Projection lens and projection device

Abstract

The present invention provides a projection lens and a projection device, which are composed of four lenses and sequentially include, along the optical axis from the projection plane to the image source plane: a front group with positive optical power, a diaphragm, and a rear group with positive optical power; the front group sequentially includes, along the optical axis from the projection plane to the image source plane: a first lens with positive optical power, whose projection-side surface is convex and image-source-side surface is concave; a second lens with positive optical power, whose projection-side surface is convex and image-source-side surface is concave; the rear group sequentially includes, along the optical axis from the projection plane to the image source plane: a third lens with optical power, whose projection-side surface is concave and image-source-side surface is convex; a fourth lens with positive optical power, whose projection-side surface is convex and image-source-side surface is concave; the effective focal length f of the projection lens and the entrance pupil diameter EPD of the projection lens satisfy: 0.65 < f / EPD < 0.85. The projection lens provided by the present invention improves the projection quality of the projection lens through the reasonable configuration of each lens surface type and the reasonable combination of optical powers.

Description

Technical Field

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

[0002] Traditional headlights include low beam and high beam, and their main function is to provide additional road lighting when the ambient light is insufficient, giving the driver a good driving vision. With the surge in the number of cars in recent years, people have put forward higher requirements for the safety, humanization and intelligence of headlights. Traditional headlights are controlled by one or several light sources, and it is impossible to accurately adjust the brightness of a certain lighting area, nor to achieve more personalized zoned lighting. In addition, due to the complex driving environment of the car, the application environment of the headlights may also be relatively harsh, and it is necessary to meet the ambient temperature of -45℃ to +85℃ to work normally, and the performance does not change much, which requires the projection lens of high-pixel headlights to have stable back focus in a large temperature range of -45℃ to +85℃. Summary of the invention

[0003] In view of the above problems, an object of the present invention is to provide a projection lens and a projection device having at least one of the advantages of a large aperture and excellent imaging quality.

[0004] The present invention provides a projection lens, which is composed of four lenses, and includes: a front group with positive focal power, an aperture, and a rear group with positive focal power in sequence from the projection surface to the image source surface along the optical axis;

[0005] The front group includes, in order from the projection surface to the image source surface along the optical axis:

[0006] A first lens having positive refractive power, whose projection side surface is convex and whose image source side surface is concave;

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

[0008] The rear group includes, in sequence from the projection surface to the image source surface along the optical axis:

[0009] a third lens having optical power, wherein the projection side surface thereof is concave and the image source side surface thereof is convex;

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

[0011] The effective focal length f of the projection lens and the entrance pupil diameter EPD of the projection lens satisfy: 0.65 <f / EPD<0.85。

[0012] More preferably, the combined focal length fa of the front group and the combined focal length fb of the rear group satisfy: 1 < fa / fb < 2.1.

[0013] More preferably, the focal length f1 of the first lens and the effective focal length f of the projection lens satisfy: 2.4 < f1 / f < 3; 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 < R1 / R2 < 0.3.

[0014] More preferably, the focal length f2 of the second lens and the effective focal length f of the projection lens satisfy: 2 < f2 / f < 5; the curvature radius R3 of the projection-side surface of the second lens and the curvature radius R4 of the image-source-side surface of the second lens satisfy: 0.2 < R3 / R4 < 1.

[0015] More preferably, the focal length f3 of the third lens and the effective focal length f of the projection lens satisfy: 5 < |f3 / f| < 14; 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: 0.5 < R5 / R6 < 1.05.

[0016] More preferably, the focal length f4 of the fourth lens and the effective focal length f of the projection lens satisfy: 1 < f4 / f < 2; the curvature radius R7 of the projection-side surface of the fourth lens and the curvature radius R8 of the image-source-side surface of the fourth lens satisfy: 0.5 < R7 / R8 < 0.6.

[0017] More preferably, the central thickness CT1 of the first lens and the edge thickness CM1 of the first lens satisfy: 3 < CT1 / CM1 < 10.

[0018] More preferably, the light-passing aperture DM11 of the projection-side surface of the first lens and the light-passing aperture DM42 of the image-source-side surface of the fourth lens satisfy: 2.9 < DM11 / DM42 < 3.6; the effective apertures DM1 of the first lens, DM2 of the second lens, DM3 of the third lens, and DM4 of the fourth lens satisfy: DM1 > DM2 > DM3 > DM4.

