Projection lens

Abstract

The invention provides a projection lens. The projection lens sequentially comprises a front group with negative focal power, a diaphragm and a rear group with positive focal power from a projection surface to an image source surface along an optical axis, the front group sequentially comprises a first lens with negative focal power, a second lens with positive focal power and a third lens with negative focal power from a projection surface to an image source surface along an optical axis; the rear group sequentially comprises a fourth lens with negative focal power, a fifth lens with positive focal power, a sixth lens with positive focal power, a seventh lens with focal power, an eighth lens with focal power and a ninth lens with positive focal power from the projection surface to the image source surface along the optical axis; the seventh lens and the eighth lens have opposite focal power; wherein a chief ray incident angle CRA of the projection lens satisfies CRAlt; 4 degrees. The projection lens provided by the invention has one or more advantages of total length, rear focal length and excellent imaging quality by reasonably setting the focal lengths and the surface types of the nine lenses.

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. Existing projection lenses are generally long in total length and short in back focus, which is not conducive to the placement of various additional polarization optical devices and lighting systems. In addition, there is a large distortion at the edge of the projected image, and it is usually necessary to eliminate the visual distortion of the projected image through electronic correction of optical distortion, which increases the cost to a certain extent and is not conducive to market promotion and application. 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 a short overall length, a long back focal length, and excellent imaging quality.

[0005] The invention provides a projection lens, which is composed of nine lenses, and includes in sequence along the optical axis from the projection surface to the image source surface: a front group with negative optical power, a stop, and a rear group with positive optical power.

[0006] The front group includes, in sequence from the projection surface to the image source surface along the optical axis: a first lens with negative optical power, a second lens with positive optical power, and a third lens with negative optical power.

[0007] The rear group includes, in sequence from the projection plane to the image source plane along the optical axis: a fourth lens with negative optical power, a fifth lens with positive optical power, a sixth lens with positive optical power, a seventh lens with optical power, an eighth lens with optical power, and a ninth lens with positive optical power; the seventh lens and the eighth lens have opposite optical powers.

[0008] Further preferably, the chief ray incident angle CRA of the projection lens satisfies: CRA<4°.

[0009] More preferably, the projection lens satisfies the conditional formula: 0.35 < BFL / TTL < 0.42, where TTL represents the overall optical length of the projection lens, and BFL represents the back focal length of the projection lens.

[0010] More preferably, the projection lens satisfies the conditional formula: -1.9 < fa / fb < -1.3, where fa represents the combined focal length of the front lens group, and fb represents the combined focal length of the rear lens group.

[0011] More preferably, the projection lens satisfies the conditional formula: -4.5 < f1 / f < -1.8, where f1 represents the focal length of the first lens, and f represents the effective focal length of the projection lens.

[0012] More preferably, the projection lens satisfies the conditional formula: 1.5 < f2 / f < 2.8, where f2 represents the focal length of the second lens, and f represents the effective focal length of the projection lens.

[0013] More preferably, the projection lens satisfies the conditional formula: -1.8 < f3 / f < -1, where f3 represents the focal length of the third lens, and f represents the effective focal length of the projection lens.

[0014] More preferably, the projection lens satisfies the conditional formula: -1.6 < f4 / f < -1, where f4 represents the focal length of the fourth lens, and f represents the effective focal length of the projection lens.

[0015] More preferably, the projection lens satisfies the conditional formula: 1 < f5 / f < 1.6, where f5 represents the focal length of the fifth lens, and f represents the effective focal length of the projection lens.

[0016] More preferably, the projection lens satisfies the conditional formula: 1.3 < f6 / f < 3, where f6 represents the focal length of the sixth lens, and f represents the effective focal length of the projection lens.

[0017] More preferably, the projection lens satisfies the conditional formula: -1.5 < f7 / f8 < -0.2, where f7 represents the focal length of the seventh lens, and f8 represents the focal length of the eighth lens.

