Projection lens and projection system

Abstract

The application discloses a projection lens and a projection system, wherein the projection lens comprises: a refractive system for imaging incident projection light; and a reflection system located on the light exit side of the refractive system for twice imaging the imaging light of the refractive system and reflecting the imaging light to a set position; the refractive system comprises: a front group mirror set located on one side close to the reflection system; a middle group mirror set located on one side of the front group mirror set away from the reflection system; and a rear group mirror set located on one side of the middle group mirror set away from the front group mirror set; the refractive system comprises a plurality of lenses, and at least one of the plurality of lenses is a liquid lens. The curvature radius of the liquid lens can change with voltage, and the effective focal length and F.NO of the projection lens can be adjusted by adjusting the curvature radius of the liquid lens, so that the projection lens can project projection images of different sizes and be applied to laser television products of different sizes.

Description

Technical Field

[0001] This invention relates to the field of projection display technology, and in particular to a projection lens and projection system. Background Technology

[0002] Due to its advantages of high brightness, high contrast, and wide color gamut, laser light sources are increasingly used in display products. The working principle of a laser TV is that light emitted from a laser projector is projected onto a projection screen, which then reflects the light back to the user's eyes. Current laser TVs typically use Digital Light Processing (DLP) technology for image display. The light emitted from the laser source is shaped and homogenized before it illuminates a Digital Micro Device (DMD). The micromirrors on the DMD modulate and reflect the light, which then illuminates the projection lens and is projected onto the projection screen to form an image.

[0003] With the rapid development of laser TV products in recent years, their application demand patterns have become increasingly diversified. However, the ultra-short-throw lenses used in current laser TVs usually have a fixed focal number (F.NO), which cannot match the diverse projection systems. Summary of the Invention

[0004] This invention provides a projection lens and projection system for adjusting the focal length of the projection lens to make it suitable for diverse application scenarios.

[0005] The first aspect of the present invention provides a projection lens, comprising: a refraction system for imaging incident projection light rays;

[0006] A reflection system, located on the light-emitting side of the refraction system, is used to perform secondary imaging of the imaging light rays from the refraction system and reflect them to a set position.

[0007] The refraction system includes:

[0008] The front group of mirrors is located on the side closest to the reflection system;

[0009] The middle group of mirrors is located on the side of the front group of mirrors that is away from the reflection system.

[0010] The rear group of lenses is located on the side of the middle group of lenses that is opposite to the front group of lenses;

[0011] The refractive system includes multiple lenses, at least one of which is a liquid lens.

[0012] In some embodiments of the present invention, the rear lens group includes a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens, an eighth lens, a ninth lens, and a tenth lens arranged sequentially along a direction gradually approaching the reflection system;

[0013] The first lens, the third lens, the fourth lens, the fifth lens, the sixth lens, the seventh lens, the ninth lens, and the tenth lens are all spherical lenses; the second lens is an aspherical lens; and the eighth lens is an aspherical lens.

[0014] The third lens and the fourth lens are cemented together to form a cemented doublet lens group;

[0015] The fifth lens, the sixth lens, and the seventh lens are cemented together to form a cemented triplet lens group. The refractive index of the sixth lens is greater than that of the seventh lens, and the refractive index of the seventh lens is greater than that of the fifth lens.

[0016] In some embodiments of the present invention, the first lens has a positive refractive power, the second lens has a positive refractive power, the third lens has a positive refractive power, the fourth lens has a positive refractive power, the fifth lens has a positive refractive power, the sixth lens has a negative refractive power, the seventh lens has a negative refractive power, the eighth lens has a positive refractive power, the ninth lens has a positive refractive power, and the tenth lens has a negative refractive power.

[0017] The focal lengths of the cemented doublet lens group and the cemented triplet lens group satisfy the following relationship:

[0018] -40 < F1 < -30;

[0019] 15 < F2 < 25;

[0020] Where F1 represents the effective focal length of the cemented doublet lens group, and F2 represents the effective focal length of the cemented triplet lens group.

[0021] In some embodiments of the present invention, the middle group of lenses includes an eleventh lens, a twelfth lens, and a thirteenth lens arranged along the direction close to the reflection system, wherein the eleventh lens is an aspherical lens, and the twelfth and thirteenth lenses are spherical lenses;

[0022] The eleventh lens is a liquid lens, and the radii of curvature of the light-incident and light-exit surfaces of the liquid lens vary with the voltage applied to the liquid lens.

[0023] In some embodiments of the present invention, the eleventh lens has a positive refractive power, the twelfth lens has a negative refractive power, and the thirteenth lens has a positive refractive power.

