Projection lens and projection device

Abstract

Embodiments of the present application provide a projection lens and a projection device; wherein the projection lens comprises, in sequence from an imaging side to an image source side along an optical axis, a first lens group, a diaphragm and a second lens group; the first lens group is composed of a first lens, a second lens and a third lens, the first lens is a plastic aspheric lens, and the second lens and the third lens are glass spherical lenses; the second lens group is composed of a fourth lens, a fifth lens and a sixth lens, the fourth lens and the fifth lens are glass spherical lenses, and the sixth lens is a glass aspheric lens; the diaphragm is located between the third lens and the fourth lens; the projection lens satisfies 2 < T / D < 3.5; wherein T is the total optical length of the projection lens, and D is the largest effective clear aperture in the first lens group.

Description

TECHNICAL FIELD

[0001] Embodiments of the present application relate to the technical field of projection display, and more particularly, to a projection lens and a projection device. BACKGROUND

[0002] With the rapid development of the projector market, laser projectors are gradually favored by consumers due to their bright colors, high color gamut, compact size and other advantages. However, laser projectors also have some technical problems, of which the most prominent is the color difference problem. Although the three-color laser light source brings rich color performance, it also brings a large color difference, which has a negative impact on the user experience of the laser projector. As a core component of the laser projector, the projection lens is currently difficult to design, and the design indicators will directly determine the subjective performance of the laser projector, such as sharpness, contrast and picture uniformity. SUMMARY

[0003] The purpose of the present application is to provide a new technical solution for a projection lens and a projection device.

[0004] In a first aspect, the present application provides a projection lens. The projection lens comprises, in order from the imaging side to the image source side along the optical axis, a first lens group, a diaphragm and a second lens group;

[0005] The first lens group is composed of a first lens, a second lens and a third lens, the first lens is a plastic aspherical lens, and the second lens and the third lens are glass spherical lenses;

[0006] The second lens group is composed of a fourth lens, a fifth lens and a sixth lens, the fourth lens and the fifth lens are glass spherical lenses, and the sixth lens is a glass aspherical lens;

[0007] The diaphragm is located between the third lens and the fourth lens;

[0008] The projection lens satisfies 2

[0009] Optionally, the effective light aperture of the first lens is D, and the projection lens satisfies 2

[0010] Optionally, the focal power of the first lens is negative, the focal power of the second lens is negative, and the focal power of the third lens is positive;

[0011] The focal power of the fourth lens is positive, the focal power of the fifth lens is negative, and the focal power of the sixth lens is positive.

[0012] Optionally, the first lens is a convex-concave lens, the second lens is a double-concave lens, and the third lens is a double-convex lens.

[0013] The fourth lens and the fifth lens are convex-concave lenses, and the sixth lens is a double-convex lens.

[0014] Optionally, the first lens group and / or the second lens group are movable along the optical axis.

[0015] Optionally, the second lens and the third lens are mutually cemented to form a first double-cemented lens group.

[0016] The fourth lens and the fifth lens are mutually cemented to form a second double-cemented lens group.

[0017] Optionally, the refractive index of the second lens is Nd2, the refractive index of the third lens is Nd3, and Nd2

[0018] The Abbe number of the second lens is Vd2, the Abbe number of the third lens is Vd3, and Vd2

[0019] Optionally, the refractive index of the fourth lens is Nd4, the refractive index of the fifth lens is Nd5, and Nd4

[0020] The Abbe number of the fourth lens is Vd4, the Abbe number of the fifth lens is Vd5, and Vd4

[0021] Optionally, the first lens has a negative focal power and has at least one aspherical surface.

[0022] The sixth lens has a positive focal power and has at least one aspherical surface.

[0023] Optionally, the effective focal length of the first lens group is F1, the total effective focal length of the projection lens is F, and 1.5

[0024] The effective focal length of the second lens group is F2, the total effective focal length of the projection lens is F, and 1.5

[0025] Optionally, the projection lens further comprises a light source, a color combining prism, and a galvanometer.

[0026] The galvanometer is arranged adjacent to the sixth lens, and the color combining prism is located between the light source and the galvanometer.

[0027] In a second aspect, the present application provides a projection device. The projection device comprises:

[0028] a housing; and

[0029] The projection lens according to the first aspect.

[0030] The application has the following beneficial effects:

[0031] The projection lens provided by the application can correct chromatic aberration, and can be applied to a projection device, especially a laser projection device. The projection lens comprises, in sequence along an optical axis from an imaging side to an image source side, a first lens group, a diaphragm, and a second lens group. The first lens group is composed of one plastic aspherical lens (i.e., a first lens) and two glass spherical lenses (i.e., a second lens and a third lens). The second lens group is composed of one glass spherical lens (i.e., a fourth lens) and two glass aspherical lenses (i.e., a fifth lens and a sixth lens). The optical total length of the projection lens and the largest effective aperture of the first lens group are also constrained in the application. Through the selected lens combination, the projection lens of the application can achieve better aberration correction and improve the imaging quality. The use of aspherical lenses is particularly helpful to reduce spherical aberration, distortion, and other optical problems, thereby providing clearer images. The projection lens satisfies the proportional relationship of 2 < T / D < 3.5, which means that while maintaining a large effective aperture D, the optical total length T of the projection lens is effectively controlled. This compact design makes the projection lens more easily integrated into various projection devices, and also helps to reduce the overall size and weight of the projection device.