[0018] More preferably, the projection lens satisfies the conditional formula: 1.5 < f9 / f < 5.2, where f9 represents the focal length of the ninth lens, and f represents the effective focal length of the projection lens.

[0019] More preferably, the projection side surface of the first lens is convex, and the image source side surface of the first lens is concave;

[0020] The projection side surface of the second lens is a convex surface, and the image source side surface of the second lens is a convex surface;

[0021] The projection side surface of the third lens is convex, and the image source side surface of the third lens is concave;

[0022] The projection side surface of the fourth lens is convex, and the image source side surface of the fourth lens is concave;

[0023] The projection side surface of the fifth lens is a convex surface, and the image source side surface of the fifth lens is a convex surface;

[0024] The image source side surface of the sixth lens is a convex surface;

[0025] The projection side surface of the seventh lens is concave, and the image source side surface of the seventh lens is convex;

[0026] The projection side surface of the eighth lens is a concave surface, and the image source side surface of the eighth lens is a convex surface;

[0027] The projection side surface of the ninth lens is a convex surface, and the image source side surface of the ninth lens is a convex surface.

[0028] Compared with the prior art, the projection lens provided by the present invention adopts nine lenses with specific optical powers. Through specific surface shape matching and reasonable optical power distribution, the lens can achieve a shorter total optical length while maintaining a longer rear working distance, which is convenient for assembling the front-end polarization device and the lighting system, and is beneficial to the integrated installation of the system; at the same time, the projection lens is set to have a smaller CRA, which can well realize the telecentric imaging of the projection lens and couple the tilted merged illumination light beam to improve the projection optical efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The above and / or additional aspects and advantages of the present invention will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0030] Figure 1 Schematic diagram of the structure of the projection lens in Embodiment 1 of the present invention.

[0031] Figure 2 It is a distortion curve diagram of the projection lens in Example 1 of the present invention.

[0032] Figure 3 Graph showing the axial aberration of the projection lens in Embodiment 1 of the present invention.

[0033] Figure 4 FIG. 4 is a vertical axis chromatic aberration curve of the projection lens in Example 1 of the present invention.

[0034] Figure 5 Schematic diagram of the structure of the projection lens in Embodiment 2 of the present invention.

[0035] Figure 6 4 is a distortion curve diagram of the projection lens in Example 2 of the present invention.

[0036] Figure 7 Graph showing the axial aberration of the projection lens in Embodiment 2 of the present invention.

[0037] Figure 8 FIG. 4 is a vertical axis chromatic aberration curve of the projection lens in Example 2 of the present invention.

[0038] Fig. 9 Schematic diagram of the structure of the projection lens in Embodiment 3 of the present invention.

[0039] Fig.10 4 is a distortion curve diagram of the projection lens in Example 3 of the present invention.

[0040] Fig.11 Graph showing the axial aberration of the projection lens in Embodiment 3 of the present invention.

[0041] Fig.12 Graph showing the vertical axis chromatic aberration of the projection lens in Embodiment 3 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 by the embodiment of the present invention is used to project light from an image source plane onto a projection plane. The projection lens is composed of nine lenses, which include: a front group with negative optical power, an aperture, and a rear group with positive optical power in sequence from the projection plane to the image source plane along the optical axis.

[0051] Specifically, the front group includes, in sequence from the projection plane to the image source plane along the optical axis: a first lens with negative optical power, a second lens with positive optical power, and a third lens with negative optical power.

[0052] The rear group includes, in sequence from the projection plane to the image source plane along the optical axis: a fourth lens with negative optical power, a fifth lens with positive optical power, a sixth lens with positive optical power, a seventh lens with optical power, an eighth lens with optical power, and a ninth lens with positive optical power; the seventh lens and the eighth lens have opposite optical powers.

[0053] 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 amplified and refracted by the projection lens and projected onto a distant projection surface to form an image.

