in terms of both total length and aperture, effectively reducing the occupied space and realizing a compact structure with small size and low cost. The projection lens satisfies TR of 1.4, 2, or 2.3, and EFL / TTL of 0.2, 0.3, or 0.5, where TR is the projection lens's throw ratio, EFL is the projection lens's effective focal length, and TTL is the total optical length; the fourth, fifth, and sixth lenses converge collimated light so that the divergence angle of light directed toward the reduction side is 1.0°, 2.0°, or 3.0°.

[0050] The optical parameters of each component of a projection system are shown in Table 3.

[0051] Table 3

[0052] In one embodiment shown in FIG4 , based on the embodiment of FIG1 , the third lens and the fourth lens are connected to form a doublet lens group, and the doublet lens group has a positive refractive power. Specifically, at least two of the fourth, fifth, and sixth lenses are made of a predetermined material, wherein the predetermined material satisfies Nd of 1.55 or 1.6, where Nd is the refractive index. The ratio of the aperture of the projection lens to the image height of the light modulator is 3, 5, or 7.5. This enables the projection lens to be small in both overall length and aperture, effectively reducing the occupied space and achieving a compact structure with small size and low cost. The projection lens satisfies TR of 1.4, 2, or 2.4, and EFL / TTL of 0.2, 0.3, or 0.5, where TR is the projection lens's throw ratio, EFL is the projection lens's effective focal length, and TTL is the total optical length. The fourth, fifth, and sixth lenses converge collimated light so that the divergence angle of light directed toward the reduction side is 1.0°, 2.0°, or 3.0°.

[0053] The optical parameters of each component of a projection system are shown in Table 4.

[0054] The above are merely preferred embodiments of the present invention. It should be noted that the above preferred embodiments should not be construed as limiting the present invention, and the scope of protection of the present invention should be determined by the scope defined in the claims. Persons skilled in the art will appreciate that improvements and modifications may be made without departing from the spirit and scope of the present invention, and such improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A projection lens, characterized in that: The lens comprises a first lens group arranged from the magnification side to the reduction side, an aperture, and a second lens group. The first lens group comprises a first lens with positive refractive power and a second lens with negative refractive power, arranged from the magnification side to the reduction side. The second lens group comprises a third lens with negative refractive power, a fourth lens with positive refractive power, a fifth lens with positive refractive power, and a sixth lens with positive refractive power, arranged from the magnification side to the reduction side.

2. The projection lens according to claim 1, wherein: The lenses of lens group 1 and lens group 2 are both spherical lenses.

3. The projection lens according to claim 1, wherein: At least two of the fourth lens, the fifth lens, and the sixth lens are made of a preset material, and the preset material satisfies Nd≥1.6, where Nd is a refractive index.

4. The projection lens according to claim 3, wherein: The preset material satisfies 1.50≤Vd / FLG≤5.00, where Vd is the dispersion coefficient and FLG is the focal length of the lens.

5. The projection lens according to claim 1, wherein: The ratio of the aperture of the projection lens to the image height of the light modulation device is less than or equal to 5.

0.

6. The projection lens according to claim 1, wherein: The projection lens satisfies 1.4≤TR≤1.8, 0.25≤EFL / TTL≤0.35, where TR is the throw ratio of the projection lens, EFL is the effective focal length of the projection lens, and TTL is the total optical length.

7. The projection lens according to claim 1, wherein: The first lens is a convex lens convex toward the magnification side, and the second lens is a meniscus lens convex toward the magnification side.

8. The projection lens according to claim 1, wherein: The fourth lens, the fifth lens and the sixth lens converge the collimated light so that the divergence angle of the light emitted to the reduction side is less than or equal to 1.7°.

9. The projection lens according to claim 1, wherein: The third lens and the fourth lens are connected to form a doublet lens group.

10. The projection lens according to claim 1, wherein: It also includes a prism and a light modulation device arranged on the reduction side of the lens group 2 from the magnification side to the reduction side.

11. A projection lens, characterized in that: The lens comprises a lens group 1, an aperture, and a lens group 2 arranged from the magnification side to the reduction side, wherein the lens group 1 comprises a first lens having positive refractive power and a second lens having negative refractive power, and the lens group 2 comprises a third lens having negative refractive power, a fourth lens having positive refractive power, a fifth lens having positive refractive power, and a sixth lens having positive refractive power, and the first lens satisfies at least one of the following conditions: 0.15<|R1 / R2|<0.5, Where R1 is the radius of curvature of the surface facing the magnification side, and R2 is the radius of curvature of the surface facing the reduction side; 25<|R2|-|R1|-CT1<130, Where R1 is the curvature radius of the surface facing the magnification side, R2 is the curvature radius of the surface facing the reduction side, and CT1 is the center thickness of the first lens.

12. The projection lens according to claim 1, wherein: At least two of the fourth lens, the fifth lens, and the sixth lens are made of a preset material, and the preset material satisfies Nd≥1.55, where Nd is a refractive index.

13. The projection lens according to claim 1, wherein: The ratio of the aperture of the projection lens to the image height of the light modulation device is less than or equal to 7.

5.

14. The projection lens according to claim 1, wherein: The projection lens satisfies 1.4≤TR≤2.4, 0.2≤EFL / TTL≤0.5, where TR is the throw ratio of the projection lens, EFL is the effective focal length of the projection lens, and TTL is the total optical length.

15. The projection lens according to claim 1, wherein: The first lens is a positive lens convex toward the magnification side, the second lens is a meniscus lens convex toward the magnification side, and the sixth lens is convex on both the magnification side and the reduction side.

16. The projection lens according to claim 1, wherein: The fourth lens, the fifth lens, and the sixth lens converge the collimated light so that the divergence angle of the light emitted toward the reduction side is less than or equal to 3.0°.

17. The projection lens according to claim 1, wherein: The lenses of lens group 1 and lens group 2 are both made of glass.

18. The projection lens according to claim 1, wherein: The third lens and the fourth lens are connected to form a doublet lens group.

19. The projection lens according to claim 1, wherein: It also includes a prism and a light modulation device arranged on the reduction side of the lens group 2 from the magnification side to the reduction side.

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