Projection lens

Abstract

The invention provides a projection lens, which sequentially comprises a first lens with positive focal power from a projection surface to an image source surface along an optical axis, a second lens with negative focal power and a third lens with positive focal power from the projection surface to the image source surface, the surface of the projection side of the second lens is a convex surface, and the surface of the image source side of the second lens is a concave surface; the surface of the projection side of the third lens is a concave surface, and the surface of the image source side of the third lens is a convex surface; the surface of the projection side of the fourth lens is a concave surface; the surface of the projection side of the fifth lens is a concave surface, and the surface of the image source side of the fifth lens is a convex surface; the surface of the projection side of the sixth lens is a convex surface, and the surface of the image source side of the sixth lens is a convex surface; a prism; a protective glass; plate glass is arranged between the prism and the protective glass, and the plate glass can be located at a first position or a second position through a switching device. According to the projection lens provided by the invention, clear imaging at two different projection distances is realized through switching of the plate glass, and switching between a close shot and a long shot is completed.

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 expectations for a better driving experience continue to rise, the use of in-vehicle projection lenses for intelligent driving is increasing, and their status in the automotive industry continues to rise. A head-up display (HUD), also known as a head-up display, utilizes optical reflection principles to project driver assistance information, navigation information, check and control information, and ADAS information onto the windshield, approximately 2 meters ahead, or above the tip of the hood. It can also display warnings from various driver assistance systems, such as lane departure warnings and pedestrian avoidance warnings from night vision assistance systems with pedestrian recognition. This prevents drivers from frequently looking down at the instrument panel or onboard screen while driving, significantly enhancing driving safety.

[0003] However, the projection lenses currently used for in-vehicle HUDs cannot achieve clear imaging at different distances while maintaining a fixed focus. Summary of the Invention

[0004] In view of the above problems, an object of the present invention is to provide a projection lens having the advantage of excellent imaging quality.

[0005] The present invention provides a projection lens, which comprises, in order from the projection surface to the image source surface along the optical axis: a first lens having positive refractive power, wherein the projection side surface thereof is convex; a second lens having negative optical power, wherein the projection-side surface thereof is convex and the image-source-side surface thereof is concave; a third lens element having positive refractive power, whose projection-side surface is concave and whose image-source-side surface is convex; a fourth lens element having negative optical power and a concave projection-side surface; a fifth lens element having positive refractive power, whose projection-side surface is concave and whose image-source-side surface is convex; a sixth lens having positive refractive power, wherein the projection-side surface thereof is convex and the image-source-side surface thereof is convex; A prism comprising an incident surface, a reflecting surface, and an exiting surface, all of which are planes; light is incident on the prism from the incident surface along the optical axis, is reflected by the reflecting surface, and exits from the exiting surface; the reflecting surface forms an angle of 45° with the optical axis of the incident surface and the optical axis of the exiting surface, respectively; The protective glass has a flat surface on the projection side and a flat surface on the image source side; A flat glass with a changeable position is provided between the prism and the protective glass. The flat glass can be located in a first position or a second position by a switching device. When the flat glass is in the first position, the light path does not pass through the flat glass. When the flat glass is in the second position, the flat glass is located on the optical axis and between the prism and the protective glass. The flat glass is parallel to the protective glass, and the light path passes through the flat glass.

[0006] Further preferably, the projection plane has a first inclination angle with the vertical plane; the protection glass and the image source plane have a second inclination angle with the horizontal plane.

[0007] Further preferably, the first inclination angle is 14°~16°; the second inclination angle is 1°~3°.

[0008] Further preferably, when the flat glass is in the first position, the distance CT0 from the projection surface to the first lens satisfies: 155mm<CT0<165mm; when the flat glass is in the second position, the distance CT0 from the projection surface to the first lens satisfies: 190mm<CT0<200mm.

[0009] Further preferably, the focal length f2 of the second lens and the effective focal length f of the projection lens satisfy: -2.4 <f2 / f<-1。

[0010] Further preferably, the real image height IH corresponding to the maximum field angle of the projection lens and the aperture value Fno of the projection lens meet the following requirements: 4mm <IH / Fno<4.5mm。

[0011] Further preferably, the back focal length BFL of the projection lens and the effective focal length f of the projection lens satisfy: 0.2 <BFL / f<0.25。

[0012] Further preferably, a curvature radius R5 of a projection-side surface of the third lens and a curvature radius R6 of an image-source-side surface of the third lens satisfy: 1<(R5+R6) / (R5-R6)<2.1.

[0013] Further preferably, the semi-aperture clear sag SAG11 of the projection side surface of the first lens, the semi-aperture clear sag SAG12 of the image source side surface of the first lens and the center thickness CT1 of the first lens satisfy: -0.3<(SAG12-SAG11) / CT1<-0.1.

[0014] Further preferably, the semi-aperture DM11 of the projection side surface of the first lens and the semi-aperture DM62 of the image source side surface of the sixth lens satisfy the following relationship: 0.9 <DM11 / DM62<1.3。

[0015] The projection lens provided by this invention achieves clear imaging at two different projection distances by switching between flat glass, enabling the switching between near and far views, effectively improving driving convenience and safety. Furthermore, through the rational configuration of lens surface shapes and the appropriate matching of optical powers, the projection lens's imaging quality is improved, aberrations are reduced, and the projection quality is enhanced, resulting in one or more advantages, including minimal distortion, low CRA, uniform illumination, and high imaging quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the following description of the embodiments with reference to the accompanying drawings, in which: Figure 1 Schematic diagram of the structure of the projection lens without flat glass in Example 1 of the present invention Figure 1 .