[0054] Further preferably, the projection side surface of the first lens is a convex surface, and the image source side surface of the first lens is a concave surface;

[0055] The projection side surface of the second lens is a convex surface, and the image source side surface of the second lens is a convex surface;

[0056] The projection side surface of the third lens is convex, and the image source side surface of the third lens is concave;

[0057] The projection side surface of the fourth lens is convex, and the image source side surface of the fourth lens is concave;

[0058] The projection side surface of the fifth lens is a convex surface, and the image source side surface of the fifth lens is a convex surface;

[0059] The projection side surface of the sixth lens may be a convex surface or a concave surface, and the image source side surface of the sixth lens is a convex surface;

[0060] The projection side surface of the seventh lens is concave, and the image source side surface of the seventh lens is convex;

[0061] The projection side surface of the eighth lens is a concave surface, and the image source side surface of the eighth lens is a convex surface;

[0062] The projection side surface of the ninth lens is a convex surface, and the image source side surface of the ninth lens is a convex surface.

[0063] In some embodiments, the projection lens may further include an aperture, which may be located between the third lens and the fourth 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 projection side surface of the fourth lens, and the effect of the aperture can be achieved by applying ink on the edge of the projection side surface of the fourth lens, which can reduce the difficulty of processing while achieving control of the amount of light entering.

[0064] In some embodiments, the projection lens may further include a filter, which is disposed between the ninth 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.

[0065] In some embodiments, two adjacent lenses in the projection lens can form a cemented lens, which can better correct the chromatic aberration of the system and provide the overall projection imaging quality. Specifically, the sixth and seventh lenses can form a cemented lens, or the seventh and eighth lenses can form a cemented lens, or other adjacent lenses can form a cemented lens. The present invention does not limit this.

[0066] Further preferably, the chief ray angle (CRA) of the projection lens satisfies: CRA < 4°. By setting the projection lens to have a smaller CRA, the intensity of the outgoing light can be made consistent with that of the projection chip in the direct outgoing 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 achieved and the tilted incident illumination beam can be coupled to improve the projection optical efficiency.

[0067] Further preferably, the projection lens satisfies the conditional formula: 0.35 < BFL / TTL < 0.42, where TTL represents the overall optical length of the projection lens, and BFL represents the back focal length of the projection lens. Meeting the above conditions can enable the lens to maintain a long back working distance while achieving a small overall optical length, facilitating the assembly of the front polarizing device and the illumination system, and being conducive to the integrated installation of the system; at the same time, it can improve the ability of the marginal beam to enter the image source plane, and on the premise of meeting the imaging quality requirements, improve the optical efficiency of the projection lens and optimize the projection uniformity.

[0068] Further preferably, the projection lens satisfies the conditional formula: -1.9 < fa / fb < -1.3, where fa represents the combined focal length of the front group, and fb represents the combined focal length of the rear group. Meeting the above conditions, by reasonably setting the focal length relationship between the front and rear groups of the aperture stop, the light at the large field of view can be collected to a greater extent, the light can enter the rear optical system smoothly, the light flux is increased while the field of view angle is increased, and at the same time, the image-side principal plane of the projection optical system can be pushed backward to achieve a large back working distance.

[0069] Further preferably, the projection lens satisfies the conditional formulas: -2.5 < fa / f < -1.5, 0.9 < fb / f < 1.3, where fa represents the combined focal length of the front group, fb represents the combined focal length of the rear group, and f represents the effective focal length of the projection lens. Meeting the above conditions, by reasonably setting the proportion of the focal lengths of the front and rear groups, it is beneficial to the convergence of light, enables the light entering the system from the front end to enter the rear optical system smoothly, makes the overall light path more gentle, optimizes the aberration, and improves the resolution.

