Projection zoom optical system

Abstract

The invention relates to the technical field of optical imaging systems, and discloses a projection zoom optical system, which sequentially comprises a light valve, a prism group, an image bias lens, a first group lens, a second group lens, a third group lens, a fourth group lens, a fifth group lens and a sixth group lens from an image source side to a projection side along an optical axis, the first group lens is composed of a first lens with positive focal power, the second group lens is composed of a second lens with positive focal power, a third lens with positive focal power, a fourth lens with negative focal power and a fifth lens with positive focal power, the third group lens is composed of a diaphragm and a sixth lens with positive focal power, and the fourth group lens is composed of a seventh lens with positive focal power. The fifth group lens is composed of an eighth lens with positive focal power and a ninth lens with negative focal power, and the sixth group lens is composed of a tenth lens with negative focal power and an eleventh lens with negative focal power, so that the performance of the zoom lens can be improved at lower cost and lower complexity; and meanwhile, the quality and definition of a projected image can be improved.

Description

Technical Field

[0001] The present invention relates to the technical field of optical imaging systems, and particularly to a projection zoom optical system. Background Art

[0002] Currently, projection display technology has been widely used in many fields such as education, home, military, transportation, and office, and the market demand is huge. However, as one of the cores, the lens technology in projection display faces many challenges, including complex design and difficult processing, especially considering cost and miniaturization while ensuring high image quality. Improving product performance, especially maintaining image clarity during zoom imaging, is one of the important difficulties in current lens design.

[0003] Current zoom projection lens technology usually adopts a system with a variable magnification plus a compensation group. After the lens is zoomed, secondary focusing is still required through the compensation group. This solution is cumbersome to operate and has poor imaging quality, making it difficult to meet the requirements of high-quality projection.

[0004] Therefore, there is an urgent need for a projection zoom optical system that can improve the performance of the zoom lens at a lower cost and lower complexity, and at the same time improve the quality and clarity of the projection image. Summary of the Invention

[0005] In order to solve the above technical problems, the present invention provides a projection zoom optical system, which sequentially includes, along the optical axis from the image source side to the projection side: A light valve for providing a high-resolution image beam; A prism group including a TIR total reflection prism and an illumination prism; The TIR total reflection prism is used to enhance the brightness and contrast of the image beam, and the illumination prism is used to improve the uniformity and distribution of the image beam; An image offset mirror for adjusting the direction and position of the image; A first group of lenses composed of a first lens with a positive optical power; A second group of lenses composed of a second lens with a positive optical power, a third lens with a positive optical power, a fourth lens with a negative optical power, and a fifth lens with a positive optical power; wherein, the third lens, the fourth lens, and the fifth lens are combined into a triple cemented lens; A diaphragm; A third group of lenses composed of a sixth lens with a positive optical power; A fourth group of lenses composed of a seventh lens with a positive optical power; The fifth group of lenses consists of an eighth lens with a positive optical power and a ninth lens with a negative optical power; the eighth lens and the ninth lens are combined into a doublet lens. The sixth group of lenses consists of a tenth lens (L10) with a negative optical power and an eleventh lens with a negative optical power.

[0006] Furthermore, the first lens, the third lens, the fourth lens, the fifth lens, the sixth lens, the eighth lens, and the ninth lens are all spherical lenses. The second lens, the seventh lens, the tenth lens, and the eleventh lens are all aspherical lenses.

[0007] Furthermore, the seventh lens, the tenth lens, and the eleventh lens are all plastic lenses.

[0008] Furthermore, the first lens, the third lens, the fourth lens, the fifth lens, the sixth lens, the eighth lens, and the ninth lens are all glass lenses.

[0009] Furthermore, the Abbe number of the fourth lens is from 20 to 30, and the thickness is from 0.5 mm to 2 mm.

[0010] Furthermore, the refractive index of the fourth lens is greater than 1.7, and the refractive indices of the third lens and the fifth lens are less than 1.7.

[0011] Furthermore, the Abbe number of the eighth lens is from 0 to 65, and the Abbe number of the ninth lens is from 0 to 65.

[0012] Furthermore, the eighth lens is a biconvex lens, and the ninth lens is a biconcave lens.

[0013] Furthermore, the distance from the light valve to the first lens is denoted as BFL, and the distance from the vertex of the first lens surface to the vertex of the eleventh lens surface is denoted as L, and they satisfy the relational expression: 0.0 < BFL / L < 0.5.