[0017] Figure 2 Schematic diagram of the structure of the projection lens without flat glass in Example 1 of the present invention Figure 2 .

[0018] Figure 3 Schematic diagram of the structure of the projection lens with flat glass in Example 1 of the present invention Figure 1 .

[0019] Figure 4 Schematic diagram of the structure of the projection lens with flat glass in Example 1 of the present invention Figure 2 .

[0020] Figure 5 Graph showing the field curvature of the projection lens in Example 1 of the present invention.

[0021] Figure 6 FIG. 4 is a graph showing the F-Tan (Theta) distortion curve of the projection lens in Example 1 of the present invention.

[0022] Figure 7 1 is an axial aberration curve diagram of the projection lens in Example 1 of the present invention.

[0023] Figure 8 2 is the vertical axis chromatic aberration curve of the projection lens in Example 1 of the present invention.

[0024] Figure 9 This is a relative illumination curve diagram of the projection lens in Example 1 of the present invention.

[0025] Figure 10 Schematic diagram of the structure of the projection lens without flat glass in Example 2 of the present invention Figure 1 .

[0026] Figure 11 Schematic diagram of the structure of the projection lens without flat glass in Example 2 of the present invention Figure 2 .

[0027] Figure 12 Schematic diagram of the structure of the projection lens with flat glass in Example 2 of the present invention Figure 1 .

[0028] Figure 13 Schematic diagram of the structure of the projection lens with flat glass in Example 2 of the present invention Figure 2 .

[0029] Figure 14 Graph showing the field curvature of the projection lens in Example 2 of the present invention.

[0030] Figure 15 FIG. 4 is a graph showing the F-Tan (Theta) distortion curve of the projection lens in Example 2 of the present invention.

[0031] Figure 16 2 is an axial aberration curve diagram of the projection lens in Example 2 of the present invention.

[0032] Figure 17 2 is the vertical axis chromatic aberration curve of the projection lens in Example 2 of the present invention.

[0033] Figure 18 This is a relative illumination curve diagram of the projection lens in Example 2 of the present invention.

[0034] Figure 19 Schematic diagram of the structure of the projection lens without flat glass in Example 3 of the present invention Figure 1 .

[0035] Figure 20 Schematic diagram of the structure of the projection lens without flat glass in Example 3 of the present invention Figure 2 .

[0036] Figure 21 Schematic diagram of the structure of the projection lens with flat glass in Example 3 of the present invention Figure 1 .

[0037] Figure 22 Schematic diagram of the structure of the projection lens with flat glass in Example 3 of the present invention Figure 2 .

[0038] Figure 23 Graph showing the field curvature of the projection lens in Example 3 of the present invention.

[0039] Figure 24 FIG. 4 is a graph showing the F-Tan (Theta) distortion curve of the projection lens in Example 3 of the present invention.

[0040] Figure 25 Graph showing the axial aberration of the projection lens in Example 3 of the present invention.

[0041] Figure 26 2 is the vertical axis chromatic aberration curve of the projection lens in Example 3 of the present invention.

[0042] Figure 27 This is a relative illumination curve diagram of the projection lens in Example 3 of the present invention.

[0043] The following specific embodiments will further illustrate the present invention in conjunction with the above-mentioned drawings. DETAILED DESCRIPTION

[0044] For a better understanding of the present application, various aspects of the present application will be described in more detail with reference to the accompanying drawings. It should be understood that these detailed descriptions are merely descriptions of 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.

[0045] It should be noted that in this specification, the terms "first," "second," "third," etc., are used solely to distinguish one feature from another and do not limit the features. Thus, the first lens discussed below could also be referred to as the second lens or the third lens without departing from the teachings of the present invention.

[0046] In the drawings, the thickness, size, and shape of the lenses are slightly exaggerated for ease of illustration. Specifically, the shapes of the spherical and aspherical surfaces shown in the drawings are provided by way of example. That is, the shapes of the spherical and aspherical surfaces are not limited to those shown in the drawings. The drawings are for illustration only and are not drawn strictly to scale.

[0047] In this article, the paraxial region refers to the area near the optical axis. If a lens surface is convex and the location of the convex surface is undefined, it means that the lens surface is convex at least in the paraxial region. If a lens surface is concave and the location of the concave surface is undefined, it means that the lens surface is concave at least in the paraxial region. The surface of each lens closest to the projection plane is called the projection-side surface of the lens, and the surface of each lens closest to the image source plane is called the image source-side surface of the lens.

[0048] 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 preclude 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 list of 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.

[0049] Unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by those skilled in the art to which this application belongs. It should also be understood that terms (such as those defined in commonly used dictionaries) should be interpreted as having a meaning consistent with their meaning in the context of the relevant technology and will not be interpreted in an idealized or overly formal sense unless expressly defined as such herein.

[0050] It should be noted that, in the absence of conflict, the embodiments and features of the embodiments in this 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.

[0051] The projection lens provided by the embodiment of the present invention comprises, along the optical axis, from the projection surface to the image source surface, a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a prism and a protective glass.

