projection lens

Abstract

The application discloses a projection lens, which comprises, in sequence from an image source side to an imaging side along an optical axis, a first lens with positive focal power, whose image source side surface is a convex surface; a second lens with negative focal power, whose image source side surface and imaging side surface are both concave surfaces; a third lens with positive focal power or negative focal power; and a fourth lens with positive focal power, whose imaging side surface is a convex surface; wherein the total effective focal length f of the projection lens and the effective focal length f4 of the fourth lens satisfy 1.5 < f / f4 < 2.5.

Description

[0001] Divisional application

[0002] This application is a divisional application of the Chinese invention patent application with the invention name “Projection Lens” and application number 201711348942.9 filed on December 15, 2017. Technical Field

[0003] The present application relates to a projection lens, and more particularly, to a projection lens comprising four lenses. Background Art

[0004] In recent years, with the continuous advancement of science and technology, interactive devices have gradually emerged, and the application scope of projection lenses has become increasingly wider. Nowadays, chip technology and intelligent algorithms are developing rapidly. By using an optical projection lens to project an image onto a spatial object and receiving the image signal, a three-dimensional image with the object's position and depth information can be calculated. The specific method is as follows: using an optical projection lens to project light emitted by an infrared laser diode (LD) or a vertical cavity surface emitting laser (VCSEL) toward the target object; after the projection beam passes through an optical diffraction element (DOE), the projected image is redistributed on the target object; using a camera lens to receive the image projected onto the object, a three-dimensional image containing the depth information of the projected object's position can be calculated. The three-dimensional image with depth information can be further used in the development of various depth applications such as biometrics.

[0005] Traditional projection lenses typically increase the number of lenses to eliminate various aberrations and improve resolution. However, this increases the overall optical length of the projection lens, hindering its miniaturization. Furthermore, conventional wide-field-of-view projection lenses suffer from significant distortion and poor image quality, and cannot be used with diffraction optical elements (DOEs) to precisely redistribute the projection beam across the target object. Summary of the Invention

[0006] The present application provides a projection lens that is applicable to portable electronic products and can at least solve or partially solve at least one of the above-mentioned shortcomings in the prior art.

[0007] The present application provides a projection lens, which may include, in order from the image source side to the imaging side along the optical axis: a first lens with positive optical power, whose image source side surface is convex; a second lens with negative optical power, whose image source side surface and imaging side surface may both be concave; a third lens with positive optical power or negative optical power; and a fourth lens with positive optical power, whose imaging side surface may be convex. The number of lenses with optical power in the projection lens is four, and the total effective focal length f of the projection lens and the effective focal length f4 of the fourth lens may satisfy 1.5<f / f4<2.5.

[0008] In one embodiment, the total effective focal length f of the projection lens and the effective focal length f1 of the first lens may satisfy 2.0<f / f1<3.5.

[0009] In one embodiment, the total effective focal length f of the projection lens and the effective focal length f2 of the second lens may satisfy f / f2≤-4.0.

[0010] In one embodiment, the effective focal length f3 of the third lens and the total effective focal length f of the projection lens may satisfy 1.0<f3 / f<5.5.

[0011] In one embodiment, in the wavelength range of 800 nm to 1000 nm, the light transmittance of the projection lens is greater than 85%.

[0012] In one embodiment, the distance TTL from the image source surface of the projection lens to the imaging side surface of the fourth lens on the optical axis and the total effective focal length f of the projection lens may satisfy TTL / f<1.0.

[0013] In one embodiment, the maximum effective semi-aperture DT42 of the imaging-side surface of the fourth lens and the maximum effective semi-aperture DT41 of the image source-side surface of the fourth lens may satisfy 1.0<DT42 / DT41<1.4.

[0014] In one embodiment, a distance T12 between the first lens and the second lens on the optical axis and a distance T23 between the second lens and the third lens on the optical axis may satisfy 0.8<T12 / T23<2.2.

[0015] In one embodiment, the center thickness CT4 of the fourth lens on the optical axis and the center thickness CT2 of the second lens on the optical axis may satisfy 1.5<CT4 / CT2<3.0.

[0016] In one embodiment, a curvature radius R8 of the image-side surface of the fourth lens and a curvature radius R1 of the image-source-side surface of the first lens may satisfy -1.5≤R8 / R1≤-1.0.

[0017] In one embodiment, a curvature radius R4 of the imaging-side surface of the second lens and a curvature radius R3 of the image-source-side surface of the second lens may satisfy -2.4<R4 / R3<-0.8.

[0018] The present application uses multiple (for example, four) lenses, and by reasonably allocating the optical focal length, surface shape, center thickness of each lens, and on-axis spacing between lenses, the above-mentioned projection lens has at least one beneficial effect of large aperture, miniaturization, and high imaging quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Other features, purposes and advantages of the present application will become more apparent through the following detailed description of non-limiting embodiments in conjunction with the accompanying drawings. In the accompanying drawings:

[0020] Figure 1 1 shows a schematic structural diagram of a projection lens according to Example 1 of the present application;

[0021] Figure 2 shows the distortion curve of the projection lens of Example 1;

[0022] Figure 3 1 shows a schematic structural diagram of a projection lens according to Example 2 of the present application;

[0023] Figure 4 shows the distortion curve of the projection lens of Example 2;

[0024] Figure 5 1 shows a schematic structural diagram of a projection lens according to Example 3 of the present application;

[0025] Figure 6 shows the distortion curve of the projection lens of Example 3;

[0026] Figure 7 1 shows a schematic structural diagram of a projection lens according to Example 4 of the present application;

[0027] Figure 8 shows the distortion curve of the projection lens of Example 4;

[0028] Figure 9 1 shows a schematic structural diagram of a projection lens according to Example 5 of the present application;

[0029] Figure 10 shows the distortion curve of the projection lens of Example 5;

[0030] Figure 11 1 shows a schematic structural diagram of a projection lens according to Example 6 of the present application;

[0031] Figure 12 shows the distortion curve of the projection lens of Example 6;

[0032] Figure 13 1 shows a schematic structural diagram of a projection lens according to Example 7 of the present application;

[0033] Figure 14 shows the distortion curve of the projection lens of Example 7;

[0034] Figure 15 1 shows a schematic structural diagram of a projection lens according to Example 8 of the present application;

[0035] Figure 16shows the distortion curve of the projection lens of Example 8;

[0036] Figure 17 1 shows a schematic structural diagram of a projection lens according to Example 9 of the present application;

[0037] Figure 18 The distortion curve of the projection lens of Example 9 is shown. DETAILED DESCRIPTION

[0038] 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 exemplary 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.

