Projection lens and projection ray machine system
By designing a projection lens including multiple lenses and optimizing the structure with lens materials of different materials, the thermal loss of focus caused by temperature during operation of the Micro LED display chip is solved, and high imaging quality and stability are achieved when temperature changes are achieved .
Patent Information
- Application Number
- CN202421337265.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-06-12
- Publication Date
- 2025-02-07
- Estimated Expiration
- 2034-06-12
AI Technical Summary
The temperature of the Micro LED display chip is high when working, causing the lens to expand and contract with the projection lens structural parts, the lens to lose focus, the resolution decreases, and the imaging blur, which affects the user experience.
Design a projection lens, including a first lens with positive power arranged in sequence from the object side to the image side, a second lens with negative power, a third lens with positive power, and a negative power The fourth lens, the lens material is optimized, including glass and plastic materials, to ensure that the back focus change of the lens is less than 5um when the temperature changes, and avoid thermal loss of focus.
Within the ambient temperature range of 20℃ to 60℃, the projection lens is basically free of thermal out-of-focus, and the imaging quality is maintained at a high level, providing high stability, enhancing user experience, and facilitating the thinning of AR glasses.
Smart Images
Figure CN222439757U_ABST
Abstract
Description
Technical Field
[0001] The utility model relates to the technical field of optical systems, in particular to a projection lens and a projection optical machine system. Background Art
[0002] With the development of near-eye display technology, more and more AR / VR display devices have been launched. The more mature solution is waveguide plus micro-projection optical machine, and the micro-projection optical machine based on Micro LED is considered to be the trend of AR display solution due to its smaller pixel size and higher brightness; however, since the Micro LED display chip has a high temperature when working, the sharp increase in temperature causes the projection lens structure to expand and contract, and the lens becomes thermally defocused, resulting in a decrease in lens resolution and blurred imaging, which greatly affects the user experience.
[0003] Traditional projection mirrors will automatically lose focus after being used for a period of time. That is to say, although the focal length is adjusted at the beginning, the lens must be refocused after a period of use. Some have added an automatic focus function to solve the problem of lens defocus. By moving the movable lens, the movable lens position corresponding to the highest clarity value within the moving range is found, and the movable lens is controlled to fall to the position with the highest clarity value within the moving range to achieve refocusing; others refocus through the overall or local structure. For AR glasses, the optical machine and glasses structure need to be very small and compact, and there is no possibility of secondary focusing. Therefore, this solution proposes a projection lens that can automatically compensate, is small in size and has high imaging quality to solve the above problems. Utility Model Content
[0004] The main purpose of the utility model is to provide a projection lens and a projection optical system, aiming to at least solve the technical problems that the existing projection lens is easily out of focus due to thermal expansion and contraction, and is difficult to readjust due to structural size limitations.
[0005] To achieve the above object, the utility model provides a projection lens, the projection lens comprises a lens body, the lens body comprises a first lens with positive optical power, a second lens with negative optical power, a third lens with positive optical power and a fourth lens with negative optical power arranged in sequence from the object side to the image side, the first lens, the second lens, the third lens and the fourth lens together form an optical axis;
[0006] The focal length of the projection lens is f,5.8mm <f<6.2mm;
[0007] The total length of the projection lens is L t , the L t ≤6.8.
[0008] In one embodiment, the refractive index of the first lens is n1, the refractive index of the second lens is n2, the refractive index of the third lens is n3, and the refractive index of the fourth lens is n4, which satisfy the following relationship:
[0009] 1.7 <n1<1.9,1.55<n2<1.7,1.5<n3<1.6,1.9<n4<2.1。
[0010] In one embodiment, at least one of the first lens and the fourth lens is made of glass, and at least one of the second lens and the third lens is made of plastic.
[0011] In one embodiment, the second lens and the third lens are made of plastic, and the second lens has a back focus variation Δf2, the fourth lens has a back focus variation Δf3, and the back focus variation of the projection lens is Δf t , satisfying the following relationship:
[0012] △f t = △f2+△f3, and the △f t <5um.