[0032] Other features of the present application and its advantages will become apparent from the following detailed description of exemplary embodiments thereof, when considered in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS

[0033] The accompanying drawings incorporated in and forming a part of the specification, illustrate embodiments of the present application and, together with the description, serve to explain the principles of the present application.

[0034] Figure 1 A structural schematic diagram of the projection lens provided by the application;

[0035] Figure 2 A light path diagram of the projection lens provided by the application;

[0036] Figure 3 A point array diagram of the projection lens provided by the application;

[0037] Figure 4 A spatial frequency modulation transfer function diagram of the projection lens provided by the application;

[0038] Figure 5 A defocus curve diagram of the projection lens provided by the application;

[0039] Figure 6Modulation transfer function versus field of view of the projection lens provided by the embodiment of the present application;

[0040] Figure 7 Field curvature versus distortion of the projection lens provided by the embodiment of the present application;

[0041] Figure 8 Axial chromatic aberration of the projection lens provided by the embodiment of the present application;

[0042] Figure 9 Relative illumination of the projection lens provided by the embodiment of the present application;

[0043] Figure 10 Ray aberration of the projection lens provided by the embodiment of the present application.

[0044] BRIEF DESCRIPTION OF DRAWINGS

[0045] 1, first lens; 2, second lens; 3, third lens; 4, fourth lens; 5, fifth lens; 6, sixth lens; 7, diaphragm; 8, galvanometer; 9, color combining prism; 10, light source; 11, protective glass. DETAILED DESCRIPTION

[0046] Various exemplary embodiments of the present application will now be described in detail with reference to the accompanying drawings. It should be noted that the relative arrangement of the components and steps set forth in the embodiments, numerical expressions, and numerical values, unless specifically stated otherwise, do not limit the scope of the present application.

[0047] The following description of at least one exemplary embodiment is merely exemplary in nature and is in no way intended to limit the scope of the application, its application, or uses.

[0048] Techniques and equipment known to those of ordinary skill in the relevant art can not be discussed in detail, but should be considered part of the specification where appropriate.

[0049] In all of the examples shown and discussed herein, any specific values should be interpreted as merely exemplary, and not as a limitation. Thus, other examples of the exemplary embodiments can have different values.

[0050] It should be noted that like numbers and letters refer to like items throughout the drawings, and once an item is defined in one drawing, it is not necessary to discuss it further in subsequent drawings.

[0051] The projection lens and the projection device provided by the embodiments of the present application will be described in detail below with reference to the accompanying drawings.

[0052] According to one embodiment of the present application, a projection lens is provided, referring to Figure 1 and Figure 2The projection lens comprises a first lens group, a diaphragm 7 and a second lens group along an optical axis from an imaging side to an image source side; wherein the first lens group is composed of a first lens 1, a second lens 2 and a third lens 3, the first lens 1 is a plastic aspheric lens, and the second lens 2 and the third lens 3 are glass spherical lenses; the second lens group is composed of a fourth lens 4, a fifth lens 5 and a sixth lens 6, the fourth lens 4 is a glass spherical lens, and the sixth lens 6 is a glass aspheric lens; the diaphragm 7 is located between the third lens 3 and the fourth lens 4; the projection lens satisfies 2

[0053] The projection lens provided by the embodiment of the present application can be a laser projection lens, which effectively overcomes the problem of large chromatic aberration existing in the prior art.

[0054] It should be noted that the projection lens provided by the embodiment of the present application includes but is not limited to a laser projection lens, and can also be a projection lens of other light sources.

[0055] The projection lens provided by the embodiment of the present application is described below with reference to Figure 1 The projection lens is arranged with two lens groups (i.e. a first lens group and a second lens group) from the imaging side to the image source side along the optical axis, and the two lens groups are separated by a diaphragm 7.

[0056] Specifically, the first lens group is composed of three lenses, i.e. a first lens 1 (a plastic aspheric lens), a second lens 2 (a glass spherical lens) and a third lens 3 (a glass spherical lens). The first lens group is located at the front end of the entire projection lens, and this lens combination design can provide a good initial aberration correction basis for the laser projection lens of the present application.

[0057] The second lens group is also composed of three lenses, i.e. a fourth lens 4 (a glass spherical lens), a fifth lens 5 (a glass spherical lens) and a sixth lens 6 (a glass aspheric lens), which further refines the aberration correction, especially the chromatic aberration correction, thereby realizing high imaging quality.

[0058] The projection lens of the embodiment of the present application further comprises a diaphragm 7. Referring to Figure 1 The diaphragm 7 is located between the third lens 3 and the fourth lens 4, and plays a key role in controlling the light flux and optimizing the image quality.

[0059] The first lens 1 to the sixth lens 6 in the present application are described in detail below.

[0060] The first lens 1 is a plastic aspheric lens. The selection of plastic material takes into account the light weight and cost effectiveness. The aspheric surface design enables more precise control of the light path, which helps to reduce aberrations, especially spherical aberration. The first lens 1 can effectively correct the initial chromatic aberration.

[0061] The second lens 2 is a glass spherical lens, which is arranged adjacent to the first lens 1. The second lens 2 cooperates with the first lens 1 to further correct aberrations. In addition, the use of glass material improves the light transmittance and thermal stability of the lens, etc.

[0062] The third lens 3 is a glass spherical lens, which is the lens closest to the diaphragm 7 in the first lens group. The third lens 3 can continue to optimize the correction of aberrations, especially field curvature and distortion. In addition, similar to the second lens 2, the third lens 3 also corrects chromatic aberration by selecting a specific glass material, and cooperates with the first lens 1 and the second lens 2.