[0014] Furthermore, the first group of lenses, the second group of lenses, the third group of lenses, the fourth group of lenses, the fifth group of lenses, and the sixth group of lenses form a zoom lens group. The equivalent focal length of the zoom lens group is F1, the equivalent focal length of the first group of lenses is F2, the equivalent focal length of the second group of lenses is F3, the equivalent focal length of the third group of lenses is F4, the equivalent focal length of the fourth group of lenses is F5, the equivalent focal length of the fifth group of lenses is F6, and the equivalent focal length of the sixth group of lenses (G6) is F7, and they satisfy the following conditions: 2 < |F2 / F1| < 5; 10 < |F3 / F1| < 50; 1 < |F4 / F1| < 4; 5 < |F5 / F1| < 10; 2 < |F6 / F1| < 5; 0 < |F7 / F1| < 3.

[0015] The embodiments of the present invention have the following technical effects: This solution adopts an innovative design of overall internal zoom and external compensation in the lens. By realizing the overall zoom function inside the lens and using an external compensation mechanism to adjust the focal length, the external compensation is mainly used to expand the projection size range to meet different projection size requirements. The internal zoom of the lens makes full use of the advantages of aspherical surfaces, effectively reducing the shift of the best focal plane, thus solving the problem of image blurring caused by focal plane shift during the zoom process. The design of overall internal zoom and external compensation is more integrated and optimized. Through the internal overall zoom structure and the external compensation mechanism, the problem of focal point shift during the zoom process is effectively solved, improving the performance and imaging quality of the lens. In contrast, the zoom plus compensation group requires more operation steps and adjustments, and usually has higher costs and complexity. This improvement can effectively reduce the focal plane shift, improve the imaging quality, and achieve good zoom performance at a lower cost and complexity. This design is commonly used in scenarios that require high-quality projection, such as conference rooms, cinemas, etc., and can achieve a flexible zoom function without sacrificing imaging clarity. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for the description of the specific embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0017] Figure 1 is a schematic structural diagram of a zoom projection system provided by an embodiment of the present invention; Figure 2 is a schematic structural diagram of another zoom projection system provided by an embodiment of the present invention; Figure 3 is a schematic diagram of TV distortion of the imaging picture of the projection system provided by an embodiment of the present invention; Figure 4 is a schematic diagram of spot light imaging of three different wavelength lights on the screen under a certain field of view condition provided by an embodiment of the present invention; Figure 5 is a schematic diagram of the image difference between three different wavelength lights and the main wavelength light on the x-axis and y-axis under normalized field of view conditions provided by an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0018] To make the objectives, technical solutions and advantages of the present invention clearer, the technical solutions of the present invention will be described clearly and completely below. Obviously, the described embodiments are only a part rather than all of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the scope protected by the present invention.

[0019] Figure 1 It is a schematic structural diagram of a zoom projection system provided by Embodiment 1 of the present invention. Refer to Figure 1 , specifically including, in order from the image source side to the projection side along the optical axis: A light valve, which is used to provide a high-resolution image beam; Specifically, the light valve is a DMD chip or an LCos chip, and the light valve is a light modulation element.

[0020] A prism group, which includes: a TIR total reflection prism and an illumination prism; The TIR total reflection prism is used to enhance the brightness and contrast of the image beam, and the illumination prism is used to improve the uniformity and distribution of the image beam; An image offset mirror, which is used to adjust the direction and position of the image; The first group of lenses G1, which is composed of a first lens L1 with a positive optical power; The second group of lenses G2, which is composed of a second lens L2 with a positive optical power, a third lens L3 with a positive optical power, a fourth lens L4 with a negative optical power, and a fifth lens L5 with a positive optical power; wherein, the third lens L3, the fourth lens L4 and the fifth lens L5 are combined into a triple cemented lens; An aperture, and the aperture moves with the second group of lenses G2, effectively improving the coma problem of the system; The third group of lenses G3, which is composed of a sixth lens L6 with a positive optical power; The fourth group of lenses G4, which is composed of a seventh lens L7 with a positive optical power; The fifth group of lenses G5, which is composed of an eighth lens L8 with a positive optical power and a ninth lens L9 with a negative optical power; the eighth lens L8 and the ninth lens L9 are combined into a double cemented lens; The sixth group of lenses G6 is composed of a tenth lens L10 with a negative focal power and an eleventh lens L11 with a negative focal power. Optionally, the tenth lens L10 and the eleventh lens L11 are the front group of lenses, and their relative positions can be fixed or in relative motion. The fixed manner can simplify the system structure, and when in relative motion, the system distortion can be better corrected.

