Projection lens

Abstract

The invention provides a projection lens which sequentially comprises a first lens with negative focal power, a second lens with negative focal power, a third lens with negative focal power and a fourth lens with negative focal power from a projection surface to an image source surface along an optical axis, the surface of the projection side of the second lens is a concave surface, and the surface of the image source side of the second lens is a convex surface; the surface of the projection side of the third lens is a convex surface, and the surface of the image source side of the third lens is a concave surface; the surface of the projection side of the fourth lens is a convex surface; the surface of the projection side of the fifth lens is a convex surface, and the surface of the image source side of the fifth lens is a plane; wherein the eccentricity alpha of the fifth lens meets the following conditions: 0 degree lt; alpha lt; the angle is 2.5 degrees; a chief ray incident angle CRA of the projection lens satisfies CRAlt; 3 degrees. According to the projection lens provided by the invention, through specific surface shape matching and reasonable focal power distribution and the design that the fifth lens is set to have certain eccentricity, on the premise that the projection imaging quality requirement is met, the optical efficiency is effectively improved, and the projection uniformity is optimized.

Description

Technical Field

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

[0002] As people's demand for driving experience continues to increase, the function of vehicle headlights has gradually shifted from single lighting to multi-functional applications. Traditional smart headlights are usually megapixels and have high precision, but relatively speaking, their beam control ability is slightly lower, and they cannot achieve extremely fine regional lighting like megapixel headlights. Million-pixel headlights can usually support more complex intelligent lighting functions. For example, when static, they can project holiday greetings, weather and other functions. When dynamic, they can realize multiple functions such as cornering light blanket lighting, vehicle distance prompts, narrow road width indication, lane change prompts, lane safety guidance, and pedestrian courtesy. It can effectively improve the driver's driving experience and is being paid attention to by more and more consumers.

[0003] The projection principle of vehicle smart headlights is similar to traditional optical projection, both based on optical imaging technology, and realized through reflection and virtual imaging. Currently, most solutions on the market use a combination of film and projection lens. This solution cannot achieve dynamic changes in graphics through the combination of film and coaxial projection lens; the other is based on DLP (Digital Light Processing) solution, which is also equipped with coaxial lens, but when used for oblique projection, due to the limitation of the installation position, the projection efficiency is affected when the projection lens matches the front lighting system, and it cannot achieve fine and dynamic image projection. Summary of the invention

[0004] In view of the above problems, an object of the present invention is to provide a projection lens having one or more advantages of excellent imaging quality and high projection optical efficiency.

[0005] The present invention provides a projection lens, which is composed of five lenses, and includes the following lenses in order from the projection surface to the image source surface along the optical axis:

[0006] The first lens has a negative optical power and its image source side surface is concave;

[0007] A second lens having positive refractive power, whose projection side surface is concave and whose image source side surface is convex;

[0008] a third lens having negative power, whose projection side surface is convex and whose image source side surface is concave;

[0009] a fourth lens having positive refractive power, whose projection side surface is convex;

[0010] a fifth lens having positive refractive power, whose projection side surface is convex and whose image source side surface is flat;

[0011] Among them, the eccentricity ɑ of the fifth lens satisfies: 0° < |ɑ| < 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 of view angle of the projection lens, IH represents the true image height corresponding to the maximum field of view angle 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 formulas: -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 adopts five lenses with specific optical powers, through specific surface shape matching and reasonable optical power distribution, and the fifth lens on the side close to the image-source surface (projection chip) is set to 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 realize the telecentric imaging of the projection lens and couple the obliquely incident illumination beam to improve the projection optical efficiency. 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 an 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 an MTF curve diagram of the projection lens in Example 2 of the present invention.

[0034] Fig. 9 Graph showing the axial aberration of the projection lens in Embodiment 2 of the present invention.

[0035] Fig.10 FIG. 4 is a vertical axis chromatic aberration curve of the projection lens in Example 2 of the present invention.

[0036] Fig.11 Schematic diagram of the structure of the projection lens in Embodiment 3 of the present invention.

[0037] Fig.12 It is a field curvature curve diagram of the projection lens in Example 3 of the present invention.

[0038] Fig.13 This is an MTF curve diagram of the projection lens in Example 3 of the present invention.

