Projection lens group, optical engine and near-eye display device

Abstract

The utility model discloses a kind of projection lens group, optical machine and near-eye display device, it is related to near-eye display technical field, wherein, projection lens group is applied to near-eye display device, the number of lens with optical power is 5 pieces, and include: first lens, with positive optical power;Second lens, with positive optical power, and is arranged in the object side of first lens;Third lens, with negative optical power, and is arranged in the object side of second lens;Fourth lens, with positive optical power, and is arranged in the object side of third lens;Fifth lens, with negative optical power, and is arranged in the object side of fourth lens.The technical scheme provided by the utility model can make near-eye display device more miniaturization.

Description

Technical Field

[0001] This utility model relates to the field of near-eye display technology, and in particular to a projection lens assembly, an optical engine, and a near-eye display device. Background Technology

[0002] Near-eye display devices require projection lenses to project the image generated by the optical engine onto the human eye. Since near-eye displays need to project from a very close distance to the eye and be wearable, miniaturization is crucial, severely limiting the space available for the light source and projection lens assembly within the optical engine. The light source, the emitting element that produces the desired projected image, acts as the "object" in the imaging process. Because the light source needs to be very close to the projection lens assembly, the object distance is extremely small. This very small object distance makes the projection lens assembly of near-eye displays prone to introducing aberrations; to eliminate these aberrations, the number of lenses needs to be increased, further increasing the size of the near-eye display and hindering its miniaturization. Utility Model Content

[0003] The main purpose of this invention is to propose a projection lens group, an optical engine, and a near-eye display device, with the aim of making the near-eye display device more miniaturized.

[0004] To achieve the above objectives, the present invention proposes a projection lens assembly for use in near-eye display devices. The projection lens assembly comprises five lenses with optical power, including a first lens, a second lens, a third lens, a fourth lens, and a fifth lens. The first lens has positive optical power; the second lens has positive optical power and is positioned on the object side of the first lens; the third lens has negative optical power and is positioned on the object side of the second lens; the fourth lens has positive optical power and is positioned on the object side of the third lens; and the fifth lens has negative optical power and is positioned on the object side of the fourth lens.

[0005] In some embodiments, the ratio of the thickness of the first lens to the total optical length of the projection lens group is greater than or equal to 10% and less than or equal to 20%; and / or The ratio of the thickness of the fifth lens to the total optical length of the projection lens group is greater than or equal to 18% and less than or equal to 28%.

[0006] In some embodiments, the refractive index of the first lens is greater than or equal to 1.48 and less than or equal to 1.66; and / or The refractive index of the second lens is greater than or equal to 1.48 and less than or equal to 1.66; and / or The refractive index of the third lens is greater than or equal to 1.48 and less than or equal to 1.66; and / or The refractive index of the fourth lens is greater than or equal to 1.48 and less than or equal to 1.66; and / or The refractive index of the fifth lens is greater than or equal to 1.77 and less than or equal to 1.85.

[0007] In some embodiments, the ratio of the sum of the thicknesses of the first lens, the fourth lens, and the fifth lens to the sum of the thicknesses of the second lens and the third lens is greater than 3 and less than 3.4.

[0008] In some embodiments, the image-side elevation of the fourth lens at its maximum aperture is a first elevation; the object-side elevation of the fourth lens at its maximum aperture is a second elevation; the ratio of the second elevation to the first elevation is greater than or equal to 2 and less than or equal to 2.5; and / or The image-side height of the fifth lens at its maximum aperture is the third height; the object-side height of the fifth lens at its maximum aperture is the fourth height, and the ratio of the third height to the fourth height is greater than or equal to 1.1 and less than or equal to 1.5.

[0009] In some embodiments, the first included angle is formed by the tangent on the image-side surface of the fourth lens at its maximum aperture, which is coplanar with the optical axis of the projection lens group, and the angle between the tangent and the optical axis of the projection lens group located radially outward of the fourth lens and towards the image-side of the fourth lens; the second included angle is formed by the tangent on the object-side surface of the fourth lens at its maximum aperture, which is coplanar with the optical axis of the projection lens group, and the angle between the tangent and the optical axis of the projection lens group located radially outward of the fourth lens and towards the image-side of the fourth lens; the difference between the first included angle and the second included angle is greater than or equal to 5° and less than or equal to 30°; the quotient of the first included angle and the second included angle is greater than 1 and less than or equal to 1.5; and / or The tangent on the image-side surface of the fifth lens at its maximum aperture, which is coplanar with the optical axis of the projection lens group, forms a third angle with the optical axis of the projection lens group located radially outward of the fifth lens and towards the image-side of the fifth lens. The tangent on the object-side surface of the fifth lens at its maximum aperture, which is coplanar with the optical axis of the projection lens group, forms a fourth angle with the optical axis of the projection lens group located radially outward of the fifth lens and towards the image-side of the fifth lens. The difference between the fourth angle and the third angle is greater than or equal to -5° and less than or equal to 30°. The quotient of the third angle and the fourth angle is greater than or equal to 0.7 and less than or equal to 1.5.

[0010] In some embodiments, the ratio of the total optical length of the projection lens group to the maximum aperture of the projection lens group is greater than or equal to 2 and less than or equal to 2.5.

[0011] In some embodiments, the effective focal length of the first lens is greater than or equal to 5 mm and less than or equal to 6 mm; and / or The effective focal length of the second lens is greater than or equal to 10mm and less than or equal to 15mm; and / or The effective focal length of the third lens is greater than or equal to -4mm and less than or equal to -3mm; and / or The effective focal length of the fourth lens is greater than or equal to 18mm and less than or equal to 27mm; and / or The effective focal length of the fifth lens is greater than or equal to -50mm and less than or equal to -30mm.

[0012] In some embodiments, the first lens, the second lens, the third lens, the fourth lens, and the fifth lens are all meniscus lenses; the concave surface of the first lens faces the object side; the concave surface of the second lens faces the object side; the concave surface of the third lens faces the object side; the concave surface of the fourth lens faces the image side; and the concave surface of the fifth lens faces the image side.

[0013] In some embodiments, the object-side surface and image-side surface of the first lens, the second lens, the third lens, the fourth lens and the fifth lens are all aspherical, and the order of the aspherical coefficient is greater than or equal to 8.

[0014] In some embodiments, the first lens, the second lens, the third lens, and the fourth lens are made of plastic; the fifth lens is made of glass.

[0015] This invention also proposes an optical engine, including the aforementioned projection lens group.

[0016] In some embodiments, the optical engine further includes a display screen; the display screen is disposed at the incident end of the projection lens group, and the display screen is configured such that outgoing light directly enters the projection lens group; the display screen is a monochrome display screen.

[0017] This utility model also proposes a near-eye display device, including the above-mentioned projection lens group or the above-mentioned optical engine.