[0070] Further preferably, the projection lens satisfies the conditional formula: -4.5 < f1 / f < -1.8, 1.5 < R1 / R2 < 3.5, where f1 represents the focal length of the first lens, f represents the effective focal length of the projection lens, R1 represents the radius of curvature of the projection-side surface of the first lens, and R2 represents the radius of curvature of the image-source-side surface of the first lens. By satisfying the above conditions and reasonably setting the focal length and surface shape of the first lens, while improving the light collection ability of the marginal field of view, the working aperture of the first lens can be reduced, which is beneficial to achieving the balance between a large aperture and a small aperture.

[0071] Further preferably, the projection lens satisfies the conditional formula: 1.5 < f2 / f < 2.8, -0.7 < R3 / R4 < -0.15, 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. By satisfying the above conditions, the light in a large range entering the system can be effectively converged, which is beneficial to avoiding excessive light deflection caused by the over-concentration of the optical power of the first lens and reducing the difficulty of correcting aberrations.

[0072] Further preferably, the projection lens satisfies the conditional formula: -1.8 < f3 / f < -1, 1.5 < R5 / R6 < 1.9, 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. By satisfying the above conditions and reasonably setting the focal length and surface shape 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 the light in each field of view, and gently diverge it to the rear lens system.

[0073] Further preferably, the projection lens satisfies the conditional formula: -1.6 < f4 / f < -1, -0.25 < R7 / R8 < -0.01, where f4 represents the focal length of the fourth lens, f represents the effective focal length of the projection lens, R7 represents the radius of curvature of the projection-side surface of the fourth lens, and R8 represents the radius of curvature of the image-source-side surface of the fourth lens. By satisfying the above conditions, the incident light can be effectively diverged, the light in the central field of view can be diverged, and at the same time, combined with the bending of the edge region of the fourth lens, the exit angle of the light in the marginal field of view can be reduced, and the relative illumination of the marginal field of view can be improved.

[0074] Further preferably, the projection lens satisfies the conditional formula: 1 < f5 / f < 1.6, -4 < R9 / R10 < -3, where f5 represents the focal length of the fifth lens, f represents the effective focal length of the projection lens, R9 represents the radius of curvature of the projection-side surface of the fifth lens, and R10 represents the radius of curvature of the image-source-side surface of the fifth lens. Meeting the above conditions is conducive to converging the diverging light to the rear optical system, shortening the optical path of the peripheral light reaching the image-source surface, effectively shortening the total length, and improving the resolution quality at the same time.

[0075] Further preferably, the projection lens satisfies the conditional formula: 1.3 < f6 / f < 3, where f6 represents the focal length of the sixth lens and f represents the effective focal length of the projection lens. Meeting the above conditions is conducive to the smooth transition of light, correcting various aberrations of the projection lens, and improving the imaging quality of the projection lens.

[0076] Further preferably, the projection lens satisfies the conditional formula: -1.5 < f7 / f8 < -0.2, where f7 represents the focal length of the seventh lens and f8 represents the focal length of the eighth lens. Meeting the above conditions, by reasonably setting the focal length relationship between the seventh and eighth lenses, is conducive to the smooth transition of light and correcting various aberrations of the projection lens, improving the imaging quality of the projection lens.

[0077] Further preferably, the projection lens satisfies the conditional formula: 1.5 < f9 / f < 5.2, where f9 represents the focal length of the ninth lens and f represents the effective focal length of the projection lens. Meeting the above conditions, the ninth lens is a biconvex lens with a positive optical power, which is conducive to gently converging the light, increasing the distance of the light reaching the image-source surface, enabling the lens to maintain a long back working distance while achieving a small optical total length, facilitating the assembly of the front polarizing device and the lighting system, and being beneficial to the integrated installation of the system.

[0078] Further preferably, the projection lens satisfies the conditional formula: 52° < (f × FOV) / IH < 58°, 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. Meeting the above conditions enables the lens to match a larger image-source surface on the basis of meeting the long focal length performance, making the projection picture of higher quality and being able to well realize fine and dynamic image projection.