[0039] It should be noted that in this specification, the terms "first," "second," etc., are used solely to distinguish one feature from another and do not limit the features. Thus, without departing from the teachings of this application, the first lens discussed below could also be referred to as the second lens, and the second lens could also be referred to as the first lens.

[0040] 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.

[0041] 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 closest to the image source in each lens is called the image source-side surface, and the surface closest to the image side in each lens is called the image-side surface.

[0042] 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.

[0043] 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.

[0044] 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.

[0045] The features, principles and other aspects of the present application are described in detail below.

[0046] The projection lens according to an exemplary embodiment of the present application may include, for example, four lenses having optical power, namely, a first lens, a second lens, a third lens, and a fourth lens, which are arranged in sequence from the image source side to the image forming side along the optical axis.

[0047] In an exemplary embodiment, the first lens may have positive optical power; the second lens may have negative optical power, and its image source side surface may be concave, and its imaging side surface may be concave; the third lens may have positive or negative optical power; and the fourth lens may have positive optical power, and its imaging side surface may be convex. The first lens with positive optical power facilitates achieving telecentricity on the image source side of the projection system, increasing the amount of light entering the projection system's off-axis field of view, and improving the resolution, brightness, and uniformity of the projected image; the second lens with negative optical power, with its image source side surface and imaging side surface being concave, facilitates moving the image source side principal surface away from the image source, thereby shortening the total optical length (TTL) of the projection system and achieving lens miniaturization; the third lens with optical power can effectively adjust the incident angle of off-axis field of view light and correct off-axis field of view aberrations; the fourth lens with positive optical power facilitates shortening the total optical length (TTL) of the projection system, and the convex imaging side surface of the fourth lens facilitates reducing spherical aberration of the projection system and improving the imaging quality of the projection system.

[0048] In example embodiments, the image source-side surface of the first lens may be a convex surface.

[0049] In an exemplary embodiment, the third lens may have positive refractive power, an image source side surface thereof may be concave, and an image forming side surface thereof may be convex.

[0050] In example embodiments, an image source-side surface of the fourth lens may be a concave surface.

[0051] In an exemplary embodiment, the projection lens of the present application may satisfy the conditional equation f / f2 ≤ -4.0, where f is the total effective focal length of the projection lens and f2 is the effective focal length of the second lens element. More specifically, f and f2 may further satisfy -10.0 ≤ f / f2 ≤ -4.0, for example, -9.80 ≤ f / f2 ≤ -5.41. Satisfying the conditional equation f / f2 ≤ -4.0 helps strike a good balance between improving the imaging quality of the projection system and achieving miniaturization of the projection system.

[0052] In an exemplary embodiment, the projection lens of the present application may satisfy the conditional expression 2.0 < f / f1 < 3.5, where f is the total effective focal length of the projection lens and f1 is the effective focal length of the first lens element. More specifically, f and f1 may further satisfy 2.30 < f / f1 < 3.40, for example, 2.41 ≤ f / f1 ≤ 3.33. Satisfying the conditional expression 2.0 < f / f1 < 3.5 facilitates achieving image source-side telecentricity in the projection system, thereby shortening the total optical length (TTL) of the projection system, and thereby facilitating a good balance between shortening the total optical length (TTL) of the projection system and improving the imaging quality of the projection system.

[0053] In an exemplary embodiment, the projection lens of the present application has a light transmittance greater than 85% in the wavelength range of about 800 nm to about 1000 nm. This configuration helps to increase the transmittance of near-infrared light through the projection lens, thereby obtaining a brighter near-infrared projected image.

[0054] In an exemplary embodiment, the projection lens of the present application may satisfy the conditional formula 1.0 < f3 / f < 5.5, where f3 is the effective focal length of the third lens, and f is the total effective focal length of the projection lens. More specifically, f3 and f may further satisfy 1.32 ≤ f3 / f ≤ 5.39. Satisfying the conditional formula 1.0 < f3 / f < 5.5 is beneficial for adjusting the optical power distribution and avoiding increased tolerance sensitivity of the projection system due to excessive concentration of optical power. At the same time, when one or all of the second and fourth lenses are made of glass, satisfying the conditional formula 1.0 < f3 / f < 5.5 is beneficial for maintaining the stability of the image plane under temperature changes, thereby improving the temperature characteristics of the projection system.

[0055] In an exemplary embodiment, the projection lens of the present application may satisfy the conditional equation: -1.5 ≤ R8 / R1 ≤ -1.0, where R8 is the radius of curvature of the image-facing surface of the fourth lens element, and R1 is the radius of curvature of the image-source-facing surface of the first lens element. More specifically, R8 and R1 may further satisfy -1.35 ≤ R8 / R1 ≤ -1.00. Satisfying the conditional equation: -1.5 ≤ R8 / R1 ≤ -1.0 helps eliminate distortion and aberrations in the projection system.

[0056] In an exemplary embodiment, the projection lens of the present application can satisfy the conditional equation 1.5 < f / f4 < 2.5, where f is the total effective focal length of the projection lens and f4 is the effective focal length of the fourth lens element. More specifically, f and f4 can further satisfy 1.63 ≤ f / f4 ≤ 2.39. Satisfying the conditional equation 1.5 < f / f4 < 2.5 helps reduce the tolerance sensitivity of the fourth lens element. Furthermore, when the fourth lens element is made of glass, it also helps reduce the temperature sensitivity of the projection system, ensuring high projection quality over a wide temperature range.

[0057] In an exemplary embodiment, the projection lens of the present application may satisfy the conditional equation: -2.4 < R4 / R3 < -0.8, where R4 is the radius of curvature of the imaging-side surface of the second lens element, and R3 is the radius of curvature of the image-source-side surface of the second lens element. More specifically, R4 and R3 may further satisfy -2.25 < R4 / R3 < -0.85, for example, -2.19 ≤ R4 / R3 ≤ -0.96. Satisfying the conditional equation: -2.4 < R4 / R3 < -0.8 helps reduce the incident and exit angles of each field of view at the second lens element, thereby reducing the tolerance sensitivity of the second lens element and thereby improving the production yield of the projection lens.