[0039] Fig.14 Graph showing the axial aberration of the projection lens in Embodiment 3 of the present invention.

[0040] Fig.15 Graph showing the vertical axis chromatic aberration of the projection lens in Embodiment 3 of the present invention.

[0041] Fig.16 A schematic diagram of the eccentricity of the fifth lens provided in an embodiment of the present invention.

[0042] The following specific implementation manner will further illustrate the present invention in conjunction with the above-mentioned drawings. DETAILED DESCRIPTION

[0043] In order to better understand the present application, a more detailed description will be made of various aspects of the present application with reference to the accompanying drawings. It should be understood that these detailed descriptions are only descriptions of the embodiments of the present application, and are not intended to limit the scope of the present 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 expressions of first, second, third, etc. are only used to distinguish one feature from another feature, and do not represent any limitation on the features. Therefore, without departing from the teaching of the present invention, the first lens discussed below may also be referred to as the second lens or the third lens.

[0045] In the drawings, the thickness, size and shape of the lenses have been slightly exaggerated for ease of explanation. Specifically, the shapes of the spherical or aspherical surfaces shown in the drawings are shown by way of example. That is, the shapes of the spherical or aspherical surfaces are not limited to the shapes of the spherical or aspherical surfaces shown in the drawings. The drawings are only examples and are not drawn 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 position of the convex surface 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 position of the concave surface 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 object is called the object side of the lens, and the surface of each lens closest to the imaging plane is called the image side of the lens.

[0047] It should also be understood that the terms "comprises", "including", "having", "includes" 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. In addition, when expressions such as "at least one of..." appear after a list of listed features, they modify the entire listed features rather than modifying the individual elements in the list. In addition, when describing embodiments of the present application, "may" is used to mean "one or more embodiments of the present application". And, the term "exemplary" is intended to refer to an example or illustration.

[0048] Unless otherwise defined, all terms (including technical terms and scientific terms) used in this article have the same meaning as commonly understood by ordinary technicians in the field to which this application belongs. It should also be understood that terms (such as terms defined in commonly used dictionaries) should be interpreted as having the same meaning as their meaning in the context of the relevant technology, and will not be interpreted in an idealized or overly formal sense unless explicitly defined in this article.

[0049] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0050] The projection lens provided in the embodiment of the present invention is used to project the light from the image source surface to the projection surface. The projection lens is composed of five lenses, and includes: a first lens, a second lens, a third lens, a fourth lens, a fifth lens, and a filter in sequence along the optical axis from the projection surface to the image source surface. It should be noted that the projection lens provided in the present application can be used as a headlight projection lens or a laser radar transmitting end lens. At this time, the light emitted from the image source surface is refracted by the projection lens and projected onto the distant projection surface for imaging. Moreover, the central optical axis of the image source surface in the present application does not coincide with the main optical axis of the projection lens, and there is a certain angle, that is, the projection lens needs to achieve a certain angle of inclined projection. In other embodiments, it is also feasible for the projection lens to achieve orthographic projection, and this application does not limit it.

[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 that the optical axis of the lens does not coincide with the mechanical axis. This deviation will affect the imaging quality, causing different refraction effects when light passes through different positions of the lens, and thus causing aberrations such as spherical aberration, chromatic aberration, and astigmatism, 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 that of 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 on 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 that of a field lens, which can improve the ability of the marginal beam to enter the image-source surface, and under the premise of meeting the imaging quality requirements, improve the optical efficiency of the projection lens and optimize the projection uniformity.

[0058] To better illustrate the eccentricity design of the fifth lens, reference can be made to Fig.16, the main optical axis of the projection lens provided by the present 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 main optical axis OX of the projection lens, and the angle is the eccentricity ɑ of the fifth lens; the central optical axis of the filter and the image source plane 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 plane and the main optical axis OX of the projection lens.

[0059] In some embodiments, the projection lens may further include an aperture, which may be located between the fourth lens and the fifth lens. It is understood that the aperture is used to limit the amount of light entering so as to change the brightness of the image. Specifically, the aperture of the present application is located on the image source side surface of the fourth lens, and the effect of the aperture can be achieved by applying ink on the edge of the image source side surface of the fourth lens, which can reduce the difficulty of processing and control the amount of light entering.

