Projection lens

Abstract

This invention provides a projection lens, comprising, along the optical axis from the projection surface to the image source surface: a first lens with negative optical power, whose image source side surface is concave; a second lens with positive optical power, whose projection side surface is concave and whose image source side surface is convex; a third lens with negative optical power, whose projection side surface is convex and whose image source side surface is concave; a fourth lens with positive optical power, whose projection side surface is convex; and a fifth lens with positive optical power, whose projection side surface is convex and whose image source side surface is planar; wherein the eccentricity α of the fifth lens satisfies: 0° < |α| < 2.5°; and the principal ray incident angle CRA of the projection lens satisfies: CRA < 3°. The projection lens provided by this invention, through specific surface shape combinations and reasonable optical power distribution, and by designing the fifth lens with a certain degree of eccentricity, effectively improves optical efficiency and optimizes projection uniformity while meeting the requirements for projection imaging quality.

Description

Technical Field

[0001] This invention relates to the technical field of imaging lenses, and in particular to a projection lens. Background Technology

[0002] As people's demands for driving experience continue to rise, the function of vehicle headlights is gradually shifting from simple illumination to multi-functional applications. Traditional smart headlights typically have tens of thousands of pixels, which also possess high precision, but relatively speaking, their beam control capability is slightly lower, unable to achieve the extremely precise area illumination of megapixel headlights. Megapixel headlights can usually support more complex intelligent lighting functions, such as projecting holiday greetings and weather information when stationary, and realizing multiple functions such as cornering light carpet illumination, distance indication, narrow road width indication, lane change indication, lane safety guidance, and pedestrian yielding when dynamic, effectively improving the driver's driving experience and attracting increasing attention from consumers.

[0003] The projection principle of intelligent headlights in vehicles is similar to that of traditional optical projection, both based on optical imaging technology and achieved through reflection and virtual imaging. Currently, most solutions on the market use a combination of film and projection lens. This solution, using a film and coaxial projection lens, cannot achieve dynamic changes in the image. Another approach is based on DLP (Digital Light Processing), which also uses a coaxial lens. However, when used for tilted projection, due to installation limitations, the projection efficiency is affected when the projection lens is matched with the front-end lighting system, preventing the achievement of fine, dynamic image projection. Summary of the Invention

[0004] To address the aforementioned problems, the present invention aims to provide a projection lens that has one or more advantages, such as excellent image quality and high projection optical efficiency.

[0005] This invention provides a projection lens composed of five lenses, which, along the optical axis from the projection surface to the image source surface, sequentially include:

[0006] The first lens with negative optical power has a concave surface on the image source side.

[0007] The second lens with positive optical power has a concave projection side surface and a convex image source side surface;

[0008] The third lens with negative optical power has a convex projection side surface and a concave image source side surface.

[0009] The fourth lens with positive optical power has a convex projection side surface;

[0010] The fifth lens with positive optical power has a convex projection side surface and a flat image source side surface.

[0011] Among them, the eccentricity α of the fifth lens satisfies: 0° < |α| < 2.5°;

[0012] The chief ray angle of incidence CRA of the projection lens satisfies: CRA < 3°;

[0013] The projection lens satisfies the conditional formula: 0.03 < BFL / TTL < 0.07, where TTL represents the overall optical length of the projection lens, and BFL represents the back focal length of the projection lens.

[0014] Further preferably, the projection lens satisfies the conditional formula: 55° < (f × FOV) / IH < 62°, where FOV represents the maximum field angle of view of the projection lens, IH represents the true image height corresponding to the maximum field angle of view of the projection lens, and f represents the effective focal length of the projection lens.

[0015] Further preferably, the projection lens satisfies the conditional formula: 0.35 < ∑CT / TTL < 0.45, where ∑CT represents the sum of the central thicknesses of the lenses of the projection lens.

[0016] Further preferably, the projection lens satisfies the conditional formula: -2 < f1 / f < -1, where f1 represents the focal length of the first lens, and f represents the effective focal length of the projection lens.

[0017] Further preferably, the projection lens satisfies the conditional formula: 2 < f2 / f < 13, where f2 represents the focal length of the second lens, and f represents the effective focal length of the projection lens.

[0018] Further preferably, the projection lens satisfies the conditional formula: -3 < f3 / f < -1.8, where f3 represents the focal length of the third lens, and f represents the effective focal length of the projection lens.