[0079] Further preferably, the projection lens satisfies the conditional formula: 1 < (f × tanθ) / (IH / 2) < 1.05, where θ represents the maximum half 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. Meeting the above conditions indicates that the projection lens has small distortion within the entire field of view, and the projected image does not require additional image processing to correct the distortion, effectively reducing costs.

[0080] Further preferably, the projection lens satisfies the conditional formula: 0.35 < ∑CT / TTL < 0.48, where ∑CT represents the sum of the central thicknesses of the lenses of the projection lens. Meeting the above conditions, by reasonably setting the sum of the central thicknesses of the lenses, the transmission of light can be made smoother, the lens can better achieve telecentric imaging in the image space, and 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.

[0081] Further preferably, the projection lens satisfies the conditional formulas: 4.5 < TTL / f < 5.6, 5.2 < TTL / IH < 6.5, where 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. Meeting the above conditions can better achieve the balance between the long focal length and the large image plane of the lens, and at the same time is beneficial to restricting the length of the lens and realizing the miniaturization of the lens volume.

[0082] In some embodiments, the projection lens satisfies the conditional formulas: 13.5 mm < f < 14.3 mm, 62 mm < TTL < 78 mm, 2.7 < Fno < 2.85, 11.5 mm < IH < 12.5 mm, 46° < FOV < 49°, 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 angle of view of the projection lens, and FOV represents the maximum field angle of view 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 a long focal length, a large image plane, and a large aperture.

[0083] In some embodiments, in order to make the lens 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.

[0084] In some embodiments, the first lens, the second lens, the third lens, the fourth lens, the fifth lens, the sixth lens, the seventh lens, the eighth lens and the ninth lens may be spherical lenses or aspherical lenses. Compared with spherical structures, aspherical structures can effectively reduce the aberration of the optical system, thereby reducing the number of lenses and the size of lenses, and better realizing the miniaturization of lenses. Spherical lenses are easier to process and have a higher processing yield. More specifically, the nine lenses in the projection lens provided by the present invention are all spherical lenses.

[0085] The present invention is further described below in multiple embodiments. In each embodiment, the thickness, radius of curvature, and material selection of each lens in the projection lens are different. For specific differences, please refer to the parameter table of each embodiment. The following embodiments are only preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the following embodiments. Any other changes, substitutions, combinations or simplifications that do not deviate 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.

[0086] Example 1

[0087] See also Figure 1 , shown is a schematic diagram of the structure of the projection lens 100 provided in Example 1 of the present invention. The projection lens 100 includes, along the optical axis from the projection surface to the image source surface S21: a front group Qa with negative optical power, an aperture ST, a rear group Qb with positive optical power, and a filter G1.

[0088] The front group Qa includes, in sequence from the projection plane to the image source plane S21 along the optical axis: a first lens L1, a second lens L2, and a third lens L3.

[0089] 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.

[0090] The second lens L2 has positive refractive power, a projection-side surface S3 thereof is a convex surface, and a image-source-side surface S4 thereof is a convex surface.

[0091] The third lens L3 has negative refractive power, a projection-side surface S5 thereof is convex, and a image-source-side surface S6 thereof is concave.

[0092] The rear group Qb includes, in order from the projection plane to the image source plane S21 along the optical axis: a fourth lens L4, a fifth lens L5, a sixth lens L6, a seventh lens L7, an eighth lens L8, and a ninth lens L9.

[0093] The fourth lens L4 has negative refractive power, a projection-side surface S7 thereof is a concave surface, and a source-side surface S8 thereof is a concave surface;

[0094] The fifth lens L5 has positive refractive power, a projection-side surface S9 thereof is a convex surface, and a image-source-side surface S10 thereof is a convex surface.

[0095] The sixth lens L6 has positive refractive power, a projection-side surface S11 thereof is concave, and a image-source-side surface S12 thereof is convex.