[0063] The fourth lens 4 is a glass spherical lens, which is the first lens of the second lens group and is also closest to the diaphragm 7. The fourth lens cooperates with the subsequent lenses to further correct aberrations. The fourth lens 4 corrects chromatic aberration by selecting a glass material, and cooperates with other lenses in the lens group to achieve overall chromatic aberration correction.

[0064] The fifth lens 5 is a glass spherical lens, which cooperates with the fourth lens 4 to continue to optimize the correction of aberrations, especially chromatic aberration and high-order aberration. The addition of the fifth lens 5 makes the entire second lens group have stronger correction ability for aberrations.

[0065] The sixth lens 6 is a glass aspheric lens. The aspheric design enables more precise control of the light path, which helps to reduce aberrations and chromatic aberration. As a key chromatic aberration correction element, the sixth lens 6 effectively suppresses chromatic aberration to a very low level through aspheric design and glass material selection, ensuring high definition and color accuracy of the imaging quality.

[0066] The projection lens provided by the embodiment of the present application satisfies the condition: 2 < T / D < 3.5; wherein, T is the total optical length of the projection lens, and D is the largest effective aperture in the first lens group.

[0067] T is the total optical length of the projection lens of the present application, which refers to the straight-line distance between the first optical surface and the last optical surface of the projection lens, which reflects the overall size and length of the entire projection lens.

[0068] For each lens, the effective aperture is the largest diameter that can allow light to pass through. This diameter determines the amount of light that the lens can collect, and in turn affects the imaging quality and brightness of the entire projection lens.

[0069] In the projection lens of the present application, the largest effective aperture D of the first lens group refers to the largest effective aperture within the first lens group. Since the diameters of different lenses can be different, there is a largest effective aperture. This largest effective aperture determines the upper limit of the light flux of the first lens group and even the entire lens, and is one of the important factors affecting the performance of the entire projection lens. When designing the projection lens, it is necessary to ensure that this aperture is large enough to collect sufficient light, while also considering factors such as the overall size and weight of the projection lens.

[0070] The first lens group, as the first group of lenses near the imaging side, plays a crucial role in aberration correction of the projection lens. The projection lens satisfies the ratio relationship of 2 < T / D < 3.5, which means that while maintaining a large effective aperture D, the total optical length T of the entire projection lens is effectively controlled. This compact design makes the lens easier to integrate into various projection devices, while also helping to reduce the overall size and weight of the device.

[0071] The projection lens of the present application, the first lens 1 to the sixth lens 6 are designed and selected by careful design and material selection, which constitutes a high-efficiency, compact and excellent color aberration correction projection lens.

[0072] The projection lens provided by the embodiments of the present application has a significant color aberration correction capability. Specifically, by using plastic aspherical lenses (first lens 1) and glass aspherical lenses (sixth lens 6), and combining with careful selection of lens materials (such as strong light-resistant resin materials and low refractive index glass), the projection lens effectively suppresses the common color aberration problem of laser projectors.

[0073] The embodiment of the present application provides a projection lens capable of achromatism, which can be applied to a projection device, in particular, a laser projection device. The projection lens comprises a first lens group, a diaphragm and a second lens group in sequence along an optical axis from an imaging side to an image source side. The first lens group is composed of one plastic aspherical lens (i.e. the first lens 1) and two glass spherical lenses (i.e. the second lens 2 and the third lens 3). The second lens group is composed of one glass spherical lens (i.e. the fourth lens 4) and two glass aspherical lenses (i.e. the fifth lens 5 and the sixth lens 6). In the present application, the total optical length of the projection lens and the largest effective light aperture in the first lens group are also constrained. The projection lens can achieve better aberration correction and improve the imaging quality by selecting the lens combination. The use of aspherical lenses is particularly helpful to reduce spherical aberration, distortion and other optical problems, thereby providing clearer and more accurate images. The projection lens satisfies the proportional relationship of 2

[0074] In addition, some lenses in the projection lens are made of glass, which has good thermal stability and chemical stability and can maintain stable performance in a wide temperature range.

[0075] In some examples of the present application, the effective light aperture of the first lens 1 is D, and the projection lens satisfies 2

[0076] Referring to Figure 1 The first lens 1 is the lens with the largest light aperture in the entire projection lens, that is, the lens with the largest light aperture in the first lens group. The first lens 1 satisfies 2

[0077] The first lens 1 as the front end element of the projection lens, its effective light aperture D directly determines the amount of light that can be collected by the projection lens. A larger D value means that more light can enter the projection lens, which is crucial for improving the brightness and contrast of the projection image. At the same time, the compact T / D ratio ensures efficient transmission and focusing of light inside the projection lens, reducing light loss and scattering. In addition, in this example of the present application, the reasonable T / D ratio can effectively correct aberration, thereby improving the clarity and accuracy of the image.

[0078] In some examples of the present application, the first lens 1 has a negative optical power, the second lens 2 has a negative optical power, the third lens 3 has a positive optical power, the fourth lens 4 has a positive optical power, the fifth lens 5 has a negative optical power, and the sixth lens 6 has a positive optical power.

[0079] The projection lens provided by the embodiments of the present application has the optical power configuration of negative, negative, positive, positive, negative, and positive from the imaging side to the image source side, which is a carefully designed optical system layout and aims to achieve high optical performance, especially in the correction of chromatic aberration and aberration.

[0080] Through the special configuration of the optical power and the selection of the lens material (glass or plastic), the projection lens of the present application can effectively correct chromatic aberration, especially suppress the sagittal chromatic aberration, and ensure the high color accuracy of the imaging.