[0019] Further preferably, the projection lens satisfies the conditional formula: 1 < f4 / f < 1.3, where f4 represents the focal length of the fourth lens, and f represents the effective focal length of the projection lens.

[0020] Further preferably, the projection lens satisfies the conditional formula: 2.1 < f5 / f < 2.3, where f5 represents the focal length of the fifth lens, and f represents the effective focal length of the projection lens.

[0021] Further preferably, the projection lens satisfies the conditional formula: -2.8 < R3 / f < -1, -1.8 < R4 / f < -1.1, where R3 represents the radius of curvature of the projection side surface of the second lens, R4 represents the radius of curvature of the image source side surface of the second lens, and f represents the effective focal length of the projection lens.

[0022] Further preferably, the projection lens satisfies the conditional formula: 0.9 < R5 / f < 2.5, 0.5 < R6 / f < 1.1, where R5 represents the radius of curvature of the projection-side surface of the third lens, R6 represents the radius of curvature of the image-source-side surface of the third lens, and f represents the effective focal length of the projection lens.

[0023] Further preferably, the projection lens satisfies the conditional formula: -2.8 < f3 / f4 < -1.5, 2 < f34 / f < 3, where f3 represents the focal length of the third lens, f4 represents the focal length of the fourth lens, f34 represents the combined focal length of the third lens and the fourth lens, and f represents the effective focal length of the projection lens.

[0024] Compared with the prior art, the projection lens provided by the present invention uses five lenses with specific optical powers. Through specific surface shape matching and reasonable optical power distribution, and setting the fifth lens on the side close to the image-source surface (projection chip) as a design similar to a field lens with a certain eccentricity, on the premise of meeting the imaging quality requirements, the optical efficiency is improved and the projection uniformity is optimized; at the same time, the lens is set to have a small CRA, which can well achieve the telecentric imaging of the projection lens and couple the obliquely incoming illumination beam, thereby improving the projection optical efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The above and / or additional aspects and advantages of the present invention will become obvious and easy to understand from the description of the embodiments in conjunction with the following drawings, where:

[0026] Figure 1 It is a schematic structural diagram of the projection lens in Embodiment 1 of the present invention.

[0027] Figure 2 It is a field curvature curve diagram of the projection lens in Embodiment 1 of the present invention.

[0028] Figure 3 It is a MTF curve diagram of the projection lens in Embodiment 1 of the present invention.

[0029] Figure 4 It is an axial aberration curve diagram of the projection lens in Embodiment 1 of the present invention.

[0030] Figure 5 It is a lateral chromatic aberration curve diagram of the projection lens in Embodiment 1 of the present invention.

[0031] Figure 6 It is a schematic structural diagram of the projection lens in Embodiment 2 of the present invention.

[0032] Figure 7 It is a field curvature curve diagram of the projection lens in Embodiment 2 of the present invention.

[0033] Figure 8 This is the MTF curve of the projection lens in Embodiment 2 of the present invention.

[0034] Figure 9 This is an axial aberration curve of the projection lens in Embodiment 2 of the present invention.

[0035] Figure 10 This is a chromatic aberration curve of the projection lens in Embodiment 2 of the present invention.

[0036] Figure 11 This is a schematic diagram of the projection lens in Embodiment 3 of the present invention.

[0037] Figure 12 This is a field curvature curve diagram of the projection lens in Embodiment 3 of the present invention.

[0038] Figure 13 This is the MTF curve of the projection lens in Embodiment 3 of the present invention.

[0039] Figure 14 This is an axial aberration curve of the projection lens in Embodiment 3 of the present invention.

[0040] Figure 15 This is a chromatic aberration curve of the projection lens in Embodiment 3 of the present invention.

[0041] Figure 16 This is a schematic diagram of the eccentricity of the fifth lens provided in an embodiment of the present invention.

[0042] The following detailed description, in conjunction with the accompanying drawings, will further illustrate the present invention. Detailed Implementation

[0043] To better understand this application, various aspects of this application will be described in more detail with reference to the accompanying drawings. It should be understood that these detailed descriptions are merely illustrative of embodiments of this application and are not intended to limit the scope of this application in any way. Throughout the specification, the same reference numerals refer to the same elements. The expression "and / or" includes any and all combinations of one or more of the associated listed items.