[0096] The seventh lens L7 has negative optical power, its projection side surface S13 is concave, and its image source side surface S14 is convex; wherein the sixth lens L6 and the seventh lens L7 form a cemented lens, and the image source side surface S12 of the sixth lens and the projection side surface S13 of the seventh lens form a cemented surface.

[0097] The eighth lens L8 has positive refractive power, a projection-side surface S15 thereof is concave, and a image-source-side surface S16 thereof is convex.

[0098] The ninth lens L9 has positive refractive power, a projection-side surface S17 thereof is a convex surface, and a image-source-side surface S18 thereof is a convex surface.

[0099] The projection side surface S19 and the image source side surface S20 of the filter G1 are both planes.

[0100] The image source surface S21 is a plane.

[0101] The first lens L1, the second lens L2, the third lens L3, the fourth lens L4, the fifth lens L5, the sixth lens L6, the seventh lens L7, the eighth lens L8 and the ninth lens L9 are all glass spherical lenses.

[0102] Table 1 shows the parameters of the lenses in the projection lens 100 in Example 1.

[0103] Table 1

[0104]

[0105]

[0106] In this embodiment, the distortion curve, axial aberration, and vertical chromatic aberration curves of the projection lens 100 are respectively as follows: Figure 2 , Figure 3 , Figure 4 shown.

[0107] Figure 2 The distortion curve of the projection lens 100 in this embodiment is shown, which represents the distortion values ​​corresponding to different field angles of the imaging surface. The horizontal axis represents the distortion amount, and the vertical axis represents the field angle (unit: °). It can be seen from the figure that the distortion amount is within (-0.02, 0), and the distortion is all negative distortion, indicating that the distortion of the projection lens 100 is well corrected.

[0108] Figure 3The 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 ±0.05mm, indicating that the projection lens 100 can correct the axial aberration well.

[0109] Figure 4 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 ±5μm, indicating that the projection lens 100 can well correct the vertical chromatic aberration.

[0110] Example 2

[0111] See also Figure 5 , which is a schematic diagram of the structure of a projection lens 200 provided in Example 2 of the present invention. Compared with Example 1, this embodiment mainly differs in that: the projection side surface S11 of the sixth lens L1 is a convex surface; and the optical parameters such as the curvature radius, lens thickness, and lens material of each lens surface are different.

[0112] The relevant parameters of each lens in the projection lens 200 in Example 2 are shown in Table 2.

[0113] Table 2

[0114]

[0115] In this embodiment, the distortion curve, axial aberration, and vertical chromatic aberration curves of the projection lens 200 are respectively as follows: Figure 6 , Figure 7 , Figure 8 shown.

[0116] from Figure 6 It can be seen from the figure that the distortion amount of this embodiment is within (-0.035, 0), and the distortion is all negative distortion, which means that the distortion of the projection lens 200 is well corrected.

[0117] from Figure 7 It can be seen from the figure that the offset of the axial aberration is controlled within ±0.05 mm, which means that the projection lens 200 can correct the axial aberration well.

[0118] from Figure 8 It can be seen that the vertical axis chromatic aberration of the longest wavelength and the shortest wavelength is controlled within ±4.5 μm, indicating that the projection lens 200 can correct the vertical axis chromatic aberration well.

[0119] Example 3

[0120] See also Fig. 9 , 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 seventh lens L7 and the eighth lens L8 form a cemented lens, the image source side surface S14 of the seventh lens and the projection side surface S15 of the eighth lens form a cemented surface, and the optical parameters such as the curvature radius of each lens surface, the lens thickness, and the lens material are different.

[0121] The relevant parameters of each lens in the projection lens 300 in Example 3 are shown in Table 3.

[0122] Table 3

[0123]

[0124]

[0125] In this embodiment, the distortion curve, axial aberration, and vertical chromatic aberration curves of the projection lens 300 are respectively as follows: Fig.10 , Fig.11 , Fig.12 shown.

[0126] from Fig.10 It can be seen from the figure that the distortion amount of this embodiment is within (-0.03, 0), and the distortion is all negative distortion, which means that the distortion of the projection lens 300 is well corrected.