[0019] More preferably, the overall optical length TTL of the projection lens and the back focal length BFL of the projection lens satisfy: 20 < TTL / BFL < 34; the back focal length BFL of the projection lens and the effective focal length f of the projection lens satisfy: 0.05 < BFL / f < 0.1.

[0020] More preferably, the projection-side surface of the first lens is provided with a surface treatment of a microlens array or a matte lens.

[0021] The present invention also provides a projection device, comprising: an image display module and the above-mentioned projection lens;

[0022] The image display module includes a light emitting diode array light source for emitting image light source information;

[0023] The projection lens is located at the light-emitting side of the image display module, and the fourth lens is arranged closer to the image display module than the first lens. The projection lens is used to image the light from the image display module.

[0024] The projection lens provided by the present invention improves the imaging quality of the projection lens, reduces aberrations, and improves the projection quality of the projection lens through the reasonable configuration of each lens surface and the reasonable matching of the optical focal length, so that the lens has one or more advantages such as large aperture, telephoto, large image surface, and high imaging quality. In addition, the projection device provided by the present invention includes a LED array light source with hundreds of pixels and a projection lens optical system designed to match it, which can project the light source to infinity with high efficiency, thereby realizing high-beam lighting; at the same time, with the ability of the LED array to switch each pixel and control the brightness and darkness, it can realize arbitrarily adjustable regional lighting. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] 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:

[0026] Figure 1 Schematic diagram of the structure of the projection lens in Embodiment 1 of the present invention.

[0027] Figure 2 is a schematic diagram of a microlens array;

[0028] Figure 3 It is a field curvature curve diagram of the projection lens in Example 1 of the present invention.

[0029] Figure 4 This is an MTF curve diagram of the projection lens in Example 1 of the present invention.

[0030] Figure 5 Graph showing the axial aberration of the projection lens in Embodiment 1 of the present invention.

[0031] Figure 6 : is the vertical axis chromatic aberration curve of the projection lens in Example 1 of the present invention.

[0032] Figure 7 Schematic diagram of the structure of the projection lens in Embodiment 2 of the present invention.

[0033] Figure 8 It is a field curvature curve diagram of the projection lens in Example 2 of the present invention.

[0034] Fig. 9 This is an MTF curve diagram of the projection lens in Example 2 of the present invention.

[0035] Fig.10 Graph showing the axial aberration of the projection lens in Embodiment 2 of the present invention.

[0036] Fig.11 Graph showing the vertical axis chromatic aberration of the projection lens in Embodiment 2 of the present invention.

[0037] Fig.12 Schematic diagram of the structure of the projection lens in Embodiment 3 of the present invention.

[0038] Fig.13 It is a field curvature curve diagram of the projection lens in Example 3 of the present invention.

[0039] Fig.14 This is an MTF curve diagram of the projection lens in Example 3 of the present invention.

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

[0041] Fig.16 : is the vertical axis chromatic aberration curve of the projection lens in Example 3 of the present invention.

[0042] Fig.17 It is a schematic diagram of the structure of the projection device in Embodiment 4 of the present invention.

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

[0044] 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.

[0045] 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.

[0046] 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.

[0047] 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 projection surface is called the projection side surface of the lens, and the surface of each lens closest to the image source surface 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 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.

[0049] 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.

[0050] 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.

[0051] The projection lens provided in an embodiment of the present invention is used to project light from an image source plane (such as an LED array light source) onto a projection plane. The projection lens is composed of four lenses, which include: a front group with positive 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.

[0052] Specifically, the front group includes, in order from the projection plane to the image source plane along the optical axis: a first lens with a positive focal power and a second lens with a positive focal power. Among them, 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 concave;

[0053] The rear group includes, in order from the projection plane to the image source plane along the optical axis: a third lens with a focal power and a fourth lens with a positive focal power. Among them, the projection-side surface of the third lens is concave, and the image-source side surface of the third lens is convex. The projection-side surface of the fourth lens is convex, and the image-source side surface of the fourth lens is concave. It can be understood that the third lens can have a positive or negative focal power.