[0044] It should be noted that in this specification, the terms "first," "second," "third," etc., are used only to distinguish one feature from another and do not imply any limitation on the features. Therefore, without departing from the teachings of the invention, the first lens discussed below may also be referred to as the second lens or the third lens.

[0045] In the accompanying drawings, the thickness, size, and shape of the lenses have been slightly exaggerated for ease of illustration. Specifically, the shapes of the spherical or aspherical surfaces shown in the drawings are illustrated by way of example. That is, the shapes of the spherical or aspherical surfaces are not limited to those shown in the drawings. The drawings are for illustrative purposes only and are not strictly to scale.

[0046] In this article, the paraxial region refers to the region near the optical axis. If the lens surface is convex and the location of the convexity is not defined, it means that the lens surface is convex at least in the paraxial region; if the lens surface is concave and the location of the concaveness is not defined, it means that the lens surface is concave at least in the paraxial region. The surface of each lens closest to the subject is called the object-side surface of the lens, and the surface of each lens closest to the imaging plane is called the image-side surface of the lens.

[0047] It should also be understood that the terms "comprising," "including," "having," "containing," and / or "comprising," when used in this specification, indicate the presence of the stated features, elements, and / or components, but do not exclude the presence or addition of one or more other features, elements, components, and / or combinations thereof. Furthermore, when expressions such as "at least one of..." appear after a list of listed features, they modify the entire list of features, not individual elements in the list. Additionally, when describing embodiments of this application, the word "may" is used to mean "one or more embodiments of this application." And the term "exemplary" is intended to refer to an example or illustration.

[0048] Unless otherwise specified, all terms used herein (including technical and scientific terms) shall have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains. It should also be understood that terms (e.g., those defined in common dictionaries) shall be interpreted as having the meaning consistent with their meaning in the context of the relevant art and shall not be interpreted in an idealized or overly formal sense unless expressly so specified herein.

[0049] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0050] The projection lens provided in this embodiment of the invention is used to project light from an image source surface onto a projection surface. The projection lens consists of five lenses, arranged sequentially along the optical axis from the projection surface to the image source surface: a first lens, a second lens, a third lens, a fourth lens, a fifth lens, and a filter. It should be noted that the projection lens provided in this application can be used as a headlight projection lens or a lidar transmitter lens. In this case, light emitted from the image source surface is refracted by the projection lens and projected onto a distant projection surface to form an image. Furthermore, the central optical axis of the image source surface in this application is not coincident with the principal optical axis of the projection lens, and there is a certain angle between them; that is, the projection lens needs to achieve a tilted projection at a certain angle. In other embodiments, it is also feasible for the projection lens to achieve orthographic projection, which is not limited in this application.

[0051] Specifically, in the projection lens provided by the present application, the first lens has a negative optical power, its projection-side surface can be convex or concave, and its image-source-side surface is concave.

[0052] The second lens has a positive optical power, its projection-side surface is concave, and its image-source-side surface is convex.

[0053] The third lens has a negative optical power, its projection-side surface is convex, and its image-source-side surface is concave.

[0054] The fourth lens has a positive optical power, its projection-side surface is convex, and its image-source-side surface is convex or flat;

[0055] The fifth lens has a positive optical power, its projection-side surface is convex, and its image-source-side surface is flat.

[0056] In conventional lens design, lenses do not need to have eccentricity. In fact, eccentricity is an error that needs to be controlled and minimized during the lens manufacturing process. Eccentricity refers to the phenomenon where the optical axis of the lens does not coincide with the mechanical axis. This deviation affects the imaging quality, causing different refraction effects when light passes through different positions of the lens, and thus leading to aberrations such as spherical aberration, chromatic aberration, astigmatism, etc., ultimately affecting the imaging quality of the system. Therefore, in the optical design and manufacturing process, the goal is to minimize the eccentricity of the lens as much as possible to ensure the performance and imaging quality of the optical system.

