Projection lens and projection device

Abstract

Embodiments of the present application provide a projection lens and a projection device. The projection lens comprises, in order from the magnification side to the demagnification side: a first lens group with negative focal power, a second lens group with positive focal power, a diaphragm, a third lens group with negative focal power, and a fourth lens group with positive focal power. The projection lens only comprises one aspherical lens, the aspherical lens is located in the first lens group, and the materials of the lenses comprised in the projection lens are all glass materials.

Description

Technical Field

[0001] This application relates to the field of optical imaging technology, and more specifically, to a projection lens and a projection device. Background Technology

[0002] With the continuous development of the market and technology, laser projectors with higher brightness and wider color gamut are gradually entering homes.

[0003] One of the most common image source chips used in current home laser projectors is the 0.47” DMD, which typically uses ultra-short-throw projection lenses, which are expensive. Specially developed long-throw laser projection lenses are less common and suffer from issues such as significant color difference, poor resolution, tolerance sensitivity, and high cost.

[0004] In view of this, it is necessary to propose a completely new optical solution for laser projection lenses for 0.47” DMD. Summary of the Invention

[0005] The purpose of this application is to provide a new technology solution for a projection lens and projection equipment.

[0006] This application provides a projection lens. The projection lens, from the magnification side to the reduction side, includes, in sequence: a first lens group with negative optical power, a second lens group with positive optical power, an aperture stop, a third lens group with negative optical power, and a fourth lens group with positive optical power;

[0007] The projection lens contains only one aspherical lens, which is located in the first lens group, and all the lenses contained in the projection lens are made of glass.

[0008] Optionally, the effective focal length of the first lens group is F1, the effective focal length of the projection lens is EFL, and the projection lens satisfies: 1.2 < |F1 / EFL| < 1.6;

[0009] The effective focal length of the second lens group is F2, the effective focal length of the projection lens is EFL, and the projection lens satisfies: 1.8 < |F2 / EFL| < 2.4;

[0010] The focal length of the third lens group is F3, the effective focal length of the projection lens is EFL, and the projection lens satisfies: 4.2 < |F3 / EFL| < 4.8;

[0011] The fourth lens group has a focal length of F4, the projection lens has an effective focal length of EFL, and the projection lens satisfies: 1.6 < |F4 / EFL| < 2.0.

[0012] Optionally, the projection lens aperture value FNO. ≤ 2.4, and the imaging circle diameter D ≥ 16mm.

[0013] Optionally, from the magnification side to the reduction side, the first lens group includes a first lens and a second lens, wherein the second lens is the aspherical lens;

[0014] Both the first lens and the second lens have negative optical power.

[0015] Optionally, the optical Abbe number of the second lens is greater than 60.

[0016] Optionally, from the magnification side to the reduction side, the second lens group includes a third lens and a fourth lens, both of which have positive optical power.

[0017] Optionally, from the magnification side to the reduction side, the third lens group includes a first cemented lens and a second cemented lens, wherein at least one of the first cemented lens and the second cemented lens has a positive optical power.

[0018] Optionally, from the magnifying side to the reducing side, the first cemented lens includes a fifth lens and a sixth lens, and the second cemented lens includes a seventh lens and an eighth lens.

[0019] Optionally, at least two lenses in the third lens group have an optical Abbe number greater than 60.

[0020] Optionally, from the magnification side to the reduction side, the fourth lens group includes a ninth lens and a tenth lens, both of which have positive optical power.

[0021] Optionally, the optical Abbe number of the tenth lens is less than 25.

[0022] Optionally, the center thickness of the first lens ranges from 3mm to 3.5mm;

[0023] The center thickness of the second lens ranges from 1.5mm to 2mm;

[0024] The center thickness of the third lens ranges from 4mm to 4.5mm.

[0025] The center thickness of the fourth lens ranges from 4.1 mm to 4.7 mm.

[0026] The center thickness of the fifth lens ranges from 3.3mm to 3.8mm.

[0027] The center thickness of the sixth lens ranges from 1.2mm to 1.6mm.

[0028] The center thickness of the seventh lens ranges from 4.5mm to 5mm.