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

[0061] Further preferably, the chief light incident angle CRA of the projection lens satisfies: CRA<3°; by setting the projection lens to have a smaller CRA, the emergent light can be made consistent with the light beam intensity of the projection chip in the positive emergent direction, so that the brightness uniformity of the projection screen of the projection lens is better, and the telecentric imaging of the projection lens can be better realized and the inclined incoming illumination light beam can be coupled to improve the projection optical efficiency.

[0062] Further preferably, 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 real image height corresponding to the maximum field angle of the projection lens, and f represents the effective focal length of the projection lens. Meeting the above conditions allows the lens to match a larger image source surface while meeting the telephoto performance, which can make the projected image quality higher and can well achieve fine and dynamic image projection.

[0063] Further preferably, the projection lens satisfies the conditional formula: 0.35<∑CT / TTL<0.45, where ∑CT represents the sum of the center thicknesses of the lenses of the projection lens. By satisfying the above condition and reasonably setting the sum of the center thicknesses of the lenses, the transmission of light can be smoother, and the telecentric imaging of the lens in the image side can be better achieved. At the same time, the total length of the projection lens can be effectively compressed, which is beneficial to the structural design and production 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 large negative refractive power, can collect light at a large field of view to a large extent, enable the light to enter the rear optical system, increase the light flux while increasing the field of view angle, and at the same time can push the image-side principal plane of the projection optical system backward to achieve a 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 light, shortening the distance for light to reach the next lens, and is 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 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 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. Meeting the above conditions, by reasonably setting the concave-convex surface type 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 total 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. Meeting the above conditions, by reasonably setting the concave-convex surface type of the third lens, the light converged by the front-end lens can be diverged so that it can reach a higher position, appropriately拉开 the optical path of each field light, and gently diverge 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. Meeting the above conditions, by reasonably setting the focal length relationship between the third and fourth lenses, the chromatic aberration of the system can be better corrected, and the overall imaging quality can be improved.

[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 of view angle of the projection lens, and f represents the effective focal length of the projection lens. Meeting the above conditions, the balance between the long focal length and the large image plane of the lens can be better achieved, and at the same time, it is beneficial to limit the length of the lens and realize the 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. Meeting the above conditions, the lens can have an appropriate back focal length, ensuring the compatibility between the lens and the fuselage, and at the same time making the structure of the lens 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 overall 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 of view angle of the projection lens, and FOV represents the maximum field of view 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 modes, 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. 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 present invention will be further described in multiple embodiments below. In each embodiment, the thickness, curvature radius, and material selection of each lens in the projection lens are partially different. For specific differences, refer to the parameter tables of each embodiment. The following embodiments are only the 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, a diaphragm ST, a fifth lens L5, and a filter G1.

[0080] The first lens L1 has negative refractive power, a projection-side surface S1 thereof is a convex surface, and an image-source-side surface S2 thereof is a concave surface.

[0081] The second lens L2 has positive refractive power, a projection-side surface S3 thereof is a concave surface, and a image-source-side surface S4 thereof is a convex surface.

[0082] The third lens L3 has negative refractive power, a projection-side surface S5 thereof is convex, and a source-side surface thereof is concave.

[0083] The fourth lens L4 has positive refractive power, its projection side surface is convex, and its image source side surface S7 is convex, wherein 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 refractive power, a projection-side surface S8 thereof is a convex surface, and a image-source-side surface S9 thereof is a plane.

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

[0086] The image source surface 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 to have an eccentricity of -2°, which can effectively reduce the deflection angle of the light emitted by the four front lenses, and can simultaneously achieve telecentric imaging and couple the inclined merged illumination light beam to improve the projection optical efficiency.

[0089] Table 1 shows the parameters of the lenses in the projection lens 100 in Example 1.