[0021] In some embodiments, in order to effectively achieve the distortion compensation of the system, it can be changed to that the tenth lens L10 forms the sixth group of lenses G6, and the eleventh lens L11 forms the seventh group of lenses G7, as Figure 2 shown.

[0022] In the present invention, the first lens L1, the third lens L3, the fourth lens L4, the fifth lens L5, the sixth lens L6, the eighth lens L8, and the ninth lens L9 are all spherical lenses; the second lens L2, the seventh lens L7, the tenth lens L10, and the eleventh lens L11 are all aspherical lenses.

[0023] In the present invention, the seventh lens L7, the tenth lens L10, and the eleventh lens L11 are all plastic lenses; the first lens L1, the third lens L3, the fourth lens L4, the fifth lens L5, the sixth lens L6, the eighth lens L8, and the ninth lens L9 are all glass lenses.

[0024] In the present invention, the Abbe number of the fourth lens L4 is from 20 to 30, and the thickness is from 0.5 mm to 2 mm; the refractive index of the fourth lens L4 is greater than 1.7, and the refractive indices of the third lens L3 and the fifth lens L5 are less than 1.7; the Abbe number of the eighth lens L8 is from 0 to 65, and the Abbe number of the ninth lens L9 is from 0 to 65; the eighth lens L8 is a biconvex lens, and the ninth lens L9 is a biconcave lens.

[0025] In the present invention, the distance from the light valve to the first lens L1 is denoted as BFL, and the distance from the vertex of the surface of the first lens L1 to the vertex of the surface of the eleventh lens L11 is denoted as L, and they satisfy the relational expression: 0.0 < BFL / L < 0.5; the first lens group G1, the second lens group G2, the third lens group G3, the fourth lens group G4, the fifth lens group G5, and the sixth lens group G6 form a zoom lens group; the equivalent focal length of the zoom lens group is F1, the equivalent focal length of the first lens group G1 is F2, the equivalent focal length of the second lens group G2 is F3, the equivalent focal length of the third lens group G3 is F4, the equivalent focal length of the fourth lens group G4 is F5, the equivalent focal length of the fifth lens group G5 is F6, and the equivalent focal length of the sixth lens group G6 is F7, and they satisfy the following conditions: 2 < |F2 / F1| < 5; 10 < |F3 / F1| < 50; 1 < |F4 / F1| < 4; 5 < |F5 / F1| < 10; 2 < |F6 / F1| < 5; 0 < |F7 / F1| < 3.

[0026] It can be seen from this that a zoom projection imaging system proposed by the present invention includes a light valve, a prism group, an image offset mirror, and a zoom lens group. The zoom lens group totally includes 11 lenses, among which there are 4 aspherical lenses and 7 spherical lenses. The optical power of the lenses in the optical system will directly affect astigmatism, field curvature, distortion, axial chromatic aberration, and lateral chromatic aberration. Therefore, different combinations of positive and negative optical powers will also play a certain role in aberration correction. Thus, the optical powers of the 11 lenses in the present invention are distributed as positive, positive, positive, negative, positive, positive, positive, positive, negative, negative, negative, and the total optical power of the zoom lens group is positive optical power. Through the above combination, the clarity of the picture resolution is maintained during the zoom process. By adopting the design of moving the entire zoom lens group, a larger picture size range can be achieved. This method effectively improves the high-resolution imaging quality of the projection and ensures the clarity and detail performance of the image.

[0027] Specifically, in the zoom lens group system, the three-piece lens is the core component. While correcting aberrations, reasonably selecting glass materials and optical power distribution can effectively balance aberrations, temperature drift, and processability. The three-piece lens is mainly used to correct chromatic aberration and balance the system temperature. Materials with a large difference in Abbe number are preferably selected for matching. Therefore, the Abbe number Vd value of the fourth lens L4 is selected in the range of 20 to 30. Selecting materials with an Abbe number in the range of 20 to 30 can effectively reduce the influence of thermal expansion and contraction of materials on the temperature drift of the system and improve the lens resolution. The third lens L3 and the fifth lens L5 are made of materials with a small refractive index to neutralize the high refractive index negative optical power of the fourth lens L4 and reduce aberrations such as spherical aberration, coma, and astigmatism of the lens (usually, the higher the refractive index, the more severe the absorption of blue light, and the light transmittance will decrease). Further, the thickness of the fourth lens L4 needs to be controlled within 0.5 - 2 mm in design to suppress the reduction of transmittance.