[0058] In an exemplary embodiment, the projection lens of the present application can satisfy the conditional equation 0.8 < T12 / T23 < 2.2, where T12 is the distance between the first and second lenses on the optical axis, and T23 is the distance between the second and third lenses on the optical axis. More specifically, T12 and T23 can further satisfy 0.88 ≤ T12 / T23 ≤ 2.11. Meeting the conditional equation 0.8 < T12 / T23 < 2.2 facilitates the proper allocation of lens spacing, adjusts the optical path distribution, and thus reduces the tolerance sensitivity of the projection system. It also facilitates lens assembly and improves the production yield of the projection system.

[0059] In an exemplary embodiment, the projection lens of the present application can satisfy the conditional equation 1.5 < CT4 / CT2 < 3.0, where CT4 is the center thickness of the fourth lens element along the optical axis, and CT2 is the center thickness of the second lens element along the optical axis. More specifically, CT4 and CT2 can further satisfy 1.59 ≤ CT4 / CT2 ≤ 2.82. Meeting the conditional equation 1.5 < CT4 / CT2 < 3.0 helps achieve a good balance between shortening the total optical length (TTL) of the projection system and improving the manufacturability of the second and fourth lenses.

[0060] In an exemplary embodiment, the projection lens of the present application may satisfy the conditional equation 1.0 < DT42 / DT41 < 1.4, where DT42 is the maximum effective semi-aperture of the imaging-side surface of the fourth lens element, and DT41 is the maximum effective semi-aperture of the image-source-side surface of the fourth lens element. More specifically, DT42 and DT41 may further satisfy 1.05 < DT42 / DT41 < 1.25, for example, 1.13 ≤ DT42 / DT41 ≤ 1.19. Satisfying the conditional equation 1.0 < DT42 / DT41 < 1.4 facilitates shortening the total optical length (TTL) of the projection system, enabling miniaturization; it also helps balance the tolerance sensitivity of the projection system.

[0061] In an exemplary embodiment, the projection lens of the present application may satisfy the conditional equation TTL / f < 1.0, where TTL is the on-axis distance from the image source plane to the image-side surface of the fourth lens element, and f is the total effective focal length of the projection lens. More specifically, TTL and f may further satisfy 0.60 < TTL / f < 0.90, for example, 0.67 ≤ TTL / f ≤ 0.82. Properly controlling the ratio of TTL and f helps maintain the miniaturization of the projection lens.

[0062] In an exemplary embodiment, the projection lens may further include at least one aperture to improve the imaging quality of the lens. For example, the aperture may be disposed between the fourth lens and the imaging side as needed.

[0063] Optionally, the projection lens may further include other well-known optical projection elements, such as a prism, a field lens, etc. Optionally, the projection lens may be used in conjunction with a diffraction element (DOE).

[0064] According to the above-mentioned embodiment of the present application, the projection lens can adopt, for example, four lenses. By reasonably allocating the optical focal length, surface shape, center thickness of each lens, and on-axis spacing between each lens, the projection lens has beneficial effects such as large aperture, miniaturization, and high imaging quality.

[0065] In the embodiments of the present application, at least one of the mirror surfaces of each lens is an aspheric surface. Aspheric lenses are characterized by a continuously varying curvature from the center to the periphery. Unlike spherical lenses, which have a constant curvature from the center to the periphery, aspheric lenses have a more optimized curvature radius characteristic, with the advantages of reducing distortion and astigmatism. The use of aspheric lenses can minimize aberrations that occur during imaging, thereby improving image quality.

[0066] However, those skilled in the art will appreciate that the number of lenses comprising the projection lens can be varied to achieve the various results and advantages described herein without departing from the claimed technical solutions. For example, while the embodiments describe a projection lens using four lenses as an example, the projection lens is not limited to four lenses. If desired, the projection lens may include other numbers of lenses.

[0067] Specific embodiments of the projection lens applicable to the above-mentioned embodiments will be further described below with reference to the accompanying drawings.

[0068] Example 1

[0069] The following reference Figures 1 to 2 The projection lens according to Embodiment 1 of the present application is described. Figure 1 A schematic structural diagram of a projection lens according to Example 1 of the present application is shown.

[0070] like Figure 1 As shown, the projection lens according to an exemplary embodiment of the present application includes, in order from the image source side to the imaging side along the optical axis, a first lens E1, a second lens E2, a third lens E3, a fourth lens E4 and a stop STO.

[0071] The first lens E1 has positive optical power, with its image source-side surface S1 being convex and its imaging-side surface S2 being concave. The second lens E2 has negative optical power, with its image source-side surface S3 being concave and its imaging-side surface S4 being concave. The third lens E3 has positive optical power, with its image source-side surface S5 being concave and its imaging-side surface S6 being convex. The fourth lens E4 has positive optical power, with its image source-side surface S7 being concave and its imaging-side surface S8 being convex. The projection lens has a light transmittance greater than 85% in the wavelength range of approximately 800 nm to approximately 1000 nm. Light from the image source sequentially passes through surfaces S1 to S8 and is ultimately imaged onto a projection surface (not shown), such as a projection screen.

[0072] Table 1 shows the surface type, curvature radius, thickness, material and conic coefficient of each lens of the projection lens of Example 1, wherein the units of curvature radius and thickness are both millimeters (mm).

[0073]

[0074] Table 1

[0075] As can be seen from Table 1, the image source side surface and the image formation side surface of any lens from the first lens E1 to the fourth lens E4 are both aspherical. In this embodiment, the surface shape x of each aspherical lens can be defined by, but is not limited to, the following aspherical formula:

[0076]

[0077] Wherein, x is the distance vector height of the aspheric surface from the vertex of the aspheric surface at a height of h along the optical axis; c is the paraxial curvature of the aspheric surface, c = 1 / R (i.e., the paraxial curvature c is the reciprocal of the curvature radius R in Table 1 above); k is the cone coefficient (given in Table 1); Ai is the correction coefficient of the i-th order of the aspheric surface. Table 2 below lists the high-order coefficients A4, A6, A8, A9, A10, A11, A12, A13, A14, A15, A16, A17, A18, A19, A20, A21, A22, A23, A24, A25, A26, A27, A28, A30, A31, A32, A33, A34, A35, A36, A37, A38, A39, A40, A41, A50, A51, A52, A53, A54, A55, A56, A57, A58, A59, A60, A61, A71, A72, A73, A74, A75, A80, A81, A9, A10, A11, A12, A13, A14, A15 10 、A 12 、A 14 and A 16 .