[0052] A switchable flat glass is positioned between the prism and the protective glass. The flat glass can be positioned between a first and second position by a switching mechanism. When the flat glass is in the first position, the optical path does not pass through the flat glass. In the second position, the flat glass is located on the optical axis and between the prism and the protective glass, parallel to the protective glass, and the optical path passes through the flat glass. By switching the flat glass, clear imaging can be achieved at two different projection distances, effectively improving driving convenience and safety. Without the flat glass, near-field imaging is possible. Adding the flat glass between the prism and the chip protective glass (using an automatically controllable switching mechanism to add or remove the flat glass) allows for far-field projection. The near-field and far-field projections are switched depending on whether the flat glass is inserted or not. It is understood that light traveling through flat glass requires a longer optical path than through air, increasing the equivalent length of the optical path and increasing the effective image distance of the system. Since the object and image movement are on the same side, the corresponding projection object distance increases. The insertion of flat glass does not change the focal length of the projection lens, but rather changes the projection distance required for clear imaging of the system through optical path control, thereby achieving dual focal plane switching.

[0053] Specifically, the first lens may have positive focal power, with its projection side surface being convex, and its image source side surface being concave or convex. The second lens may have negative focal power, with its projection side surface being convex, and its image source side surface being concave. The third lens may have positive focal power, with its projection side surface being concave, and its image source side surface being convex. The fourth lens may have negative focal power, with its projection side surface being concave, and its image source side surface being concave or convex. The fifth lens may have positive focal power, with its projection side surface being concave, and its image source side surface being convex. The sixth lens may have positive focal power, with its projection side surface being convex, and its image source side surface being convex. The protective glass has a plane surface on its projection side and a plane surface on its image source side. The protective glass serves to protect the projection lens and prevent damage to the photosensitive chip.

[0054] The prism can be a right-angled triangular prism, comprising a flat incident surface, a reflective surface, and an output surface. Light enters the prism along the optical axis from the incident surface, is reflected by the reflective surface, and exits from the output surface. The reflective surface forms a 45° angle with the optical axes of the incident and output surfaces, respectively. The prism can be used to change the direction of the light path, bending it so that the direction of the incident light is perpendicular to the arrangement of the multiple lenses, thereby reducing the overall thickness of the optical system.

[0055] In some embodiments, the third lens and the fourth lens can be cemented to form a cemented lens group with optical focal length, which can effectively correct the chromatic aberration of the projection lens, reduce the decentration sensitivity of the projection lens, balance the aberration of the projection lens, and improve the imaging quality of the projection lens; it can also reduce the assembly sensitivity of the projection lens, thereby reducing the difficulty of the processing technology of the projection lens and improving the assembly yield of the projection lens.

[0056] In some embodiments, the projection lens may further include an aperture, which may be located between the second and third lenses. It will be appreciated that the aperture is used to limit the amount of light entering, thereby varying the brightness of the resulting image. Positioning the aperture between the second and third lenses facilitates correction of aperture aberrations.

[0057] In some embodiments, the projection plane has a first tilt angle relative to the vertical plane, while the protective glass and image source plane have a second tilt angle relative to the horizontal plane. The first tilt angle is 14° to 16°, and the second tilt angle is 1° to 3°. It is understood that the projection plane is tilted relative to the first lens, while the flat glass, protective glass, and image source plane are tilted relative to the prism.

[0058] In some embodiments, when the flat glass is in the first position, the distance CT0 from the projection plane to the first lens satisfies: 155 mm < CT0 < 165 mm; when the flat glass is in the second position, the distance CT0 from the projection plane to the first lens satisfies: 190 mm < CT0 < 200 mm. After adding the flat glass, the corresponding optimal projection plane distance is farther, which can satisfy clear imaging at two different projection distances, effectively improving the convenience and safety of driving.

[0059] In some embodiments, the focal length f2 of the second lens and the effective focal length f of the projection lens satisfy: -2.4 < f2 / f < -1. Meeting the above conditions, the negative lens of the second lens can adjust the principal ray angle and reduce lens distortion.

[0060] In some embodiments, the true image height IH corresponding to the maximum field angle of the projection lens and the aperture value Fno of the projection lens satisfy: 4 mm < IH / Fno < 4.5 mm. Meeting the above range is beneficial to achieving the large image plane characteristic and improving the imaging quality of the projection lens.

[0061] In some embodiments, the back focal length BFL of the projection lens and the effective focal length f of the projection lens satisfy: 0.2 < BFL / f < 0.25. Meeting the above range helps to achieve a short back focal length and limit the length of the lens.

[0062] In some embodiments, the curvature radius R5 of the projection side surface of the third lens and the curvature radius R6 of the image source side surface of the third lens satisfy: 1 < (R5 + R6) / (R5 - R6) < 2.1. Meeting the above range can make the light trend smoother; at the same time, it can correct coma and field curvature, improve the flatness of imaging, and enhance the imaging quality of the projection lens.

[0063] In some embodiments, the sagittal height SAG11 of the clear aperture semi-diameter of the projection side surface of the first lens, the sagittal height SAG12 of the clear aperture semi-diameter of the image source side surface of the first lens, and the central thickness CT1 of the first lens satisfy: -0.3 < (SAG12 - SAG11) / CT1 < -0.1. Meeting the above range helps to control the trend of marginal field light and highlight the detailed information of the central field of the projection lens.

[0064] In some embodiments, the clear aperture semi-diameter DM11 of the projection side surface of the first lens and the clear aperture semi-diameter DM62 of the image source side surface of the sixth lens satisfy: 0.9 < DM11 / DM62 < 1.3. Meeting the above range, by reasonably setting the aperture relationship between the first and last lenses, while ensuring that as much light as possible enters the system, the area of light entering the image plane is increased, achieving a high relative illuminance of the lens.