[0081] That is, in the present application, the optical power configuration (negative, negative, positive, positive, negative, and positive) of the first lens 1 to the sixth lens 6 is a high-efficiency and compact optical system design, which can achieve excellent chromatic aberration and aberration correction effect and ensure the high imaging quality of the laser projector.

[0082] In some examples of the present application, referring to Figure 1 , the first lens 1 is a convex-concave lens, the second lens 2 is a double-concave lens, and the third lens 3 is a double-convex lens; the fourth lens 4 and the fifth lens 5 are concave-convex lenses, and the sixth lens 6 is a double-convex lens.

[0083] In this example of the present application, the surface type configuration of the first lens 1 to the sixth lens 6 is convex-concave, double-concave, double-convex, concave-convex, concave-convex, and double-convex, respectively, which is an important part of the optical design of the projection lens of the present application and has a direct impact on the optical performance of the entire projection lens.

[0084] Referring to Figure 1 , the first lens 1 in the first lens group is taken as an example for description.

[0085] The surface of the first lens 1 away from the diaphragm 7 is the front surface, and the surface of the first lens 1 close to the diaphragm 7 is the back surface. In this example of the present application, the front surface of the first lens 1 is a convex surface, and the back surface of the first lens 1 is a concave surface. Based on this, the front and back surfaces of the second lens 2 are both concave surfaces. The front and back surfaces of the third lens 3 are both convex surfaces.

[0086] Please continue to refer to Figure 1 , the fourth lens 4 in the second lens group is taken as an example for description.

[0087] The surface of the fourth lens 4 close to the diaphragm 7 is the front surface, and the surface far from the diaphragm 7 is the back surface. In this example of the present application, the front surface of the fourth lens 4 is concave, and the back surface is convex. Based on this, the front surface of the fifth lens 5 is concave, and the back surface is convex. The front and back surfaces of the sixth lens 6 are both convex.

[0088] The first lens 1 of the present application is a convex-concave lens. This convex-concave lens has a surface type of one convex and one concave. This design can correct aberrations, including chromatic aberration, to some extent. The convex-concave lens can refract light of different wavelengths to different degrees through its special optical surface type, thereby reducing chromatic aberration to some extent.

[0089] The second lens 2 of the present application is a double-concave lens. This double-concave lens has a surface type of both surfaces being concave. In the lens combination provided in the present application, the second lens 2 is designed as a double-concave lens, which can be used in cooperation with other lenses to change the propagation path and convergence of light, thereby affecting the performance of chromatic aberration. That is, the double-concave lens introduced in the present application helps to balance the chromatic aberration of the entire projection lens.

[0090] The third lens 3 of the present application is a double-convex lens. This double-convex lens has a surface type of both surfaces being convex, and it belongs to converging lenses. In the lens combination provided in the present application (the combination of six lenses), the double-convex lens can be used in cooperation with other lenses to achieve overall chromatic aberration correction.

[0091] The fourth lens 4 and the fifth lens 5 of the present application are both convex-concave lenses. These two lenses have a surface type similar to that of the first lens 1, which has one convex and one concave surface, and also has a certain aberration correction ability. In the lens combination provided in the present application (i.e., the combination of six lenses), the cooperation of multiple convex-concave lenses can significantly improve the effect of chromatic aberration suppression.

[0092] The sixth lens 6 of the present application is a double-convex lens. Like the third lens 3, the double-convex lens has a shape of both surfaces being convex, and it is a converging lens. Similarly, in the lens combination provided in the present application (the combination of six lenses), the last double-convex lens arranged can work together with other lenses to achieve overall chromatic aberration correction.

[0093] In this example of the present application, multiple types of lenses are used, including convex-concave lenses, double-concave lenses, double-convex lenses, and convex-concave lenses. This diversified design can provide more degrees of freedom to correct chromatic aberration and other aberrations.

[0094] Through precise design and calculation, the six lenses in the present application can cooperate with each other to effectively suppress chromatic aberration. For example, the convex-concave lens and the concave-convex lens can be used for preliminary correction of chromatic aberration, and the double-concave lens can help balance the chromatic aberration of the entire lens combination. Finally, the double-convex lens can work together with other lenses to achieve overall chromatic aberration correction.

[0095] In summary, the lens combination in this example of the present application has certain advantages in chromatic aberration suppression. Through precise design and calculation, these lenses can cooperate with each other to effectively correct chromatic aberration, thereby improving the imaging quality of the projection lens.

[0096] In some examples of the present application, the first lens group and / or the second lens group can move along the optical axis.

[0097] That is, the projection lens provided by the embodiments of the present application, wherein the first lens group and the second lens group are designed to be movable. Specifically, at least one of the first lens group and the second lens group can move along the optical axis.

[0098] When one of the first lens group and the second lens group moves relative to the other along the optical axis, the distance between the two lens groups can be changed.

[0099] When the first lens group and the second lens group move simultaneously, the distance between the two lens groups and the color combining prism behind them can be changed.

[0100] Through the movement of the first lens group and / or the second lens group along the optical axis, the focal length of the projection lens can be changed, thereby realizing the zoom function. In other words, by changing the relative position between the two lens groups, the focal length of the projection lens can be adjusted, thereby changing the size of the projection image. This design allows the projection lens to be focused within a certain focal length range to adapt to different projection distances and screen sizes.

[0101] The change of the focal length will directly affect the size of the projection image.

[0102] For example, the focal length becomes longer, and the projection image becomes smaller.

[0103] For another example, the focal length becomes shorter, and the projection image becomes larger.