[0029] The center thickness of the eighth lens ranges from 5mm to 5.5mm.

[0030] The center thickness of the ninth lens ranges from 4mm to 4.5mm.

[0031] The center thickness of the tenth lens ranges from 3mm to 3.5mm.

[0032] Optionally, the projection device includes a projection lens as described in the first aspect.

[0033] According to an embodiment of this application, a projection lens is provided, in which all lenses are made of glass, and the first lens group contains only one aspherical lens. Through reasonable allocation of optical power and matching of lens materials, the lens has the characteristics of small chromatic aberration, small distortion, high resolution, stable temperature performance, and low cost, thus meeting market demand.

[0034] Other features and advantages of this specification will become clear from the following detailed description of exemplary embodiments with reference to the accompanying drawings. Attached Figure Description

[0035] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments of this specification and, together with their description, serve to explain the principles of this specification.

[0036] Figure 1 This is one of the structural schematic diagrams of the projection lens provided in the embodiments of this application.

[0037] Figure 2 for Figure 1 The MTF curve of the projection lens is shown.

[0038] Figure 3 for Figure 1 A schematic diagram of the dot array of the projection lens is shown.

[0039] Figure 4 for Figure 1 The diagram shows the field curvature distortion of the projection lens.

[0040] Figure 5 for Figure 1 The diagram showing the vertical chromatic aberration of the projection lens is shown.

[0041] Figure 6 This is a second schematic diagram of the projection lens provided in an embodiment of this application.

[0042] Figure 7 for Figure 6 The MTF curve of the projection lens is shown.

[0043] Figure 8 for Figure 6 A schematic diagram of the dot array of the projection lens is shown.

[0044] Figure 9 for Figure 6 The diagram shows the field curvature distortion of the projection lens.

[0045] Figure 10 for Figure 6 The diagram showing the vertical chromatic aberration of the projection lens is shown.

[0046] Figure 11 This is the third schematic diagram of the projection lens provided in the embodiments of this application.

[0047] Figure 12 for Figure 11 The MTF curve of the projection lens is shown.

[0048] Figure 13 for Figure 11 A schematic diagram of the dot array of the projection lens is shown.

[0049] Figure 14 for Figure 11 The diagram shows the field curvature distortion of the projection lens.

[0050] Figure 15 for Figure 11 The diagram showing the vertical chromatic aberration of the projection lens is shown.

[0051] Explanation of reference numerals in the attached figures:

[0052] 100. First lens group; 200. Second lens group; 300. Third lens group; 400. Fourth lens group;

[0053] 1. First lens; 2. Second lens; 3. Third lens; 4. Fourth lens; 5. Fifth lens; 6. Sixth lens; 7. Seventh lens; 8. Eighth lens; 9. Ninth lens; 10. Tenth lens; 11. Aperture; 12. Dithering device; 13. Beam splitter; 14. Display chip. Detailed Implementation

[0054] Various exemplary embodiments of the present application will now be described in detail with reference to the accompanying drawings. It should be noted that, unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps set forth in these embodiments do not limit the scope of the present application.

[0055] The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the scope of this application and its application or use.

[0056] Technologies and equipment known to those skilled in the art may not be discussed in detail, but where appropriate, such technologies and equipment should be considered part of the specification.

[0057] In all the examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values.

[0058] It should be noted that similar labels and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be discussed further in subsequent figures.

[0059] This application provides a projection lens. (Refer to...) Figure 1 , Figure 6 and Figure 11 The projection lens, from the magnification side to the reduction side, includes: a first lens group 100 with negative optical power, a second lens group 200 with positive optical power, an aperture stop 11, a third lens group 300 with negative optical power, and a fourth lens group 400 with positive optical power.

[0060] The projection lens contains only one aspherical lens, which is located in the first lens group 100, and all the lenses contained in the projection lens are made of glass.

[0061] In this embodiment of the application, the projection lens includes, from the magnification side to the reduction side, the following components in sequence: a first lens group 100, a second lens group 200, an aperture 11, a third lens group 300, a fourth lens group 400, a dithering device 12, a beam splitter 13, and a display chip 14. A protective glass may also be disposed between the beam splitter 13 and the display chip 14.