[0065] In some embodiments, the back focal length BFL of the projection lens and the total optical length TTL of the projection lens satisfy: 0.06 < BFL / TTL < 0.08. The back focal length BFL is the distance from the exit surface of the prism to the image source surface on the optical axis. Meeting the above conditions and reasonably configuring the ratio of the back focal length of the projection lens to the total optical length of the projection lens is conducive to achieving a short back focal length of the projection lens, and is conducive to miniaturizing the projection lens while ensuring sufficient space for the installation of optical elements (flat glass).

[0066] In some embodiments, the total optical length TTL of the projection lens and the effective focal length f of the projection lens satisfy: 2.5 < TTL / f < 3. Meeting the above conditions can effectively limit the length of the lens and is conducive to miniaturizing the projection lens.

[0067] In some embodiments, the effective focal length f of the projection lens, the maximum field angle FOV of the projection lens, and the true image height IH corresponding to the maximum field angle of the projection lens satisfy: 50° < (f × FOV) / IH < 60°. Meeting the above conditional formula and reasonably restricting the relationship between the focal length, field angle, and image height of the projection lens is conducive to achieving the balance of a super-large field angle and a large target surface imaging of the projection lens.

[0068] In some embodiments, the true image height IH corresponding to the maximum field angle of the projection lens and the effective focal length f of the projection lens satisfy: 0.5 < IH / f < 0.6. Meeting the above conditions can achieve a larger field angle and imaging range, and can achieve the large image surface characteristics while ensuring the depth of field of the projection lens, thereby improving the imaging quality of the optical system.

[0069] In some embodiments, the total optical length TTL of the projection lens and the true image height IH corresponding to the maximum field angle of the projection lens satisfy: 4.5 < TTL / IH < 5.5. Meeting the above conditions can better achieve the miniaturization of the lens, and at the same time ensure that the lens has a larger image surface under the same total length, and can match a larger size imaging chip to achieve high-definition imaging.

[0070] In some embodiments, the focal length f1 of the first lens and the effective focal length f of the projection lens satisfy: 1.7 < f1 / f < 3.6. Meeting the above range and reasonably setting the focal length of the first lens is conducive to slowing down the change degree of the incident light refraction angle, avoiding excessive aberration caused by too strong refraction change, and at the same time helping more light to enter the rear optical system, increasing the field angle of the lens and improving the overall imaging quality.

[0071] In some embodiments, the focal length f3 of the third lens and the effective focal length f of the projection lens satisfy: 0.3 < f3 / f < 0.55; the focal length f4 of the fourth lens and the effective focal length f of the projection lens satisfy: -0.5 < f4 / f < -0.25. Meeting the above conditions, the third lens and the fourth lens are cemented to form a doublet lens. The third lens and the fourth lens can have opposite optical powers, so that various aberrations of the optical system are fully corrected. On the premise of a compact structure, the resolution can be improved and the optical performance such as distortion can be optimized.

[0072] In some embodiments, the focal length f5 of the fifth lens and the effective focal length f of the projection lens satisfy: 1 < f5 / f < 1.5. Meeting the above conditions, by reasonably setting the focal length of the fifth lens, it is beneficial to the smooth transition of light, facilitating the correction of astigmatism and field curvature, improving the imaging quality of the projection lens, and ensuring the stability of the optical system.

[0073] In some embodiments, the focal length f6 of the sixth lens and the effective focal length f of the projection lens satisfy: 1.1 < f6 / f < 1.4. Meeting the above range can make the sixth lens have an appropriate positive optical power, which is beneficial to converging light while reducing the light deflection angle, making the light trend transition smoothly, and improving the projection quality of the projection lens.

[0074] In some embodiments, the true image height IH corresponding to the maximum field angle of the projection lens and the entrance pupil diameter EPD of the projection lens satisfy: 1.3 < IH / EPD < 1.6. Meeting the above range can increase the width of the light beam entering the projection lens, improve the relative illumination, and avoid vignetting.

[0075] In some embodiments, the curvature radius R1 of the projection side surface of the first lens and the curvature radius R2 of the image source side surface of the first lens satisfy: -0.8 < R1 / R2 < 0.2. Meeting the above range can reasonably set the surface shape of the first lens and enhance the light collection ability of the first lens.

[0076] In some embodiments, the curvature radius R5 of the projection side surface of the third lens and the curvature radius R6 of the image source side surface of the third lens satisfy: 2.8 < R5 / R6 < 22. By making the optical system satisfy the above relationship, it is beneficial to the reasonable configuration of the ratio of the curvature radius of the projection side surface of the third lens to the curvature radius of the image source side surface of the third lens, controlling the shape of the third lens, comprehensively balancing the spherical aberration, chromatic aberration and field curvature of the optical system, reducing the risk of ghost imaging, improving the resolution ability of the optical system, and at the same time, it is also beneficial to reducing the processing difficulty of the third lens.

[0077] In some embodiments, the radius of curvature R3 of the projection side surface of the second lens and the radius of curvature R4 of the image source side surface of the second lens satisfy: 3 < (R3 + R4) / (R3 - R4) < 5. Satisfying the above range can reduce the angle between the incident light and the projection side surface of the first lens, and can effectively reduce the working aperture of the first lens, which is beneficial to the miniaturization of the projection lens.

[0078] In some embodiments, the radius of curvature R11 of the projection side surface of the sixth lens and the radius of curvature R12 of the image source side surface of the sixth lens satisfy: -0.5 < (R11 + R12) / (R11 - R12) < 0.2. Satisfying the above range is beneficial to increasing the divergence degree of light, increasing the area of light entering the imaging surface, achieving large target surface imaging of the lens, and improving the imaging quality of the projection lens.