[0078]

[0079]

[0080] Table 2

[0081] Table 3 shows the total effective focal length f of the projection lens and the effective focal lengths f1 to f4 of each lens in Example 1.

[0082] parameter f(mm) f1(mm) f2(mm) f3(mm) f4(mm) Numerical 4.50 1.45 -0.59 5.96 2.31

[0083] Table 3

[0084] The projection lens in Example 1 satisfies:

[0085] f / f2=-7.63, where f is the total effective focal length of the projection lens, and f2 is the effective focal length of the second lens E2;

[0086] f / f1=3.10, where f is the total effective focal length of the projection lens, and f1 is the effective focal length of the first lens E1;

[0087] f3 / f=1.32, where f3 is the effective focal length of the third lens E3, and f is the total effective focal length of the projection lens;

[0088] R8 / R1=-1.35, where R8 is the curvature radius of the image-side surface S8 of the fourth lens element E4, and R1 is the curvature radius of the image-source-side surface S1 of the first lens element E1;

[0089] f / f4=1.95, where f is the total effective focal length of the projection lens, and f4 is the effective focal length of the fourth lens element E4;

[0090] R4 / R3=-1.25, where R4 is the curvature radius of the image-side surface S4 of the second lens element E2, and R3 is the curvature radius of the image-source-side surface S3 of the second lens element E2;

[0091] T12 / T23=0.91, where T12 is the distance between the first lens E1 and the second lens E2 on the optical axis, and T23 is the distance between the second lens E2 and the third lens E3 on the optical axis;

[0092] CT4 / CT2=2.14, where CT4 is the center thickness of the fourth lens element E4 on the optical axis, and CT2 is the center thickness of the second lens element E2 on the optical axis;

[0093] DT42 / DT41=1.19, where DT42 is the maximum effective semi-aperture of the image-side surface S8 of the fourth lens element E4, and DT41 is the maximum effective semi-aperture of the image-source-side surface S7 of the fourth lens element E4;

[0094] TTL / f=0.73, where TTL is the on-axis distance from the image source plane OBJ to the imaging-side surface S8 of the fourth lens E4, and f is the total effective focal length of the projection lens.

[0095] Figure 2 The distortion curve of the projection lens of Example 1 is shown, which represents the distortion value under different viewing angles. Figure 2 It can be seen that the projection lens provided in Example 1 can achieve good imaging quality.

[0096] Example 2

[0097] The following reference Figures 3 and 4 The projection lens according to Example 2 of the present application is described. In this embodiment and the following embodiments, for the sake of brevity, some descriptions similar to those in Example 1 will be omitted. Figure 3 A schematic structural diagram of a projection lens according to embodiment 2 of the present application is shown.

[0098] like Figure 3 As shown, the projection lens according to an exemplary embodiment of the present application includes, in order from the image source side to the imaging side along the optical axis, a first lens E1, a second lens E2, a third lens E3, a fourth lens E4 and a stop STO.

[0099] The first lens E1 has positive optical power, with its image source-side surface S1 being convex and its imaging-side surface S2 being concave. The second lens E2 has negative optical power, with its image source-side surface S3 being concave and its imaging-side surface S4 being concave. The third lens E3 has positive optical power, with its image source-side surface S5 being concave and its imaging-side surface S6 being convex. The fourth lens E4 has positive optical power, with its image source-side surface S7 being concave and its imaging-side surface S8 being convex. The projection lens has a light transmittance greater than 85% in the wavelength range of approximately 800 nm to approximately 1000 nm. Light from the image source sequentially passes through surfaces S1 to S8 and is ultimately imaged onto a projection surface (not shown), such as a projection screen.

[0100] Table 4 shows the surface type, curvature radius, thickness, material, and conic coefficient of each lens of the projection lens of Example 2, wherein the units of curvature radius and thickness are both millimeters (mm).

[0101]

[0102]

[0103] Table 4

[0104] As can be seen from Table 4, in Example 2, both the image source-side surface and the image-side surface of any of the first lens element E1 through the fourth lens element E4 are aspherical surfaces. Table 5 shows the high-order coefficients of the various aspherical mirror surfaces that can be used in Example 2, where the surface shape of each aspherical surface can be defined by Formula (1) given in Example 1.

[0105] Face number A4 A6 A8 A10 A12 A14 A16 S1 8.0505E-01 -4.6397E+00 2.2410E+01 -5.7501E+01 6.0022E+01 1.3993E+01 -5.6479E+01 S2 4.0667E-01 -5.2418E+00 4.3291E+01 -2.4489E+02 7.6653E+02 -1.2375E+03 8.0725E+02 S3 -6.2410E-02 -3.5615E+01 8.5155E+02 -1.2697E+04 1.0081E+05 -3.6719E+05 4.9109E+05 S4 5.6913E-01 -2.4765E+01 9.0322E+02 -1.9548E+04 2.3017E+05 -1.3869E+06 3.4008E+06 S5 -1.1151E-01 3.6489E+00 -6.7726E+01 6.7578E+02 -3.5458E+03 9.2598E+03 -9.2559E+03 S6 -1.3269E-01 5.7543E+00 -7.3179E+01 4.1421E+02 -1.1769E+03 1.5811E+03 -7.5435E+02 S7 -2.3580E-02 2.2522E+00 -2.7978E+01 1.4827E+02 -3.9351E+02 5.0908E+02 -2.5340E+02 S8 1.3259E-02 -1.8760E-01 1.5473E+00 -6.4581E+00 1.4063E+01 -1.5225E+01 6.4491E+00

[0106] Table 5

[0107] Table 6 shows the total effective focal length f of the projection lens in Example 2 and the effective focal lengths f1 to f4 of each lens.

[0108] parameter f(mm) f1(mm) f2(mm) f3(mm) f4(mm) Numerical 4.50 1.50 -0.67 6.59 2.76

[0109] Table 6

[0110] Figure 4 The distortion curve of the projection lens of Example 2 is shown, which represents the distortion value under different viewing angles. Figure 4 It can be seen that the projection lens provided in Example 2 can achieve good imaging quality.

[0111] Example 3

[0112] The following reference Figures 5 and 6 A projection lens according to Embodiment 3 of the present application is described. Figure 5 A schematic structural diagram of a projection lens according to Example 3 of the present application is shown.