[0057] However, in the present application, in order to improve the coupling efficiency of the front-end illumination beam and achieve uniform telecentric illumination, without affecting the imaging effect, according to the incident angle of the coupled illumination beam and the imaging position of the projection source, the fifth lens is designed to have an eccentricity similar to a field lens. Specifically, the eccentricity ɑ of the fifth lens satisfies: 0° < |ɑ| < 2.5°. It should be noted that a field lens refers to a lens that works at the focal plane of the objective lens. Moreover, the projection lens of the present application satisfies the conditional formula: 0.03 < BFL / TTL < 0.07, where TTL represents the optical total length of the projection lens, and BFL represents the optical back focal length of the projection lens, that is, the distance from the image-source-side surface of the fifth lens to the image-source surface on the optical axis. From the above conditional formula, it can be seen that the image-source-side surface of the fifth lens is very close to the image-source surface, that is, close to the focal plane of the image-source surface. Therefore, the fifth lens has a design similar to a field lens, which can improve the ability of the marginal beam to enter the image-source surface, and on the premise of meeting the imaging quality requirements, improve the optical efficiency of the projection lens and optimize the projection uniformity.

[0058] For a better illustration of the eccentricity design of the fifth lens, reference can be made to Figure 16The schematic diagram shows that the principal optical axis of the projection lens provided in this application is OX, the central optical axis of the fifth lens is OL5, and there is a certain angle between the central optical axis OL5 of the fifth lens and the principal optical axis OX of the projection lens. This angle is the eccentricity α of the fifth lens. The central optical axis of the filter and the image source surface is parallel to the central optical axis OL5 of the fifth lens, and there is also a certain angle between the central optical axis of the filter and the image source surface and the principal optical axis OX of the projection lens.

[0059] In some embodiments, the projection lens may further include an aperture stop, which may be located between the fourth lens and the fifth lens. It is understood that the aperture stop is used to limit the amount of light entering the lens, thereby changing the brightness of the image. Specifically, in this application, the aperture stop is located on the image source side surface of the fourth lens. The aperture stop function can be achieved by coating the edge of the image source side surface of the fourth lens with ink, which reduces manufacturing difficulty while enabling control over the amount of light entering the lens.

[0060] In some embodiments, the projection lens may further include a filter disposed between the fifth lens and the image source surface. The filter is used to filter out interfering light and prevent interfering light from reaching the projection lens and affecting the normal projection image quality.

[0061] More preferably, the main ray incident angle CRA of the projection lens satisfies: CRA < 3°; by setting the projection lens to have a small CRA, the intensity of the emitted light and the beam of the projection chip in the positive emission direction can be kept consistent, thereby making the brightness uniformity of the projected image of the projection lens better, and also enabling the telecentric imaging of the projection lens and coupling the tilted illumination beam to improve the projection optical efficiency.

[0062] More preferably, the projection lens satisfies the condition: 55° < (f × FOV) / IH < 62°, where FOV represents the maximum field of view of the projection lens, IH represents the true image height corresponding to the maximum field of view of the projection lens, and f represents the effective focal length of the projection lens. Satisfying this condition allows the lens to match a larger image source surface while meeting telephoto performance requirements, resulting in higher projected image quality and enabling fine, dynamic image projection.

[0063] More preferably, the projection lens satisfies the condition: 0.35 < ∑CT / TTL < 0.45, where ∑CT represents the sum of the center thicknesses of all lenses in the projection lens. By satisfying this condition and rationally setting the sum of the center thicknesses of each lens, light transmission can be smoother, allowing for better telecentric imaging on the image side. Simultaneously, the overall length of the projection lens can be effectively reduced, which is beneficial for the structural design and manufacturing process of the projection lens.

[0064] Further preferably, the projection lens satisfies the conditional formula: -2 < f1 / f < -1, where f1 represents the focal length of the first lens and f represents the effective focal length of the projection lens. Meeting the above conditions, the first lens has a relatively large negative refractive power, which can collect light at a large field of view to a greater extent, allowing the light to enter the subsequent optical system, increasing the light flux while enhancing the field angle, and at the same time being able to push the image-side principal plane of the projection optical system backward to achieve a relatively large back working distance.

[0065] Further preferably, the projection lens satisfies the conditional formulas: 2 < f2 / f < 13, 0.6 < R3 / R4 < 1.8, where f2 represents the focal length of the second lens, f represents the effective focal length of the projection lens, R3 represents the radius of curvature of the projection-side surface of the second lens, and R4 represents the radius of curvature of the image-source-side surface of the second lens. Meeting the above conditions, by reasonably defining the optical power and surface shape of the second lens, it is beneficial to converge light while reducing the deflection angle of the light, shortening the distance for the light to reach the next lens, and being beneficial to reducing the total length of the lens.