[0013] In one embodiment, the projection lens further includes an aperture and an imaging element, wherein the aperture is disposed on a side of the first lens away from the second lens along the optical axis, and the imaging element is disposed on a side of the fourth lens away from the third lens along the optical axis.
[0014] In one embodiment, the total length of the projection lens is L t is the distance from the aperture to the imaging element.
[0015] In one embodiment, the aperture radius is d0, and the distance from the aperture to the first lens is L0, which satisfies the following relationship:
[0016] 1mm <d0<2.5mm,L0<1.5mm。
[0017] In one embodiment, the semi-aperture of the first lens is d1, the semi-aperture of the second lens is d2, the semi-aperture of the third lens is d3, and the semi-aperture of the fourth lens is d4, satisfying the relationship:
[0018] 2.2mm <d1<2.5mm、2mm<d2<2.3mm、1.6mm<d3<1.9mm、1.3mm<d4<1.6mm;
[0019] The lens core thickness of the first lens is L1, the lens core thickness of the second lens is L2, the lens core thickness of the third lens is L3, and the lens core thickness of the fourth lens is L4, satisfying the following relational expressions:
[0020] 1mm < L1 < 1.4mm, 0.3mm < L2 < 0.6mm, 0.9mm < L3 < 1.2mm, and the lens core thickness 0.3mm < L4 < 0.6mm.
[0021] In one embodiment, at least one of the second lens, the third lens, and the fourth lens is an aspherical lens.
[0022] The present utility model also provides a projection optical machine system. The projection optical machine system includes a projection lens. The projection lens includes a first lens with a positive optical power, a second lens with a negative optical power, a third lens with a positive optical power, and a fourth lens with a negative optical power arranged in sequence from the object side to the image side. The first lens, the second lens, the third lens, and the fourth lens together form an optical axis;
[0023] Wherein, the focal length of the projection lens is f, and 5.8mm < f < 6.2mm;
[0024] The total length of the projection lens is L t , and the L t ≤ 6.8.
[0025] In the technical solution of the present utility model, the projection lens provided by the present utility model performs self-compensation of optical power through plastic lenses. When operating within the temperature fluctuation range of 20°C to 60°C, the projection lens has basically no thermal defocusing and the imaging quality of the projection lens remains at a high level, providing high stability for consumer-grade glasses and enhancing the user experience.
[0026] The total length of the projection lens provided by the present utility model is less than 6.8mm. The small size and high imaging quality are beneficial to the thinning of the AR glasses display solution, greatly enhancing the user experience. BRIEF DESCRIPTION OF THE DRAWINGS
[0027] In order to more clearly illustrate the technical solutions in the embodiments of the present utility model or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present utility model. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on the structures shown in these drawings.
[0028] Figure 1 It is a schematic diagram of the lens arrangement structure of an embodiment of the projection lens provided by the present utility model;
[0029] Figure 2 for Figure 1 Schematic diagram of the lens surface shape of the projection lens;
[0030] Figure 3 for Figure 1 Schematic diagram of the imaging MTF and defocus performance of the projection lens at different temperatures;
[0031] Figure 4 for Figure 1 Field curvature and distortion performance curves of the projection lens;
[0032] Figure 5 To include Figure 1 The projection optical system point diagram of the projection lens;
[0033] Figure 6 for Figure 5 Schematic diagram of relative illumination of projection optical-mechanical system;
[0034] Figure 7 for Figure 1 Appearance diagram of the projection lens.
[0035] Description of Figure Numbers:
[0036] 100. Projection lens; 1. First lens; 2. Second lens; 3. Third lens; 4. Fourth lens; 5. Aperture; 6. Imaging element; 7. Housing.
[0037] The realization of the purpose, functional features and advantages of the utility model will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION
[0038] The following will be combined with the drawings in the embodiments of the utility model to clearly and completely describe the technical solutions in the embodiments of the utility model. Obviously, the described embodiments are only part of the embodiments of the utility model, not all of the embodiments. Based on the embodiments of the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.
[0039] It should be noted that if the embodiments of the present invention involve directional indications (such as up, down, left, right, front, back...), the directional indications are only used to explain the relative position relationship, movement status, etc. between the components in a certain specific posture. If the specific posture changes, the directional indications will also change accordingly.