[0113] like Figure 5 As shown, the projection lens according to an exemplary embodiment of the present application includes, in order from the image source side to the imaging side along the optical axis, a first lens E1, a second lens E2, a third lens E3, a fourth lens E4 and a stop STO.

[0114] The first lens E1 has positive optical power, with its image source-side surface S1 being convex and its imaging-side surface S2 being concave. The second lens E2 has negative optical power, with its image source-side surface S3 being concave and its imaging-side surface S4 being concave. The third lens E3 has positive optical power, with its image source-side surface S5 being concave and its imaging-side surface S6 being convex. The fourth lens E4 has positive optical power, with its image source-side surface S7 being concave and its imaging-side surface S8 being convex. The projection lens has a light transmittance greater than 85% in the wavelength range of approximately 800 nm to approximately 1000 nm. Light from the image source sequentially passes through surfaces S1 to S8 and is ultimately imaged onto a projection surface (not shown), such as a projection screen.

[0115] Table 7 shows the surface type, curvature radius, thickness, material, and conic coefficient of each lens of the projection lens of Example 3, wherein the units of the curvature radius and thickness are both millimeters (mm).

[0116]

[0117] Table 7

[0118] As can be seen from Table 7, in Example 3, both the image source-side surface and the image-side surface of any of the first lens element E1 through the fourth lens element E4 are aspherical surfaces. Table 8 shows the high-order coefficients of the various aspherical mirror surfaces that can be used in Example 3, where the surface shape of each aspherical surface can be defined by Formula (1) given in Example 1.

[0119]

[0120]

[0121] Table 8

[0122] Table 9 shows the total effective focal length f of the projection lens in Example 3 and the effective focal lengths f1 to f4 of each lens.

[0123] parameter f(mm) f1(mm) f2(mm) f3(mm) f4(mm) Numerical 4.49 1.54 -0.65 6.18 2.31

[0124] Table 9

[0125] Figure 6 The distortion curve of the projection lens of Example 3 is shown, which represents the distortion value under different viewing angles. Figure 6 It can be seen that the projection lens provided in Example 3 can achieve good imaging quality.

[0126] Example 4

[0127] The following reference Figures 7 and 8 A projection lens according to Embodiment 4 of the present application is described. Figure 7 A schematic structural diagram of a projection lens according to Example 4 of the present application is shown.

[0128] like Figure 7 As shown, the projection lens according to an exemplary embodiment of the present application includes, in order from the image source side to the imaging side along the optical axis, a first lens E1, a second lens E2, a third lens E3, a fourth lens E4 and a stop STO.

[0129] The first lens E1 has positive optical power, with its image source-side surface S1 being convex and its imaging-side surface S2 being concave. The second lens E2 has negative optical power, with its image source-side surface S3 being concave and its imaging-side surface S4 being concave. The third lens E3 has positive optical power, with its image source-side surface S5 being concave and its imaging-side surface S6 being convex. The fourth lens E4 has positive optical power, with its image source-side surface S7 being concave and its imaging-side surface S8 being convex. The projection lens has a light transmittance greater than 85% in the wavelength range of approximately 800 nm to approximately 1000 nm. Light from the image source sequentially passes through surfaces S1 to S8 and is ultimately imaged onto a projection surface (not shown), such as a projection screen.

[0130] Table 10 shows the surface type, curvature radius, thickness, material, and conic coefficient of each lens of the projection lens of Example 4, where the units of curvature radius and thickness are both millimeters (mm).

[0131]

[0132]

[0133] Table 10

[0134] As can be seen from Table 10, in Example 4, both the image source-side surface and the image-side surface of any of the first lens element E1 through the fourth lens element E4 are aspherical surfaces. Table 11 shows the high-order coefficients of the various aspherical mirror surfaces that can be used in Example 4, where the surface shape of each aspherical surface can be defined by Formula (1) given in Example 1 above.

[0135] Face number A4 A6 A8 A10 A12 A14 A16 S1 5.9190E-01 -9.5682E-01 1.5246E+00 1.4408E+00 -1.8549E+00 0.0000E+00 0.0000E+00 S2 6.7315E-01 5.7754E+00 -6.1253E+01 4.1049E+02 -1.2852E+03 1.8107E+03 -9.4551E+02 S3 -6.1430E-02 -1.4837E+01 5.6080E+02 -1.2459E+04 1.4614E+05 -8.9912E+05 2.2470E+06 S4 1.7728E+00 -7.6106E+00 9.0300E+01 -1.0970E+03 8.7712E+03 -3.8775E+04 7.1022E+04 S5 -3.5555E-01 8.0956E-01 8.4511E+00 -7.6330E+01 3.0721E+02 -5.9416E+02 4.4787E+02 S6 1.4957E-01 -7.1230E-02 2.7423E+00 -1.2480E+01 3.4176E+01 -4.7353E+01 2.8473E+01

[0136] Table 11

[0137] Table 12 shows the total effective focal length f of the projection lens in Example 4 and the effective focal lengths f1 to f4 of each lens.

[0138] parameter f(mm) f1(mm) f2(mm) f3(mm) f4(mm) Numerical 4.49 1.86 -0.68 7.74 1.92

[0139] Table 12

[0140] Figure 8 The distortion curve of the projection lens of Example 4 is shown, which represents the distortion value under different viewing angles. Figure 8It can be seen that the projection lens provided in Example 4 can achieve good imaging quality.

[0141] Example 5

[0142] The following reference Figures 9 and 10 A projection lens according to Embodiment 5 of the present application is described. Figure 9 A schematic structural diagram of a projection lens according to Example 5 of the present application is shown.

[0143] like Figure 9 As shown, the projection lens according to an exemplary embodiment of the present application includes, in order from the image source side to the imaging side along the optical axis, a first lens E1, a second lens E2, a third lens E3, a fourth lens E4 and a stop STO.

[0144] The first lens E1 has positive optical power, with its image source-side surface S1 being convex and its imaging-side surface S2 being concave. The second lens E2 has negative optical power, with its image source-side surface S3 being concave and its imaging-side surface S4 being concave. The third lens E3 has positive optical power, with its image source-side surface S5 being concave and its imaging-side surface S6 being convex. The fourth lens E4 has positive optical power, with its image source-side surface S7 being concave and its imaging-side surface S8 being convex. The projection lens has a light transmittance greater than 85% in the wavelength range of approximately 800 nm to approximately 1000 nm. Light from the image source sequentially passes through surfaces S1 to S8 and is ultimately imaged onto a projection surface (not shown), such as a projection screen.