[0018] In the technical solution of this application, the projection lens group uses only five lenses to eliminate aberrations to a usable level. Specifically, the five lenses in the projection lens group are arranged in the order of positive, positive, negative, positive, negative in the direction from the image space to the object space of the projection lens group; it can be seen that the positive and negative distribution of the optical power of the lenses on both sides of the third lens is not symmetrical about the third lens. This is different from the design concept of related technologies that emphasizes reducing aberrations through symmetry; that is, considering the extremely small object distance of near-eye display devices, the difference between the object distance and the image distance is very large, and the required imaging optical path itself has a large asymmetry. Therefore, the optical power arrangement of the lenses is also designed to be asymmetrical to adapt to the application scenario of near-eye display devices; this allows aberrations to be suppressed to a usable level using only 5 lenses, making near-eye display devices more miniaturized. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0020] Figure 1 This is a schematic diagram of the structure of the first embodiment of the projection lens group provided by this utility model; Figure 2 The first embodiment of the projection lens assembly provided by this utility model is in Figure 1 A magnified view of a section at point A in the middle; Figure 3 The first embodiment of the projection lens assembly provided by this utility model is in Figure 1 A magnified view of a section at point B in the middle; Figure 4 This is a schematic diagram of the structure of one embodiment of the optomechanic provided by this utility model; Figure 5 A schematic diagram of one embodiment of the near-eye display device provided by this utility model; Figure 6 Optical path diagram of the first embodiment of the projection lens group provided by this utility model; Figure 7 Distortion diagram of the first embodiment of the projection lens group provided by this utility model; Figure 8 A modulation transfer function diagram of the first embodiment of the projection lens group provided by this utility model; Figure 9 Optical path diagram of the second embodiment of the projection lens group provided by this utility model; Figure 10 Modulation transfer function diagram of the second embodiment of the projection lens group provided by this utility model; Figure 11 Optical path diagram of the third embodiment of the projection lens group provided by this utility model; Figure 12 A modulation transfer function diagram of a third embodiment of the projection lens group provided by this utility model; Figure 13 Optical path diagram of the fourth embodiment of the projection lens group provided by this utility model; Figure 14 A modulation transfer function diagram of the fourth embodiment of the projection lens group provided by this utility model; Figure 15 Optical path diagram of the fifth embodiment of the projection lens group provided by this utility model; Figure 16 The modulation transfer function diagram of the fifth embodiment of the projection lens group provided by this utility model.

[0021] Explanation of icon numbers: Near-eye display device 1000; frame 1100; temples 1200; Optical engine 100; Display screen 110; Projection lens group 10; first lens 11; second lens 12; third lens 13; fourth lens 14; fifth lens 15.

[0022] The realization of the purpose, functional features and advantages of this utility model will be further explained in conjunction with the implementation methods and with reference to the accompanying drawings. Detailed Implementation

[0023] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] It should be noted that if the embodiments of this utility model involve directional indicators (such as up, down, left, right, front, back, etc.), the directional indicators are only used to explain the relative positional relationship and movement of the components in a specific posture. If the specific posture changes, the directional indicators will also change accordingly.

[0025] Furthermore, if the embodiments of this utility model involve descriptions such as "first" or "second," these descriptions are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, the use of "and / or" or "and / or" throughout the text includes three parallel solutions. For example, "A and / or B" includes solution A, solution B, or a solution that simultaneously satisfies A and B. Furthermore, the technical solutions of various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by this utility model.

[0026] This utility model proposes a projection lens group.

[0027] Please see Figure 1 The projection lens group 10 proposed in this utility model is applied to near-eye display devices. The projection lens group 10 has five lenses with optical power, including a first lens 11, a second lens 12, a third lens 13, a fourth lens 14, and a fifth lens 15. The first lens 11 has positive optical power; the second lens 12 has positive optical power and is disposed on the object side of the first lens 11; the third lens 13 has negative optical power and is disposed on the object side of the second lens 12; the fourth lens 14 has positive optical power and is disposed on the object side of the third lens 13; and the fifth lens 15 has negative optical power and is disposed on the object side of the fourth lens 14.

[0028] Near-eye display devices are those that project images onto the human eye at a relatively close distance. These can be AR (Augmented Reality), VR (Virtual Reality), or MR (Mixed Reality) devices. Their VID (Virtual Image Distance) needs to be at least as close as possible to the human eye's visual distance; for users without refractive errors, the VID can be set to infinity.

[0029] A projection lens group is a lens group used to shape the light beam carrying image information output from a near-eye display device and project it towards the human eye. It should be noted that the projection lens group is primarily for beam shaping, and therefore may not include components for reversing the light path, such as optical waveguides or total internal reflection prisms. In some embodiments, the light emitted from the projection lens group can also be used to directly enter the human eye.

[0030] In the projection lens group, the five lenses with optical power are the first lens, the second lens, the third lens, the fourth lens, and the fifth lens. The object side and image side of these five lenses are consistent with the object side and image side of the projection lens group. When the projection lens group is working, the side of the projection lens group on which the light carrying the image information is incident is the object side of the projection lens group, and the side of the projection lens group on which the light carrying the image information is emitted is the image side of the projection lens group. Similarly, the object side and image side of the lens are also the sides on which the image light is incident and emitted, respectively.

[0031] exist Figure 1 Since there is no reference object, the "object side" and "image side" of the projection lens group are labeled in words. For each lens (first lens, second lens, third lens, fourth lens and fifth lens), the object side and image side are respectively the side facing the object side of the projection lens group and the side facing the image side of the projection lens group.

[0032] It can be seen that the first lens, second lens, third lens, fourth lens and fifth lens can also be considered to be arranged sequentially from the image side to the object side, so as to form a coaxial lens group to complete the modulation of light carrying image information.

[0033] In related technologies, aberrations are eliminated by alternating positive and negative optical power, such as the Cooke Triplet lens. This lens uses three lenses with a positive-negative-positive optical power distribution (the middle lens has negative optical power, while the two outer lenses have negative optical power), which can eliminate various aberrations. It is evident that the positive-negative distribution of optical power is symmetrical compared to the middle lens. Furthermore, this type of lens is often used in devices such as cameras. Cameras are much larger than near-eye display devices, allowing for a larger image distance (since the camera lens is used for imaging and the projection lens group is used for projection, the image and object are reversed; therefore, the image distance corresponds to the object distance of the projection lens group).

[0034] Applying the aforementioned symmetrical distribution design to projection lens groups would require seven or even nine lenses to achieve a sufficiently high modulation transfer function within a wide field of view, thus meeting the need for clear projection.

[0035] In the technical solution of this application, the middle lens is the third lens. It can be seen that the positive and negative distributions of optical power of the first and second lenses on the image side of the third lens are not symmetrical with those of the fourth and fifth lenses on the object side of the third lens. This can meet the needs of near-eye display devices.

[0036] Because the space for near-eye display devices is limited, the components that emit light carrying image information (such as the display screen or laser light source mentioned below) are very close to the object side of the projection lens group. This makes the object distance of the projection lens group (i.e., the distance between the component emitting light carrying image information and the object principal point of the projection lens group) very small, but the image information needs to be imaged at a distance that the human eye can see clearly, that is, at least around the distance of clear vision or even at infinity. Thus, the image distance of the projection lens group (the distance between the image position and the image principal point of the projection lens group) is much larger than the object distance.