[0040] In addition, if there are descriptions involving "first", "second", etc. in the embodiments of the utility model, the descriptions of "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of technical features indicated. Therefore, the features limited to "first" and "second" may explicitly or implicitly include at least one of the features. In addition, if "and / or" or "and / or" appears in the full text, its meaning includes three parallel solutions. Taking "A and / or B" as an example, it includes solution A, solution B, or solutions that satisfy both A and B. In addition, the technical solutions between the various embodiments can be combined with each other, but it must be based on the ability of ordinary technicians in this field to implement. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such combination of technical solutions does not exist and is not within the scope of protection required by the utility model.
[0041] With the development of near-eye display technology, more and more AR / VR display devices have been launched. The more mature solution is waveguide plus micro-projection optical machine, and the micro-projection optical machine based on Micro LED is considered to be the trend of AR display solution due to its smaller pixel size and higher brightness; however, since the temperature of Micro LED display chip is relatively high when working, the sharp increase in temperature causes the lens of the projection lens 100 structural component to expand and contract due to heat, and the lens becomes thermally defocused, resulting in a decrease in lens resolution and blurred imaging, which greatly affects the user experience.
[0042] Traditional projection lenses will automatically lose focus after being used for a period of time. That is to say, although the focal length is adjusted at the beginning, the lens must be refocused after a period of use. Some have added an automatic focus function to solve the problem of lens defocusing. By moving the movable lens, the movable lens position corresponding to the highest clarity value within the moving range is found, and the movable lens is controlled to fall at the position with the highest clarity value within the moving range to achieve refocusing; some are refocused through the overall or local structure. For AR glasses, the optical machine and glasses structure need to be very small and compact, and there is no possibility of secondary focusing. Therefore, this solution proposes a projection lens 100 that can automatically compensate, is small in size, and has high imaging quality to solve the above problems.
[0043] The utility model provides a projection lens and a projection optical machine system, aiming to at least solve the technical problems that the existing projection lens is easy to lose focus due to thermal expansion and contraction, and is difficult to readjust due to the limitation of structure size.
[0044] See also Figure 1, in an embodiment of the present invention, the projection lens 100 includes a lens body, the lens body includes a first lens 1 with a positive optical power, a second lens 2 with a negative optical power, a third lens 3 with a positive optical power, and a fourth lens 4 with a negative optical power arranged in sequence from the object side to the image side. The first lens 1, the second lens 2, the third lens 3, and the fourth lens 4 together form an optical axis. Among them, the focal length of the projection lens 100 is f, and 5.8mm < f < 6.2mm; the total length of the projection lens 100 is L t , the L t ≤6.8. And the projection lens 100 further includes a housing 7, and the housing 7 is used to accommodate the first lens 1, the second lens 2, the third lens 3, and the fourth lens 4. In this embodiment, there are a total of four lenses. Along the optical axis direction, the total length Lt of the projection lens 100 including the four lenses is less than 6.8, which is beneficial to the thinning of the AR glasses display solution and greatly improves the user experience while ensuring the imaging quality.
[0045] Among them, the above four lenses have different refractive indices. Specifically, the refractive index of the first lens 1 is n1, the refractive index of the second lens 2 is n2, the refractive index of the third lens 3 is n3, and the refractive index of the fourth lens 4 is n4. The refractive indices of different lenses satisfy the following relationship: 1.7 < n1 < 1.9, 1.55 < n2 < 1.7, 1.5 < n3 < 1.6, 1.9 < n4 < 2.1.
[0046] In order to enable the lens body to still ensure good focus when the entire projection lens 100 heats up, and to avoid, due to the imaging element 6, specifically, the Micro LED display chip has a relatively high temperature during operation, and the large increase in temperature causes the multiple lens elements in the projection lens 100 to expand and contract thermally, resulting in thermal defocus of the entire projection lens 100, leading to a decrease in the resolution of the projection lens 100 and blurred imaging, which greatly affects the user experience. In this embodiment, at least one of the first lens 1 and the fourth lens 4 is made of glass material, and at least one of the second lens 2 and the third lens 3 is made of plastic material.