[0054] In some embodiments, the aperture stop is located between the second lens and the third lens. It can be understood that the aperture stop is used to limit the amount of incident light to change the brightness of the imaging. When the aperture stop is located between the second lens and the third lens, it is convenient for the correction of aperture aberration.

[0055] In some embodiments, the effective focal length f of the projection lens and the entrance pupil diameter EPD of the projection lens satisfy: 0.65 < f / EPD < 0.85. Meeting the above conditions can make the projection lens have a smaller aperture value (F-number), and the F-number is within 0.85, which can effectively increase the amount of incident light, make the whole system have a high transmission efficiency, and provide sufficient illumination brightness at the target position.

[0056] In some embodiments, the combined focal length fa of the front group and the combined focal length fb of the rear group satisfy: 1 < fa / fb < 2.1. Meeting the above conditions, by reasonably setting the focal length relationship of the lens groups before and after the aperture stop, it helps the light to transition smoothly, and at the same time realizes the large-aperture performance of the system, making the whole projection system have a high transmission efficiency.

[0057] In some embodiments, the focal length f1 of the first lens and the effective focal length f of the projection lens satisfy: 2.4 < f1 / f < 3; 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 < R1 / R2 < 0.3. Meeting the above conditions, by reasonably setting the focal length and surface shape of the first lens, it is beneficial for the light to transition smoothly to the rear of the lens, and it is beneficial to improve the resolution quality while realizing a large aperture.

[0058] In some embodiments, the focal length f2 of the second lens and the effective focal length f of the projection lens satisfy: 2 < f2 / f < 5; 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: 0.2 < R3 / R4 < 1. Meeting the above conditions, by reasonably setting the focal length and surface shape of the second lens, it is beneficial to collect light, enabling the light path to transition smoothly, and at the same time facilitating the entry of as much light as possible into the second lens at the large edge field of view, thereby enhancing the relative illumination of the system.

[0059] In some embodiments, the focal length f3 of the third lens and the effective focal length f of the projection lens satisfy: 5 < |f3 / f| < 14; the radius of curvature R5 of the projection-side surface of the third lens and the radius of curvature R6 of the image-source-side surface of the third lens satisfy: 0.5 < R5 / R6 < 1.05. Meeting the above conditions is beneficial for further adjusting the incident light angle, smoothly transitioning the peripheral light, reducing the sensitivity of the third lens, and improving the imaging quality.

[0060] In some embodiments, the focal length f4 of the fourth lens and the effective focal length f of the projection lens satisfy: 1 < f4 / f < 2; the radius of curvature R7 of the projection-side surface of the fourth lens and the radius of curvature R8 of the image-source-side surface of the fourth lens satisfy: 0.5 < R7 / R8 < 0.6. Meeting the above conditions is beneficial for the fourth lens to have a large positive refractive power, facilitating the convergence of the incident light onto the fourth lens, effectively reducing the CRA of the lens, and enabling the lens to have a high resolution even when used in a relatively dark low-light environment.

[0061] In some embodiments, the central thickness CT1 of the first lens and the edge thickness CM1 of the first lens satisfy: 3 < CT1 / CM1 < 10. Meeting the above conditions, the first lens has a large edge-thickness ratio, which can better converge the light at the large edge field of view, and at the same time facilitates the processing and molding of the lens, improving the lens yield.

[0062] In some embodiments, the clear aperture DM11 of the projection-side surface of the first lens and the clear aperture DM42 of the image-source-side surface of the fourth lens satisfy: 2.9 < DM11 / DM42 < 3.6. Meeting the above conditions enables the first lens to have a large aperture, which is beneficial for providing a large projection screen magnification ratio, resulting in a better interaction effect and better meeting the requirements for a high-quality projection screen.

[0063] In some embodiments, the effective aperture DM1 of the first lens, the effective aperture DM2 of the second lens, the effective aperture DM3 of the third lens, and the effective aperture DM4 of the fourth lens satisfy: DM1 > DM2 > DM3 > DM4. Meeting the above conditions, from the projection plane to the image source plane direction of the projection lens, the effective aperture of the lens decreases in sequence, and the image light source within a relatively small range (such as 15°) can be projected and magnified to the greatest extent, while making the lens have a smaller size, achieving miniaturization of the lens.