[0037] The asymmetrical arrangement of the lens power perfectly accommodates the severe asymmetry between object distance and image distance, thereby reducing aberrations to a usable level with a relatively small number of lenses. For details, please refer to the optical performance diagrams of the five embodiments (first, second, third, fourth, and fifth embodiments) of the projection lens group in this application. Figure 7 , 8 10, 12, 14 and 16.

[0038] In the above optical performance diagram, Figure 8 , 10 Figures 12, 14, and 16 show the modulation transfer function (MTF) plots, where the horizontal axis represents the spatial frequency in millimeters (per period), and the vertical axis represents the magnitude of the optical transfer function (EMF), i.e., the optical modulation transfer function. Each plot contains multiple straight lines, each reflecting the variation of the optical modulation function with the spatial period at a specific field of view, along either the sagittal or meridional direction. Each implementation was tested at an 11.5° field of view, demonstrating an MTF exceeding 0.95 at low frequencies (around 12.5° on the horizontal axis) and exceeding 0.85 at mid-frequency frequencies (around 50° on the horizontal axis), significantly exceeding usable levels. Figure 7 The scanning distortion shown was suppressed to within 2% within a field of view of 11.5° (maximum value of the vertical axis).

[0039] Considering the symmetry of the field of view of the projection lens group, at least a usable field of view of 23° can be obtained in the above embodiment, which meets the field of view size required by near-eye display devices.

[0040] It is evident that the projection lens group proposed in this application can eliminate aberrations to a usable level using only five lenses. The reduced number of lenses allows for a more miniaturized near-eye display device.

[0041] Please refer to Figure 1 In some embodiments, the ratio of the thickness of the first lens to the total optical length of the projection lens group is greater than or equal to 10% and less than or equal to 20%. The thickness of the first lens refers to its dimension along its own optical axis. For an example, please refer to... Figure 1 The visible optical axis O intersects the image side and the object side of the first lens at two points, and the thickness of the first lens is the distance between these two points.

[0042] The total track length (TTL) of a projection lens group refers to the distance along the optical axis of the projection lens group from the image-side vertex of the first lens to the side of the near-eye display device (e.g., a screen) facing the projection lens group. When the location of the light-emitting element of the near-eye display device cannot be determined, the object-side focal plane of the projection lens group can be used to represent the light-emitting element to determine the total track length.

[0043] The first lens is the emitting lens for the emitted light. In one example, please refer to... Figure 6 As can be seen, light from each pixel on the display screen passes through the entire first lens after reaching it. Therefore, if the first lens is too thick, light from pixel units with large incident angles on the first lens is prone to overflowing from the edges during propagation, resulting in a decrease in the relative illumination of the final projection. On the other hand, if the first lens is too thin, it is impossible to set a suitable size and surface curvature to achieve sufficient light-receiving area and modulation capability.

[0044] Understandably, since projection lens groups are used in near-eye display devices, the installation space is limited, and the total optical length must not be too long, which also restricts the setting of the first lens. Therefore, under this constraint, when the ratio of the thickness of the first lens to the total optical length of the projection lens group is greater than or equal to 10% and less than or equal to 20%, the decrease in relative illumination can be avoided, and sufficient light-receiving area and beam modulation capability can be achieved.

[0045] In one example, the ratio of the thickness of the first lens to the total optical length of the projection lens group can be any of 10%, 11%, 12%, 13%, 14%, 14.91%, 15%, 15.56%, 16%, 17%, 18%, 19%, and 20%.

[0046] Please refer to Figure 1 In some embodiments, the ratio of the thickness of the fifth lens to the total optical length of the projection lens group is greater than or equal to 18% and less than or equal to 28%.

[0047] The thickness of the fifth lens is also its dimension along its own optical axis. For an example, please refer to... Figure 1 The distance between the two intersection points of the optical axis O and the fifth lens is the thickness of the fifth lens.

[0048] The fifth lens is the receiving lens for the incident light. In one example, please refer to... Figure 6 As can be seen, light from each pixel on the display screen 110 can directly enter the fifth lens. Considering that pixels of light-emitting elements (such as displays) often have a certain half-angle width of light intensity, the emitted light from a single pixel unit cannot be equivalent to a single-centered beam with a large divergence angle, but rather a single-centered beam with a relatively limited divergence angle. Therefore, the position where the emitted light from different pixels illuminates the fifth lens is different.

[0049] It is evident that if the fifth lens is too thick, the light emitted from different pixel units will follow different paths within the fifth lens, causing varying degrees of chromatic dispersion. Since this dispersion is also related to the position of the pixel units, subsequent lenses will find it difficult to correct such dispersion, resulting in chromatic aberration. If the fifth lens is too thin, it will be impossible to set appropriate dimensions and surface curvature to achieve sufficient modulation capability.

[0050] Understandably, since projection lens groups are used in near-eye display devices, the space for setting them is limited, and the total optical length must not be too long, which also restricts the setting of the fifth lens. Therefore, when the ratio of the thickness of the fifth lens to the total optical length of the projection lens group is greater than or equal to 18% and less than or equal to 28%, the resulting chromatic dispersion is low and can be effectively suppressed. At the same time, appropriate dimensions and surface curvature can be set to achieve sufficient modulation capability of the light beam.

[0051] In one example, the ratio of the thickness of the fifth lens to the total optical length of the projection lens group can be any of 18%, 19%, 20%, 21%, 22%, 22.62%, 22.83%, 23%, 24%, 25%, 26%, 27%, and 28%.

[0052] Please refer to Figure 1 In some embodiments, the refractive index of the first lens is greater than or equal to 1.48 and less than or equal to 1.66.

[0053] If the refractive index of the first lens is too high, it will cause excessive chromatic aberration without changing the shape and Abbe number of the first lens. Conversely, if the refractive index of the first lens is too low, its ability to refract the light beam will weaken without changing its shape and Abbe number, resulting in a decrease in modulation capability. When the refractive index of the first lens is greater than or equal to 1.48 and less than or equal to 1.66, the resulting chromatic aberration is small, and the modulation capability of the light beam is sufficient.

[0054] In one example, the refractive index of the first lens can be any of 1.48, 1.50, 1.52, 1.54, 1.56, 1.58, 1.60, 1.62, 1.64, and 1.66.

[0055] Please refer to Figure 1In some embodiments, the refractive index of the second lens is greater than or equal to 1.48 and less than or equal to 1.66.

[0056] If the refractive index of the second lens is too high, it will cause excessive chromatic aberration without changing the shape and Abbe number of the second lens. Conversely, if the refractive index of the second lens is too low, its ability to refract the light beam will weaken without changing its shape and Abbe number, resulting in a decrease in modulation capability. When the refractive index of the second lens is greater than or equal to 1.48 and less than or equal to 1.66, the resulting chromatic aberration is small, and the modulation capability of the light beam is sufficient.

[0057] In one example, the refractive index of the second lens can be any of 1.48, 1.50, 1.52, 1.54, 1.56, 1.58, 1.60, 1.62, 1.64, and 1.66.