[0028] The eighth lens L8 and the ninth lens L9 form a doublet lens. The Abbe number Vd values of the eighth lens L8 and the ninth lens L9 are selected to be less than 65. The reason for this selection is that the remaining chromatic aberration of the lens is small, and materials with relatively close Abbe numbers need to be selected for matching. Further, by designing the eighth lens L8 and the ninth lens L9 as a combination of biconvex and biconcave, no additional chromatic aberration will be generated during the zoom movement to affect the system performance.

[0029] In the embodiments of the present invention, the effective focal lengths of the respective lenses (L1 - L11) of the optical system are shown in the following table:

[0030] Figure 3 It is a schematic diagram of TV distortion of the imaging picture of the projection system provided by the embodiments of the present invention. As Figure 3 shown, in the left coordinate system, the horizontal coordinate represents the magnitude of field curvature, with the unit of mm; the vertical coordinate represents the normalized image height, without a unit; from Figure 3 it can be seen that the field curvature of the projection system provided in this embodiment in the horizontal direction is effectively controlled, that is, when imaging, the image quality at the center and the image quality at the periphery have a small difference; in the right coordinate system, the horizontal coordinate represents the magnitude of distortion, with the unit of %; the vertical coordinate represents the normalized image height, without a unit; from Figure 3 it can be seen that the imaging distortion of the projection system provided in this embodiment in the horizontal direction is controlled.

[0031] Figure 4It shows the spot distributions of light rays of three wavelengths (0.45μm, 0.55μm, 0.62μm) on the imaging screen under different field-of-view conditions. The normalized spot diagrams show the influence of different wavelengths on the imaging effect; 0.45μm light ray: a short-wavelength light ray with a smaller spot, showing a higher resolution; 0.55μm light ray: a medium-wavelength light ray with a spot size between that of the short-wavelength and long-wavelength light rays; 0.62μm light ray: a long-wavelength light ray with a larger spot, showing a lower resolution.

[0032] Figure 5 The rayfan diagram of the light rays contains 10 different graphs, and each graph corresponds to a normalized field-of-view condition; the horizontal axis represents the pupil height position under a specific field-of-view condition, which is related to the height at which the light rays enter the optical system and reflects the angles of different light ray incidences; the vertical axis represents the error values between the light rays of each wavelength (0.45μm, 0.55μm, 0.62μm) and the chief ray, that is, the aberration. This kind of error usually stems from design defects or material characteristics of the optical system and reflects the possible deviations of different wavelengths during imaging. Each graph in each field of view contains two parts, showing a symmetric relationship centered on the optical axis, which indicates that for each wavelength of light ray, there are similar patterns and trends in the aberrations on the x-axis and y-axis.

[0033] The present invention only uses lenses made of glass and plastic materials, having a lighter mass and lower manufacturing cost; the lens is composed of 11 lenses in total. Among them, by using cemented lenses, the chromatic aberration and aberration of the projection lens can be reduced, ensuring the imaging quality of the system and reducing the total length of the system, further reducing the system volume; by reasonably setting and adjusting the focal lengths of six groups and adopting the scheme of overall internal zoom and external compensation of the lens, the role of compensation is only to meet a larger projection size range. The internal zoom of the lens makes full use of the advantages of aspherical surfaces, effectively reducing the shift of the best focal plane and solving the problem of unclear imaging caused by the shift of the focal plane during the zooming process. The image is clear and does not require secondary focusing.

[0034] It should be noted that the terms used in the present invention are only for describing specific embodiments and do not limit the scope of the present application. As shown in the specification of the present invention, unless the context clearly indicates an exception, words such as "a", "an", "one" and / or "the" are not specifically singular and may also include the plural. The term "comprising", "including" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method or device including a series of elements not only includes those elements but also includes other elements not explicitly listed, or also includes elements inherent to such a process, method or device. Without further limitation, an element defined by the statement "including one..." does not exclude the existence of another identical element in the process, method or device including the said element.