[0066] Further preferably, the projection lens satisfies the conditional formulas: -3 < f3 / f < -1.8, 1.5 < R5 / R6 < 2.5, where f3 represents the focal length of the third lens, f represents the effective focal length of the projection lens, R5 represents the radius of curvature of the projection-side surface of the third lens, and R6 represents the radius of curvature of the image-source-side surface of the third lens. Meeting the above conditions, it can effectively balance the aberration of the lens and improve the imaging quality.

[0067] Further preferably, the projection lens satisfies the conditional formula: 1 < f4 / f < 1.3, where f4 represents the focal length of the fourth lens and f represents the effective focal length of the projection lens. Meeting the above conditions, it is beneficial to collect light at a large field of view while reducing the deflection angle of the light, enabling the light to have a smooth transition in its trend, and improving the imaging quality of the projection lens.

[0068] Further preferably, the projection lens satisfies the conditional formula: 2.1 < f5 / f < 2.3, where f5 represents the focal length of the fifth lens and f represents the effective focal length of the projection lens. Meeting the above conditions, it is beneficial to converge light while reducing the deflection angle of the light, achieving the imaging effect of image-side telecentricity, and improving the imaging quality of the projection lens.

[0069] Further preferably, the projection lens satisfies the conditional formula: -2.8 < R3 / f < -1, -1.8 < R4 / f < -1.1, where R3 represents the radius of curvature of the projection-side surface of the second lens, R4 represents the radius of curvature of the image-source-side surface of the second lens, and f represents the effective focal length of the projection lens. By satisfying the above conditions and reasonably setting the concave and convex surface types of the second lens, it is beneficial to converge light while reducing the deflection angle of light, shortening the distance for light to reach the next lens, and facilitating the reduction of the overall length of the lens.

[0070] Further preferably, the projection lens satisfies the conditional formula: 0.9 < R5 / f < 2.5, 0.5 < R6 / f < 1.1, where R5 represents the radius of curvature of the projection-side surface of the third lens, R6 represents the radius of curvature of the image-source-side surface of the third lens, and f represents the effective focal length of the projection lens. By satisfying the above conditions and reasonably setting the concave and convex surface types of the third lens, the light converged by the front-end lens can be diverged, enabling it to reach a higher position, appropriately separating the optical paths of light in each field of view, and gently diverging it to the rear lens system.

[0071] Further preferably, the third lens and the fourth lens form a cemented lens group, and the projection lens satisfies the conditional formula: -2.8 < f3 / f4 < -1.5, 2 < f34 / f < 3, where f3 represents the focal length of the third lens, f4 represents the focal length of the fourth lens, f34 represents the combined focal length of the third lens and the fourth lens, and f represents the effective focal length of the projection lens. By satisfying the above conditions and reasonably setting the focal length relationship between the third and fourth lenses, the chromatic aberration of the system can be better corrected, improving the overall imaging quality.

[0072] Further preferably, the projection lens satisfies the conditional formula: 6.3 < TTL / f < 7.8, 9 < TTL / IH < 11, where IH represents the true image height corresponding to the maximum field angle of the projection lens, and f represents the effective focal length of the projection lens. By satisfying the above conditions, a better balance between the long focal length and large image plane of the lens can be achieved, while facilitating the limitation of the lens length and realizing miniaturization of the lens volume.

[0073] Further preferably, the projection lens satisfies the conditional formula: 0.25 < BFL / f < 0.4, where f represents the effective focal length of the projection lens. By satisfying the above conditions, the lens can have an appropriate back focal length, ensuring compatibility between the lens and the camera body, while making the lens structure more compact.

[0074] In some embodiments, the projection lens satisfies the conditional formula: 7.1 mm < f < 7.5 mm, 45 mm < TTL < 58 mm, 2.1 < Fno < 2.3, 5 mm < IH < 5.25 mm, 40° < FOV < 43°, where f represents the effective focal length of the projection lens, TTL represents the total optical length of the projection lens, Fno represents the aperture value of the projection lens, IH represents the true image height corresponding to the maximum field angle of the projection lens, and FOV represents the maximum field angle of the projection lens. Meeting the above conditions indicates that the projection lens provided by the embodiments of the present invention has at least the characteristics of long focal length, large image plane, and miniaturization.