[0058] Please refer to Figure 1 In some embodiments, the refractive index of the third lens is greater than or equal to 1.48 and less than or equal to 1.66.

[0059] If the refractive index of the third lens is too high, it will cause excessive chromatic aberration without changing the shape and Abbe number of the third lens. Conversely, if the refractive index of the third lens is too low, its ability to refract the light beam will weaken without changing its shape and Abbe number, resulting in a decrease in modulation capability. When the refractive index of the third lens is greater than or equal to 1.48 and less than or equal to 1.66, the resulting chromatic aberration is small, and the modulation capability of the light beam is sufficient.

[0060] In one example, the refractive index of the third lens can be any of 1.48, 1.50, 1.52, 1.54, 1.56, 1.58, 1.60, 1.62, 1.64, and 1.66.

[0061] Please refer to Figure 1 In some embodiments, the refractive index of the fourth lens is greater than or equal to 1.48 and less than or equal to 1.66.

[0062] If the refractive index of the fourth lens is too high, it will cause excessive chromatic aberration without changing its shape and Abbe number. Conversely, if the refractive index of the fourth lens is too low, its ability to refract the light beam will weaken without changing its shape and Abbe number, resulting in a decrease in modulation capability. When the refractive index of the fourth lens is greater than or equal to 1.48 and less than or equal to 1.66, the resulting chromatic aberration is small, and the modulation capability of the light beam is sufficient.

[0063] In one example, the refractive index of the fourth lens can be any of 1.48, 1.50, 1.52, 1.54, 1.56, 1.58, 1.60, 1.62, 1.64, and 1.66.

[0064] Please refer to Figure 1 In some embodiments, the refractive index of the fifth lens is greater than or equal to 1.77 and less than or equal to 1.85.

[0065] If the refractive index of the fifth lens is too high, it will cause excessive chromatic aberration without changing the shape and Abbe number of the fifth lens. Conversely, if the refractive index of the fifth lens is too low, its ability to refract the light beam weakens, resulting in a decrease in modulation capability, which is not conducive to the fifth lens coupling incident light with different incident angles into the fourth lens. When the refractive index of the fifth lens is greater than or equal to 1.77 and less than or equal to 1.85, the chromatic aberration is small, and the modulation capability of the light beam is sufficient, making it easy to couple light incident at large angles (the angle relative to the optical axis of the fifth lens) into the fourth lens.

[0066] In one example, the refractive index of the fifth lens could be any of 1.77, 1.78, 1.79, 1.80, 1.81, 1.82, 1.83, 1.84, and 1.85.

[0067] Please refer to Figure 1 In some embodiments, the ratio of the sum of the thicknesses of the first, fourth, and fifth lenses to the sum of the thicknesses of the second and third lenses is greater than 3 and less than 3.4.

[0068] The thickness of the lenses mentioned above refers to their dimensions along their own optical axis. Similarly, the thicknesses of the second, third, and fourth lenses can be defined by referring to the meaning of the thickness of the first and fifth lenses mentioned above.

[0069] Please refer to Figure 6 It can be seen that the fourth and fifth lenses can perform preliminary shaping and refraction of the incident light, basically forming the aperture plane of the projection lens group (that is, the position with the smallest cross-sectional area of ​​the beam, which does not necessarily have an aperture element). That is, the aperture plane can be formed between the third and fourth lenses.

[0070] Considering that the projection lens group is used in near-eye display devices, there is a limitation on the total optical length of the projection lens group; therefore, the ratio of the sum of the thicknesses of the first, fourth, and fifth lenses to the sum of the thicknesses of the second and third lenses limits the proportion of the space in which the lenses are set on the optical axis of the projection lens group. The larger the ratio, the larger the space in which the first, fourth, and fifth lenses are set, and vice versa.

[0071] Since the first, fourth, and fifth lenses are located on either side of the second and third lenses, and also on either side of the aperture stop, if the space for the first, fourth, and fifth lenses is too large, it will compress the space for the second and third lenses, thus limiting their surface configuration and making it difficult for them to fully utilize their aberration correction capabilities. If the space for the first, fourth, and fifth lenses is too small, it will be difficult to form sufficient incident and exit light areas, resulting in an excessively small field of view for the projection lens group.

[0072] When the ratio of the sum of the thicknesses of the first, fourth, and fifth lenses to the sum of the thicknesses of the second and third lenses is greater than or equal to 3 and less than or equal to 3.4, the aberration correction capabilities of the second and third lenses can be fully utilized to make the aberrations of the projection lens group smaller. At the same time, the first, fourth, and fifth lenses can form sufficient incident and exit light areas to ensure the field of view of the projection lens group.

[0073] In one example, the ratio of the sum of the thicknesses of the first, fourth, and fifth lenses to the sum of the thicknesses of the second and third lenses can be any one of 3.01, 3.05, 3.10, 3.15, 3.20, 3.21, 3.22, 3.25, 3.30, 3.35, and 3.39.

[0074] Please refer to Figure 1 In some embodiments, the image-side height of the fourth lens at the maximum aperture is the first height; the object-side height of the fourth lens at the maximum aperture is the second height; the ratio of the second height to the first height is greater than or equal to 2 and less than or equal to 2.5.

[0075] The image-side and object-side surfaces of a lens are both refractive surfaces that participate in light modulation. That is, the radial side surfaces of the lens are not included. If some axial surfaces do not participate in light refraction, they are also not included in the image-side or object-side surfaces of the lens.

[0076] The image-side surface of a lens is the surface on the image side of the lens that participates in light refraction; the object-side surface of a lens is the surface on the object side of the lens that participates in light refraction.

[0077] In the direction perpendicular to the optical axis of the lens, the position where the image-side has the largest size is the same as the position where the object-side has the largest size is the same as the position where the object-side has the largest diameter. The sag at this point is often the maximum sag of either the object-side or image-side lens.

[0078] The first and second sags largely limit the size relationship between the object-side and image-side surfaces of the fourth lens. Since the cross-sectional area of ​​the beam to be received by the object-side surface of the fourth lens is larger than the cross-sectional area of ​​the beam to be emitted by the image-side surface, and the beam is generally converged within the fourth lens (the optical power of the fourth lens is positive), if the above ratio is too large, the light-receiving area (area of ​​the object-side surface) of the fourth lens is much larger than the light-emitting area, resulting in some beams not reaching the light-emitting surface (image-side surface) of the fourth lens and being lost. If the above ratio is too small, the light-receiving area of ​​the fourth lens does not exceed the light-emitting area to a sufficient extent, resulting in some light-emitting surface of the fourth lens being wasted.

[0079] When the ratio of the second sag to the first sag is greater than or equal to 2 and less than or equal to 2.5, the size ratio of the image side and the object side of the fourth lens is appropriate, which will not cause a waste of light flux or a waste of the refractive surface.

[0080] In one example, the ratio of the second elevation to the first elevation can be any one of 2.0, 2.1, 2.2, 2.3, 2.4, and 2.5.