[0104] The movement of the lens group in the present application can be manually controlled or electrically controlled.

[0105] Through the design of moving the lens group along the optical axis, the projection lens can be more flexible to adapt to different application scenarios and needs. For example, in the case of needing to adjust the projection size and focal length, this design can greatly improve the practicality of the projection lens.

[0106] In one example of the present application, when the first lens group and the second lens group move together, the moving range is -0.011mm to 0.013mm, and the corresponding projection size change is 40 inches to 100 inches. It should be noted that the first lens group and the second lens group can move together towards the direction close to the color combining prism 9, or move away from the color combining prism 9.

[0107] In some examples of the present application, referring to Figure 1 In the first lens group, the second lens 2 and the third lens 3 are mutually cemented to form a first double cemented lens group; in the second lens group, the fourth lens 4 and the fifth lens 5 are mutually cemented to form a second double cemented lens group.

[0108] In the projection lens provided by the present application, the first double cemented lens group and the second double cemented lens group are respectively arranged on the two sides of the diaphragm 7, which can optimize the off-axis chromatic aberration. That is, the two sides of the diaphragm 7 are both cemented lens groups.

[0109] The design of the double cemented lens group helps to achieve more consistent color performance on the entire projection image. The design of the double cemented lens group also helps to reduce aberration and improve the imaging quality of the projection lens.

[0110] The design of the double cemented lens group can also optimize the space utilization inside the projection lens. By tightly cementing two lenses together, the space inside the projection lens can be more effectively utilized, making the projection lens more compact and miniaturized. In addition, the design of the double cemented lens group can simplify the assembly process of the projection lens.

[0111] The design of the double cemented lens group can improve the stability of the entire projection lens. Since the lenses are tightly bonded together, they are less susceptible to external environmental influences and disturbances. This helps to ensure that the lens maintains stable imaging quality and performance under different working conditions.

[0112] In this example of the present application, the first double cemented lens group and the second double cemented lens group are respectively located on the two sides of the diaphragm 7, which helps to more evenly correct chromatic aberration within the entire field of view.

[0113] In some examples of the present application, the refractive index of the second lens 2 is Nd2, the refractive index of the third lens 3 is Nd3, and Nd2 < Nd3; the Abbe number of the second lens 2 is Vd2, the Abbe number of the third lens 3 is Vd3, and Vd2 > Vd3.

[0114] In some examples of the present application, the fourth lens 4 has a refractive index Nd4, the fifth lens 5 has a refractive index Nd5, and Nd4 < Nd5; the fourth lens 4 has an Abbe number Vd4, the fifth lens 5 has an Abbe number Vd5, and Vd4 > Vd5.

[0115] The projection lens provided by the embodiments of the present application is provided with a double cemented lens group on each side of the diaphragm 7, i.e. the first double cemented lens group and the second double cemented lens group in the above examples. The design of such double cemented lens groups is very effective in chromatic aberration correction. By selecting appropriate lens materials, especially lens combinations with high Abbe number (low dispersion) and low refractive index (high dispersion), the sagittal chromatic aberration can be significantly reduced.

[0116] In the examples of the present application, the first double cemented lens group and the second double cemented lens group are respectively composed of lenses with different refractive indices and Abbe numbers, which can accurately correct the chromatic aberration caused by light rays of different wavelengths, and improve the color reproduction and clarity of the projected image.

[0117] Specifically, for the first double cemented lens group, it is composed of the second lens 2 and the third lens 3. The refractive index relationship involved in the first double cemented lens group is that the refractive index Nd2 of the second lens 2 is less than the refractive index Nd3 of the third lens 3, and the Abbe number relationship is that the Abbe number Vd2 of the second lens 2 is greater than the Abbe number Vd3 of the third lens 3. Such a combination of refractive index and Abbe number helps to correct chromatic aberration. Since the third lens 3 has a higher refractive index, it can bend the light rays in a shorter path, while the second lens 2 has a lower refractive index and a higher Abbe number (i.e. lower dispersion), which can compensate for the dispersion introduced by the third lens 3 to some extent. Such a combination helps to reduce the chromatic aberration caused by the different speeds of light rays of different wavelengths passing through the lens, thereby improving the color reproduction and clarity of the projected image.

[0118] By carefully designing the refractive index and Abbe number of the second lens 2 and the third lens 3, the present application can also optimize other aberrations such as spherical aberration and coma, thereby improving the imaging quality of the projected image.

[0119] Specifically, for the second double cemented lens group, it is composed of the fourth lens 4 and the fifth lens 5. The refractive index relationship involved therein is that the refractive index Nd4 of the fourth lens 4 is less than the refractive index Nd5 of the fifth lens 5, and the Abbe number relationship is that the Abbe number Vd4 of the fourth lens 4 is greater than the Abbe number Vd5 of the fifth lens 5.

[0120] Similar to the combination of the second lens 2 and the third lens 3, the combination of the fourth lens 4 and the fifth lens 5 is also designed to correct chromatic aberration. The fifth lens has a higher refractive index for effectively bending light rays, while the fourth lens has a lower refractive index and a higher Abbe number for compensating for chromatic dispersion. This combination helps to achieve more comprehensive chromatic aberration correction in the entire projection lens.

[0121] In addition, by optimizing the refractive index and Abbe number of the second lens 2 to the fifth lens 5, other optical performances of the projection lens can also be improved, such as contrast, resolution, and distortion control, etc. The improvement of these performances works together to make the projection picture clearer, finer and more realistic.