[0024] The range of curvature radii of the incident and exit surfaces of the eleventh lens satisfies the following relationship:

[0025] -80 < C1 < -40;

[0026] 45 < C2 < 95;

[0027] Wherein, C1 represents the radius of curvature of the light-incident surface of the eleventh lens, and C2 represents the radius of curvature of the light-exit surface of the eleventh lens.

[0028] In some embodiments of the present invention, the front group of lenses includes a fourteenth lens, a fifteenth lens, a sixteenth lens, and a seventeenth lens arranged along the direction close to the reflection system;

[0029] The fourteenth, fifteenth, and seventeenth lenses are all spherical lenses, while the sixteenth lens is an aspherical lens.

[0030] In some embodiments of the present invention, the refractive power of the fourteenth lens is positive, the refractive power of the fifteenth lens is negative, the refractive power of the sixteenth lens is negative, and the refractive power of the seventeenth lens is negative.

[0031] The radius of curvature of the sixteenth lens satisfies the following relationship:

[0032] 2 < (R1 - R2) / F3 < 2.5;

[0033] Wherein, R1 represents the radius of curvature of the light-incident surface of the sixteenth lens, R2 represents the radius of curvature of the light-outceasing surface of the sixteenth lens, and F3 represents the effective focal length of the sixteenth lens.

[0034] In some embodiments of the present invention, the projection lens satisfies the following relationship:

[0035] 2 < BFL / TD1 < 2.5;

[0036] Where BFL represents the back working distance of the projection lens, and TD1 represents the axial distance from the light-emitting side surface of the first lens to the light-incident side surface of the second lens.

[0037] In some embodiments of the present invention, the projection ratio of the projection lens is 0.2 to 0.3;

[0038] The projection lens satisfies the following relationship:

[0039] 22 < TD2 / EFL < 27;

[0040] Wherein, TD2 represents the on-axis distance between the front group of lenses and the middle group of lenses, and EFL represents the effective focal length of the projection lens.

[0041] A second aspect of the present invention provides a projection system, including any of the above-described projection lenses and a projection screen located on the light-emitting side of the projection lens; the projection system further includes:

[0042] Projection light source, used to emit projection light;

[0043] An illumination system is located on the light-emitting side of the projection light source; the illumination system includes a light modulation component for modulating incident light; a projection lens is located on the light-emitting side of the light modulation component;

[0044] The projection lens also includes an aperture stop; the projection system satisfies the following relationship:

[0045] 0.2 < SL / TTL < 0.4;

[0046] Wherein, SL is the distance between the optical modulation component and the aperture, and TTL is the distance between the optical modulation component and the reflection system.

[0047] The beneficial effects of this invention are as follows:

[0048] This invention provides a projection lens and projection system. The projection lens includes: a refraction system for imaging incident projection light; and a reflection system located on the light-emitting side of the refraction system for secondary imaging of the imaging light from the refraction system and reflecting it to a predetermined position. The refraction system includes: a front group of lenses located near the reflection system; a middle group of lenses located on the side of the front group of lenses away from the reflection system; and a rear group of lenses located on the side of the middle group of lenses away from the front group of lenses. The refraction system includes multiple lenses, at least one of which is a liquid lens. The radius of curvature of the liquid lens can vary with voltage. By adjusting the radius of curvature of the liquid lens, the effective focal length and F.NO of the projection lens can be adjusted, allowing the projection lens to project images of different sizes, applicable to laser television products of different sizes. Attached Figure Description

[0049] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the embodiments of the present invention will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0050] Figure 1 This is a schematic diagram of the projection system provided in an embodiment of the present invention;

[0051] Figure 2 This is a schematic diagram of the projection lens provided in an embodiment of the present invention;

[0052] Figure 3 This is a schematic diagram of the optical path of a projection lens provided in an embodiment of the present invention;

[0053] Figure 4 This is one of the modulation transfer function curves of the projection lens provided in the embodiments of the present invention;

[0054] Figure 5 The second type of modulation transfer function curve of the projection lens provided in the embodiments of the present invention;

[0055] Figure 6 The third type of modulation transfer function curve of the projection lens provided in the embodiments of the present invention;

[0056] Figure 7 The fourth graph of the modulation transfer function of the projection lens provided in the embodiments of the present invention;

[0057] Figure 8 Fifth of the modulation transfer function curves of the projection lens provided in the embodiments of the present invention;

[0058] Figure 9 This is a schematic diagram of the field curvature curve of the projection lens provided in an embodiment of the present invention;

[0059] Figure 10 This is a schematic diagram of the distortion curve of a projection lens provided in an embodiment of the present invention. Detailed Implementation

[0060] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, the present invention will be further described below in conjunction with the accompanying drawings and embodiments. However, the exemplary embodiments can be implemented in many forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided to make the present invention more comprehensive and complete, and to fully convey the concept of the exemplary embodiments to those skilled in the art. The same reference numerals in the figures denote the same or similar structures, and therefore repeated descriptions of them will be omitted. Terms describing position and direction in the present invention are illustrative based on the accompanying drawings, but changes can be made as needed, and all such changes are included within the scope of protection of the present invention. The accompanying drawings of the present invention are for illustrative purposes only and do not represent actual proportions.