[0047] Specifically, both the first lens 1 and the fourth lens 4 are made of glass, which are not affected by temperature changes or have very small deformation amounts due to temperature changes; both the second lens 2 and the third lens 3 are made of plastic, and their deformation amounts are relatively more affected by temperature. By using different lens materials, when the temperature of the positive lens increases, the back focal length of the lens moves in the X- direction, and when the temperature of the negative lens increases, the back focal length of the lens moves in the X+ direction. The main focal length change is reflected in the second lens 2 and the third lens 3. In this embodiment, through the optimized material and surface shape of the adopted architecture, the second lens 2 and the third lens 3 cause the back focal length change amount △f t = △f2 + △f3, and the △f t < 5um, where △f2 and △f3 are the back focal length change amounts of the second lens 2 and the third lens 3 respectively. Through the above settings, within the range of the ambient temperature from 20°C to 60°C, the projection lens 100 operates without defocusing, and the MTF is higher than 0.5 in the full-frequency state. The optical engine for the AR glasses has a good resolution effect, and there is almost no thermal defocusing of the optical engine under normal use temperatures.
[0048] The projection lens 100 further includes a diaphragm 5 and an imaging element 6. The diaphragm 5 is disposed on the side of the first lens 1 away from the second lens 2 along the optical axis direction, and the imaging element 6 is disposed on the side of the fourth lens 4 away from the third lens 3 along the optical axis direction.
[0049] Wherein, the total length of the projection lens 100 is L t which is the distance from the diaphragm 5 to the imaging element 6.
[0050] Moreover, since the optical engine is for AR glasses and is mostly matched with diffractive optical waveguides, the radius d0 of the diaphragm 5 is set between 1 mm and 2.5 mm, and the distance L0 from the diaphragm 5 to the first lens 1 < 1.5 mm. The semi-aperture of the first lens 1 is d1, the semi-aperture of the second lens 2 is d2, the semi-aperture of the third lens 3 is d3, and the semi-aperture of the fourth lens 4 is d4, satisfying the relational expressions: 2.2 mm < d1 < 2.5 mm, 2 mm < d2 < 2.3 mm, 1.6 mm < d3 < 1.9 mm, 1.3 mm < d4 < 1.6 mm. The lens core thickness of the first lens 1 is L1, the lens core thickness of the second lens 2 is L2, the lens core thickness of the third lens 3 is L3, and the lens core thickness of the fourth lens 4 is L4, satisfying the following relational expressions: 1 mm < L1 < 1.4 mm, 0.3 mm < L2 < 0.6 mm, 0.9 mm < L3 < 1.2 mm, and the lens core thickness 0.3 mm < L4 < 0.6 mm.
[0051] It should be noted that at least one of the first lens 1 , the second lens 2 , the third lens 3 and the fourth lens 4 is an aspherical lens.
[0052] The surface formulas of the above four lenses are:
[0053]
[0054] The first expression is the same as the standard surface form, and the second is the sum of the normalized coordinate power series. i is the aspheric coefficient, expressed in lens units, so the normalized radial coordinate ρ is used.
[0055] When the lens surface is curved to the left, the lens surface shape is +, and when the lens surface is curved to the right, the lens surface shape is -. In this scheme, the eight surface shapes of the four lenses are +, +, +, +, +, -, -, - respectively.
[0056] In this embodiment, basic parameters of the projection lens 100 are shown in Table 1.
[0057] Table 1:
[0058]
[0059] The above chart information is the lens curvature, material, aperture, and cone coefficient information of the lens after optimization in this solution.
[0060] Table 2:
[0061]
[0062] The above chart information is the lens curvature coefficient of the lens after optimization in this solution.
[0063] The utility model further proposes a projection optical system, which includes a projection lens 100. The specific structure of the projection lens 100 refers to the above embodiment. Since the projection optical system adopts all the technical solutions of all the above embodiments, it has at least all the beneficial effects brought by the technical solutions of the above embodiments, which will not be described one by one here.
[0064] The projection optical system adopts a 0.13-inch Micro LED chip, and the projection optical system has the advantages of small size, high resolution quality, weak thermal defocusing effect, and high manufacturing tolerance.