[0075] In some embodiments, in order to enable the lens to have good thermal stability performance, all the lenses in the projection lens can be made of glass material lenses, which can effectively compensate for the image plane shift caused by thermal expansion of the lens at -40°C to +105°C; in other embodiments, in order to effectively reduce the cost and volume of the lens, the projection lens can adopt a combination of glass and plastic, and can also achieve good imaging effects and thermal stability.

[0076] In some embodiment manners, the first lens, the second lens, the third lens, the fourth lens, and the fifth lens can adopt spherical lenses or aspherical lenses. Compared with the spherical structure, the aspherical structure can effectively reduce the aberration of the optical system, thereby reducing the number of lenses and the size of the lenses, and better realizing the miniaturization of the lens. And the spherical lens is easier to process and has a higher processing yield. More specifically, all five lenses in the projection lens provided by the present invention adopt spherical lenses.

[0077] The following further illustrates the present invention through multiple embodiments. In each embodiment, the thickness, curvature radius, and material selection of each lens in the projection lens are somewhat different. For specific differences, refer to the parameter tables of each embodiment. The following embodiments are only preferred embodiments of the present invention, but the embodiments of the present invention are not limited only by the following embodiments. Any other changes, substitutions, combinations, or simplifications made without departing from the innovative points of the present invention should be regarded as equivalent replacement methods and are included in the protection scope of the present invention.

[0078] Embodiment 1

[0079] Please refer to Figure 1 , which shows a schematic structural diagram of a projection lens 100 provided in Embodiment 1 of the present invention. The projection lens 100 sequentially includes, along the optical axis from the projection plane to the image source plane S12: a first lens L1, a second lens L2, a third lens L3, a fourth lens L4, an aperture ST, a fifth lens L5, and a filter G1.

[0080] The first lens L1 has negative optical power, its projection side surface S1 is convex, and its image source side surface S2 is concave.

[0081] The second lens L2 has positive optical power, its projection side surface S3 is concave, and its image source side surface S4 is convex.

[0082] The third lens L3 has negative optical power, its projection side surface S5 is convex, and its image source side surface is concave.

[0083] The fourth lens L4 has positive optical power, its projection side surface is convex, and its image source side surface S7 is convex. The third lens L3 and the fourth lens L4 form a cemented lens, and the image source side surface of the third lens and the projection side surface of the fourth lens form a cemented surface S6.

[0084] The fifth lens L5 has positive optical power, its projection side surface S8 is convex, and its image source side surface S9 is flat.

[0085] The projection side surface S10 and the image source side surface S11 of the filter G1 are both planar.

[0086] Image source plane S12 is a plane.

[0087] The first lens L1, the second lens L2, the third lens L3, the fourth lens L4, and the fifth lens L5 are all glass spherical lenses.

[0088] The fifth lens L5 and the filter G1 are designed with an eccentricity of -2°, which can effectively reduce the deflection angle of the light emitted from the four front lenses, and can simultaneously achieve telecentric imaging and couple the tilted illumination beam to improve the projection optical efficiency.

[0089] The relevant parameters of each lens in the projection lens 100 in Example 1 are shown in Table 1.

[0090] Table 1

[0091]

[0092] In this embodiment, the field curvature curve, MTF curve, axial aberration, and transverse chromatic aberration curves of the projection lens 100 are respectively as follows: Figure 2 , Figure 3 , Figure 4 , Figure 5 As shown.

[0093] Figure 2The field curvature curve of the projection lens 100 in this embodiment is shown, which represents the field curvature of light in the meridional and sagittal image planes. The horizontal axis represents the offset (unit: mm), and the vertical axis represents the half field of view (unit: °). As can be seen from the figure, the field curvature of the meridional and sagittal image planes is controlled within ±0.80 mm, indicating that the projection lens 100 can effectively correct the field curvature.

[0094] Figure 3 The MTF (Modulation Transfer Function) curve of the projection lens 100 in this embodiment is shown, which represents the lens imaging modulation at different spatial frequencies under various fields of view. The horizontal axis represents the spatial frequency (unit: lp / mm), and the vertical axis represents the MTF value. As can be seen from the figure, the MTF value of this embodiment is above 0.35, and the MTF curve decreases smoothly and evenly from the center to the edge of the field of view, indicating that the projection lens 100 has good imaging quality and good detail resolution.