[0061] The working principle of a laser TV is that light emitted from a laser projector is projected onto a projection screen, which then reflects the light back to the user's eyes. Current laser TVs are typically based on DLP technology. The projector usually includes a light source, an illumination system, and a projection lens. The DMD (Digital Microdisk Device) is the core component of the illumination system, and the projection lens is mounted on the light-emitting side of the DMD. The laser light emitted from the light source enters the illumination system, is shaped and homogenized, and then enters the DMD. It is then modulated and reflected by the DMD before exiting into the projection lens, where it is imaged and finally projected onto the projection screen to form a displayed image.

[0062] Laser TVs utilize ultra-short-throw reflective projection systems, with ultra-short-throw lenses capable of projecting large images from very short distances. The F.NO value of the projection lens affects its light transmission and focal length, thus influencing the brightness and image quality of the projected image. Specifically, a smaller F.NO value allows more light to pass through the lens, resulting in higher light transmission, greater brightness, and higher light utilization. In other words, changing the F.NO value alters the brightness of the projected image, thereby meeting the brightness requirements of laser TVs. However, because the ultra-short-throw lenses currently used in laser TVs typically have a fixed F.NO value, the types of projection systems that a single ultra-short-throw lens can be matched with are limited, making it difficult to apply them to different usage scenarios to meet the increasingly diverse user needs.

[0063] In view of this, embodiments of the present invention provide a projection lens with an adjustable F.NO value and a projection system including the projection lens, which can improve the versatility of the projection lens.

[0064] Figure 1 This is a schematic diagram of the projection system provided in an embodiment of the present invention.

[0065] like Figure 1 As shown, the embodiment of the present invention employs a projection system based on DLP technology, which may include: a projection light source 100, an illumination system 200, a projection lens 300, and a projection screen 400.

[0066] The projection light source 100 uses a laser light source. Due to the high brightness and strong monochromaticity of laser light, the projected image can have better brightness and color performance. The projection light source 100 can use lasers that emit different colors of laser light, or it can be composed of multiple lasers that emit different colors of laser light, or it can use a monochromatic laser. When the projection light source 100 uses a monochromatic laser, such as a blue laser, a color wheel also needs to be set in the projection system. The color wheel can be used to convert the incident monochromatic laser into other colors of laser light for emission, thereby achieving full-color projection.

[0067] The lighting system 200 is located on the light-emitting side of the projection light source 100. The lighting system 200 may include a light-diffusing component, a lens group, and a light modulation component D, etc.

[0068] Specifically, the light-diffusing component in the lighting system 200 can be a light guide or a compound eye lens group, etc., and the light-diffusing component can be used to shape and homogenize the incident light beam.

[0069] The lighting system may also include lens groups, which can function to focus, diverge, and shape light. The number, type, and arrangement of the lenses can be determined through optical design based on specific application requirements. Figure 1 The diagram shows a prism group L located on the light-emitting side of the light modulation component D. In a specific implementation, the prism group L can be a total internal reflection (TIR) ​​prism group. The prism group L can adjust the direction of the incident light so that it enters the light modulation component D at a set angle.

[0070] The light modulation component D is the core component of the lighting system 200, used to modulate incident light. Specifically, the light modulation component D can be a DMD chip, which consists of thousands of micromirrors. Each micromirror is a precision, miniature reflector, and each micromirror can control one pixel on the projection plane. Each micromirror in the DMD chip can be tilted to an open or closed state. Under the control of digital drive signals, each micromirror can be driven by a rotating device below it, rapidly adjusting its angle and direction. Light incident on the surface of the micromirror in the open state is reflected into the projection lens 300. In this embodiment of the invention, the number, type, and arrangement of the components in the lighting system 200 are not limited.

[0071] The projection lens 300 is located on the light-emitting side of the light modulation component D, and the projection screen 400 is located on the light-emitting side of the projection lens 300. The projection lens 300 can be used to image the light incident upon it and project it onto the projection screen 400. The projection screen of the laser TV can be an ambient light rejecting screen, which can resist the influence of ambient light and thus improve the viewing experience.