[0081] Please refer to Figure 1 In some embodiments, the image-side height of the fifth lens at the maximum aperture is the third height; the object-side height of the fifth lens at the maximum aperture is the fourth height, and the ratio of the third height to the fourth height is greater than or equal to 1.1 and less than or equal to 1.5.

[0082] Like the fourth lens, the fifth lens has positive optical power. However, as the lens that initially receives the light beam, the object-side surface needs to have a larger and gentler curvature, while the image-side surface needs to have a smaller curvature and stronger modulation capability. Therefore, while the light-receiving area of ​​the object-side surface is larger than that of the image-side surface, its sag can be smaller. If this ratio is too large, the light-receiving area of ​​the fifth lens does not sufficiently exceed its light-emitting area, resulting in some of the light-emitting surface being wasted. If this ratio is too small, the light-receiving area of ​​the fifth lens is much larger than its light-emitting area, causing some of the light beam to fail to reach the light-emitting surface of the fifth lens and be lost.

[0083] When the ratio of the third sag to the fourth sag is greater than or equal to 1.1 and less than or equal to 1.5, the size ratio of the image side and the object side of the fifth lens is appropriate, which will not cause a waste of light flux or a waste of the refractive surface.

[0084] In one example, the ratio of the third elevation to the fourth elevation can be any one of 1.1, 1.2, 1.3, 1.4, and 1.5.

[0085] Please refer to Figure 1 and Figure 2In some embodiments, the image-side surface of the fourth lens is tangent to the optical axis of the projection lens group at its maximum aperture. Figure 2 (indicated by T1), and the optical axis of the projection lens group ( Figure 2 The axis parallel to the optical axis is marked with O' (equivalent to the optical axis O). The angle between the first angle (radially outside the fourth lens and towards the image side of the fourth lens) is the first angle. Figure 2 (Identified by β1); the tangent on the object side of the fourth lens at its maximum aperture, which is coplanar with the optical axis of the projection lens group ( Figure 2 (Identified as T2 in the text), the angle between the optical axis of the projection lens group and the optical axis of the projection lens group, which is radially outward of the fourth lens and towards the image side of the fourth lens, is the second angle. Figure 2 (denoted by β2); the difference between the first included angle and the second included angle is greater than or equal to 5° and less than or equal to 30°; the quotient of the first included angle and the second included angle is greater than 1 and less than or equal to 1.5.

[0086] The fourth lens can be formed using processes such as plastic injection molding or glass injection molding. During the cooling process, its shape may change. The degree of deformation is more pronounced at the edges in the radial direction of the lens. When the absolute value of the difference between the first and second included angles is too small, the edges of the object-side and image-side surfaces of the fourth lens tend to be parallel. Even slight shape changes can result in a significant deviation from this near-parallel state, leading to a large difference between the formed lens and the designed shape, which can easily cause significant aberrations. When the absolute value of the difference between the first and second included angles is too large, the edges of the object-side and image-side surfaces of the fourth lens become closer to perpendicular, increasing the difficulty of processing and making it easier for processing errors to cause the actual shape to differ from the designed shape.

[0087] Meanwhile, after fixing the difference between the first and second included angles, the quotient of the first and second included angles is defined, which is equivalent to defining the absolute value range of the first and second included angles. This ensures that the overall curvature of the fourth lens at the edge is not too small, resulting in a weak degree of light refraction and weak modulation capability, nor too large, resulting in curling and deformation during cooling and causing aberrations.

[0088] It is evident that, under the constraints of the relationship between the first and second included angles, the fourth lens can achieve minimal deformation during the forming process, making it less prone to manufacturing errors, and possessing sufficient refractive power for the light beam, thus ensuring minimal aberrations in the projection lens group.

[0089] In one example, the difference between the first included angle and the second included angle can be any of 5°, 7°, 10°, 13°, 16°, 18°, 20°, 22°, 24°, 25°, 27°, 29° and 30°; at the same time, the quotient of the first included angle and the second included angle can be any of 1.1, 1.2, 1.3, 1.4 and 1.5.

[0090] Please refer to Figure 1 and Figure 3 In some embodiments, the image-side surface of the fifth lens is tangent to the optical axis of the projection lens group at its maximum aperture. Figure 3 (marked with T3 in the middle), and the optical axis of the projection lens group ( Figure 3 The axis parallel to the optical axis is marked with O' (equivalent to the optical axis O). The angle between the axis and the image side of the fifth lens, located radially outside the fifth lens, is the third angle. Figure 3 (Identified by γ1); the tangent on the object side of the fifth lens at its maximum aperture, which is coplanar with the optical axis of the projection lens group ( Figure 3 The fourth included angle (marked as T4 in the figure) is the angle between the optical axis of the projection lens group and the optical axis of the projection lens group located radially outside the fifth lens and towards the image side of the fifth lens. The difference between the fourth included angle and the third included angle is greater than or equal to -5° and less than or equal to 30°. The quotient of the third included angle and the fourth included angle is greater than or equal to 0.7 and less than or equal to 1.5.

[0091] The fifth lens can be molded using processes such as plastic injection molding or glass injection molding. During the cooling process, its shape may change. The degree of deformation is more pronounced at the edges in the radial direction of the lens. When the absolute value of the difference between the third and fourth included angles is too small, the edges of the object-side and image-side surfaces of the fifth lens tend to be parallel. Even slight shape changes can result in a significant deviation from this near-parallel state, leading to a large difference between the molded lens and the designed shape, which can easily cause significant aberrations. When the absolute value of the difference between the third and fourth included angles is too large, the edges of the object-side and image-side surfaces of the fifth lens become closer to perpendicular, increasing the difficulty of processing and making it easier for processing errors to cause the actual shape to differ from the designed shape.

[0092] Meanwhile, after fixing the difference between the third and fourth included angles, the quotient between the third and fourth included angles is defined, which is equivalent to defining the absolute value range of the third and fourth included angles. This ensures that the overall curvature of the fifth lens at the edge is not too small, resulting in weak light refraction and weak modulation capability, nor too large, resulting in curling and deformation during cooling and causing aberrations.

[0093] It is evident that, under the constraints of the relationship between the third and fourth included angles, the fifth lens can achieve minimal deformation during the forming process, making it less prone to manufacturing errors, and possessing sufficient refractive power for the light beam, thus ensuring minimal aberrations in the projection lens group.

[0094] In one example, the difference between the third and fourth included angles can be any of -5°, -4°, -2°, 0°, 3°, 5°, 7°, 10°, 13°, 16°, 18°, 20°, 22°, 24°, 25°, 27°, 29°, and 30°; while the quotient of the third and fourth included angles can be any of 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, and 1.5.

[0095] Please refer to Figure 1 In some embodiments, the ratio of the total optical length of the projection lens group to the maximum aperture of the projection lens group is greater than or equal to 2 and less than or equal to 2.5.

[0096] The maximum aperture of a projection lens group refers to the largest size of the image-side and object-side surfaces of the first, second, third, fourth, and fifth lenses in the direction perpendicular to the optical axis of the projection lens group; or it can be understood as the largest size of the optical surfaces in the projection lens group that participate in the refraction of the light beam in the direction perpendicular to the optical axis of the projection lens group.