[0079] In some embodiments, the radius of curvature R1 of the projection side surface of the first lens and the effective focal length f of the projection lens satisfy: 1.2 < R1 / f < 5. Satisfying the above range, by reasonably setting the surface shape of the projection side of the first lens, the brightness of the projection lens can be effectively improved.

[0080] In some embodiments, the radius of curvature R12 of the image source side surface of the sixth lens and the effective focal length f of the projection lens satisfy: -3.3 < R12 / f < -1.2. Satisfying the above range is beneficial to increasing the imaging area, reducing chromatic aberration, and improving the imaging quality.

[0081] In some embodiments, the focal length f1 of the first lens and the focal length f6 of the sixth lens satisfy: 1.5 < f1 / f6 < 2.8. Satisfying the above conditions, by reasonably setting the focal length relationship between the first and last lenses in the lens, while ensuring that as much light as possible enters the system, the area of light entering the imaging surface is increased, which is beneficial to achieving large image surface imaging of the lens, and at the same time increasing the light input and improving the relative illuminance of the system.

[0082] In some embodiments, the central thickness CT1 of the first lens and the central thickness CT2 of the second lens satisfy: 0.9 < CT1 / CT2 < 1.5. Satisfying the above conditions enables a reasonable configuration of the ratio of the thickness of the first lens on the optical axis to the thickness of the second lens on the optical axis. The first lens and the second lens can regulate each other to maintain the characteristics of the miniaturization of the optical system.

[0083] In some embodiments, the total optical length TTL of the projection lens and the sum ∑CT of the central thicknesses of the first lens to the sixth lens along the optical axis respectively satisfy: 0.3 < ∑CT / TTL < 0.45. Satisfying the above conditions can effectively compress the total length of the projection lens.

[0084] In some embodiments, the central thickness CT2 of the second lens and the edge thickness ET2 of the second lens satisfy: 1.1 < CT2 / ET2 < 1.4. By making the optical system satisfy the above relational expression, it is beneficial to the processing and forming of the lens, beneficial to reducing the assembly difficulty, and can effectively correct the field curvature of the system.

[0085] In some embodiments, the curvature radius R1 of the projection-side surface of the first lens, the curvature radius R2 of the image-source-side surface of the first lens, and the central thickness CT1 of the first lens satisfy: -0.8 < R1 / (R2 + CT1) < 0.3. Satisfying the above range can reduce the correction difficulty of the peripheral field distortion and control the distortion within a reasonable range.

[0086] In some embodiments, the clear aperture sag SAG61 of the projection-side surface of the sixth lens, the clear aperture sag SAG62 of the image-source-side surface of the sixth lens, and the central thickness CT6 of the sixth lens satisfy: -0.7 < (SAG62 - SAG61) / CT6 < -0.5. Satisfying the above range, by controlling the relationship between the sag height difference between the image-source-side surface and the projection-side surface of the sixth lens and the central thickness of the sixth lens, it is beneficial to correct the coma of the off-axis field and beneficial to improving the imaging quality of the off-axis field of the projection lens.

[0087] In some embodiments, the clear aperture diameter DM11 of the projection-side surface of the first lens and the true image height IH corresponding to the maximum field angle of the projection lens satisfy: 0.8 < DM11 / IH < 1. Satisfying the above range can ensure the balance between the front port diameter and the image plane size of the projection lens.

[0088] In some embodiments, the effective focal length f of the projection lens, the maximum field angle FOV of the projection lens, and the true image height IH corresponding to the maximum field angle of the projection lens satisfy: 0.98 < (2×f×tan(FOV / 2)) / IH < 1. Satisfying the above conditions indicates that the distortion of the projection lens ≤ 2%, which can make the lens have a smaller distortion value, can provide a high-definition imaging effect, improve the resolution of the projection lens, can achieve a better projection effect, and is more suitable for human eyes to view.

[0089] In some embodiments, the chief ray angle of incidence CRA at the maximum image height of the projection lens satisfies: 0.85 < CRA < 1. Satisfying the above range limits that the projection lens has a smaller CRA, making the brightness uniformity of the projection screen of the projection lens better.

[0090] In some embodiments, the projection lens satisfies the conditional formula: 18 mm < f < 20 mm, 50 mm < TTL < 60 mm, 2.5 < Fno < 2.6, 10 mm < IH < 12 mm, 30° < FOV < 35°; where f represents the effective focal length of the projection lens, TTL represents the total optical length of the projection lens, Fno represents the aperture value of the projection lens, IH represents the true image height corresponding to the maximum field angle of the projection lens, and FOV represents the maximum field angle of the projection lens. Meeting the above conditions indicates that the projection lens provided by the embodiments of the present invention has at least the characteristics of a large image plane and miniaturization.

[0091] In some embodiments, the lens material in the projection lens provided by the present invention can be glass or plastic. When the lens material is plastic, the production cost can be effectively reduced. When the lens material is glass, the geometric chromatic aberration of the optical system can be effectively corrected by the low dispersion characteristic of the glass itself. More specifically, the six lenses in the projection lens provided by the present invention can all be glass spherical lenses, which can improve the imaging stability of the projection lens in different temperature environments on the premise of meeting high pixels.

[0092] 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 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 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.