[0095] Figure 4 The diagram shows the axial aberration curve of the projection lens 100 in this embodiment, which represents the aberration of each wavelength on the optical axis at the imaging plane. The horizontal axis represents the axial aberration value (unit: mm), and the vertical axis represents the normalized pupil radius. As can be seen from the figure, the axial aberration offset is controlled within ±0.1 mm, indicating that the projection lens 100 can effectively correct axial aberration.

[0096] Figure 5 The diagram shows the chromatic aberration curve of the projection lens 100 in this embodiment. It represents the chromatic aberration of each wavelength relative to the center wavelength (550nm) at different image heights on the imaging plane. The horizontal axis represents the chromatic aberration value of each wavelength relative to the center wavelength (unit: μm), and the vertical axis represents the normalized field of view. As can be seen from the figure, the chromatic aberration of the longest and shortest wavelengths is controlled within ±1.5μm, indicating that the projection lens 100 can effectively correct the chromatic aberration.

[0097] Example 2

[0098] Please see Figure 6 The diagram shows a schematic of the projection lens 200 provided in Embodiment 2 of the present invention. The main difference between this embodiment and Embodiment 1 is that the projection side surface S1 of the first lens L1 is concave; the optical parameters such as the radius of curvature, lens thickness, and lens material of each lens surface are different.

[0099] The relevant parameters of each lens in the projection lens 200 in Example 2 are shown in Table 2.

[0100] Table 2

[0101]

[0102]

[0103] In this embodiment, the field curvature curve, MTF curve, axial aberration, and transverse chromatic aberration curves of the projection lens 200 are respectively as follows: Figure 7 , Figure 8 , Figure 9 , Figure 10 As shown.

[0104] from Figure 7 As can be seen, the field curvature of the meridional and sagittal image planes is controlled within ±0.80mm, indicating that the projection lens 200 can effectively correct the field curvature.

[0105] from Figure 8 As can be seen, the MTF value of this embodiment is above 0.35, and the MTF curve decreases smoothly and evenly from the center to the edge of the field of view, indicating that the projection lens 200 has good imaging quality and good detail resolution.

[0106] from Figure 9 As can be seen, the axial aberration offset is controlled within ±0.1mm, indicating that the projection lens 200 can effectively correct axial aberration.

[0107] from Figure 10 As can be seen, the vertical chromatic difference between the longest and shortest wavelengths is controlled within ±1.5μm, indicating that the projection lens 200 can effectively correct the vertical chromatic difference.

[0108] Example 3

[0109] Please see Figure 11 The diagram shown is a schematic diagram of the projection lens 300 provided in Embodiment 3 of the present invention. The main difference between this embodiment and Embodiment 1 is that the image source side surface S8 of the fourth lens L4 is a plane; the optical parameters such as the radius of curvature, lens thickness, and lens material of each lens surface are different.

[0110] The relevant parameters of each lens in the projection lens 300 in Example 3 are shown in Table 3.

[0111] Table 3

[0112]

[0113]

[0114] In this embodiment, the field curvature curve, MTF curve, axial aberration, and transverse chromatic aberration curves of the projection lens 300 are respectively as follows: Figure 12 , Figure 13 , Figure 14 , Figure 15 As shown.

[0115] from Figure 12 As can be seen, the field curvature of the meridional and sagittal image planes is controlled within ±0.18mm, indicating that the projection lens 300 can effectively correct the field curvature.

[0116] from Figure 13 As can be seen, the MTF value of this embodiment is above 0.35, and the MTF curve decreases smoothly and evenly from the center to the edge of the field of view, indicating that the projection lens 300 has good imaging quality and good detail resolution.

[0117] from Figure 14 As can be seen, the axial aberration offset is controlled within ±0.1mm, indicating that the projection lens 300 can effectively correct axial aberration.

[0118] from Figure 15 As can be seen, the vertical chromatic difference between the longest and shortest wavelengths is controlled within ±2μm, indicating that the projection lens 300 can effectively correct the vertical chromatic difference.

[0119] Please refer to Table 4 for the optical characteristics corresponding to each of the above embodiments, including the effective focal length f, total optical length TTL, aperture value Fno, maximum field of view FOV, true image height IH corresponding to the maximum field of view, principal ray incident angle CRA at the maximum image height, and the value corresponding to each conditional expression in each embodiment.