[0097] The total optical length of a projection lens group characterizes how far a beam modulated by the projection lens group needs to travel from the light source (light-emitting element) to exit the projection lens group. The maximum aperture of the projection lens group, on the other hand, characterizes the maximum light-transmitting area of ​​the projection lens group (often the area of ​​the image-side surface of the first lens or the object-side surface of the fifth lens). Figure 1 The implementation method described herein refers to the area of ​​the object-side surface of the fifth lens.

[0098] Therefore, when the ratio of the total optical length of the projection lens group to the maximum aperture of the projection lens group is too large, the beam cannot be expanded too much in the projection lens group, otherwise it may exceed the edge of the lens and cause light loss. However, this will also prevent the lens from refracting the beam to a large extent, thus limiting the lens's modulation capability. When the ratio of the total optical length of the projection lens group to the maximum aperture of the projection lens group is too small, even if the lens refracts the beam to a large degree, it will not be able to form a beam that can cover the entire aperture of the projection lens group, resulting in some parts of the refractive surface being unusable.

[0099] When the ratio of the total optical length of the projection lens group to the maximum aperture of the projection lens group is greater than or equal to 2 and less than or equal to 2.5, the lens group can modulate the beam to a sufficient degree to suppress aberrations, while making full use of each refractive surface to avoid the lateral (perpendicular to the optical axis) dimension of the projection lens group being too large.

[0100] In one example, the ratio of the total optical length of the projection lens group to the maximum aperture of the projection lens group can be any of 2.0, 2.1, 2.2, 2.3, 2.4, and 2.5.

[0101] Please refer to Figure 1 In some embodiments, the effective focal length of the first lens is greater than or equal to 5 mm and less than or equal to 6 mm.

[0102] The first lens is the lens closest to the image side and is used for output light. Therefore, it is the last lens in the projection lens group to modulate the output light. When the absolute value of the focal length of the first lens is too small, its refractive power is too strong, which can easily lead to dispersion and cause chromatic aberration. When the absolute value of the focal length of the first lens is too large, its refractive power is weak and it cannot cause the beam to deflect to a large extent, which can easily limit the size of the field of view formed by the projection lens group.

[0103] When the effective focal length of the first lens is greater than or equal to 5mm and less than or equal to 6mm, it can have an appropriate focal length, which is not easy to cause chromatic aberration and can ensure that the field of view formed by the projection lens group is large enough.

[0104] In one example, the effective focal length of the first lens can be any of 5.0mm, 5.1mm, 5.2mm, 5.3mm, 5.4mm, 5.5mm, 5.6mm, 5.7mm, 5.8mm, 5.9mm, and 6.0mm.

[0105] Please refer to Figure 1 In some embodiments, the effective focal length of the second lens is greater than or equal to 10 mm and less than or equal to 15 mm.

[0106] The second lens can act as a relay lens, coupling the beam emitted from the third lens into the first lens. If the absolute value of the focal length of the second lens is too large, it cannot effectively couple the beam emitted from the third lens into the first lens; if the absolute value of the focal length of the second lens is too small, the modulation of the beam is too great, which can easily introduce new aberrations. When the focal length of the second lens is greater than or equal to 10mm and less than or equal to 15mm, it has a suitable focal length, which can couple the light emitted from the third lens into the first lens without causing too many additional aberrations.

[0107] In one example, the effective focal length of the second lens can be any of 10mm, 11mm, 12mm, 13mm, 14mm, and 15mm.

[0108] Please refer to Figure 1 In some embodiments, the effective focal length of the third lens is greater than or equal to -4mm and less than or equal to -3mm.

[0109] The third lens can bear a heavier burden of aberration correction, thus allowing for a relatively small effective focal length. However, if the absolute value of the third lens's focal length is too small, it increases manufacturing difficulty, leading to a significant discrepancy between the refractive surface shape and the design, introducing aberrations. Conversely, if the absolute value of the third lens's focal length is too large, it becomes difficult to possess sufficient refractive power to suppress aberrations. When the effective focal length of the third lens is greater than or equal to -4mm and less than or equal to -3mm, it achieves a suitable level of manufacturing difficulty while maintaining sufficient refractive power to suppress aberrations.

[0110] In one example, the effective focal length of the third lens can be any of -4.0mm, -3.9mm, -3.8mm, -3.7mm, -3.6mm, -3.5mm, -3.4mm, -3.3mm, -3.2mm, -3.1mm, and -3.0mm.

[0111] Please refer to Figure 1 In some embodiments, the effective focal length of the fourth lens is greater than or equal to 18mm and less than or equal to 27mm.

[0112] The fourth lens can be used to couple the light emitted from the fifth lens into the aperture of the projection lens group. Therefore, if the absolute value of the focal length is too large, it will be difficult to have sufficient beam-gathering ability; if the absolute value of the focal length is too small, it will easily introduce excessive aberrations that are difficult to suppress by subsequent lenses. When the effective focal length of the fourth lens is greater than or equal to 18mm and less than or equal to 27mm, it can have a suitable focal length that can couple the light emitted from the fifth lens into the aperture of the projection lens group without causing excessive aberrations.

[0113] In one example, the effective focal length of the fourth lens could be 18mm, 19mm, 20mm, 21mm, 22mm, 23mm, 24mm, 25mm, 26mm, and 27mm.

[0114] Please refer to Figure 1 In some embodiments, the effective focal length of the fifth lens is greater than or equal to -50mm and less than or equal to -30mm.

[0115] The fifth lens is used to receive the emitted light from the light source (light-emitting element), and can also act as a relay lens, coupling the emitted light from the light source into the fourth lens. When the absolute value of the focal length of the fifth lens is too large, the degree of refraction of the beam by the fifth lens is difficult to match the object side of the fourth lens; when the absolute value of the focal length of the fifth lens is too small, the fifth lens is prone to causing excessively strong aberrations, which are difficult to be suppressed by subsequent lenses.

[0116] When the effective focal length of the fifth lens is greater than or equal to -50mm and less than or equal to -30mm, it can be adapted to the object side of the fourth lens without causing excessive aberrations.

[0117] In one example, the effective focal length of the fifth lens can be any of -50mm, -48mm, -46mm, -44mm, -42mm, -40mm, -38mm, -36mm, -34mm, -32mm, and -30mm.

[0118] Please refer to Figure 1 In some embodiments, the first lens, the second lens, the third lens, the fourth lens, and the fifth lens are all meniscus lenses; the concave surface of the first lens faces the object side; the concave surface of the second lens faces the object side; the concave surface of the third lens faces the object side; the concave surface of the fourth lens faces the image side; and the concave surface of the fifth lens faces the image side.

[0119] A meniscus lens is a lens in which the center of curvature of both the object-side and image-side surfaces along the optical axis faces either the object-side or the image-side. A concave surface is a surface that is recessed into the lens along the optical axis. For the first lens, the concave surface is its object-side surface; for the second lens, the concave surface is its object-side surface; for the third lens, the concave surface is its object-side surface; for the fourth lens, the concave surface is its image-side surface; and for the fifth lens, the concave surface is its image-side surface.

