Glass-plastic hybrid passive athermalization projection lens and system

Abstract

The invention discloses a glass-plastic hybrid passive athermalization projection lens and system. The glass-plastic hybrid passive athermalization projection lens is sequentially provided with a first lens, a second lens, a third lens and a fourth lens from an object side and an image side along a main optical axis; the first lens close to the object side is a convex surface, and the first lens close to the image side is a concave surface; the second lens close to the object side is a plane, and the second lens close to the image side is a convex surface; the third lens is a doublet lens formed by embedding a biconcave lens with negative focal power and a biconvex lens with positive focal power; the third lens close to the object side is a concave surface, and the third lens close to the image side is a convex surface; the fourth lens close to the object side is a convex surface, and the fourth lens close to the image side is a concave surface. Through the glass-plastic mixed material and the reasonable lens curvature layout, the optical system can still keep a stable focus position in different temperature environments, so that the thermal defocus phenomenon is reduced, and the definition of a projection picture is improved.

Description

Technical Field

[0001] The present invention relates to the field of optical projection technology, and in particular to a glass-plastic hybrid passive athermal projection lens and system. Background Art

[0002] With the development and diversification of projection technology, the consumer market has an increasingly broad demand for projection equipment, especially in the area of miniaturization. Miniaturized projection equipment is designed to meet people's daily needs for portability and practicality. Therefore, various application scenarios are accompanied by requirements for lightweight, compact size, and good ambient temperature adaptability. This ensures that people's daily use of projectors will not be affected by the ambient temperature and the heat of the projector itself, causing the projector to experience thermal defocusing that affects consumers' visual perception.

[0003] Currently, mainstream small projectors primarily rely on LED or laser light source technology, combined with compact optical path designs to achieve compact size. For thermal management, manufacturers generally adopt a hybrid solution combining active cooling (e.g., micro-fans) and passive cooling (e.g., graphene heat spreaders and vapor chambers), supplemented by temperature sensors to monitor the status of key components in real time. Some high-end models have also attempted to improve heat dissipation efficiency through liquid cooling microcirculation systems, but due to size and cost constraints, this has yet to become widespread in consumer products. While existing technologies have achieved certain breakthroughs, fluctuations in ambient temperature and heat generated by the projector's light source in different application scenarios can cause thermal expansion and contraction of the lens material, as well as changes in the lens' refractive index. Furthermore, the lens barrel material also expands and contracts to varying degrees at different temperatures, affecting the light propagation path through the optical components. This can cause the focal point of the optical system's image plane to shift with temperature, resulting in thermal defocus. This causes the focal points of different fields of view to be offset from the same image plane, making the projected image unclear.

[0004] To solve the above problems, the embodiment of the present invention is directed to a glass-plastic hybrid passive athermal projection lens and system, which aims to solve the problem of thermal defocusing when the projector is in use. Summary of the Invention

[0005] The main purpose of the present invention is to provide a glass-plastic hybrid passive athermal projection lens and system, aiming to solve the technical problem of thermal defocusing when the projector is in use.

[0006] To achieve the above objectives, the present invention proposes a glass-plastic hybrid passive athermal projection lens, which is provided with a first lens, a second lens, a third lens and a fourth lens in sequence along the principal optical axis from the object side and the image side; the first lens has a convex surface close to the object side and a concave surface close to the image side; the second lens has a flat surface close to the object side and a convex surface close to the image side; the third lens is a doublet lens composed of a negative optical power biconcave lens and a positive optical power biconvex lens embedded in each other; the third lens has a concave surface close to the object side and a convex surface close to the image side; the fourth lens has a convex surface close to the object side and a concave surface close to the image side.

[0007] Optionally, the focal length f of the glass-plastic hybrid passive athermal projection lens and the total length L of the lens satisfy the following relationship: .

[0008] Optionally, the focal length of the first lens and focal length f satisfy the following relationship: .

[0009] Optionally, the focal length of the second lens and focal length f satisfy the following relationship: .

[0010] Optionally, the focal length of the fourth lens and focal length f satisfy the following relationship: .

[0011] Optionally, the total length L of the lens is equal to the total length from the image side to the image side IMA of the fourth lens. The following relationship is satisfied: .

[0012] Optionally, the focal length of the first lens and minimum optical effective diameter The following relationship is also satisfied: .

[0013] Optionally, the focal length of the second lens and minimum optical effective diameter The following relationship is also satisfied: .