[0093] Embodiment 1 Please refer to Figures 1 to 4 , 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 S0 to the image source plane S18: a first lens L1, a second lens L2, an aperture ST, a third lens L3, a fourth lens L4, a fifth lens L5, a sixth lens L6, a prism L7, and a protective glass G1; at the same time, a flat glass G2 with a changeable position is further provided between the prism L7 and the protective glass G1. The flat glass G2 can be located at a first position or a second position through a switching device. When the flat glass G2 is in the first position, the optical path does not pass through the flat glass G2; when the flat glass G2 is in the second position, the flat glass G2 is located on the optical axis and between the prism L7 and the protective glass G1, and the flat glass G2 is parallel to the protective glass G1, and the optical path passes through the flat glass G2.

[0094] The projection plane S0 has a first inclination angle of 15° with the vertical plane. The protective glass G1 and the image source plane S18 have a second inclination angle of 2° with the horizontal plane. It can be understood that the projection plane is tilted relative to the first lens L1; the flat glass G2, the protective glass G1, and the image source plane S18 are tilted relative to the prism L7.

[0095] The first lens L1 has positive refractive power, its projection-side surface S1 is convex, and its image-source-side surface S2 is convex. The second lens L2 has negative refractive power, its projection-side surface S3 is convex, and its image-source-side surface S4 is concave; The third lens L3 has positive refractive power, its projection-side surface S5 is concave, and its image-source-side surface is convex; The fourth lens L4 has negative refractive power, its projection-side surface is concave, and its image-source-side surface S7 is also concave. The third lens L3 and the fourth lens L4 form a cemented lens group having optical power, that is, the cemented surface between the image source side surface of the third lens L3 and the projection side surface of the fourth lens L4 is S6; The fifth lens L5 has positive refractive power, its projection-side surface S8 is concave, and its image-source-side surface S9 is convex; The sixth lens L6 has positive refractive power, its projection-side surface S10 is convex, and its image-source-side surface S11 is convex. Prism L7 can be a right-angled triangular prism, including an incident surface S12, a reflective surface R0, and an exit surface S13; the incident surface S12, reflective surface R0, and exit surface S13 are all planes. The reflective surface of the prism forms a 45° angle with the optical axes of the incident and exit surfaces of the prism, respectively. It can be understood that the incident surface S12 faces the projection surface, and the exit surface S13 faces the image source surface. Light enters the prism from the incident surface, is reflected by the reflective surface, and exits from the exit surface. The angle between the incident and exit surfaces is 90°.

[0096] The projection side surface S14 and the image source side surface S15 of the flat glass G2 are both planes; The projection side surface S16 and the image source side surface S17 of the protective glass G1 are both planes; The image source surface S18 is a plane.

[0097] The first lens L1, the second lens L2, the third lens L3, the fourth lens L4, the fifth lens L5, and the sixth lens L6 are all glass spherical lenses.

[0098] The relevant parameters of each lens in the projection lens 100 in Example 1 are shown in Table 1-1 and Table 1-2. Specifically, when the flat glass G2 is in the first position (i.e., there is no flat glass between the prism L7 and the protective glass G1), the parameters are as shown in Table 1-1; when the flat glass G2 is in the second position (i.e., there is a flat glass between the prism L7 and the protective glass G1), the parameters are as shown in Table 1-2.

[0099] Table 1-1 Table 1-2 As shown in the table, when the flat glass G2 is in the first position, the distance between the projection plane S0 and the first lens L1 on the optical axis is 159.612 mm. When the flat glass G2 is in the second position, the distance between the projection plane S0 and the first lens L1 on the optical axis is 193.388 mm. It is understandable that the addition of the flat glass increases the corresponding optimal projection plane distance.

[0100] Figure 5 The following figure shows the field curvature curves for Example 1, which represent the degree of curvature of light of different wavelengths in the meridional and sagittal image planes. The horizontal axis represents the offset (unit: mm), and the vertical axis represents the half field angle (unit: degrees). As can be seen from the figure, the field curvature of the meridional and sagittal image planes is controlled within ±0.1mm, indicating that the projection lens is able to effectively correct for field curvature.

[0101] Figure 6 The F-Tan (Theta) distortion curve for Example 1 shows the F-Tan (Theta) distortion of light at different field angles on the imaging plane. The horizontal axis represents the F-Tan (Theta) distortion value (unit: %), and the vertical axis represents the half field angle (unit: °). As can be seen from the figure, the F-Tan (Theta) distortion of the projection lens is controlled within a range of -1% to 0, indicating that the projection lens is capable of excellent distortion correction.

[0102] Figure 7 The following graph shows the axial aberration curve for Example 1, which plots the aberration along the optical axis at the imaging plane for each wavelength. The horizontal axis represents the axial aberration value (unit: mm), and the vertical axis represents the normalized pupil radius. As can be seen from the graph, the axial aberration offset is controlled within a range of -0.06mm to 0.02mm, demonstrating that the projection lens is well-suited for correcting axial aberration.

[0103] Figure 8A graph of vertical chromatic aberration for Example 1 shows the chromatic aberration at various image heights relative to the center wavelength (0.53 μm) for each wavelength. The horizontal axis represents the vertical chromatic aberration value relative to the center wavelength (unit: μm), and the vertical axis represents the normalized field of view. As can be seen from the graph, the vertical chromatic aberration for both the longest and shortest wavelengths is within 0 to 3 μm, demonstrating that this projection lens is capable of effectively correcting chromatic aberration.