[0145] Table 13 shows the surface type, curvature radius, thickness, material, and conic coefficient of each lens of the projection lens of Example 5, where the units of the curvature radius and thickness are both millimeters (mm).

[0146]

[0147] Table 13

[0148] As can be seen from Table 13, in Example 5, both the image source-side surface and the image-side surface of any of the first lens element E1 through the fourth lens element E4 are aspherical surfaces. Table 14 shows the high-order coefficients of the various aspherical mirror surfaces that can be used in Example 5, where the surface shape of each aspherical surface can be defined by Formula (1) given in Example 1 above.

[0149]

[0150]

[0151] Table 14

[0152] Table 15 shows the total effective focal length f of the projection lens in Example 5 and the effective focal lengths f1 to f4 of each lens.

[0153] parameter f(mm) f1(mm) f2(mm) f3(mm) f4(mm) Numerical 4.47 1.55 -0.67 8.98 2.23

[0154] Table 15

[0155] Figure 10 The distortion curve of the projection lens of Example 5 is shown, which represents the distortion value under different viewing angles. Figure 10 It can be seen that the projection lens provided in Example 5 can achieve good imaging quality.

[0156] Example 6

[0157] The following reference Figures 11 to 12 A projection lens according to Example 6 of the present application is described. Figure 11 A schematic structural diagram of a projection lens according to Example 6 of the present application is shown.

[0158] like Figure 11 As shown, the projection lens according to an exemplary embodiment of the present application includes, in order from the image source side to the imaging side along the optical axis, a first lens E1, a second lens E2, a third lens E3, a fourth lens E4 and a stop STO.

[0159] The first lens E1 has positive optical power, with its image source-side surface S1 being convex and its imaging-side surface S2 being concave. The second lens E2 has negative optical power, with its image source-side surface S3 being concave and its imaging-side surface S4 being concave. The third lens E3 has positive optical power, with its image source-side surface S5 being concave and its imaging-side surface S6 being convex. The fourth lens E4 has positive optical power, with its image source-side surface S7 being concave and its imaging-side surface S8 being convex. The projection lens has a light transmittance greater than 85% in the wavelength range of approximately 800 nm to approximately 1000 nm. Light from the image source sequentially passes through surfaces S1 to S8 and is ultimately imaged onto a projection surface (not shown), such as a projection screen.

[0160] Table 16 shows the surface type, curvature radius, thickness, material, and conic coefficient of each lens of the projection lens of Example 6, where the units of the curvature radius and thickness are both millimeters (mm).

[0161]

[0162] Table 16

[0163] As can be seen from Table 16, in Example 6, both the image source-side surface and the image-side surface of any of the first lens element E1 through the fourth lens element E4 are aspherical surfaces. Table 17 shows the high-order coefficients of the various aspherical mirror surfaces that can be used in Example 6, where the surface shape of each aspherical surface can be defined by Formula (1) given in Example 1.

[0164] Face number A4 A6 A8 A10 A12 A14 A16 S1 7.7309E-01 -1.2329E+00 1.5965E+00 6.2851E+00 -1.3052E+01 0.0000E+00 0.0000E+00 S2 9.4646E-01 5.7194E+00 -1.0454E+02 1.0912E+03 -5.6163E+03 1.2871E+04 -1.0593E+04 S3 8.1481E-01 1.6495E+01 -1.2105E+03 2.5863E+04 -2.9970E+05 1.6837E+06 -3.4325E+06 S4 3.9765E+00 -2.6956E+01 2.7356E+02 -3.5215E+03 3.2010E+04 -1.6161E+05 3.4395E+05 S5 -3.5554E-01 2.6437E+00 -1.5112E+01 7.9214E+01 -2.3434E+02 3.5795E+02 -2.1981E+02 S6 -2.3670E-02 -3.0676E+00 3.4836E+01 -1.9511E+02 5.7765E+02 -8.3985E+02 4.8062E+02 S7 -2.8650E-02 -1.8915E+00 1.7194E+01 -8.4513E+01 2.1753E+02 -2.7457E+02 1.3378E+02 S8 -2.2260E-02 -1.4160E-02 -4.6485E-01 2.4129E+00 -6.2830E+00 7.6431E+00 -3.5857E+00

[0165] Table 17

[0166] Table 18 shows the total effective focal length f of the projection lens in Example 6 and the effective focal lengths f1 to f4 of each lens.

[0167] parameter f(mm) f1(mm) f2(mm) f3(mm) f4(mm) Numerical 4.90 1.47 -0.50 8.80 2.05

[0168] Table 18

[0169] Figure 12 The distortion curve of the projection lens of Example 6 is shown, which represents the distortion value under different viewing angles. Figure 12 It can be seen that the projection lens provided in Example 6 can achieve good imaging quality.

[0170] Example 7

[0171] The following reference Figures 13 and 14 A projection lens according to Example 7 of the present application is described. Figure 13 A schematic structural diagram of a projection lens according to Example 7 of the present application is shown.

[0172] like Figure 13 As shown, the projection lens according to an exemplary embodiment of the present application includes, in order from the image source side to the imaging side along the optical axis, a first lens E1, a second lens E2, a third lens E3, a fourth lens E4 and a stop STO.

[0173] The first lens E1 has positive optical power, with its image source-side surface S1 being convex and its imaging-side surface S2 being concave. The second lens E2 has negative optical power, with its image source-side surface S3 being concave and its imaging-side surface S4 being concave. The third lens E3 has positive optical power, with its image source-side surface S5 being concave and its imaging-side surface S6 being convex. The fourth lens E4 has positive optical power, with its image source-side surface S7 being concave and its imaging-side surface S8 being convex. The projection lens has a light transmittance greater than 85% in the wavelength range of approximately 800 nm to approximately 1000 nm. Light from the image source sequentially passes through surfaces S1 to S8 and is ultimately imaged onto a projection surface (not shown), such as a projection screen.

[0174] Table 19 shows the surface type, curvature radius, thickness, material, and conic coefficient of each lens of the projection lens of Example 7, where the units of the curvature radius and thickness are both millimeters (mm).