[0064] In some embodiments, the optical total length TTL of the projection lens and the back focal length BFL of the projection lens satisfy: 20 < TTL / BFL < 34; the back focal length BFL of the projection lens and the effective focal length f of the projection lens satisfy: 0.05 < BFL / f < 0.1. Meeting the above conditions can make the lens have an appropriate back focus, ensure the imaging quality of the projection lens, avoid interference between the lens and other components, and reduce the assembly process difficulty between the lens and the image display module.

[0065] In some embodiments, the projection side surface of the first lens can be set to a surface treatment of a microlens array or a matte lens. Adopting the surface treatment method of a microlens array or a matte lens for the projection side surface of the first lens can make the light rays emitted from the projection lens present a uniformly distributed and delicate effect, making the light scattering more natural and uniform, and the light distribution relatively soft, so that the light intensity transition in the illumination area is more uniform, and it can be better applied to scenarios that require uniform illumination. Specifically, the microlens array includes a plurality of microlens units, and the microlens array can be arranged in an M×N arrangement or a full distribution arrangement, etc. The specific size and arrangement method of the microlens units are not limited and are subject to actual needs.

[0066] In some embodiments, the optical total length TTL of the projection lens and the effective focal length f of the projection lens satisfy: 1.95 < TTL / f < 2.45. Meeting the above conditions can effectively limit the total length of the lens and achieve miniaturization of the lens.

[0067] In some embodiments, the optical total length TTL of the projection lens and the true image height IH corresponding to the maximum field of view angle of the projection lens satisfy: 3.6 < TTL / IH < 4.5. Meeting the above conditions can effectively limit the total length of the lens and achieve miniaturization of the lens.

[0068] In some embodiments, the focal length f1 of the first lens and the focal length f2 of the second lens satisfy: 0.5 < f1 / f2 < 1.3. Meeting the above conditions is beneficial to the smooth transition of light rays, and at the same time corrects various aberrations of the projection lens, improving the imaging quality of the projection lens.

[0069] In some embodiments, the central thickness CT1 of the first lens and the central thickness CT2 of the second lens satisfy: 0.5 < CT1 / CT2 < 1. Meeting the above conditions can effectively converge a wide range of light entering the system, thereby achieving the miniaturization of the projection lens and the balance of high pixels.

[0070] In some embodiments, the combined focal length fa of the front group and the effective focal length f of the projection lens satisfy: 1.2 < fa / f < 1.65; the combined focal length fb of the rear group and the effective focal length f of the projection lens satisfy: 0.6 < fb / f < 1.3. Meeting the above conditions is conducive to the smooth transition of light, while correcting various aberrations of the projection lens and improving the imaging quality of the projection lens.

[0071] In some embodiments, the projection lens satisfies the conditional formula: 33mm < f < 34mm, 66mm < TTL < 82mm, 0.65 < Fno < 0.85, 18mm < IH < 18.5mm, 30° < FOV < 31°; 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, FOV represents the maximum field of view angle of the projection lens, and BFL represents the back focal length of the projection lens. Meeting the above conditions indicates that the projection lens provided by the embodiments of the present invention has at least the characteristics of long focal length, large image plane, large aperture, etc.

[0072] As an embodiment, the projection lens can use all-glass lenses or a combination of glass and plastic, both of which can achieve good imaging effects; in this application, the projection lens uses four all-glass lenses. While being convenient for processing, the lens can have good thermal stability performance, can effectively compensate for the image plane shift caused by thermal expansion of the lens at -40°C to +85°C, and ensure stable imaging performance of the lens in high and low temperature environments.

[0073] In some embodiment modes, the first lens, the second lens, the third lens, and the fourth lens can use spherical lenses or aspherical lenses. Compared with the spherical structure, the aspherical structure can effectively reduce the aberration of the optical system, thereby reducing the number of lenses and the size of the lenses, and better realizing the miniaturization of the lens. The spherical lens is easier to process and has a higher processing yield. More specifically, all four lenses provided by the present invention use spherical lenses.