[0090] Table 1

[0091]

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

[0093] Figure 2The field curvature curve of the projection lens 100 in this embodiment is shown, which represents the field curvature of light on the meridional image plane and the sagittal image plane, the horizontal axis represents the offset (unit: mm), and the vertical axis represents the half field angle (unit: °). It can be seen from the figure that the field curvature of the meridional image plane and the sagittal image plane is controlled within ±0.80mm, indicating that the projection lens 100 can well 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 degree of different spatial frequencies under each field of view, the horizontal axis represents the spatial frequency (unit: lp / mm), and the vertical axis represents the MTF value. It can be seen from the figure that the MTF value of this embodiment is above 0.35, and the MTF curve decreases evenly and smoothly 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 ability.

[0095] Figure 4 The axial aberration curve of the projection lens 100 in this embodiment is shown, 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. It can be seen from the figure that the offset of the axial aberration is controlled within ±0.1mm, indicating that the projection lens 100 can correct the axial aberration well.

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

[0097] Example 2

[0098] See also Figure 6 , shown is a schematic diagram of the structure of a projection lens 200 provided in Example 2 of the present invention. Compared with Example 1, the main differences of this embodiment are: the projection side surface S1 of the first lens L1 is a concave surface; the optical parameters such as the curvature radius, 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 vertical chromatic aberration curves of the projection lens 200 are shown as follows: Figure 7 , Figure 8 , Fig. 9 , Fig.10 shown.

[0104] from Figure 7 It can be seen that the field curvatures of the meridional image plane and the sagittal image plane are controlled within ±0.80 mm, indicating that the projection lens 200 can correct the field curvature well.

[0105] from Figure 8 It can be seen that the MTF value of this embodiment is above 0.35, and the MTF curve decreases evenly and smoothly 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 capability.

[0106] from Fig. 9 It can be seen from the figure that the offset of the axial aberration is controlled within ±0.1 mm, which means that the projection lens 200 can correct the axial aberration well.

[0107] from Fig.10 It can be seen that the vertical axis chromatic aberration of the longest wavelength and the shortest wavelength is controlled within ±1.5 μm, indicating that the projection lens 200 can correct the vertical axis chromatic aberration well.

[0108] Example 3

[0109] See also Fig.11 , which is a schematic diagram of the structure of a projection lens 300 provided in Example 3 of the present invention. Compared with Example 1, this embodiment mainly differs in that: the image source side surface S8 of the fourth lens L4 is a plane; and the optical parameters such as the curvature radius, 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 vertical chromatic aberration curves of the projection lens 300 are shown as follows: Fig.12 , Fig.13 , Fig.14 , Fig.15 shown.

[0115] from Fig.12 It can be seen that the field curvatures of the meridional image plane and the sagittal image plane are controlled within ±0.18 mm, indicating that the projection lens 300 can correct the field curvature well.

[0116] from Fig.13 It can be seen that the MTF value of this embodiment is above 0.35, and the MTF curve decreases evenly and smoothly 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 capability.

[0117] from Fig.14 It can be seen from the figure that the offset of the axial aberration is controlled within ±0.1 mm, which means that the projection lens 300 can correct the axial aberration well.

[0118] from Fig.15 It can be seen that the vertical axis chromatic aberration of the longest wavelength and the shortest wavelength is controlled within ±2 μm, indicating that the projection lens 300 can correct the vertical axis chromatic aberration well.

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

[0120] Table 4

[0121]

[0122]

[0123] In summary of the above embodiments, 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 a specific surface shape setting and reasonable optical focal length distribution, the fifth lens on the side close to the image source surface is set to a design similar to a field lens with a certain eccentricity. Under the premise of meeting the imaging quality requirements, the optical efficiency is improved and the projection uniformity is optimized.

[0125] (2) By setting the projection lens to have a smaller CRA, the brightness uniformity of the projection image of the projection lens is better, and the telecentric imaging of the projection lens can be better achieved and the tilted illumination beam can be coupled to improve the projection optical efficiency.

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

[0127] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0128] The above-mentioned embodiments only express several implementation methods of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the patent of the present invention. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A projection lens, consisting of five lenses, characterized in that: It successively includes from the projection surface to the image source surface along the optical axis: 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; A fifth lens with positive optical power, whose projection side surface is convex and whose 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 of view angle of the projection lens, IH represents the true image height corresponding to the maximum field of view 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, wherein: 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, wherein: 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, wherein: 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, wherein: 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, wherein: 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, wherein: 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, wherein: 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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