[0175]

[0176] Table 19

[0177] As can be seen from Table 19, in Example 7, both the image source-side surface and the image-image-side surface of any of the first lens element E1 through the fourth lens element E4 are aspherical surfaces. Table 20 shows the high-order coefficients of the various aspherical mirror surfaces that can be used in Example 7, where the surface shape of each aspherical surface can be defined by Formula (1) given in Example 1 above.

[0178] Face number A4 A6 A8 A10 A12 A14 A16 S1 4.8361E-01 -3.2341E-01 2.6070E-01 -3.1058E-01 -9.5350E-02 0.0000E+00 0.0000E+00 S2 4.5980E-01 4.4671E+00 -4.1977E+01 2.5620E+02 -1.0182E+03 2.0564E+03 -1.5903E+03 S3 -1.9670E-01 1.0073E+01 -6.5709E+02 1.4866E+04 -1.9436E+05 1.3028E+06 -3.4935E+06 S4 2.4263E+00 -4.4909E+00 -1.3788E+02 3.0152E+03 -3.0798E+04 1.5720E+05 -3.1835E+05 S5 -5.6710E-01 4.6274E+00 -3.0735E+01 1.7618E+02 -6.1353E+02 1.1174E+03 -8.1790E+02 S6 1.8892E-01 -1.0114E+00 1.0131E+01 -5.1681E+01 1.5016E+02 -2.2435E+02 1.3825E+02 S7 1.2243E-01 -1.3146E+00 9.3104E+00 -4.0508E+01 9.3836E+01 -1.0927E+02 5.0130E+01 S8 -5.0800E-03 -1.0316E-01 2.0290E-01 1.4868E-01 -2.2665E+00 3.9620E+00 -2.2084E+00

[0179] Table 20

[0180] Table 21 shows the total effective focal length f of the projection lens in Example 7 and the effective focal lengths f1 to f4 of each lens.

[0181] parameter f(mm) f1(mm) f2(mm) f3(mm) f4(mm) Numerical 4.50 1.71 -0.68 11.51 2.00

[0182] Table 21

[0183] Figure 14 The distortion curve of the projection lens of Example 7 is shown, which represents the distortion value under different viewing angles. Figure 14 It can be seen that the projection lens provided in Example 7 can achieve good imaging quality.

[0184] Example 8

[0185] The following reference Figures 15 and 16 A projection lens according to Example 8 of the present application is described. Figure 15 A schematic structural diagram of a projection lens according to Example 8 of the present application is shown.

[0186] like Figure 15 As shown, the projection lens according to an exemplary embodiment of the present application includes, in order from the image source side to the imaging side along the optical axis, a first lens E1, a second lens E2, a third lens E3, a fourth lens E4 and a stop STO.

[0187] The first lens E1 has positive optical power, with its image source-side surface S1 and imaging-side surface S2 being convex. The second lens E2 has negative optical power, with its image source-side surface S3 and imaging-side surface S4 being concave. The third lens E3 has positive optical power, with its image source-side surface S5 and imaging-side surface S6 being concave. The fourth lens E4 has positive optical power, with its image source-side surface S7 and imaging-side surface S8 being concave. The projection lens has a light transmittance greater than 85% in the wavelength range of approximately 800 nm to approximately 1000 nm. Light from the image source sequentially passes through surfaces S1 to S8 and is ultimately imaged onto a projection surface (not shown), such as a projection screen.

[0188] Table 22 shows the surface type, curvature radius, thickness, material, and conic coefficient of each lens of the projection lens of Example 8, where the units of curvature radius and thickness are both millimeters (mm).

[0189]

[0190] Table 22

[0191] As can be seen from Table 22, in Example 8, both the image source-side surface and the image-side surface of any of the first lens element E1 through the fourth lens element E4 are aspherical surfaces. Table 23 shows the high-order coefficients of the various aspherical mirror surfaces that can be used in Example 8, where the surface shape of each aspherical surface can be defined by Formula (1) given in Example 1.

[0192] Face number A4 A6 A8 A10 A12 A14 A16 S1 2.0451E-01 -7.6718E-01 1.3377E-01 3.0263E+00 -7.9566E+00 0.0000E+00 0.0000E+00 S2 3.9981E-01 -1.2211E+00 4.9526E+00 -1.7683E+01 3.8928E+00 5.0109E+01 -4.2296E+01 S3 1.3489E-01 -7.5732E+00 5.2784E+01 -8.8773E+02 9.8831E+03 -6.1758E+04 1.6268E+05 S4 3.0761E+00 -2.1121E+01 2.3813E+02 -2.9466E+03 2.6793E+04 -1.3781E+05 2.9792E+05 S5 -6.1013E-01 4.1908E+00 -1.7786E+01 5.3101E+01 -8.4057E+01 3.3219E+01 4.2226E+01 S6 -4.0151E-01 2.4365E-01 1.8245E+01 -1.1416E+02 3.3874E+02 -4.9319E+02 2.8408E+02 S7 -3.4922E-01 -1.1731E-01 1.0731E+01 -5.9213E+01 1.5296E+02 -1.9217E+02 9.2682E+01 S8 -5.8220E-02 -2.9410E-02 -8.0880E-02 1.1590E+00 -4.7132E+00 7.4302E+00 -4.3784E+00

[0193] Table 23

[0194] Table 24 shows the total effective focal length f of the projection lens in Example 8 and the effective focal lengths f1 to f4 of each lens.

[0195] parameter f(mm) f1(mm) f2(mm) f3(mm) f4(mm) Numerical 4.00 1.43 -0.74 12.16 2.24

[0196] Table 24

[0197] Figure 16 The distortion curve of the projection lens of Example 8 is shown, which represents the distortion value under different viewing angles. Figure 16 It can be seen that the projection lens provided in Example 8 can achieve good imaging quality.

[0198] Example 9

[0199] The following reference Figures 17 and 18 A projection lens according to Example 9 of the present application is described. Figure 17 A schematic structural diagram of a projection lens according to Example 8 of the present application is shown.

[0200] like Figure 17 As shown, the projection lens according to an exemplary embodiment of the present application includes, in order from the image source side to the imaging side along the optical axis, a first lens E1, a second lens E2, a third lens E3, a fourth lens E4 and a stop STO.