[0120] This arrangement allows the projection lens group to have a certain degree of symmetry (although it is still asymmetrical overall) compared to the plane between the third and fourth lenses and perpendicular to the optical axis of the projection lens group. This can reduce aberrations such as coma and distortion, and improve the imaging effect.

[0121] Please refer to Figure 1 In some embodiments, the object-side surface and image-side surface of the first lens, the second lens, the third lens, the fourth lens and the fifth lens are all aspherical, and the order of the aspherical coefficient is greater than or equal to 8.

[0122] Aspherical surfaces can effectively suppress aberrations such as spherical aberration and distortion. Increasing the aspherical coefficient enhances the lens's ability to correct aberrations. If the object and image sides of five lenses are both aspherical, then there are ten aspherical refractive surfaces. These ten refractive surfaces can work together to significantly reduce aberrations.

[0123] The order of aspherical coefficients typically starts from 4 and only even numbers are chosen. Therefore, the order of aspherical coefficients is 8, meaning that the coefficients of higher-order correction terms of orders 4, 6, and 8 are all non-zero. Since the order of aspherical coefficients can also be greater than 8, in other implementations, the coefficients of higher-order correction terms of orders 10 or 12, etc., can also be non-zero.

[0124] In some embodiments, the first lens, the second lens, the third lens, and the fourth lens are made of plastic; the fifth lens is made of glass.

[0125] When making lenses from plastic, the cost can be kept low only if the refractive index of the plastic is within a certain range. Similarly, when making lenses from glass, the cost can be kept low only if the refractive index is within another range. However, projection lens assemblies require lenses with different refractive indices to work together to suppress aberrations. Furthermore, since projection lens assemblies are used in near-eye display devices, weight and durability must be considered.

[0126] By making the first, second, third, and fourth lenses from plastic, the mass of the projection lens assembly can be significantly reduced, improving its impact resistance and thus its durability. Meanwhile, a fifth lens made of glass can create a difference in refractive index with the first, second, third, and fourth lenses at a lower cost, thereby suppressing aberrations.

[0127] Please refer to Figure 4 This utility model also proposes an optical engine 100, including the aforementioned projection lens group. The specific structure of the projection lens group is as described in the above embodiments. Since this optical engine adopts all the technical solutions of all the above embodiments, it has at least all the beneficial effects brought about by the technical solutions of the above embodiments, which will not be elaborated here.

[0128] Please refer to Figure 4 In some embodiments, the optical engine 100 further includes a display screen 110; the display screen 110 is disposed at the incident end of the projection lens group, and the display screen 110 is configured such that the outgoing light directly enters the projection lens group; the display screen 110 is a monochrome display screen.

[0129] The incident end of the projection lens group, i.e., the end where the object side of the fifth lens is located. The display screen can be a type of display screen such as a Micro-LED display screen. A monochrome display screen refers to a display screen that displays a single color, but the wavelength of the light it emits can have a certain range, for example, it can be in the 520-550nm range, i.e., the wavelength range of green light.

[0130] Monochrome displays reduce the effort required to correct chromatic aberration in the projection lens assembly, thereby improving the field of view and image sharpness. Please refer to [reference needed]. Figure 8 , 10 The implementation methods corresponding to figures 1, 12, 14 and 16 all use monochrome displays, have a large field of view (around 23°), and good imaging clarity (with a high modulation transfer function within the field of view).

[0131] Please refer to Figure 5This utility model also proposes a near-eye display device 1000, including the above-described projection lens group or the above-described optical engine. The specific structure of the projection lens group is as described in the above-described embodiments; the specific structure of the optical engine is as described in the above-described embodiments. Since this near-eye display device adopts all the technical solutions of all the embodiments of the above-described projection lens group or optical engine, it has at least all the beneficial effects brought about by the technical solutions of the embodiments of the above-described projection lens group or optical engine, which will not be described in detail here.

[0132] In some implementations of reflection, please refer to Figure 5 The near-eye display device 1000 can be AR glasses, which may include temples 1200 and frames 1100; an optical engine or projection lens group can be set on the temples 1200, and components such as optical waveguides or total internal reflection lenses can be set on the frames 1100 to deflect and refract the light emitted from the optical engine or projection lens group toward the human eye.

[0133] In other embodiments, the near-eye display device may be a VR headset or an AR headset, etc.

[0134] In particular, to demonstrate the projection effect of the projection lens group and to facilitate those skilled in the art to implement the technical solutions proposed in this application through this specification, a specific embodiment of each of the first, second, third, fourth, and fifth embodiments of the projection lens group of this application is provided.

[0135] Specific embodiments of the first implementation method:

[0136] Aspherical parameters:

[0137] In the table, the labels refer to the lens numbers of the projection lens group. The label 1 indicates the first lens; the label 2 indicates the second lens; the label 3 indicates the third lens; the label 4 indicates the fourth lens; and the label 5 indicates the fifth lens.

[0138] In the table, under the same reference numeral, the top row describes the image-side surface of the lens with that reference numeral, and the bottom row describes the object-side surface of the lens with that reference numeral. The radius of curvature refers to the radius of curvature along the optical axis, in mm. Under the same reference numeral, the thickness in the top row refers to the dimension of the lens itself along the optical axis (with the same meaning as the lens thickness mentioned above), and the thickness in the bottom row refers to the distance between the lens with that reference numeral and the lens with the next reference numeral, on the optical axis, in mm. Specifically, the thickness in the second row for the fifth lens refers to the distance from the object-side surface of the fifth lens to the display screen along the optical axis; therefore, summing all the thicknesses in each row of the table yields the total optical length of this embodiment.

[0139] In the table, for the same number, the first parameter is the refractive index of the lens, the second parameter is the Abbe number of the lens, and the third parameter is the relative dispersion coefficient of the lens.

[0140] In the table, the sign of the radius of curvature is positive when the center of curvature faces the object side of the projection lens group, or is considered to be facing the display screen; and negative when the center of curvature faces the image side of the projection lens group, or is considered to be facing away from the display screen.

[0141] The same explanation applies to the remaining tables below, and will not be repeated here.

[0142] Please refer to the optical path diagram based on the parameter settings in the table above. Figure 6 Please refer to the distortion diagram. Figure 7 Please refer to its modulation transfer function diagram. Figure 8 This embodiment can achieve clear imaging within a field of view of approximately 23°.

[0143] Specific embodiments of the second implementation method:

[0144] Aspheric coefficient:

[0145] Please refer to the optical path diagram based on the parameter settings in the table above. Figure 9 Please refer to its modulation transfer function diagram. Figure 10 This embodiment can achieve clear imaging within a field of view of approximately 23°.

[0146] Specific embodiments of the third implementation method:

[0147] Aspheric coefficient:

[0148] Please refer to the optical path diagram based on the parameter settings in the table above. Figure 11 Please refer to its modulation transfer function diagram. Figure 12 This embodiment can achieve clear imaging within a field of view of approximately 23°.