[0127] from Fig.11 It can be seen that the offset of the axial aberration is controlled within ±0.08 mm, which means that the projection lens 300 can correct the axial aberration well.

[0128] from Fig.12 It can be seen that the vertical axis chromatic aberration of the longest wavelength and the shortest wavelength is controlled within ±4 μm, indicating that the projection lens 300 can correct the vertical axis chromatic aberration well.

[0129] 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.

[0130] Table 4

[0131]

[0132]

[0133] In summary of the above embodiments, the projection lens provided by the present invention has at least the following advantages:

[0134] (1) The projection lens provided by the present invention uses nine lenses with specific optical powers. Through the combination of specific surface shapes and reasonable optical power distribution, the lens can achieve a short optical total length while maintaining a long rear working distance, which is convenient for assembling the front-end polarization device and the lighting system, and is conducive to the integrated installation of the system.

[0135] (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.

[0136] (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.

[0137] 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.

[0138] 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 nine lenses, characterized in that: Along the optical axis, from the projection plane to the image source plane, it successively includes: a front group with negative focal power, a diaphragm, and a rear group with positive focal power; The front group successively includes, along the optical axis from the projection plane to the image source plane: a first lens with negative focal power, a second lens with positive focal power, and a third lens with negative focal power; The rear group successively includes, along the optical axis from the projection plane to the image source plane: a fourth lens with negative focal power, a fifth lens with positive focal power, a sixth lens with positive focal power, a seventh lens with focal power, an eighth lens with focal power, and a ninth lens with positive focal power; the seventh lens and the eighth lens have opposite focal powers; Wherein, the chief ray angle of incidence CRA of the projection lens satisfies: CRA < 4°; The projection lens satisfies the conditional formula: 0.35 < BFL / TTL < 0.42, 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: -1.9 < fa / fb < -1.3, where fa represents the combined focal length of the front group, and fb represents the combined focal length of the rear group.

3. The projection lens according to claim 1, characterized in that: The projection lens satisfies the conditional formula: -4.5 < f1 / f < -1.8, where f1 represents the focal length of the first lens, and f represents the effective focal length of the projection lens.

4. The projection lens according to claim 1, characterized in that: The projection lens satisfies the conditional formula: 1.5 < f2 / f < 2.8, where f2 represents the focal length of the second 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: -1.8 < f3 / f < -1, where f3 represents the focal length of the third 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: -1.6 < f4 / f < -1, where f4 represents the focal length of the fourth 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 < f5 / f < 1.6, where f5 represents the focal length of the fifth 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: 1.3 < f6 / f < 3, where f6 represents the focal length of the sixth 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: -1.5 < f7 / f8 < -0.2, where f7 represents the focal length of the seventh lens, and f8 represents the focal length of the eighth lens.

10. The projection lens according to claim 1, wherein: The projection lens satisfies the conditional formula: 1.5 < f9 / f < 5.2, where f9 represents the focal length of the ninth lens, and f represents the effective focal length of the projection lens.

11. The projection lens according to claim 1, wherein The projection-side surface of the first lens is convex, and the image-source-side surface of the first lens is concave; The projection-side surface of the second lens is convex, and the image-source-side surface of the second lens is convex; The projection-side surface of the third lens is convex, and the image-source-side surface of the third lens is concave; The projection-side surface of the fourth lens is convex, and the image-source-side surface of the fourth lens is concave; The projection side surface of the fifth lens is a convex surface, and the image source side surface of the fifth lens is a convex surface; The image source side surface of the sixth lens is a convex surface; The projection side surface of the seventh lens is concave, and the image source side surface of the seventh lens is convex; The projection side surface of the eighth lens is a concave surface, and the image source side surface of the eighth lens is a convex surface; The projection side surface of the ninth lens is a convex surface, and the image source side surface of the ninth lens is a convex surface.

Images