[0014] Optionally, the Abbe number of at least one of the third lens and the fourth lens is between 70 and 90.

[0015] A glass-plastic hybrid passive athermal projection system is also proposed, which includes an aperture, a galvanometer, a prism, a protective glass and the glass-plastic hybrid passive athermal projection lens as described above; the aperture is arranged on one side of the second lens; a third lens is provided on one side of the fourth lens, and the galvanometer, the prism and the protective glass are provided in sequence on the other side of the fourth lens.

[0016] Compared with the prior art, the present invention has the following beneficial effects: The glass-plastic hybrid lens achieves "source heat suppression." An aperture placed on the side of the second lens element blocks direct heat from the light source from entering the subsequent optical path, reducing temperature rise in heat-sensitive components such as the prism and galvanometer. The galvanometer is placed behind the fourth lens element to reduce air resistance and accelerate galvanometer heat dissipation (galvanometer power consumption typically accounts for 15% to 20% of the system). A 45-degree prism reflection is employed, and heat sink fins are arranged on the side of the lens barrel, increasing the effective heat dissipation area by 15%. The protective glass protects the internal optical path from sudden changes in ambient temperature, while also serving as a heat spreader to expand the heat dissipation surface, achieving optical path-heat dissipation synergy. Through materials and layout, the three major heat sources, the light source (laser), galvanometer, and chip, are physically isolated, forming independent heat dissipation paths. This shifts thermal management from traditional "post-heat dissipation" to "source heat control." The passive athermalization of the glass-plastic hybrid lens achieves a compact, thin, and passively athermalized optical system. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying any creative work.

[0018] Figure 1 Schematic diagram of the structure of a glass-plastic hybrid passive athermal projection system according to an embodiment of the present invention; Figure 2 Graphs showing field curvature and distortion of a glass-plastic hybrid passive athermal projection system according to an embodiment of the present invention; Figure 3 This is a schematic diagram showing an MTF of 95 lp / mm for a glass-plastic hybrid passive athermal projection system according to an embodiment of the present invention; Figure 4 This is a schematic diagram showing an MTF of 95mp / mm at ambient temperature of 27°C for a glass-plastic hybrid passive athermal projection system according to an embodiment of the present invention; Figure 5This is a schematic diagram showing an MTF of 95 mp / mm at an ambient temperature of 65° C. for a glass-plastic hybrid passive athermal projection system according to an embodiment of the present invention; Figure 6 This is a schematic diagram showing that the MTF of a glass-plastic hybrid passive athermal projection system according to an embodiment of the present invention is 95 mp / mm at an ambient temperature of -15°C; Figure 7 Schematic diagram of the structure of a glass-plastic hybrid passive athermal projection system according to an embodiment of the present invention; Figure 8 Graphs showing field curvature and distortion of a glass-plastic hybrid passive athermal projection system according to an embodiment of the present invention; Figure 9 This is a schematic diagram showing an MTF of 20 lp / mm for a glass-plastic hybrid passive athermal projection system according to an embodiment of the present invention; Figure 10 This is a schematic diagram showing an MTF of 95mp / mm at ambient temperature of 27°C for a glass-plastic hybrid passive athermal projection system according to an embodiment of the present invention; Figure 11 This is a schematic diagram showing that the MTF of a glass-plastic hybrid passive athermal projection system according to an embodiment of the present invention is 95 mp / mm at an ambient temperature of 65°C; Figure 12 This is a schematic diagram showing that the MTF of a glass-plastic hybrid passive athermal projection system according to an embodiment of the present invention is 95 mp / mm at an ambient temperature of -15°C.

[0019] Description of Figure Numbers: G1, first lens; G2, second lens; G3, biconcave lens; G4, biconvex lens; G5, fourth lens; ST0, aperture; 600, galvanometer; 700, prism; 800, protective glass.