[0149] Specific embodiments of the fourth implementation method:

[0150] Aspheric coefficient:

[0151] Please refer to the optical path diagram based on the parameter settings in the table above. Figure 13Please refer to its modulation transfer function diagram. Figure 14 This embodiment can achieve clear imaging within a field of view of approximately 23°.

[0152] Specific embodiments of the fifth implementation method:

[0153] Aspheric coefficient:

[0154] Please refer to the optical path diagram based on the parameter settings in the table above. Figure 15 Please refer to its modulation transfer function diagram. Figure 16 This embodiment can achieve clear imaging within a field of view of approximately 23°.

[0155] It should be noted that the above embodiments can all achieve an optical engine with a projection lens group focal length of 9.879mm, a field of view (FOV) of 23°, an entrance pupil diameter greater than or equal to 2.9mm and less than or equal to 3.1mm, an entrance pupil distance of 0.2mm, a pixel size of 4μm, distortion less than 2%, an operating wavelength greater than or equal to 520nm and less than or equal to 550nm, and an image plane size greater than or equal to 3.8mm and less than or equal to 4.2mm. Furthermore, the total length of the implemented optical engine is 9.2mm, and the maximum effective aperture can be 4mm.

[0156] The above description is merely an exemplary embodiment of the present utility model and does not limit the scope of protection of the present utility model. Any equivalent structural transformations made based on the technical concept of the present utility model and the contents of the present utility model specification and drawings, or direct / indirect applications in other related technical fields, are included within the scope of protection of the present utility model.

Claims

1. A projection lens assembly, characterized in that, For use in near-eye display devices, the projection lens group has 5 lenses with optical power, and the projection lens group includes: The first lens has positive optical power; The second lens has positive optical power and is disposed on the object side of the first lens; The third lens has negative optical power and is disposed on the object side of the second lens; A fourth lens, having positive optical power, is disposed on the object side of the third lens; The fifth lens has negative optical power and is disposed on the object side of the fourth lens.

2. The projection lens assembly as described in claim 1, characterized in that, The ratio of the thickness of the first lens to the total optical length of the projection lens group is greater than or equal to 10% and less than or equal to 20%. and / or The ratio of the thickness of the fifth lens to the total optical length of the projection lens group is greater than or equal to 18% and less than or equal to 28%.

3. The projection lens assembly as described in claim 1, characterized in that, The refractive index of the first lens is greater than or equal to 1.48 and less than or equal to 1.66; and / or The refractive index of the second lens is greater than or equal to 1.48 and less than or equal to 1.66; and / or The refractive index of the third lens is greater than or equal to 1.48 and less than or equal to 1.66; and / or The refractive index of the fourth lens is greater than or equal to 1.48 and less than or equal to 1.66; and / or The refractive index of the fifth lens is greater than or equal to 1.77 and less than or equal to 1.

85.

4. The projection lens assembly as described in claim 1, characterized in that, The ratio of the sum of the thicknesses of the first lens, the fourth lens, and the fifth lens to the sum of the thicknesses of the second lens and the third lens is greater than 3 and less than 3.

4.

5. The projection lens assembly as described in claim 1, characterized in that, The image-side height of the fourth lens at its maximum aperture is the first height; the object-side height of the fourth lens at its maximum aperture is the second height; the ratio of the second height to the first height is greater than or equal to 2 and less than or equal to 2.

5. and / or The image-side height of the fifth lens at its maximum aperture is the third height; the object-side height of the fifth lens at its maximum aperture is the fourth height, and the ratio of the third height to the fourth height is greater than or equal to 1.1 and less than or equal to 1.

5.

6. The projection lens assembly as described in claim 1, characterized in that, The first included angle is formed by the tangent on the image-side surface of the fourth lens at its maximum aperture, which is coplanar with the optical axis of the projection lens group, and the angle between this tangent and the optical axis of the projection lens group, which is radially outward from the fourth lens and towards the image-side of the fourth lens. The second included angle is formed by the tangent on the object-side surface of the fourth lens at its maximum aperture, which is coplanar with the optical axis of the projection lens group, and the angle between this tangent and the optical axis of the projection lens group, which is radially outward from the fourth lens and towards the image-side of the fourth lens. The difference between the first and second included angles is greater than or equal to 5° and less than or equal to 30°. The quotient of the first and second included angles is greater than 1 and less than or equal to 1.

5. The tangent on the image-side surface of the fifth lens at its maximum aperture, which is coplanar with the optical axis of the projection lens group, forms a third angle with the optical axis of the projection lens group located radially outward of the fifth lens and towards the image-side of the fifth lens. The tangent on the object-side surface of the fifth lens at its maximum aperture, which is coplanar with the optical axis of the projection lens group, forms a fourth angle with the optical axis of the projection lens group located radially outward of the fifth lens and towards the image-side of the fifth lens. The difference between the fourth angle and the third angle is greater than or equal to -5° and less than or equal to 30°. The quotient of the third angle and the fourth angle is greater than or equal to 0.7 and less than or equal to 1.

5.

7. The projection lens assembly as described in claim 1, characterized in that, The ratio of the total optical length of the projection lens group to the maximum aperture of the projection lens group is greater than or equal to 2 and less than or equal to 2.

5.

8. The projection lens assembly as described in claim 1, characterized in that, The effective focal length of the first lens is greater than or equal to 5mm and less than or equal to 6mm; and / or The effective focal length of the second lens is greater than or equal to 10mm and less than or equal to 15mm; and / or The effective focal length of the third lens is greater than or equal to -4mm and less than or equal to -3mm; and / or The effective focal length of the fourth lens is greater than or equal to 18mm and less than or equal to 27mm; and / or The effective focal length of the fifth lens is greater than or equal to -50mm and less than or equal to -30mm.

9. The projection lens assembly as described in claim 1, characterized in that, The first lens, the second lens, the third lens, the fourth lens, and the fifth lens are all meniscus lenses; the concave surface of the first lens faces the object side; the concave surface of the second lens faces the object side; the concave surface of the third lens faces the object side; the concave surface of the fourth lens faces the image side; and the concave surface of the fifth lens faces the image side.

10. The projection lens assembly as claimed in claim 1, characterized in that, The object-side surface and image-side surface of the first lens, the second lens, the third lens, the fourth lens and the fifth lens are all aspherical, and the order of the aspherical coefficient is greater than or equal to 8.

11. The projection lens assembly as claimed in claim 1, characterized in that, The first lens, the second lens, the third lens, and the fourth lens are made of plastic; the fifth lens is made of glass.

12. An optical engine, characterized in that, Includes the projection lens group as described in any one of claims 1-11.

13. The optical engine as described in claim 12, characterized in that, The optical engine also includes a display screen; the display screen is disposed at the incident end of the projection lens group, and the display screen is configured such that the outgoing light directly enters the projection lens group; the display screen is a monochrome display screen.

14. A near-eye display device, characterized in that, Includes the projection lens group as described in any one of claims 1-11 or the optical engine as described in claim 12 or 13.

Images