[0120] Table 4

[0121]

[0122]

[0123] In summary, the projection lens provided by the present invention has at least the following advantages:

[0124] (1) The projection lens provided by the present invention adopts a five-lens structure. Through specific surface shape settings and reasonable optical power distribution, and setting the fifth lens on the side closer to the image source surface as a field lens with a certain degree of eccentricity, the optical efficiency is improved and the projection uniformity is optimized while meeting the imaging quality requirements.

[0125] (2) By setting the projection lens to have a small CRA, the brightness uniformity of the projected image is better, and the telecentric imaging of the projection lens can be better realized and coupled with the tilted illumination beam, thereby improving the projection optical efficiency.

[0126] (3) The projection lens provided by the present invention adopts an all-glass structure, which not only gives the lens good thermal stability, but also greatly reduces the production cost of the lens, reduces the size of the lens, and achieves better miniaturization of the lens.

[0127] In the description of this specification, references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0128] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A projection lens, comprising five lenses, characterized in that, It successively includes from the projection plane to the image source plane along the optical axis: A first lens with negative optical power, and its image source side surface is concave; A second lens with positive optical power, its projection side surface is concave, and its image source side surface is convex; A third lens with negative optical power, its projection side surface is convex, and its image source side surface is concave; A fourth lens with positive optical power, its projection side surface is convex; A fifth lens with positive optical power, its projection side surface is convex, and its image source side surface is flat; Wherein, the eccentricity ɑ of the fifth lens satisfies: 0° < |ɑ| < 2.5°; The chief ray angle of incidence CRA of the projection lens satisfies: CRA < 3°; The projection lens satisfies the conditional formula: 0.03 < BFL / TTL < 0.07, where TTL represents the overall optical length of the projection lens, and BFL represents the back focal length of the projection lens.

2. The projection lens according to claim 1, characterized in that, The projection lens satisfies the conditional formula: 55° < (f × FOV) / IH < 62°, where FOV represents the maximum field angle of the projection lens, IH represents the true image height corresponding to the maximum field angle of the projection lens, and f represents the effective focal length of the projection lens.

3. The projection lens according to claim 1, characterized in that, The projection lens satisfies the conditional formula: 0.35 < ∑CT / TTL < 0.45, where ∑CT represents the sum of the central thicknesses of the lenses of the projection lens.

4. The projection lens according to claim 1, characterized in that, The projection lens satisfies the conditional formula: -2 < f1 / f < -1, where f1 represents the focal length of the first lens, and f represents the effective focal length of the projection lens.

5. The projection lens according to claim 1, characterized in that, The projection lens satisfies the conditional formula: 2 < f2 / f < 13, where f2 represents the focal length of the second lens, and f represents the effective focal length of the projection lens.

6. The projection lens according to claim 1, characterized in that, The projection lens satisfies the conditional formula: -3 < f3 / f < -1.8, where f3 represents the focal length of the third lens, and f represents the effective focal length of the projection lens.

7. The projection lens according to claim 1, characterized in that, The projection lens satisfies the conditional formula: 1 < f4 / f < 1.3, where f4 represents the focal length of the fourth lens, and f represents the effective focal length of the projection lens.

8. The projection lens according to claim 1, characterized in that, The projection lens satisfies the conditional formula: 2.1 < f5 / f < 2.3, where f5 represents the focal length of the fifth lens, and f represents the effective focal length of the projection lens.

9. The projection lens according to claim 1, characterized in that, The projection lens satisfies the conditional formula: -2.8 < R3 / f < -1, -1.8 < R4 / f < -1.1, where R3 represents the radius of curvature of the projection side surface of the second lens, R4 represents the radius of curvature of the image source side surface of the second lens, and f represents the effective focal length of the projection lens.

10. The projection lens according to claim 1, characterized in that, The projection lens satisfies the conditional formula: 0.9 < R5 / f < 2.5, 0.5 < R6 / f < 1.1, where R5 represents the radius of curvature of the projection side surface of the third lens, R6 represents the radius of curvature of the image source side surface of the third lens, and f represents the effective focal length of the projection lens.

11. The projection lens according to claim 1, characterized in that, The projection lens satisfies the conditional formula: -2.8 < f3 / f4 < -1.5, 2 < f34 / f < 3, where f3 represents the focal length of the third lens, f4 represents the focal length of the fourth lens, f34 represents the combined focal length of the third lens and the fourth lens, and f represents the effective focal length of the projection lens.

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