[0122] In this application, by selecting lens materials with different refractive indices and Abbe numbers for cementing, the degradation of image quality caused by monochromatic aberration and chromatic aberration can be effectively compensated.

[0123] In some examples of this application, the first lens 1 has at least one aspheric surface; the sixth lens 6 has at least one aspheric surface.

[0124] Since the first lens 1 and the sixth lens 6 are located at both ends of the entire lens combination respectively, their aspheric surfaces can effectively compensate for chromatic aberration caused by lens materials, thereby improving the color reproduction capability of the projection lens.

[0125] The design of aspheric surfaces enables the projection lens of this application to better correct various aberrations, including spherical aberration, coma, astigmatism, etc., thereby improving the clarity and contrast of the image.

[0126] By designing the power and aspheric surface of the first lens 1 and the sixth lens 6, the imaging performance of the entire projection lens can be optimized to achieve a high-definition, high-contrast projection picture.

[0127] In addition, the use of aspheric lenses can reduce the number of lenses required, thereby simplifying the structure of the projection lens, which helps to reduce the size of the lens and reduce manufacturing costs.

[0128] In this example of this application, the aspheric surface design of the first lens 1 and the sixth lens 6 and their power configuration are one of the key factors to achieve high imaging quality. By designing these parameters, the projection lens can effectively correct chromatic aberration and aberration, improve the clarity and contrast of the image. At the same time, this design also helps to reduce the size of the projection lens and reduce manufacturing costs.

[0129] In this application, all aspheric surfaces are even aspheric surfaces, and the sag of the surface type is given by the following formula:

[0130]

[0131] z is the surface sag, c is the reciprocal of the curvature radius, k is the conic constant, and a1-a8 are even-order aspheric coefficients.

[0132] In some examples of the present application, the effective focal length of the first lens group is F1, and the total effective focal length of the projection lens is F, and 1.5≤|F1 / F|≤1.85; the effective focal length of the second lens group is F2, and the total effective focal length of the projection lens is F, and 1.5≤|F2 / F|≤1.85.

[0133] In this example of the present application, the proportional relationship between the effective focal length of the first lens group (consisting of one plastic aspheric lens, two glass spherical lenses) and the total effective focal length of the entire projection lens, and the proportional relationship between the effective focal length of the second lens group (consisting of two glass spherical lenses and one glass aspheric lens) and the total effective focal length of the entire projection lens are mentioned. Specifically, both of these proportional relationships are limited to the range of 1.5 to 1.85, which can bring the following technical effects.

[0134] By setting the ratio of the effective focal length (F1, F2) of the first lens group and the second lens group to the total effective focal length F of the entire projection lens within the range of 1.5 to 1.85, which is neither too loose nor too strict, a reasonable match between the focal length of each lens group and the total focal length F of the entire lens is ensured. In this way, it can be ensured that the light rays can be well focused and aberration-corrected when passing through each lens group. This helps to reduce various aberrations such as chromatic aberration, spherical aberration, coma, etc., thereby improving the clarity, contrast, and color reproduction of the projected image.

[0135] Specifically, when |F1 / F| or |F2 / F| is greater than the upper limit value 1.85, it means that the first lens group or the second lens group is relatively large with respect to the total focal length F of the entire projection lens. Since a longer focal length lens group may require larger lens size and more complex structure to maintain the required imaging performance, it will increase the overall volume and weight of the designed lens. Therefore, the relationship between imaging performance and volume control needs to be balanced during design. In addition, a longer focal length lens group requires higher precision in lens processing and assembly, which may increase manufacturing difficulty and cost.

[0136] When |F1 / F| or |F2 / F| is less than the lower limit value 1.5, it means that the first lens group or the second lens group is relatively short with respect to the focal length of the entire lens. This will reduce the control ability of the lens group on the light rays, thereby affecting the imaging quality of the lens.

[0137] In some examples of the present application, see Figure 2 and Figure 2The projection lens further comprises a light source 10, a color combining prism 9 and a galvanometer 8; wherein the galvanometer 8 is arranged adjacent to the sixth lens 6, and the color combining prism 9 is located between the light source 10 and the galvanometer 8.

[0138] The light source 10 is a core light-emitting component of the projection lens of the present application, which is responsible for providing projection light. In this example of the present application, the light source 10 is placed behind the color combining prism 9, serving as the starting point of the entire projection light path.

[0139] In the present application, the light source 10 is, for example, a three-color laser light source.

[0140] The light-emitting surface of the light source 10 is, for example, provided with a protective glass 11.

[0141] The color combining prism 9 plays a crucial role in the projection lens of the present application, which is responsible for combining light beams from different light sources (usually red, green and blue) into a composite light beam. In this way, the projection lens can achieve full-color projection. In this example of the present application, the color combining prism 9 is located between the light source 10 and the galvanometer 8, ensuring that the three primary colors of light can be accurately combined and directed to the subsequent optical system.

[0142] The galvanometer 8 plays a crucial role in the projection lens of the present application. The galvanometer 8 is arranged behind the light source 10 and the color combining prism 9, and in front of the sixth lens 6. It not only can accurately control the projection position of laser light, but also is one of the key technologies to achieve high-definition, color and dynamic image projection.

[0143] The projection lens provided by the embodiments of the present application is shown in Figure 1 The projection light, such as laser light, emitted by the light source 10 is finally converged onto a plane to form an image.