[0020] The purpose, features and advantages of the present invention will be further described with reference to the accompanying drawings and in conjunction with the embodiments. DETAILED DESCRIPTION

[0021] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0022] It should be noted that if the embodiments of the present invention involve directional indications (such as up, down, left, right, front, back, etc.), such directional indications are only used to explain the relative position relationship, movement status, etc. between the various components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0023] In addition, the descriptions of "first", "second", etc. in the present invention are only for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In addition, "and / or" in the full text includes three solutions. Taking A and / or B as an example, it includes technical solution A, technical solution B, and technical solution that satisfies both A and B. In addition, the technical solutions between the various embodiments can be combined with each other, and must be based on the ability of ordinary technicians in this field to implement. When the combination of technical solutions is mutually contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0024] A glass-plastic hybrid passive athermal projection lens and system. To make the objectives, advantages, and solutions of the embodiments more clearly expressed, the invention is further described in detail below in conjunction with the optical system structure diagram, such as the accompanying drawings and embodiments. The embodiments described herein are only some embodiments of the present invention and cannot represent all embodiments. The steps and execution order of the embodiments may be adjusted accordingly based on the understanding of technicians in this field. Therefore, all derived embodiments of the present invention obtained by technicians in this field without creativity fall within the scope of protection of the present invention.

[0025] The present invention proposes a glass-plastic hybrid passive athermal projection lens and system, which aims to solve the problem of existing projectors being too long and aims to make them smaller, lighter and thinner so as to meet the needs of daily carrying without taking up space. In addition, with different application scenarios, changes in external ambient temperature and the heat generated by the projector light source itself will cause the lens material to expand and contract with heat and the refractive index of the lens to change. At the same time, the barrel material will also expand and contract to varying degrees at different temperatures, causing the propagation path of light in optical components to be affected, thereby causing the focus of the optical system image plane to shift with temperature changes, resulting in thermal defocusing, so that the focus of each field of view is not on the same image plane, making it impossible to maintain clarity in the projected image. The glass-plastic hybrid lens is passively athermalized to achieve a small and thin lens and a passive athermalization of the optical system.

[0026] The present invention discloses a glass-plastic hybrid passive athermal projection lens. The glass-plastic hybrid passive athermal projection lens is provided with a first lens G1, a second lens G2, a third lens, and a fourth lens G5 in sequence along the principal optical axis from the object side and the image side; the first lens G1 has a convex surface close to the object side and a concave surface close to the image side; the second lens G2 has a flat surface close to the object side and a convex surface close to the image side; the third lens is a doublet lens composed of a negative-power biconcave lens G3 and a positive-power biconvex lens G4 that are embedded with each other; the third lens has a concave surface close to the object side and a convex surface close to the image side; the fourth lens has a convex surface close to the object side and a concave surface close to the image side.

[0027] It should be noted that, combined with Figure 1 The first lens G1, the second lens G2, the third lens G5 and the fourth lens G5 are arranged in sequence along the main optical axis to form the entire optical system. Among them, the first lens G1 is a meniscus aspherical lens with negative optical power. A meniscus lens refers to a lens structure with a crescent-shaped appearance. An aspherical lens means that one or more surfaces of the lens are not strictly spherical, so as to correct spherical aberration and increase the field of view. The second lens G2 is a plano-convex lens with positive optical power, used to collect light. The third lens is composed of a biconcave lens G3 with negative optical power and a biconvex lens G4 with positive optical power. The lens is stacked to form a doublet, with the biconcave lens G3 diverging light and the biconvex lens G4 converging light. One side of the biconcave lens G3 is tightly bonded to the other side of the biconvex lens G4, forming a composite lens structure that helps correct spherical aberration and chromatic aberration, as well as passively athermalize the lens. The fourth lens G5 is a positive-power biconvex aspheric lens. Its biconvex structure further enhances convergence, while its aspheric design helps optimize optical performance, reduce aberrations, and correct spherical aberration and athermalize the system. The lenses are arranged sequentially along the principal optical axis, with the first lens G1 located on the object side, i.e., the side closest to the object, and the fourth lens G5 located on the image side, i.e., the location where the image is projected. Each lens is mounted and fixed to the lens barrel or related bracket according to established design parameters. The first lens G1 and the second lens G2, the second lens G2 and the third lens, and the third lens and the fourth lens G5 can be connected by mechanical fixing, bonding, or snap fastening to form a complete optical system. This ensures that the lenses maintain stable relative positions during use, preventing optical performance from being affected by vibration or temperature changes. This structure maintains relatively stable imaging quality over a wide range of temperature fluctuations, achieving an athermal effect and enabling the lens to maintain stable performance in complex environments. Furthermore, to meet the system's imaging requirements, the first lens element G1 is a plastic aspheric surface, the second lens element G2 is a glass spherical surface, the biconcave lens element is a glass spherical surface, the biconvex lens element is a glass spherical surface, and the fourth lens element G5 is a glass aspheric surface. Compared to traditional projection lenses made of a single material of glass or plastic, this solution offers the advantages of lighter weight, lower manufacturing costs, and more stable optical performance. Furthermore, through a rational lens combination and athermal design, the impact of ambient temperature changes on image quality can be effectively reduced, enabling the projection system to maintain good focal length stability in different temperature environments, avoiding image blur or out-of-focus issues, and improving the clarity and consistency of the projected display.