[0201] The first lens E1 has positive optical power, with its image source-side surface S1 and imaging-side surface S2 being convex. The second lens E2 has negative optical power, with its image source-side surface S3 and imaging-side surface S4 being concave. The third lens E3 has positive optical power, with its image source-side surface S5 and imaging-side surface S6 being concave. The fourth lens E4 has positive optical power, with its image source-side surface S7 and imaging-side surface S8 being concave. The projection lens has a light transmittance greater than 85% in the wavelength range of approximately 800 nm to approximately 1000 nm. Light from the image source sequentially passes through surfaces S1 to S8 and is ultimately imaged onto a projection surface (not shown), such as a projection screen.

[0202] Table 25 shows the surface type, curvature radius, thickness, material, and conic coefficient of each lens of the projection lens of Example 9, where the units of the curvature radius and thickness are both millimeters (mm).

[0203]

[0204]

[0205] Table 25

[0206] As can be seen from Table 25, in Example 9, both the image source-side surface and the image-image-side surface of any of the first lens element E1 through the fourth lens element E4 are aspherical surfaces. Table 26 shows the high-order coefficients of the various aspherical mirror surfaces that can be used in Example 9, where the surface shape of each aspherical surface can be defined by Formula (1) given in Example 1 above.

[0207] Face number A4 A6 A8 A10 A12 A14 A16 S1 3.6323E-01 -9.6699E-01 1.9994E-01 2.8178E+00 -7.4025E+00 0.0000E+00 0.0000E+00 S2 4.4282E-01 -1.3810E-01 -4.5518E+00 2.8758E+01 -1.2061E+02 2.1459E+02 -1.2413E+02 S3 3.3197E-01 -9.9161E+00 1.0597E+02 -1.7647E+03 1.8742E+04 -1.1157E+05 2.8453E+05 S4 3.0244E+00 -1.9525E+01 2.1702E+02 -2.7327E+03 2.5851E+04 -1.3854E+05 3.1237E+05 S5 -9.2369E-01 7.0146E+00 -3.5276E+01 1.2828E+02 -2.9140E+02 3.6266E+02 -1.7435E+02 S6 -3.6876E-01 -7.5200E-03 2.3023E+01 -1.4295E+02 4.3183E+02 -6.6276E+02 4.1416E+02 S7 -3.3232E-01 -1.4068E-01 1.2417E+01 -7.2617E+01 2.0287E+02 -2.8620E+02 1.6007E+02 S8 -4.6560E-02 -3.6610E-02 -1.1030E-02 6.6582E-01 -3.3885E+00 6.1323E+00 -4.2951E+00

[0208] Table 26

[0209] Table 27 shows the total effective focal length f of the projection lens in Example 9 and the effective focal lengths f1 to f4 of each lens.

[0210] parameter f(mm) f1(mm) f2(mm) f3(mm) f4(mm) Numerical 4.25 1.61 -0.74 22.92 2.04

[0211] Table 27

[0212] Figure 18 The distortion curve of the projection lens of Example 9 is shown, which represents the distortion value under different viewing angles. Figure 18 It can be seen that the projection lens provided in Example 9 can achieve good imaging quality.

[0213] In summary, Examples 1 to 9 respectively satisfy the relationships shown in Table 28.

[0214]

[0215]

[0216] Table 28

[0217] The above description is merely a preferred embodiment of the present application and an illustration of the technical principles employed. Those skilled in the art should understand that the scope of the invention herein is not limited to the technical solutions formed by the specific combination of the above-mentioned technical features, but also encompasses other technical solutions formed by any combination of the above-mentioned technical features or their equivalents without departing from the inventive concept. For example, a technical solution formed by replacing the above-mentioned features with (but not limited to) technical features having similar functions disclosed in this application.

Claims

1. A projection lens, characterized in that: The projection lens includes, in order from the image source side to the image side along the optical axis: a first lens having positive refractive power, wherein the image source side surface thereof is convex; a second lens having negative optical power, wherein both its image source side surface and its image image side surface are concave; a third lens element having positive refractive power, whose image source side surface is concave and whose image forming side surface is convex; and The fourth lens has positive refractive power, its image source side surface is concave, and its image side surface is convex. Wherein, the number of lenses having optical power of the projection lens is four; The total effective focal length f of the projection lens and the effective focal length f4 of the fourth lens satisfy 1.63≤f / f4≤2.39; The total effective focal length f of the projection lens and the effective focal length f2 of the second lens satisfy -9.80≤f / f2≤-5.

41.

2. The projection lens according to claim 1, wherein: The total effective focal length f of the projection lens and the effective focal length f1 of the first lens satisfy 2.41≤f / f1≤3.

33.

3. The projection lens according to claim 1, wherein: The third lens has positive refractive power, and its effective focal length f3 and the total effective focal length f of the projection lens satisfy 1.32≤f3 / f≤5.

39.

4. The projection lens according to any one of claims 1 to 3, wherein: In the light waveband of 800nm ​​to 1000nm, the light transmittance of the projection lens is greater than 85%.

5. The projection lens according to any one of claims 1 to 3, wherein: A distance TTL from the image source surface of the projection lens to the imaging side surface of the fourth lens on the optical axis and a total effective focal length f of the projection lens satisfy 0.67≤TTL / f≤0.

82.

6. The projection lens according to any one of claims 1 to 3, wherein: The maximum effective semi-aperture DT42 of the imaging-side surface of the fourth lens and the maximum effective semi-aperture DT41 of the image source-side surface of the fourth lens satisfy 1.13≤DT42 / DT41≤1.

19.

7. The projection lens according to any one of claims 1 to 3, characterized in that: A distance T12 between the first lens and the second lens on the optical axis and a distance T23 between the second lens and the third lens on the optical axis satisfy 0.88≤T12 / T23≤2.

11.

8. The projection lens according to any one of claims 1 to 3, wherein: A center thickness CT4 of the fourth lens on the optical axis and a center thickness CT2 of the second lens on the optical axis satisfy 1.59≤CT4 / CT2≤2.

82.

9. The projection lens according to claim 8, wherein: A curvature radius R8 of an imaging-side surface of the fourth lens and a curvature radius R1 of an image-source-side surface of the first lens satisfy -1.35≤R8 / R1≤-1.

00.

10. The projection lens according to claim 8, wherein: A curvature radius R4 of an imaging-side surface of the second lens and a curvature radius R3 of an image-source-side surface of the second lens satisfy -2.19≤R4 / R3≤-0.96.

Images