[0072] In this embodiment of the invention, the projection device may further include an image shifting mirror group P, which is located between the light modulation component D and the projection lens 300. In a specific implementation, the image shifting mirror group P may consist of only a flat glass plate, which can vibrate at high frequency. Typically, its vibration direction can be along the direction of the pixel diagonal of the projected image, thereby improving the resolution of the projected image without changing the physical resolution of the projection system.

[0073] Figure 2 This is a schematic diagram of the projection lens provided in an embodiment of the present invention.

[0074] like Figure 2As shown, the projection lens includes a refraction system 310 and a reflection system 320, with the reflection system 320 located on the light-emitting side of the refraction system 310. The refraction system 310 is used to image the incident projection light, and the reflection system 320 is used to re-image the image light from the refraction system 310 and reflect it to a designated location, which is the location where the projection screen 400 is set. In practice, the projection screen 400 can be positioned on the side of the refraction system 310 away from the reflection system 320, thus reducing the distance between the projection lens and the projection screen and saving space.

[0075] Specifically, the refraction system 310 may include a front group of mirrors 311, a middle group of mirrors 312, and a rear group of mirrors 313, and the front group of mirrors 311, the middle group of mirrors 312, the rear group of mirrors 313, and the reflection system 320 are coaxially arranged. The front group of mirrors 311 is located closer to the reflection system 320, the middle group of mirrors 312 is located on the side of the front group of mirrors 311 away from the reflection system 320, and the rear group of mirrors 313 is located on the side of the middle group of mirrors 312 away from the front group of mirrors 311. The reflection system 320 may include a reflector, which may specifically be a concave aspherical reflector. The reflection system 320 is used to fold the light path for imaging, thereby reducing the length of the projection lens and thus reducing the size of the projection lens.

[0076] like Figure 2 As shown, the rear lens group 313 includes a first lens 1, a second lens 2, a third lens 3, a fourth lens 4, a fifth lens 5, a sixth lens 6, a seventh lens 7, an eighth lens 8, a ninth lens 9, and a tenth lens 10 arranged sequentially along the direction gradually approaching the reflection system.

[0077] Specifically, lens 1, lens 3, lens 4, lens 5, lens 6, lens 7, lens 9, and lens 10 are all spherical lenses, while lens 2 and lens 8 are aspherical lenses. Lens 1 has a positive refractive power, as do lens 2, lens 3, lens 4, lens 5, lens 6, lens 7, lens 8, lens 9, and lens 10.

[0078] The third lens 3 and the fourth lens 4 are cemented together to form a cemented doublet lens group T1, and the focal length of the cemented doublet lens group T1 satisfies the following relationship:

[0079] -40 < F1 < -30;

[0080] F1 represents the effective focal length of the cemented doublet lens group T1.

[0081] Lens 5 (fifth lens), 6 (sixth lens), and 7 (seventh lens) are cemented together to form a cemented triplet lens group T2. The refractive index of lens 6 is greater than that of lens 7, and the refractive index of lens 7 is greater than that of lens 5. The focal length of the cemented triplet lens group T2 satisfies the following relationship:

[0082] 15 < F2 < 25;

[0083] Where F2 represents the effective focal length of the triplex lens group T2.

[0084] Cemented doublet lens group T1 and cemented triplet lens group T2 can be used to improve the aberrations of projection lenses.

[0085] The second lens 2 is an axisymmetric biconvex aspherical lens. The second lens 2 can be used to improve the telecentricity of the projection lens. In this embodiment of the invention, the telecentricity of the projection lens is less than 0.5°.

[0086] The eighth lens 8 is an axisymmetric biconvex aspherical lens. The eighth lens 8 can be used to reduce the refractive height, thereby reducing aberrations.

[0087] In this embodiment of the invention, an aperture stop (not shown in the figure) may also be provided between the seventh lens 7 and the eighth lens 8. The aperture stop can be used to limit the divergence range of light in the refraction system 310.

[0088] like Figure 2 As shown, the middle lens group 312 includes an eleventh lens 11, a twelfth lens 12 and a thirteenth lens 13 arranged along the direction close to the reflection system 320.

[0089] Specifically, the eleventh lens 11 is an aspherical lens, while the twelfth and thirteenth lenses 12 and 13 are spherical lenses. The refractive power of the eleventh lens 11 is positive, the refractive power of the twelfth lens 12 is negative, and the refractive power of the thirteenth lens 13 is positive.