[0028] Furthermore, the focal length f of the glass-plastic hybrid passive athermal projection lens and the total length L of the lens satisfy the following relationship: .

[0029] It should be noted that under the requirements of short focus and large field of view, the aspheric design of the glass-plastic hybrid lens group (plastic lenses are easy to process aspheric surfaces) can fully correct aberrations, while avoiding the stray light problem caused by excessive folding of the optical path. Within a limited volume, the entropy increase (performance degradation) of the optical system caused by thermal disturbances is close to zero.

[0030] Furthermore, the focal length of the first lens G1 is and focal length f satisfy the following relationship: .

[0031] It should be noted that in the optical system, the focal length of the first lens G1 is The proportional relationship with the focal length f is the result of the coordinated optimization of aberration correction, optical path convergence and system compactness. It is further supplemented that the focal length ratio of the negative lens must satisfy Petzval and ( ,in: : the refractive index of the material of the i-th lens; : The focal length of the i-th lens (the unit is consistent with the total focal length f of the system)) convergence condition to suppress field curvature. Too small (such as ), the negative lens contribution is insufficient, making it difficult to correct the field curvature; if Big (such as ), it may introduce excessive barrel distortion, so This ratio ensures that the divergence angle of the negative lens to the marginal light matches the convergence ability of the subsequent positive lens, avoiding the accumulation of high-order aberrations.

[0032] Furthermore, the focal length of the second lens G2 is and focal length f satisfy the following relationship: .

[0033] The focal length of the fourth lens G5 and focal length f satisfy the following relationship: .

[0034] It should be noted that the focal length ratio of the second lens G2 ensures that the divergence angle of the negative lens to the marginal light matches the convergence ability of the subsequent positive lens, avoiding the accumulation of high-order aberrations. The second lens G2 re-converges the light diverged by the first lens G1, controls the angle of the main light, and avoids the subsequent lens group from being too large in diameter. It also forms a "divergence-convergence" combination with the first negative lens to jointly correct spherical aberration, coma and chromatic aberration. It also participates in passive athermal compensation by matching the thermal properties of the material (refractive index temperature coefficient, thermal expansion coefficient) with the focal length ratio. If the first negative lens =−1.6, second positive lens =3, then the contribution ratio of the two is Subsequent lenses need to be further balanced to approach zero.

[0035] The fourth lens G5 is a positive lens at the end of the optical path. Its focal length ratio adjusts the final convergence state of the Petzval sum to ensure a flat image plane and reserve sufficient back focal length for the sensor or display chip.

[0036] Furthermore, the total length L of the lens is equal to the total length from the image side to the image side IMA of the fourth lens G5. The following relationship is satisfied: .

[0037] The focal length of the first lens G1 and minimum optical effective diameter The following relationship is also satisfied: The focal length of the second lens G2 and minimum optical effective diameter The following relationship is also satisfied: .

[0038] The Abbe number of at least one of the third lens and the fourth lens G5 is between 70 and 90.

[0039] Furthermore, the lens aperture F# of the glass-plastic hybrid passive athermal projection lens satisfies the following relationship: .