[0074] In addition, the present invention also provides a projection device, including: an image display module and the above projection lens;

[0075] The image display module includes a light-emitting diode array light source for emitting image light source information;

[0076] The projection lens is located at the light-emitting side of the image display module, and the fourth lens is arranged closer to the image display module than the first lens. The projection lens is used to image the light from the image display module.

[0077] Specifically, the projection device provided by the present invention includes a light emitting diode (LED) array light source and a projection lens designed to match it, which can project the array light source to infinity with high efficiency, thereby realizing high beam lighting; at the same time, with the ability of the LED array to switch each pixel and control the brightness and darkness, it can realize arbitrarily adjustable regional lighting.

[0078] More specifically, the LED array light source in the embodiment of the present invention may have a size of approximately 17.77 mm × 3.19 mm, a single pixel size of 0.81 mm, and a pixel spacing of 50 um. In practical applications, light sources with various other pixel sizes may also be used, which is not limited in this embodiment.

[0079] 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.

[0080] Example 1

[0081] See also Figure 1 , which is a schematic diagram of the structure of a projection lens 100 provided in Embodiment 1 of the present invention, wherein the projection lens 100 includes, along the optical axis from the projection plane to the image source plane S9, a front group with positive optical power, a stop, and a rear group with positive optical power;

[0082] The front group includes a first lens L1 and a second lens L2 in sequence from the projection plane to the image source plane along the optical axis;

[0083] The first lens L1 has positive refractive power, its projection side surface S1 is convex, and its image source side surface S2 is concave;

[0084] The second lens L2 has positive refractive power, its projection side surface S3 is convex, and its image source side surface S4 is concave;

[0085] The rear group includes a third lens L3 and a fourth lens L4 in sequence from the projection plane to the image source plane along the optical axis;

[0086] The third lens L3 has negative refractive power, its projection side surface S5 is concave, and its image source side surface S6 is convex;

[0087] The fourth lens L4 has positive refractive power, a projection-side surface S7 thereof is a convex surface, and an image-source-side surface S8 thereof is a concave surface;

[0088] The first lens L1, the second lens L2, the third lens L3 and the fourth lens L4 are all glass spherical lenses.

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

[0090] Table 1-1

[0091]

[0092] In this embodiment, the projection side surface S1 of the first lens can be treated by a microlens array or a pockmarked lens, so that the light emitted from the projection lens presents a uniform distribution and delicate effect, making the light scattering more natural and uniform, and the light distribution softer, so that the light intensity transition in the illuminated area is more uniform, which can be better applied to scenes requiring uniform lighting. In other embodiments, if there is no requirement for the uniform light effect of the output light of the projection lens, the projection side surface S1 of the first lens can also be treated by a smooth surface of a conventional lens, which is not limited here.

[0093] The schematic diagram of the above-mentioned microlens array can be found in Figure 2 The microlens array of this embodiment includes a plurality of microlens units. The microlens array may be arranged in an M×N manner or in a full array manner. The size and arrangement of the specific microlens units are not limited and are subject to actual needs.

[0094] In this embodiment, the field curvature curve, MTF curve, axial aberration curve, and vertical chromatic aberration curve of the projection lens 100 are respectively as follows: Figure 3 , Figure 4 , Figure 5 , Figure 6 shown.

[0095] Figure 3 The field curvature curve of Example 1 is shown, which indicates the degree of curvature of light of different wavelengths on the meridional image plane and the sagittal image plane, the horizontal axis indicates the offset (unit: mm), and the vertical axis indicates the half field angle (unit: °). It can be seen from the figure that the field curvature of the meridional image plane and the sagittal image plane is controlled within -0.7mm~0.2mm, indicating that the projection lens can well correct the field curvature.

[0096] Figure 4The MTF (Modulation Transfer Function) curve of Example 1 is shown, which represents the imaging modulation degree of the lens at different spatial frequencies under each field of view, the horizontal axis represents the spatial frequency (unit: lp / mm), and the vertical axis represents the MTF value. It can be seen from the figure that the MTF value of this embodiment is above 0.48 in the entire field of view, and the MTF curve decreases evenly and smoothly from the center to the edge of the field of view, with good imaging quality and good detail resolution.

[0097] Figure 5 The axial aberration curve of Example 1 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 -0.3mm~0.5mm, indicating that the projection lens can correct the axial aberration well.