[0090] The eleventh lens 11 is a liquid lens, which may contain two immiscible liquids with different refractive indices. One liquid may be a conductive aqueous solution, and the other may be a non-conductive oily solution. The two liquids are encapsulated in a cylindrical container that is transparent on both sides. The container walls are hydrophobically treated, allowing the aqueous solution to accumulate in a dome-shaped pattern at the center of the container. This creates two convex surfaces between the aqueous and oily solutions, which can be considered the incident and exit surfaces of the eleventh lens 11. Applying different voltages to the liquid lens causes the radii of curvature of the incident and exit surfaces to change due to the electrowetting effect of the liquid.

[0091] In this embodiment of the invention, the range of curvature radii of the eleventh lens 11 on the light-incident side and the light-outcrystal side satisfies the following relationship:

[0092] -80 < C1 < -40;

[0093] 45 < C2 < 95;

[0094] Wherein, C1 represents the radius of curvature of the light-incident surface of the eleventh lens 11, and C2 represents the radius of curvature of the light-exit surface of the eleventh lens 11.

[0095] In this embodiment of the invention, the eleventh lens 11 is set as a liquid lens. The curvature radius of the light-incident surface and the light-outcrystal surface of the eleventh lens 11 can be changed by adjusting the voltage, thereby adjusting the F.NO of the projection lens. As a result, the projection lens can be used to project projection images of different sizes. At the same time, it can also assist in focusing, making the projection image clearer. This allows the projection lens provided by this embodiment of the invention to be applied to more diverse laser TV products.

[0096] In some embodiments of the present invention, other lenses in the refraction system may be set as liquid lenses, or multiple liquid lenses may be set in the refraction system, all of which can achieve the effect of adjusting the F.NO of the projection lens. However, it should be noted that the farther the liquid lens is from the aperture stop, the less obvious its adjustment effect is. Therefore, the number and position of liquid lenses in the projection lens are not limited, as long as the expected F.NO adjustment range and the range of projectable screen size are met.

[0097] like Figure 2 As shown, the front group of lenses 311 includes a fourteenth lens 14, a fifteenth lens 15, a sixteenth lens 16, and a seventeenth lens 17 arranged along the direction close to the reflection system 320.

[0098] Specifically, the fourteenth lens 14, the fifteenth lens 15, and the seventeenth lens 17 are all spherical lenses, while the sixteenth lens 16 is an aspherical lens. The refractive power of the fourteenth lens 14 is positive, the refractive power of the fifteenth lens 15 is negative, the refractive power of the sixteenth lens 16 is negative, and the refractive power of the seventeenth lens 17 is negative.

[0099] Among them, the sixteenth lens 16 is an axisymmetric aspherical lens, and its radius of curvature satisfies the following relationship:

[0100] 2 < (R1 - R2) / F3 < 2.5;

[0101] Where R1 represents the radius of curvature of the light-incident surface of the sixteenth lens 16, R2 represents the radius of curvature of the light-outceasing surface of the sixteenth lens 16, and F3 represents the effective focal length of the sixteenth lens 16. The sixteenth lens 16 can be used to improve coma and distortion of the projection lens.

[0102] In this embodiment of the invention, the projection ratio of the projection lens is 0.2 to 0.3, which can make the distance between the projection lens and the projection screen extremely small, and achieve large-size image display within a very short projection distance.

[0103] In this embodiment of the invention, the projection system also satisfies the following relationship:

[0104] 2 < BFL / TD1 < 2.5;

[0105] Where BFL represents the back working distance of the projection lens 300, i.e., the axial distance from the light modulation component D to the first lens 1, and TD1 represents the axial distance from the light-emitting side surface of the first lens 1 to the light-incident side surface of the second lens 2.

[0106] 22 < TD2 / EFL < 27;

[0107] Wherein, TD2 represents the on-axis distance between the front group of mirrors 311 and the middle group of mirrors 312, and EFL represents the effective focal length of the projection lens 300. By controlling this ratio, it is helpful to reduce the system size and better balance system aberrations.

[0108] 0.2 < SL / TTL < 0.4;

[0109] Wherein, SL is the distance between the optical modulation component D and the aperture S, and TTL is the distance between the optical modulation component D and the reflection system 320.

[0110] The embodiments of the present invention also perform ray tracing on the designed projection lens and provide an image quality evaluation diagram of the projection lens.

[0111] Figure 3 This is a schematic diagram of the optical path of a projection lens provided in an embodiment of the present invention.