[0040] It should be noted that, first, the total length of the lens L and the total length from the convex surface of the image side of the fourth lens G5 to the image side IMA satisfy This relationship mainly optimizes the optical path layout of the lens, ensuring that the system can maintain reasonable optical performance while being miniaturized. Due to the limited size of small projection equipment, the optical path needs to be shortened as much as possible. The limitation of this relationship can control the overall length of the optical system while ensuring the imaging quality, and reduce the impact of the system's thermal expansion on the stability of the optical axis. At the same time, this design makes the lens structure compact, reduces the problem of uneven material stress caused by temperature changes, thereby reducing the possibility of optical axis offset and improving the stability of the projection equipment. Secondly, regarding the focal length of the first lens Its minimum optical effective diameter The relationship between , this parameter limitation is mainly to optimize the control of the incident light beam, so that the first lens G1 can reasonably guide the light and reduce the influence of spherical aberration and thermal aberration. Under high temperature conditions, the thermal expansion coefficient of the lens material will cause a slight change in the focal length, thereby affecting the imaging quality of the system. This proportional relationship ensures that the optical effective aperture of the first lens G1 is moderate, so that it can effectively collect light without causing the non-thermal design of the optical system to fail due to an excessively large aperture, thereby reducing the impact of thermal expansion on imaging and improving the system's adaptability to changes in ambient temperature. Again, regarding the focal length of the second lens Minimum optical effective diameter The relationship between This limiting relationship is mainly to optimize the luminous flux control of the lens and improve the uniformity of the optical system. Since the light source of the projection equipment usually uses laser, and the luminous flux of these light sources varies under different temperature environments, if the optical effective aperture of the lens is too large, it may lead to unstable projection brightness, while if it is too small, it may limit the luminous flux and affect the brightness of the picture. By reasonably setting range, enabling the optical system to maintain a stable light flux distribution under different temperature conditions, reduce optical distortion and improve imaging consistency. By leveraging both the optical and thermodynamic properties of high-Abbe-number materials, this design achieves: Suppressing chromatic aberration and thermal drift at the source, eliminating the need for temperature compensation algorithms; passively offsetting thermal expansion and optical axis offset, overcoming the physical limitations of insufficient heat dissipation surface area; and reducing system complexity by replacing redundant structures with innovative materials, breaking the vicious cycle of "lightweight-poor heat dissipation-low reliability." Essentially, this upgrades the traditional engineering approach of "heat generation first, remediation later" to a physical-layer structure that combines "suppressing thermal disturbances with adaptive material heat resistance," providing a cost-effective path to reliability for consumer-grade micro-projectors.

[0041] In summary, these relationships achieve a balance between optical system miniaturization, stability, and heat resistance, reducing the risk of optical axis deviation in high-temperature environments and improving image quality stability. Ultimately, this effectively mitigates the optical system failure problem caused by limited heat dissipation in small projection systems. This optimization solution plays a significant role in enhancing the adaptability of projection equipment in complex environments, improving equipment reliability, and extending its service life.

[0042] Furthermore, the glass-plastic hybrid passive athermal projection system includes an aperture ST0, a galvanometer 600, a prism 700, a protective glass 800 and the glass-plastic hybrid passive athermal projection lens as described above; the aperture ST0 is arranged on one side of the second lens G2; a third lens is provided on one side of the fourth lens G5, and the galvanometer 600, the prism 700 and the protective glass 800 are provided in sequence on the other side of the fourth lens G5.

[0043] It should be noted that the optical system lens layout of the glass-plastic hybrid passive athermal projection lens and system is as follows: first lens G1, second lens G2, aperture ST0, third lens, fourth lens G5 along the principal optical axis from the object side to the image side. The lens group constitutes a complete projection system together with the optical system including the galvanometer 600, prism 700, protective glass 800.

[0044] In summary, the glass-plastic hybrid lens achieves "source heat suppression." The aperture ST0, placed on the side of the second lens element G2, blocks direct heat from the light source from entering the subsequent optical path, reducing the temperature rise of heat-sensitive components such as the prism 700 and the galvanometer 600. Placing the galvanometer 600 behind the fourth lens element G5 reduces the thermal resistance of the air layer and accelerates heat dissipation from the galvanometer 600 (which typically accounts for 15% to 20% of the system's power consumption). A 45° prism 700 is used for reflection, and heat sink fins are arranged on the side of the lens barrel, increasing the effective heat dissipation area by 15%. The external protective glass 800 isolates the internal optical path from the effects of sudden changes in external ambient temperature and acts as a heat spreader to expand the heat dissipation surface, achieving optical path-heat dissipation synergy. Through materials and layout, the three major heat sources, the light source (laser), the galvanometer 600, and the chip, are physically isolated, forming independent heat dissipation paths. This shifts thermal management from traditional "post-heat dissipation" to "source heat control," achieving greater heat dissipation within the same volume.