[0104] Figure 9 The relative illumination curve for Example 1 is shown, representing the relative illumination values ​​at different field angles on the imaging plane. The horizontal axis represents the half field angle (unit: degrees), and the vertical axis represents the relative illumination (unit: %). As can be seen from the graph, the relative illumination value of the projection lens is still greater than 88% at the maximum half field angle, indicating that the projection lens has excellent relative illumination.

[0105] Example 2 See also Figures 10 to 13 , shown is a schematic structural diagram of a projection lens 200 provided in Example 2 of the present invention. Compared with Example 1, this embodiment mainly differs in that: the image source side surface S7 of the fourth lens L4 is convex; and the optical parameters such as the curvature radius and lens thickness of each lens surface are different.

[0106] The relevant parameters of each lens in the projection lens 200 in Example 2 are shown in Table 2-1 and Table 2-2.

[0107] Table 2-1 Table 2-2 As shown in the table, when the flat glass G2 is in the first position, the distance between the projection plane S0 and the first lens L1 on the optical axis is 157.451 mm. When the flat glass G2 is in the second position, the distance between the projection plane S0 and the first lens L1 on the optical axis is 191.079 mm. It is understandable that the addition of the flat glass increases the corresponding optimal projection plane distance.

[0108] Figure 14 The following figure shows the field curvature curves for Example 2, which represent the degree of curvature of light of different wavelengths in the meridional and sagittal image planes. The horizontal axis represents the offset (unit: mm), and the vertical axis represents the half field angle (unit: degrees). As can be seen from the figure, the field curvature of the meridional and sagittal image planes is controlled within ±0.1mm, indicating that the projection lens is able to effectively correct for field curvature.

[0109] Figure 15The F-Tan (Theta) distortion curve for Example 2 shows the F-Tan (Theta) distortion of light at different field angles on the imaging plane. The horizontal axis represents the F-Tan (Theta) distortion value (unit: %), and the vertical axis represents the half field angle (unit: °). As can be seen from the figure, the F-Tan (Theta) distortion of the projection lens is controlled within a range of -1% to 0, indicating that the projection lens is capable of excellent distortion correction.

[0110] Figure 16 The following graph shows the axial aberration curve for Example 2, which plots the aberration along the optical axis at the imaging plane for each wavelength. The horizontal axis represents the axial aberration value (unit: mm), and the vertical axis represents the normalized pupil radius. As can be seen from the graph, the axial aberration offset is controlled within a range of -0.06mm to 0.03mm, demonstrating that the projection lens is well-suited for correcting axial aberration.

[0111] Figure 17 A graph of vertical chromatic aberration for Example 2 shows the chromatic aberration of each wavelength relative to the center wavelength (0.53 μm) at different image heights on the imaging plane. The horizontal axis represents the vertical chromatic aberration value of each wavelength relative to the center wavelength (unit: μm), and the vertical axis represents the normalized field of view. As can be seen from the graph, the vertical chromatic aberration for both the longest and shortest wavelengths is controlled within a range of -1 μm to 3 μm, demonstrating that this projection lens is capable of effectively correcting chromatic aberration.

[0112] Figure 18 The relative illumination curve for Example 2 is shown, representing the relative illumination values ​​at different field angles on the imaging plane. The horizontal axis represents the half field angle (unit: degrees), and the vertical axis represents the relative illumination (unit: %). As can be seen from the graph, the relative illumination value of the projection lens remains greater than 90% at the maximum half field angle, indicating that the projection lens has excellent relative illumination.

[0113] Example 3 See also Figures 19 to 22 , shown is a schematic structural diagram 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 S2 of the first lens L1 is concave; and the optical parameters such as the curvature radius and lens thickness of each lens surface are different.

[0114] The relevant parameters of each lens in the projection lens 300 in Example 3 are shown in Tables 3-1 and 3-2.

[0115] Table 3-1 Table 3-2 As shown in the table, when the flat glass G2 is in the first position, the distance between the projection plane S0 and the first lens L1 on the optical axis is 162.210 mm. When the flat glass G2 is in the second position, the distance between the projection plane S0 and the first lens L1 on the optical axis is 195.991 mm. It is understandable that the addition of the flat glass increases the corresponding optimal projection plane distance.

[0116] Figure 23 The following figure shows the field curvature curves for Example 3, which represent the degree of curvature of light of different wavelengths in the meridional and sagittal image planes. The horizontal axis represents the offset (unit: mm), and the vertical axis represents the half field angle (unit: degrees). As can be seen from the figure, the field curvature of the meridional and sagittal image planes is controlled within ±0.1mm, indicating that the projection lens is able to effectively correct for field curvature.

[0117] Figure 24 The F-Tan (Theta) distortion curve for Example 3 shows the F-Tan (Theta) distortion of light at different field angles on the imaging plane. The horizontal axis represents the F-Tan (Theta) distortion value (unit: %), and the vertical axis represents the half field angle (unit: °). As can be seen from the figure, the F-Tan (Theta) distortion of the projection lens is controlled within a range of -1% to 0, indicating that the projection lens is capable of excellent distortion correction.

[0118] Figure 25 The following graph shows the axial aberration curve for Example 3, which plots the aberration along the optical axis at the imaging plane for each wavelength. The horizontal axis represents the axial aberration value (unit: mm), and the vertical axis represents the normalized pupil radius. As can be seen from the graph, the axial aberration offset is controlled within a range of -0.04mm to 0.01mm, demonstrating that the projection lens is capable of effectively correcting axial aberration.