[0112] Reference Figure 2 and Figure 3 The projection lens provided in this embodiment of the invention includes three aspherical lenses, 14 spherical lenses, and one aspherical reflector. One of the aspherical lenses is a liquid lens, and the radius of curvature of its incident and emitting surfaces can change with the voltage applied to the lens. In the projection device, the projection light, after being modulated and reflected by the light modulation component D, forms an image after passing through each lens in the refraction system 310. The imaging light emitted from the refraction system 310 forms a second image after being reflected by the reflection system 320. By adjusting the radius of curvature of the liquid lens, its optical power can be changed, thereby achieving focusing and changing the F.N. of the projection lens.

[0113] Figure 4 This is one of the modulation transfer function curves of the projection lens provided in the embodiments of the present invention; Figure 5 The second graph shows the modulation transfer function of the projection lens provided in an embodiment of the present invention.

[0114] Figure 4 and Figure 5 The graphs show the modulation transfer function (MTF) curves of the projection lens when the F.NO is 2.2 and the projected image size is 100 inches, with and without a liquid lens. The horizontal axis represents the defocus position in mm, and the vertical axis represents the MTF value.

[0115] contrast Figure 4 and Figure 5 It is known that when a liquid lens is used in a projection lens, the MTF value of the projection lens is higher, and the depth of focus of the projection lens is increased. That is, using a liquid lens in a projection lens can improve the performance of the projection lens to a certain extent.

[0116] Figure 6 The third type of modulation transfer function curve of the projection lens provided in the embodiments of the present invention; Figure 7 The fourth graph of the modulation transfer function of the projection lens provided in the embodiments of the present invention; Figure 8 The fifth graph shows the modulation transfer function of the projection lens provided in this embodiment of the invention.

[0117] In this embodiment of the invention, optical simulation software is used for simulation. When the radius of curvature of the liquid lens, i.e., the eleventh lens 11, changes from C1 = -54.48, C2 = 46.14 to C1 = -54.9, C2 = 45.0, the F.NO value of the projection lens can vary in the range of 1.9 to 2.2. Here, C1 represents the radius of curvature of the light-incident surface of the eleventh lens 11, and C2 represents the radius of curvature of the light-excising surface of the eleventh lens 11.

[0118] Figure 6 , Figure 7 and Figure 8 The MTF curves of the projection lens are shown for projection image size of 80 inches, with F.NO values ​​of 2.2, 2.0, and 1.9 respectively. Figure 6 , Figure 7 , Figure 8 It can be seen that the MTF curve of the projection lens does not change much, and its on-axis MTF value is always greater than 60%. That is, in the projection lens provided by the embodiment of the present invention, the F.NO value of the projection lens can be changed within a certain range by finely adjusting the curvature radius of the liquid lens, while the impact on its MTF value is small, and good imaging quality can be maintained.

[0119] The surface parameters of each optical component within the projection lens provided in this embodiment of the invention are shown in the table below:

[0120]

[0121]

[0122] Wherein, OBJ is the object plane, S1 is the surface of the DMD, S1 to S40 are the surfaces of the respective optical components sequentially passed along the optical path direction, and STO is the stop surface.

[0123] The F.NO value of the projection lens satisfies the following relationship:

[0124]

[0125] Wherein, EFL denotes the effective focal length of the projection lens, and 2nsinθ denotes the entrance pupil diameter of the projection lens. The EFL of the projection lens can vary with the change of the focal length of the liquid lens. In the embodiment of the present invention, the focal length of the liquid lens can range from -35mm to negative infinity.

[0126] The projection lens satisfying the parameters shown in the above table also meets the following conditions: the effective focal length is 1.9mm; the F.NO value satisfies 1.8<F.NO<2.0; the offset, that is, the offset range between the optical axis of the projection lens and the center of the DMD, is 140% to 157%; the resolution capability can reach 93lp / mm; the projectable size is 70 to 150 inches; and the projection ratio is 0.2 to 0.3.

[0127] In the embodiment of the present invention, by adjusting the curvature radius of the liquid lens, the focal length of the liquid lens can be adjusted, so that the effective focal length of the projection lens can be adjusted, so that the projection lens can project projection images of different sizes, which is suitable for laser television products of different sizes. Meanwhile, since the effective focal length of the projection lens determines the F.NO of the projection lens, the embodiment of the present invention can also adjust the brightness of the projection image emitted by the projection lens, thereby effectively improving the brightness of the laser television and achieving a better display effect.

[0128] Figure 9 is a schematic diagram of the field curvature curve of the projection lens provided by the embodiment of the present invention; Figure 10 is a schematic diagram of the distortion curve of the projection lens provided by the embodiment of the present invention.