[0045] Example 1: In the embodiment of the present invention, Figure 1As shown, the glass-plastic hybrid passive athermal projection lens and system of the present application includes, along the principal optical axis from the object side to the image side, the following: a first lens G1, a second lens G2, an aperture ST0, a third lens, a fourth lens G5, a galvanometer 600, a prism 700, a protective glass 800, and a chip to form a complete optical system, wherein the first lens G1 is a meniscus aspheric lens with negative focal length, the second lens G2 is a plano-convex lens with positive focal length, the third lens is a doublet lens composed of a negative focal length biconcave lens G3 and a positive focal length biconvex lens G4 stacked on each other, and the fourth lens G5 is a positive focal length biconvex aspheric lens; wherein S1 is the screen end of the first lens G1, S2 is the image source end of the first lens G1, and S3 is the second lens G2 is the screen end, S4 is the image source end of the second lens G2, S5 (ST0) represents the aperture ST0, S6 is the screen end of the biconcave lens G3, S7 is the image source end of the bi-lens, and at the same time, S7 is also the screen end of the biconvex lens G4, S8 is the image source end of the biconvex lens G4, S9 is the screen end of the fourth lens G5, S10 is the image source end of the fourth lens G5, S11 is the screen end of the galvanometer 600, S12 is the image source end of the galvanometer 600, S13 is the screen end of the prism 700, S14 is the image source end of the prism 700, S15 is the screen end of the protective glass 800, S16 is the image source end of the protective glass 800, and the solid line on the right side of S16 is the image source end (IMA surface, image surface), which is S17.

[0046] In addition, the first lens G1 has a convex surface on the object side and a concave surface on the image side; the second lens G2 has a flat surface on the object side and a convex surface on the image side; the biconcave lens G3 has a concave surface on the object side and a concave surface on the image side; the biconvex lens G4 has a convex surface on the object side and a convex surface on the image side; and the fourth lens G5 has a convex surface on the object side and a convex surface on the image side.

[0047] In this embodiment, by better compensating for aberrations, distortions, and thermal equation conditions to achieve better compensation for various materials and a better system to shorten the size of the entire optical system and reduce optical costs, it can also better ensure that the lens and the entire system can be used in a high and low temperature environment of -15°C to 65°C without athermalization and better imaging quality.

[0048] In passive athermalization design, the optical system needs to be athermalized. During the design process, each lens element and structure must satisfy the following athermalization equation: Where, is the incident height of the first paraxial ray at each lens, is the system optical power, is the focal power of each lens, is the thermal expansion coefficient of each lens material, is the thermal expansion coefficient of the lens barrel, and L is the mechanical length of the lens barrel. In the optical system of this embodiment, the lens barrel structure is made of aluminum alloy, and its thermal expansion coefficient is .

[0049] Furthermore, the first lens G1 to the fourth lens constitute the focusing group of the entire system, which moves along the main optical axis to achieve focusing; and under the condition of sufficient brightness, clear focusing can be achieved within the projection range of 0.15m to 5m. In order to meet the high-resolution imaging requirements of the system, the first lens G1 is a plastic aspherical surface, the second lens G2 is a glass spherical surface, the biconcave lens is a glass spherical surface, the biconvex lens is a glass spherical surface, and the fourth lens is a glass aspherical surface.

[0050] The optical system of the present invention adopts a two-aspheric solution, one glass and one plastic, based on cost and athermalization considerations. This solution plays an important role in optimizing aspheric aberrations, and can reduce the number of lenses in the system, significantly controlling both cost and spherical aberration. In addition to cost considerations, the glass aspheric surface is chosen for the fourth lens element based on the athermalization of the control system. This is because materials with a high thermal expansion coefficient and a negative refractive index temperature coefficient can be selected in the lens to compensate for the defocus caused by other lenses with a positive refractive index temperature coefficient, thereby achieving an athermal design.

[0051] As described above, the present invention uses a passive athermal design to match the thermal properties of the optical system lens material with the thermal properties of the mechanical materials of the structural components, so that the thermal properties of the lenses and structural components of the entire optical system are reasonably matched during use. When the internal and external ambient temperatures change, the changes in the thermal properties of the various components caused by heat can offset each other, thereby achieving a passive athermal effect.

[0052] In this embodiment, the system parameters are shown in Tables 1 and 2 below. The full FOV of the optical system is 56°, and the focal length is 3.7.

[0053] Table 1: Where R is the radius of curvature, D is the lens thickness or air space, nd material represents the refractive index, and vd material represents the Abbe number.

[0054] Table 2: The aspheric formula is as follows: ; Where Z is the sagittal height at the vertex of the aspheric surface when the aspheric surface is at a height r along the optical axis, k is the cone coefficient, and c is the curvature of the surface vertex. ...etc. are the coefficients of higher-order aspheric surfaces.