[0119] Figure 26 A graph of vertical chromatic aberration for Example 3 is shown. It plots the chromatic aberration of each wavelength relative to the center wavelength (0.53 μm) at different image heights on the imaging plane. The horizontal axis represents the vertical chromatic aberration value of each wavelength relative to the center wavelength (unit: μm), and the vertical axis represents the normalized field of view. As can be seen from the graph, the vertical chromatic aberration for both the longest and shortest wavelengths is controlled within a range of -1 μm to 3 μm, demonstrating that this projection lens is capable of effectively correcting chromatic aberration.

[0120] Figure 27 The relative illumination curve for Example 3 is shown, representing the relative illumination values ​​at different field angles on the imaging plane. The horizontal axis represents the half field angle (unit: degrees), and the vertical axis represents the relative illumination (unit: %). As can be seen from the graph, the relative illumination value of the projection lens remains greater than 90% at the maximum half field angle, indicating that the projection lens has excellent relative illumination.

[0121] Please refer to Table 4, which shows the optical characteristics corresponding to the above embodiments, including the effective focal length f of the projection lens; the total optical length TTL; the aperture value Fno; the real image height IHj corresponding to the maximum field of view angle when the flat glass is in the first position, the chief ray incident angle CRAj at the maximum image height, and the maximum field of view angle FOVj; the real image height IHy corresponding to the maximum field of view angle when the flat glass is in the second position, the chief ray incident angle CRAy at the maximum image height, and the maximum field of view angle FOVy, as well as the numerical values ​​corresponding to each conditional expression in each embodiment.

[0122] Table 4 In summary, the projection lens provided by the present invention achieves clear imaging at two different projection distances by switching between flat glass, enabling switching between near and far views, effectively improving driving convenience and safety. Furthermore, through the rational configuration of lens surface shapes and the appropriate matching of optical powers, the projection lens's imaging quality is improved, aberrations are reduced, and the projection quality is enhanced, resulting in one or more advantages, including minimal distortion, low CRA, uniform illumination, and high imaging quality.

[0123] Throughout this specification, reference to terms such as "one embodiment," "some embodiments," "examples," "specific examples," or "some examples" means that a specific feature, structure, material, or characteristic described in conjunction with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0124] The above-described embodiments merely illustrate several implementations of the present invention, and while their descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be determined by the appended claims.

Claims

1. A projection lens, characterized in that: Along the optical axis from the projection surface to the image source surface, it includes: a first lens having positive refractive power, wherein the projection side surface thereof is convex; a second lens having negative optical power, wherein the projection-side surface thereof is convex and the image-source-side surface thereof is concave; a third lens element having positive refractive power, whose projection-side surface is concave and whose image-source-side surface is convex; a fourth lens element having negative optical power and a concave projection-side surface; a fifth lens element having positive refractive power, whose projection-side surface is concave and whose image-source-side surface is convex; a sixth lens having positive refractive power, wherein the projection-side surface thereof is convex and the image-source-side surface thereof is convex; A prism comprising an incident surface, a reflecting surface, and an exiting surface, all of which are planes; light is incident on the prism from the incident surface along the optical axis, is reflected by the reflecting surface, and exits from the exiting surface; the reflecting surface forms an angle of 45° with the optical axis of the incident surface and the optical axis of the exiting surface, respectively; The protective glass has a flat surface on the projection side and a flat surface on the image source side; A flat glass with a changeable position is provided between the prism and the protective glass. The flat glass can be located in a first position or a second position by a switching device. When the flat glass is in the first position, the light path does not pass through the flat glass. When the flat glass is in the second position, the flat glass is located on the optical axis and between the prism and the protective glass. The flat glass is parallel to the protective glass, and the light path passes through the flat glass.

2. The projection lens according to claim 1, wherein: The projection surface has a first inclination angle with the vertical plane; the protection glass and the image source surface have a second inclination angle with the horizontal plane.

3. The projection lens according to claim 2, wherein: The first inclination angle is 14°~16°; the second inclination angle is 1°~3°.

4. The projection lens according to claim 1, wherein: When the flat glass is in the first position, the distance CT0 from the projection surface to the first lens satisfies: 155mm<CT0<165mm; when the flat glass is in the second position, the distance CT0 from the projection surface to the first lens satisfies: 190mm<CT0<200mm.

5. The projection lens according to claim 1, wherein: The focal length f2 of the second lens and the effective focal length f of the projection lens satisfy: -2.4 <f2 / f<-1。 6. The projection lens according to claim 1, wherein: The real image height IH corresponding to the maximum field angle of the projection lens and the aperture value Fno of the projection lens meet the following requirements: 4mm <IH / Fno<4.5mm。 7. The projection lens according to claim 1, wherein: The back focal length BFL of the projection lens and the effective focal length f of the projection lens satisfy: 0.2 <BFL / f<0.25。 8. The projection lens according to claim 1, wherein: The curvature radius R5 of the projection side surface of the third lens and the curvature radius R6 of the image source side surface of the third lens satisfy: 1<(R5+R6) / (R5-R6)<2.

1.

9. The projection lens according to claim 1, wherein: The clear semi-aperture sag SAG11 of the projection side surface of the first lens, the clear semi-aperture sag SAG12 of the image source side surface of the first lens and the center thickness CT1 of the first lens satisfy: -0.3<(SAG12-SAG11) / CT1<-0.

1.

10. The projection lens according to claim 1, wherein: The semi-aperture DM11 of the projection side surface of the first lens and the semi-aperture DM62 of the image source side surface of the sixth lens satisfy: 0.9 <DM11 / DM62<1.3。

Images