[0144] The projection lens provided by the embodiments of the present application has strong applicability. The design index of the projection lens is as follows: F / # is 2.2, projection ratio is 1.2, Offset = 100%, optical total length of the projection lens is 36.9mm, telecentricity <1°, off-axis chromatic aberration <0.15Pixel, full field MTF >0.75, focal length = 6.2, root mean square radius RMS radius <0.34Pixel, relative luminance >85%.

[0145] The design index of the projection lens of the present application indicates that it is suitable for various projection devices and can meet the needs of different users.

[0146] It should be noted that the projection lens provided by the present application can further adjust the projection size by changing the relative positions of the first lens group and the second lens group, thereby increasing the flexibility and applicability of the projection device using the projection lens.

[0147] In summary, the projection lens of the embodiments of the present application realizes effective suppression of chromatic aberration, compactness of volume, and significant improvement of imaging quality through ingenious optical design and selection of lens materials.

[0148] According to another embodiment of the present application, a projection device is also provided, characterized in that it comprises a housing and the projection lens as described above.

[0149] The projection device provided by the embodiments of the present application is, for example, a laser projector. The laser projector has the advantages of bright colors, high color gamut, compact volume, and effectively overcomes the problem of large chromatic aberration in the prior art.

[0150] It should be noted that the projection device of the present application includes but is not limited to a laser projector.

[0151] The projection lens of the present application is described in detail below through Embodiment 1.

[0152] Embodiment 1

[0153] Referring to Surface No. The projection lens provided by Embodiment 1 comprises, in order from the imaging side to the light source side along the optical axis, a first lens group, a diaphragm 7, a second lens group, a galvanometer 8, a color combining prism 9, and a light source 10.

[0154] The first lens group is composed of a first lens 1, a second lens 2, and a third lens 3. The first lens 1 is a plastic aspherical lens, and its focal power is negative. The second lens 2 and the third lens 3 are glass spherical lenses. The focal power of the second lens 2 is negative, and the focal power of the third lens 3 is positive.

[0155] The second lens group is composed of a fourth lens 4, a fifth lens 5, and a sixth lens 6. The fourth lens 4 and the fifth lens 5 are glass spherical lenses, and the sixth lens 6 is a glass aspherical lens. The focal power of the fourth lens 4 is positive, the focal power of the fifth lens 5 is negative, and the focal power of the sixth lens 6 is positive.

[0156] The diaphragm 7 is located between the third lens 3 and the fourth lens 4.

[0157] The first lens 1 is a convex-concave lens, the second lens 2 is a double-concave lens, the third lens 3 is a double-convex lens, the fourth lens 4 and the fifth lens 5 are concave-convex lenses, and the sixth lens 6 is a double-convex lens.

[0158] The first lens group and / or the second lens group can move along the optical axis.

[0159] The second lens 2 and the third lens 3 are mutually cemented to form a first double-cemented lens group, and the fourth lens 4 and the fifth lens 5 are mutually cemented to form a second double-cemented lens group.

[0160] The refractive index of the second lens 2 is Nd2, the refractive index of the third lens 3 is Nd3, and Nd2 < Nd3; the Abbe number of the second lens 2 is Vd2, the Abbe number of the third lens 3 is Vd3, and Vd2 > Vd3.

[0161] The refractive index of the fourth lens 4 is Nd4, the refractive index of the fifth lens 5 is Nd5, and Nd4 < Nd5; the Abbe number of the fourth lens 4 is Vd4, the Abbe number of the fifth lens 5 is Vd5, and Vd4 > Vd5.

[0162] The first lens 1 has a negative refractive power and at least one aspherical surface; and the sixth lens 6 has a positive refractive power and at least one aspherical surface.

[0163] The effective focal length of the first lens group is F1, the total effective focal length of the projection lens is F, and 1.5 ≤ |F1 / F| ≤ 1.85; the effective focal length of the second lens group is F2, the total effective focal length of the projection lens is F, and 1.5 ≤ |F2 / F| ≤ 1.85.

[0164] The projection lens satisfies 2 < T / D < 3.5; wherein T is the total optical length of the projection lens, and D is the effective clear aperture of the first lens 1.

[0165] The light source 10 is a laser light source.

[0166] Tables 1 and 2 are various parameters of the projection lens, which are as follows.

[0167] Table 1: Lens Parameter Table

[0168]

[0169] Table 2: Aspherical Surface Coefficient Table

[0170] Conic Coefficient (K) 1 2 10 11 Second Order Aspheric Coefficient -3.423 -1.517 -1.244 -10.347 Fourth Order Aspheric Coefficient 0.00 0.00 0.00 0.00 Sixth Order Aspheric Coefficient 2.00E-05 7.74E-04 4.22E-05 -5.08E-04 Eighth Order Aspheric Coefficient -9.12E-07 7.13E-06 -2.00E-05 -1.38E-06 Tenth Order Aspheric Coefficient 7.25E-09 -5.77E-09 -5.60E-08 5.55E-07 Figure 1 5.81E-11 -5.74E-09 1.11E-10 1.89E-10

[0171] It should be noted that the surface numbers in Tables 1 and 2 are 1-18, i.e., there are 18 surfaces in total, which are shown in Figures 3 to 10 The optical architecture of the projection lens is shown from left to right, and there are 18 surfaces.

[0172] The projection lens of the present application not only exhibits excellent performance in suppressing chromatic aberration, but also realizes significant reduction in volume. That is, it can realize the dual requirements of miniaturization of laser projectors and high-definition imaging, such as Figure 3 detailed display.

[0173] Figure 4 The point-spread function (PSF) plot shows that the root mean square (RMS) radius of the projection lens of the present embodiment 1 is ≤1.831 μm, which is equivalent to 0.34 pixel width, showing excellent optical accuracy.