[0055] In this system, the distortion correction is less than 0.5% at the maximum field of view. Figure 2 The minimal deformation in the projection system image meets the normal use needs of people. At the same time, the entire optical system has a high resolution. For example, when used on a 0.6-inch chip, its MTF (Modulation Transfer Function) can reach a maximum of 95lp / mm ≥ 0.64, indicating that this lens has excellent ability to restore image details. Figure 3 The glass-plastic hybrid passive athermal projection lens and system can achieve an MTF performance of 95lp / mm≥0.64 at room temperature 27℃. Figure 4 The glass-plastic hybrid passive athermal projection lens and system can achieve an MTF performance of 95lp / mm≥0.39 at a high temperature of 65°C. Figure 5 The glass-plastic hybrid passive athermal projection lens and system can achieve an MTF performance of 95lp / mm≥0.39 at a low temperature of -15℃. Figure 6 The MTF performance at these temperatures demonstrates that the lens maintains stable performance under varying environmental conditions, including high and low temperatures. The lens also demonstrates excellent athermalization of its passive defocus compensation at both high and low temperatures. This ensures that the lens can reproduce image detail even under varying temperatures.

[0056] Example 2: like Figure 7As shown in the optical system structure diagram of the athermal lens, it includes, along the main optical axis from the object side to the image side: a first lens G1, an aperture ST0, a second lens G2, a third lens and a fourth lens G5. The galvanometer 600, the prism 700, the protective glass 800 and the chip at the optical machine end form a complete optical system. The first lens G1 is a meniscus aspheric lens with negative focal length, the second lens G2 is a plano-convex lens with positive focal length, the third lens is a doublet lens composed of a negative focal length biconcave lens G3 and a positive focal length biconvex lens G4 stacked on each other, and the fourth lens is a positive focal length biconvex aspheric lens; wherein S1 is the screen end of the first lens G1, S2 is the image source end of the first lens G1, and S3 represents the light Stop ST0, S4 is the screen end of the second lens G2, S5 is the image source end of the second lens G2, S6 is the screen end of the biconcave lens G3, S7 is the image source end of the biconvex lens, and at the same time, S7 is also the screen end of the biconvex lens G4, S8 is the image source end of the biconvex lens G4, S9 is the screen end of the fourth lens G5, S10 is the image source end of the fourth lens G5, S11 is the screen end of the galvanometer 600, S12 is the image source end of the galvanometer 600, S13 is the screen end of the prism 700, S14 is the image source end of the prism 700, S15 is the screen end of the protective glass 800, S16 is the image source end of the protective glass 800, and the solid line on the right side of S16 is the image source end (IMA surface, image surface), that is, S17.

[0057] In this embodiment, the system parameters are shown in Tables 3 and 4 below. The full FOV of the optical system is 56°, and the focal length is 3.75.

[0058] In this system, the distortion correction is less than 0.5% at the maximum field of view. Figure 8 The minimal deformation in the projection system image can meet people's normal use needs. At the same time, the entire optical system has a high resolution. For example, when used on a 0.6-inch chip, its MTF can reach a maximum of 95lp / mm≥0.64, indicating that this lens has an excellent ability to restore image details. Figure 9 The glass-plastic hybrid passive athermal projection lens and system can achieve an MTF performance of about 95lp / mm≥0.5 at room temperature of 27℃. Figure 10 The glass-plastic hybrid passive athermal projection lens and system can achieve an MTF performance of 95lp / mm≥0.5 at a high temperature of 65°C. Figure 11 The glass-plastic hybrid passive athermal projection lens and system can achieve an MTF performance of 95lp / mm≥0.5 at a low temperature of -15℃. Figure 12 The MTF performance at these temperatures demonstrates that the lens maintains stable performance under varying environmental conditions, including high and low temperatures. The lens also demonstrates excellent athermalization of its passive defocus compensation at both high and low temperatures. This ensures that the lens can reproduce image detail even under varying temperatures.

[0059] Table 3: Where R is the radius of curvature, D is the lens thickness or air space, nd material represents the refractive index, and vd material represents the Abbe number.

[0060] Table 4: The aspheric formula is as follows: ; Where Z is the sagittal height at the vertex of the aspheric surface when the aspheric surface is at a height r along the optical axis, k is the cone coefficient, and c is the curvature of the surface vertex. ...etc. are the coefficients of higher-order aspheric surfaces.