[0098] Figure 6 The vertical chromatic aberration curve of Example 1 is shown, which represents the chromatic aberration of each wavelength relative to the central wavelength (0.54μm) 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 -28μm~20μm, indicating that the projection lens can correct chromatic aberration very well.

[0099] Example 2

[0100] See also Figure 7 , 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, the main differences of this embodiment are: the third lens L3 has positive focal length; and the optical parameters such as the curvature radius, lens thickness, and lens material of each lens surface are different.

[0101] The relevant parameters of each lens in the projection lens 200 in Example 2 are shown in Table 2-1.

[0102] Table 2-1

[0103]

[0104] In this embodiment, the field curvature curve, MTF curve, axial aberration curve, and vertical chromatic aberration curve of the projection lens 200 are respectively as follows: Figure 8 , Fig. 9 , Fig.10 , Fig.11 shown.

[0105] from Figure 8 It can be seen that the field curvature of the meridian image plane and the sagittal image plane is controlled within -0.6mm~0.2mm, indicating that the projection lens can correct the field curvature well.

[0106] from Fig. 9 It can be seen that the MTF value of this embodiment is above 0.65 in the entire field of view, and the MTF curve decreases evenly and smoothly from the center to the edge of the field of view, with good imaging quality and good detail resolution.

[0107] from Fig.10 It can be seen that the offset of the axial aberration is controlled within -0.2mm~0.3mm, which means that the projection lens can correct the axial aberration well.

[0108] from Fig.11 It can be seen that the vertical axis chromatic aberration of the longest wavelength and the shortest wavelength is controlled within -60μm~50μm, indicating that the projection lens can correct chromatic aberration very well.

[0109] Example 3

[0110] See also Fig.12 , 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 third lens L3 has positive focal length; and the optical parameters such as the curvature radius, lens thickness, and lens material of each lens surface are different.

[0111] The relevant parameters of each lens in the projection lens 300 in Example 3 are shown in Table 3-1.

[0112] Table 3-1

[0113]

[0114] In this embodiment, the field curvature curve, MTF curve, axial aberration curve, and vertical chromatic aberration curve of the projection lens 300 are shown as follows: Fig.13 , Fig.14 , Fig.15 , Fig.16 shown.

[0115] from Fig.13 It can be seen that the field curvature of the meridian image plane and the sagittal image plane is controlled within -0.4mm~0.7mm, indicating that the projection lens can correct the field curvature well.

[0116] from Fig.14 It can be seen that the MTF value of this embodiment is above 0.78 in the entire field of view, and the MTF curve decreases evenly and smoothly from the center to the edge of the field of view, with good imaging quality and good detail resolution.

[0117] from Fig.15It can be seen that the offset of the axial aberration is controlled within -0.3mm~0.3mm, which means that the projection lens can correct the axial aberration well.

[0118] from Fig.16 It can be seen that the vertical axis chromatic aberration of the longest wavelength and the shortest wavelength is controlled within -25μm~20μm, indicating that the projection lens can correct chromatic aberration very well.

[0119] 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 IH corresponding to the maximum field of view angle, the chief ray incident angle CRA at the maximum image height, and the maximum field of view angle FOV, as well as the numerical values ​​corresponding to each conditional expression in each embodiment.

[0120] Table 4

[0121]

[0122] In summary of the above embodiments, the projection lens provided by the present invention has a high system transmission efficiency through the reasonable configuration of each lens surface shape and the reasonable matching of optical focal length, can provide sufficient lighting brightness at the target position, improve the imaging quality of the projection lens, reduce aberrations, have high relative illumination, improve the projection quality of the projection lens, and make the lens have one or more advantages such as large aperture, telephoto, large image surface, and high imaging quality. At the same time, the projection lens adopts a full glass lens, which can make the lens have good thermal stability, can achieve stable imaging performance in the high and low temperature range of -40℃-85℃, and can keep the image quality at a high level in the high and low temperature range.

[0123] Example 4

[0124] like Fig.17 As shown, this embodiment provides a projection device 400, which includes an image display module 10 and a projection lens (such as projection lens 100) in any of the above embodiments of the present application. The image display module 10 includes a light emitting diode (LED) array light source for emitting image light source information. The projection lens is located on the light emitting side of the image display module 10, and the fourth lens is arranged closer to the image display module 10 than the first lens. The projection lens is used to image the light of the image display module 10.