[0129] Figure 9 where the horizontal axis represents the magnitude of the field curvature in mm, and the vertical axis represents the field of view, from Figure 9 it can be known that the field curvature of the projection lens imaging is less than 0.025mm; Figure 10 where the horizontal axis represents the distortion percentage, and the vertical axis represents the field of view, from Figure 10 it can be known that the distortion of the projection lens is less than 1%. The projection lens provided by the embodiment of the present invention has good field curvature and distortion performance, and can achieve good imaging quality.

[0130] According to the first inventive concept, the projection lens includes a refraction system and a reflection system. The reflection system is used to perform secondary imaging of the imaging light from the refraction system and reflect it to a set position. The reflection system can fold the light path to form an image, thereby reducing the length of the projection lens and thus reducing its size. By placing the projection screen on the side of the refraction system away from the reflection system, the distance between the projection lens and the projection screen can be relatively small, saving space.

[0131] According to the second inventive concept, in the rear group of mirrors of the refraction system, the second lens is an axisymmetric biconvex aspherical lens, which can improve the telecentricity of the projection lens, and the telecentricity of the projection lens is less than 0.5°; the eighth lens is an axisymmetric biconvex aspherical lens, which can reduce the refractive height, thereby reducing aberrations; the third and fourth lenses are cemented together to form a cemented doublet lens group, and the fifth, sixth and seventh lenses are cemented together to form a cemented triplet lens group. The cemented doublet lens group and the cemented triplet lens group can improve the aberrations of the projection lens.

[0132] According to the third inventive concept, in the middle group of the refractive system, the eleventh lens is a liquid lens. By adjusting the voltage to change the curvature radius of the light-incident and light-excising surfaces of the eleventh lens, the F.NO of the projection lens can be adjusted. Thus, the projection lens can be used to project images of different sizes. At the same time, it can also assist in focusing, making the projected image clearer. Therefore, the projection lens provided by the embodiments of the present invention can be applied to more diverse laser TV products.

[0133] According to the fourth inventive concept, other lenses in the refraction system can be set as liquid lenses, or multiple liquid lenses can be set in the refraction system, both of which can achieve the effect of adjusting the projection lens F.NO.

[0134] According to the fifth inventive concept, in the front group of mirrors of the refractive system, the sixteenth lens is an axisymmetric aspherical lens, which can be used to improve the coma and distortion of the projection lens.

[0135] According to the sixth inventive concept, when a liquid lens is used in the projection lens, the MTF value of the projection lens is higher, and the depth of focus of the projection lens is increased, thereby improving the performance of the projection lens to a certain extent.

[0136] According to the seventh inventive concept, by adjusting the curvature radius of the liquid lens, the focal length of the liquid lens can be adjusted, so that the effective focal length of the projection lens can be adjusted, enabling the projection lens to project projection images of different sizes to meet the requirements of laser TV products of different sizes. Meanwhile, since the effective focal length of the projection lens determines the F.NO of the projection lens, the embodiment of the present invention can also adjust the brightness of the projection image emitted by the projection lens, thereby effectively improving the brightness of the laser TV and achieving a better display effect. In the embodiment of the present invention, the throw ratio of the projection lens is 0.2 to 0.3, the F.NO value satisfies 1.8 < F.NO < 2.0, the offset, that is, the offset between the optical axis of the projection lens and the center of the DMD, ranges from 140% to 157%; the resolution capability can reach 93 lp / mm; and the projectable size is 70 to 150 inches.

[0137] Although the preferred embodiments of the present invention have been described, those skilled in the art can make additional changes and modifications to these embodiments once they learn the basic inventive concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all variations and modifications falling within the scope of the present invention.

[0138] Obviously, those skilled in the art can make various alterations and variations to the present invention without departing from the spirit and scope of the present invention. In this way, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalent technologies, the present invention is also intended to cover these alterations and variations.