[0061] Through the above embodiments, the glass-plastic hybrid passive athermal projection lens and system: the optical system lens layout of the optical lens is arranged in the order from the object side to the image side along the principal optical axis, and the lenses are arranged as follows: a first lens G1 plastic aspheric surface, a second lens G2 glass spherical surface, an aperture ST0, a biconcave lens G3 glass spherical surface, a biconvex lens G4 glass spherical surface, and a fourth lens G5 glass aspheric surface; or an imaging lens is arranged as follows: a first lens G1 plastic aspheric surface, an aperture ST0, a second lens G2 glass spherical surface, a biconcave lens G3 glass spherical surface, a biconvex lens G4 glass spherical surface, and a fourth glass aspheric surface lens; and the galvanometer 600 and prism 600 of the optical machine end of the present invention are used. 700, protective glass 800 and the chip constitute a complete imaging optical system; at the same time, through the reasonable matching of important parameters such as surface curvature, spacing, lens material characteristics and special materials of lens barrel structural parts among each lens, as well as the definition and selection of the system focusing system, the light path can be effectively controlled during focusing, the lens size can be greatly shortened, the geometric efficiency of the lens can be effectively improved while reducing the lens cost, and the spherical aberrations of each optical imaging system can be effectively controlled, thereby improving the imaging quality, improving the light efficiency and reasonably matching the athermal properties of the lens and the structural parts, so that the system has better thermal stability in a hot environment and realizes a passive athermal effect.

[0062] The above description is only a preferred embodiment of the present invention and does not limit the patent scope of the present invention. All equivalent structural transformations made by using the contents of the present invention description and drawings under the inventive concept of the present invention, or direct / indirect application in other related technical fields are included in the patent protection scope of the present invention.

Claims

1. A glass-plastic hybrid passive athermal projection lens, characterized in that: The glass-plastic hybrid passive athermal projection lens is provided with a first lens, a second lens, a third lens and a fourth lens in sequence from the object side and the image side along the main optical axis; The first lens has a convex surface close to the object side and a concave surface close to the image side; The second lens has a flat surface close to the object side and a convex surface close to the image side; The third lens is a doublet lens consisting of a negative-power biconcave lens and a positive-power biconvex lens embedded in each other; The third lens has a concave surface close to the object side and a convex surface close to the image side; The fourth lens has a convex surface close to the object side and a concave surface close to the image side.

2. The glass-plastic hybrid passive athermal projection lens according to claim 1, characterized in that: The focal length f of the glass-plastic hybrid passive athermal projection lens and the total length L of the lens satisfy the following relationship: 。 3. The glass-plastic hybrid passive athermal projection lens according to claim 2, characterized in that: The focal length of the first lens and focal length f satisfy the following relationship: 。 4. The glass-plastic hybrid passive athermal projection lens according to claim 3, characterized in that: The focal length of the second lens and focal length f satisfy the following relationship: 。 5. The glass-plastic hybrid passive athermal projection lens according to claim 4, characterized in that: The focal length of the fourth lens and focal length f satisfy the following relationship: 。 6. The glass-plastic hybrid passive athermal projection lens according to claim 2, characterized in that: The total length L of the lens is equal to the total length from the image side to the image side IMA of the fourth lens. The following relationship is satisfied: 。 7. The glass-plastic hybrid passive athermal projection lens according to claim 3, characterized in that: The focal length of the first lens and minimum optical effective diameter The following relationship is also satisfied: 。 8. The glass-plastic hybrid passive athermal projection lens according to claim 4, characterized in that: The focal length of the second lens and minimum optical effective diameter The following relationship is also satisfied: 。 9. The glass-plastic hybrid passive athermal projection lens according to claim 1, characterized in that: The Abbe number of at least one of the third lens and the fourth lens is between 70 and 90.

10. A glass-plastic hybrid passive athermal projection system, characterized in that: The glass-plastic hybrid passive athermal projection system comprises an aperture, a galvanometer, a prism, a protective glass, and the glass-plastic hybrid passive athermal projection lens according to any one of claims 1 to 9; The aperture is provided on one side of the second lens; The third lens is provided on one side of the fourth lens, and the galvanometer, the prism and the protective glass are sequentially provided on the other side of the fourth lens.

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