[0125] The projection device of this embodiment can project the array light source to infinity with high efficiency, thereby realizing high-beam lighting; at the same time, with the ability of the LED array to switch each pixel and control the brightness and darkness, it can realize arbitrarily adjustable regional lighting.

[0126] The LED array light source used in this embodiment may be a light source with a size of approximately 17.77 mm × 3.19 mm, a single pixel size of 0.81 mm, and a pixel interval of 50 um; in actual applications, it may also be applicable to light sources with other pixel sizes, which is not limited in this embodiment.

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

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

Claims

1. A projection lens, consisting of four lenses, characterized in that: Along the optical axis from the projection plane to the image source plane, it sequentially includes: a front group with positive optical power, a diaphragm, and a rear group with positive optical power; The front group sequentially includes along the optical axis from the projection plane to the image source plane: A first lens with positive optical power, whose projection side surface is convex and whose image source side surface is concave; A second lens with positive optical power, whose projection side surface is convex and whose image source side surface is concave; The rear group sequentially includes along the optical axis from the projection plane to the image source plane: A third lens with optical power, whose projection side surface is concave and whose image source side surface is convex; A fourth lens with positive optical power, whose projection side surface is convex and whose image source side surface is concave; Wherein, the effective focal length f of the projection lens and the entrance pupil diameter EPD of the projection lens satisfy: 0.65 < f / EPD < 0.

85.

2. The projection lens according to claim 1, characterized in that: The combined focal length fa of the front group and the combined focal length fb of the rear group satisfy: 1 < fa / fb < 2.

1.

3. The projection lens according to claim 1, characterized in that: The focal length f1 of the first lens and the effective focal length f of the projection lens satisfy: 2.4 < f1 / f < 3; 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 < R1 / R2 < 0.

3.

4. The projection lens according to claim 1, characterized in that: The focal length f2 of the second lens and the effective focal length f of the projection lens satisfy: 2 < f2 / f < 5; the curvature radius R3 of the projection side surface of the second lens and the curvature radius R4 of the image source side surface of the second lens satisfy: 0.2 < R3 / R4 < 1.

5. The projection lens according to claim 1, wherein: The focal length f3 of the third lens and the effective focal length f of the projection lens satisfy: 5 < |f3 / f| < 14; 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: 0.5 < R5 / R6 < 1.

05.

6. The projection lens according to claim 1, wherein: The focal length f4 of the fourth lens and the effective focal length f of the projection lens satisfy: 1 < f4 / f < 2; the curvature radius R7 of the projection side surface of the fourth lens and the curvature radius R8 of the image source side surface of the fourth lens satisfy: 0.5 < R7 / R8 < 0.

6.

7. The projection lens according to claim 1, wherein: The central thickness CT1 of the first lens and the edge thickness CM1 of the first lens satisfy: 3 < CT1 / CM1 < 10.

8. The projection lens according to claim 1, wherein: The clear aperture DM11 of the projection side surface of the first lens and the clear aperture DM42 of the image source side surface of the fourth lens satisfy: 2.9 < DM11 / DM42 < 3.6; the effective aperture DM1 of the first lens, the effective aperture DM2 of the second lens, the effective aperture DM3 of the third lens, and the effective aperture DM4 of the fourth lens satisfy: DM1 > DM2 > DM3 > DM4.

9. The projection lens according to claim 1, wherein: The overall optical length TTL of the projection lens and the back focal length BFL of the projection lens satisfy: 20 < TTL / BFL < 34; the back focal length BFL of the projection lens and the effective focal length f of the projection lens satisfy: 0.05 < BFL / f < 0.

1.

10. The projection lens according to claim 1, wherein: The projection side surface of the first lens is provided with a surface treatment of a microlens array or a matte lens.

11. A projection device, characterized in that: It includes: An image display module and the projection lens according to any one of claims 1-10; The image display module includes a light emitting diode array light source for emitting image light source information; The projection lens is located at the light-emitting side of the image display module, and the fourth lens is arranged closer to the image display module than the first lens. The projection lens is used to image the light from the image display module.

Images