[0065] Figure 3The imaging MTF and defocus performance of the projection lens 100 proposed in this solution at temperatures between 20°C and 60°C show that, as the temperature increases, the MTF of the projection lens 100 decays slightly, and the lens shows a trend of thermal defocusing. However, at 60°C, both the MTF and the defocus are maintained at a high level. The projection lens 100 corresponds to an optical machine for AR glasses, and users may consider this performance to be unchanged.
[0066] Figure 4 The field curvature and distortion performance of the projection lens 100 proposed in this solution shows that the projection lens 100 can compress the distortion to less than 1.8% under this architecture. Since the binocular display AR glasses need to have a combined image, if the projection optical system has large distortion, it will affect the binocular image and display effect of the final glasses.
[0067] Figure 6 From the relative illumination of the projection optical system provided in this solution, it can be seen that the projection lens 100 can maintain a relative illumination of more than 0.8 in the entire field of view, ensuring that the optical system has a high light efficiency.
[0068] The above description is only an exemplary embodiment of the present invention, and does not limit the patent scope of the present invention. All equivalent structural changes made by using the contents of the present invention specification and drawings under the technical concept of the present invention, or directly / indirectly applied in other related technical fields are included in the patent protection scope of the present invention.
Claims
1. A projection lens, characterized in that: The projection lens includes a lens body which includes a first lens with a positive optical power, a second lens with a negative optical power, a third lens with a positive optical power, and a fourth lens with a negative optical power arranged in sequence from the object side to the image side. The first lens, the second lens, the third lens, and the fourth lens together form an optical axis; Among them, the focal length of the projection lens is f, and 5.8mm < f < 6.2mm; The total length of the projection lens is L t , the L t ≤6.
8.
2. The projection lens according to claim 1, wherein: The refractive index of the first lens is n1, the refractive index of the second lens is n2, the refractive index of the third lens is n3, and the refractive index of the fourth lens is n4, satisfying the following relational expressions: 1.7 < n1 < 1.9, 1.55 < n2 < 1.7, 1.5 < n3 < 1.6, 1.9 < n4 < 2.
1.
3. The projection lens according to claim 2, wherein: At least one of the first lens and the fourth lens is made of glass, and at least one of the second lens and the third lens is made of plastic.
4. The projection lens according to claim 3, wherein: The second lens and the third lens are both made of plastic, and the second lens has a back focus variation △f2, the fourth lens has a back focus variation △f3, and the back focus variation of the projection lens is △f t , satisfying the following relationship: △f t = △f2+△f3, and the △f t <5um.
5. The projection lens according to claim 1, wherein: The projection lens further includes a diaphragm and an imaging element. The diaphragm is arranged on the side of the first lens away from the second lens along the optical axis direction, and the imaging element is arranged on the side of the fourth lens away from the third lens along the optical axis direction.
6. The projection lens according to claim 5, wherein: The total length of the projection lens is L t is the distance from the aperture to the imaging element.
7. The projection lens according to claim 5, wherein: The radius of the diaphragm is d0, and the distance from the diaphragm to the first lens is L0, satisfying the following relational expressions: 1mm < d0 < 2.5mm, L0 < 1.5mm.
8. The projection lens according to claim 1, wherein: At least one of the first lens, the second lens, the third lens, and the fourth lens is an aspherical lens.
9. The projection lens according to claim 1, wherein: The semi-aperture of the first lens is d1, the semi-aperture of the second lens is d2, the semi-aperture of the third lens is d3, and the semi-aperture of the fourth lens is d4, satisfying the relational expressions: 2.2mm < d1 < 2.5mm, 2mm < d2 < 2.3mm, 1.6mm < d3 < 1.9mm, 1.3mm < d4 < 1.6mm; The core thickness of the first lens is L1, the core thickness of the second lens is L2, the core thickness of the third lens is L3, and the core thickness of the fourth lens is L4, satisfying the following relational expressions: 1mm < L1 < 1.4mm, 0.3mm < L2 < 0.6mm, 0.9mm < L3 < 1.2mm, 0.3mm < L4 < 0.6mm for the core thickness.
10. A projection optical system, characterized in that: The projection optical machine system includes the projection lens according to any one of claims 1 to 9.