[0035] It should also be noted that the orientation or positional relationship indicated by terms such as "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation to the present invention. Unless otherwise clearly specified and defined, terms such as "installed", "connected", "coupled" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection, an electrical connection; it can be directly connected, or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[0036] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or equivalently replace some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the technical solutions of the embodiments of the present invention.

Claims

1. A projection zoom optical system, characterized in that, From the image source side to the projection side along the optical axis are successively: A light valve for providing a high-resolution image beam; A prism group including a TIR total reflection prism and an illumination prism; The TIR total reflection prism is used to enhance the brightness and contrast of the image beam, and the illumination prism is used to improve the uniformity and distribution of the image beam; An image offset mirror for adjusting the direction and position of the image; The first lens group (G1) consisting of a first lens (L1) with a positive focal power; The second lens group (G2) consisting of a second lens (L2) with a positive focal power, a third lens (L3) with a positive focal power, a fourth lens (L4) with a negative focal power, and a fifth lens (L5) with a positive focal power; among them, the third lens (L3), the fourth lens (L4), and the fifth lens (L5) are combined into a triple cemented lens; An aperture stop; The third lens group (G3) consisting of a sixth lens (L6) with a positive focal power; The fourth lens group (G4) consisting of a seventh lens (L7) with a positive focal power; The fifth lens group (G5) consisting of an eighth lens (L8) with a positive focal power and a ninth lens (L9) with a negative focal power; the eighth lens (L8) and the ninth lens (L9) are combined into a double cemented lens; The sixth lens group (G6) consisting of a tenth lens (L10) with a negative focal power and an eleventh lens (L11) with a negative focal power.

2. The projection zoom optical system according to claim 1, wherein: The first lens (L1), the third lens (L3), the fourth lens (L4), the fifth lens (L5), the sixth lens (L6), the eighth lens (L8), and the ninth lens (L9) are all spherical lenses; The second lens (L2), the seventh lens (L7), the tenth lens (L10), and the eleventh lens (L11) are all aspherical lenses.

3. The projection zoom optical system according to claim 1, wherein: The seventh lens (L7), the tenth lens (L10), and the eleventh lens (L11) are all plastic lenses.

4. The projection zoom optical system according to claim 1, wherein: The first lens (L1), the second lens (L2), the third lens (L3), the fourth lens (L4), the fifth lens (L5), the sixth lens (L6), the eighth lens (L8), and the ninth lens (L9) are all glass lenses.

5. The projection zoom optical system according to claim 1, wherein: The Abbe number of the fourth lens (L4) is 20 to 30, and the thickness is 0.5 mm to 2 mm.

6. The projection zoom optical system according to claim 1, characterized in that: The refractive index of the fourth lens (L4) is greater than 1.7, and the refractive indices of the third lens (L3) and the fifth lens (L5) are less than 1.

7.

7. The projection zoom optical system according to claim 1, characterized in that: The Abbe number of the eighth lens (L8) is from 0 to 65, and the Abbe number of the ninth lens (L9) is from 0 to 65.

8. The projection zoom optical system according to claim 1, characterized in that: The eighth lens (L8) is a biconvex lens, and the ninth lens (L9) is a biconcave lens.

9. The projection zoom optical system according to claim 1, characterized in that: The distance from the light valve to the first lens (L1) is denoted as BFL, and the distance from the vertex of the surface of the first lens (L1) to the vertex of the surface of the eleventh lens (L11) is denoted as L, and the relational expression is satisfied: 0.0 < BFL / L < 0.

5.

10. The projection zoom optical system according to claim 1, characterized in that: The first lens group (G1), the second lens group (G2), the third lens group (G3), the fourth lens group (G4), the fifth lens group (G5), and the sixth lens group (G6) form a zoom lens group; The equivalent focal length of the zoom lens group is F1, the equivalent focal length of the first lens group (G1) is F2, the equivalent focal length of the second lens group (G2) is F3, the equivalent focal length of the third lens group (G3) is F4, the equivalent focal length of the fourth lens group (G4) is F5, the equivalent focal length of the fifth lens group (G5) is F6, and the equivalent focal length of the sixth lens group (G6) is F7, and the following conditions are satisfied: 2 < |F2 / F1| < 5; 10 < |F3 / F1| < 50; 1 < |F4 / F1| < 4; 5 < |F5 / F1| < 10; 2 < |F6 / F1| < 5; 0 < |F7 / F1| < 3.

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