[0174] Figure 5 The spatial frequency modulation transfer function (MTF) plot, Figure 6 the defocus curve and Figure 7 the modulation transfer function versus field of view plot together confirm that the modulation transfer function of the projection lens of the present embodiment 1 still maintains a high level of more than 75% at a spatial frequency of 93 lp / mm, and the depth of focus range is wide, more than ±0.015 mm, and the MTF value of the full field of view is also stably higher than 0.75, which together ensures the delicate presentation of image details and depth levels.

[0175] From the field curvature and distortion plot shown in Figure 8 it can be seen that the field curvature of the projection lens of the present embodiment 1 is ≤0.016 mm, and the distortion rate is ≤1.3%.

[0176] From the axial chromatic aberration plot shown in Figure 9 it can be seen that the red-blue (R-B) chromatic aberration is less than 0.8 μm (i.e. 0.148 pixels), the red-green (R-G) chromatic aberration is less than 0.43 μm (0.07 pixels), and the blue-green (B-G) chromatic aberration is less than 0.32 μm (0.059 pixels), and the chromatic aberration is extremely effectively inhibited.

[0177] From the relative luminance plot of Figure 10 it can be seen that the full-screen luminance uniformity is more than 85%, the edge light is fully retained, the brightness loss is avoided, and the overall brightness and balance of the screen are ensured.

[0178] Figure 10 is a ray aberration plot, which expresses a function plot of the ray linear aberration changing with the pupil coordinate, also called a ray fan (Ray Fan). From Figure 10 it can be seen that it includes 10 groups corresponding to 10 fields of view, and each group includes 2 pictures, which are the meridional aberration and sagittal aberration changing with the pupil, respectively. These pictures directly show the excellent compensation ability of the design for various aberrations, and it can be determined from ​ that most of the aberrations are effectively corrected, further improving the clarity and visual effect of the image.

[0179] The above embodiments mainly describe the differences between the embodiments, and the different optimization features of the embodiments can be combined to form a better embodiment as long as they are not contradictory. Considering the brevity of the writing, it will not be repeated here.

[0180] While certain embodiments of the application have been described herein in detail, those skilled in the art will appreciate that modifications can be made without departing from the scope and spirit of the application. The scope of the application is defined by the appended claims.

Claims

1. A projection lens, characterized in that, Along the optical axis from the imaging side to the image source side, it includes the first lens group, the aperture stop (7), and the second lens group in sequence; The first lens group consists of a first lens (1), a second lens (2) and a third lens (3). The first lens (1) is a plastic aspherical lens, and the second lens (2) and the third lens (3) are glass spherical lenses. The second lens group consists of a fourth lens (4), a fifth lens (5) and a sixth lens (6), wherein the fourth lens (4) and the fifth lens (5) are spherical glass lenses and the sixth lens (6) is an aspherical glass lens; The aperture stop (7) is located between the third lens (3) and the fourth lens (4); The projection lens satisfies: 2 < T / D < 3.5; where T is the total optical length of the projection lens and D is the largest effective aperture in the first lens group. The second lens (2) and the third lens (3) are cemented together to form a first cemented doublet lens group; the fourth lens (4) and the fifth lens (5) are cemented together to form a second cemented doublet lens group; The effective focal length of the first lens group is F1, and the total effective focal length of the projection lens is F, where 1.5 ≤ |F1 / F| ≤ 1.85; The effective focal length of the second lens group is F2, and the total effective focal length of the projection lens is F, 1.5≤|F2 / F|≤1.85; The first lens (1) has a negative optical power, the second lens (2) has a negative optical power, the third lens (3) has a positive optical power, the fourth lens (4) has a positive optical power, the fifth lens (5) has a negative optical power, and the sixth lens (6) has a positive optical power. The first mirror group and / or the second mirror group are movable along the optical axis.

2. The projection lens according to claim 1, characterized in that, The effective aperture of the first lens (1) is D, and the projection lens satisfies: 2 < T / D < 3.

5.

3. The projection lens according to claim 1, characterized in that, The first lens (1) is a convex-concave lens, the second lens (2) is a biconcave lens, the third lens (3) is a biconvex lens, the fourth lens (4) and the fifth lens (5) are concave-convex lenses, and the sixth lens (6) is a biconvex lens.

4. The projection lens according to claim 1, characterized in that, The refractive index of the second lens (2) is Nd2, and the refractive index of the third lens (3) is Nd3, and Nd2 < Nd3; The Abbe number of the second lens (2) is Vd2, and the Abbe number of the third lens (3) is Vd3, and Vd2 > Vd3.

5. The projection lens according to claim 4, characterized in that, The refractive index of the fourth lens (4) is Nd4, the refractive index of the fifth lens (5) is Nd5, and Nd4 < Nd5; The Abbe number of the fourth lens (4) is Vd4, and the Abbe number of the fifth lens (5) is Vd5, and Vd4 > Vd5.

6. The projection lens according to claim 1, characterized in that, The first lens (1) has at least one aspherical surface; The sixth lens (6) has at least one aspherical surface.

7. The projection lens according to any one of claims 1-6, characterized in that, The projection lens also includes: a light source (10), a color combining prism (9), and a galvanometer (8). The galvanometer (8) is arranged adjacent to the sixth lens (6), and the color-combining prism (9) is located between the light source (10) and the galvanometer (8).

8. A projection device, characterized in that, include: shell; and The projection lens as described in any one of claims 1-7.

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