Claims

1. A projection lens, characterized in that, include: A refraction system used to image incident projected light rays; A reflection system, located on the light-emitting side of the refraction system, is used to perform secondary imaging of the imaging light rays from the refraction system and reflect them to a set position. The refraction system includes: The front group of mirrors is located on the side closest to the reflection system; The middle group of mirrors is located on the side of the front group of mirrors that is away from the reflection system. The rear group of lenses is located on the side of the middle group of lenses that is opposite to the front group of lenses; The refraction system includes multiple lenses, at least one of which is a liquid lens; the refraction system consists of 17 lenses, and the reflection system consists of one mirror; the mirror is a concave mirror located near the front group of lenses. The rear group of lenses includes a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens, an eighth lens, a ninth lens, and a tenth lens arranged sequentially along the direction gradually approaching the reflection system; the middle group of lenses includes an eleventh lens, a twelfth lens, and a thirteenth lens arranged along the direction approaching the reflection system; and the front group of lenses includes a fourteenth lens, a fifteenth lens, a sixteenth lens, and a seventeenth lens arranged along the direction approaching the reflection system. The first lens, the second lens, the third lens, the fourth lens, the fifth lens, the eighth lens, the ninth lens, the eleventh lens, the thirteenth lens, and the fourteenth lens all have positive refractive power, while the sixth lens, the seventh lens, the tenth lens, the twelfth lens, the fifteenth lens, the sixteenth lens, and the seventeenth lens all have negative refractive power. Along the direction gradually approaching the reflection system, the two side surfaces of the first lens, the seventh lens, and the fourteenth lens are respectively configured as convex lenses and concave lenses; the two side surfaces of the second lens, the third lens, the fifth lens, the eighth lens, the eleventh lens, and the thirteenth lens are respectively configured as convex lenses and convex lenses; the two side surfaces of the fourth lens and the ninth lens are respectively configured as concave lenses and convex lenses; the two side surfaces of the sixth lens, the tenth lens, the twelfth lens, the fifteenth lens, the sixteenth lens, and the seventeenth lens are respectively configured as concave lenses and concave lenses.

2. The projection lens as described in claim 1, characterized in that, The first lens, the third lens, the fourth lens, the fifth lens, the sixth lens, the seventh lens, the ninth lens, and the tenth lens are all spherical lenses; the second lens is an aspherical lens; and the eighth lens is an aspherical lens. The third lens and the fourth lens are cemented together to form a cemented doublet lens group; The fifth lens, the sixth lens, and the seventh lens are cemented together to form a cemented triplet lens group. The refractive index of the sixth lens is greater than that of the seventh lens, and the refractive index of the seventh lens is greater than that of the fifth lens.

3. The projection lens as described in claim 2, characterized in that, The focal lengths of the cemented doublet lens group and the cemented triplet lens group satisfy the following relationship: -40＜F1＜-30； 15＜F2＜25； Where F1 represents the effective focal length of the cemented doublet lens group, and F2 represents the effective focal length of the cemented triplet lens group.

4. The projection lens as described in claim 1, characterized in that, The eleventh lens is an aspherical lens, and the twelfth and thirteenth lenses are spherical lenses; The eleventh lens is a liquid lens, and the radii of curvature of the light-incident and light-exit surfaces of the liquid lens vary with the voltage applied to the liquid lens.

5. The projection lens as described in claim 4, characterized in that, The range of curvature radii of the incident and exit surfaces of the eleventh lens satisfies the following relationship: -80＜C1＜-40； 45＜C2＜95； Wherein, C1 represents the radius of curvature of the light-incident surface of the eleventh lens, and C2 represents the radius of curvature of the light-exit surface of the eleventh lens.

6. The projection lens as described in claim 1, characterized in that, The fourteenth, fifteenth, and seventeenth lenses are all spherical lenses, while the sixteenth lens is an aspherical lens.

7. The projection lens as described in claim 6, characterized in that, The radius of curvature of the sixteenth lens satisfies the following relationship: 2 < (R1 - R2) / F3 < 2.5; Wherein, R1 represents the radius of curvature of the light-incident surface of the sixteenth lens, R2 represents the radius of curvature of the light-outceasing surface of the sixteenth lens, and F3 represents the effective focal length of the sixteenth lens.

8. The projection lens as described in claim 2 or 3, characterized in that, The projection lens satisfies the following relationship: 2 < BFL / TD1 < 2.5; Where BFL represents the back working distance of the projection lens, and TD1 represents the axial distance from the light-emitting side surface of the first lens to the light-incident side surface of the second lens.

9. The projection lens as described in any one of claims 1 to 7, characterized in that, The projection ratio of the projection lens is 0.2 to 0.3; The projection lens satisfies the following relationship: 22 < TD2 / EFL < 27; Wherein, TD2 represents the on-axis distance between the front group of lenses and the middle group of lenses, and EFL represents the effective focal length of the projection lens.

10. A projection system, characterized in that, Includes a projection lens as described in any one of claims 1 to 9 and a projection screen located on the light-emitting side of the projection lens; The projection system also includes: Projection light source, used to emit projection light; An illumination system is located on the light-emitting side of the projection light source; the illumination system includes a light modulation component for modulating incident light; a projection lens is located on the light-emitting side of the light modulation component; The projection lens also includes an aperture stop; the projection system satisfies the following relationship: 0.2 < SL / TTL < 0.4; Wherein, SL is the distance between the optical modulation component and the aperture, and TTL is the distance between the optical modulation component and the reflection system.

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