[0062] The display chip 14 can be a Digital Micromirror Device (DMD) chip. A DMD consists of many matrix-arranged digital micromirrors. During operation, each micromirror can deflect and lock in both directions, thus projecting light in a predetermined direction and oscillating at a frequency of tens of thousands of hertz. The light beam from the illumination source is reflected by the flipping of the micromirrors into the optical system and imaged on the screen. DMDs have advantages such as high resolution and no need for digital-to-analog conversion. This embodiment uses a 0.47-inch DMD chip. Of course, the display chip 14 can also be a Liquid Crystal on Silicon (LCOS) chip or other display elements that can emit light; this application does not impose any limitations on this.

[0063] The dithering device 12 can improve the resolution of the projection system when it is working; the beam splitter 13 is a TIR or RTIR prism in the projection lens, which has the same optical path. An aperture stop 11 is provided between the second lens group 200 and the third lens group 300 to control the light-passing aperture of the lens. Setting the aperture stop 11 at this location can control the overall size of the projection lens.

[0064] The first lens group 100 has a negative optical power and includes an aspherical lens. The first lens group 100 is used to deflect large-angle field rays and correct optical distortion using an aspherical lens.

[0065] The second lens group 200 has a positive optical power and is used to compensate for field curvature, astigmatism, and spherical aberration.

[0066] The third lens group 300 has a negative optical power, which can effectively improve lens chromatic aberration and reduce tolerance sensitivity.

[0067] The fourth lens group 400 has a positive optical power and can be used to converge light rays and reduce the light emission angle.

[0068] Therefore, in this embodiment of the application, all lenses in the projection lens are made of glass, and the first lens group 100 contains only one aspherical lens. Through reasonable optical power distribution and lens material matching, the lens has the characteristics of small chromatic aberration, small distortion, high resolution, stable temperature performance, and low cost, which meets market demand.

[0069] In one embodiment, the focal length of the first lens group 100 is F1, the effective focal length of the projection lens is EFL, and the projection lens satisfies: 1.2 < |F1 / EFL| < 1.6;

[0070] The second lens group 200 has a focal length of F2, the effective focal length of the projection lens is EFL, and the projection lens satisfies: 1.8 < |F2 / EFL| < 2.4.

[0071] The focal length of the third lens group 300 is F3, the effective focal length of the projection lens is EFL, and the projection lens satisfies: 4.2 < |F3 / EFL| < 4.8.

[0072] The fourth lens group 400 has a focal length of F4, the effective focal length of the projection lens is EFL, and the projection lens satisfies: 1.6 < |F4 / EFL| < 2.0.

[0073] In this embodiment, the present application reasonably sets the corresponding focal length range for each of the four lens groups of the above-mentioned group architecture, and all of them satisfy a certain ratio with the focal length of the projection lens and are adjustable. By combining and matching the focal length ranges of the above-mentioned four group architectures, the tolerance sensitivity between the projection lens groups is reduced, and the projection lens further has high resolution.

[0074] In one embodiment, the aperture value FNO. ≤ 2.4 and the image circle diameter D ≥ 16mm. Specifically, a suitable aperture value FNO. and image circle diameter allow the lens to perfectly match a 0.47-inch DMD, achieving an optimal balance between the projection lens's light transmission, resolution, and cost.

[0075] In one embodiment, refer to Figure 1 , Figure 6 and Figure 11 From the magnifying side to the reducing side, the first lens group 100 includes a first lens 1 and a second lens 2, the second lens 2 being the aspherical lens; the optical power of both the first lens 1 and the second lens 2 is negative.

[0076] In this embodiment, the first lens group 100 includes two lenses with negative optical power. The first lens group 100 is used to deflect large-angle field of view light, and at the same time, aspherical lenses are used to correct optical distortion.

[0077] Specifically, the first lens group 100 includes a first lens 1 and a second lens 2. The first lens 1 is a meniscus spherical glass lens with negative optical power, its object-side surface S1 is convex, and its image-side surface S2 is concave. The first lens 1, being a meniscus negative lens, can quickly deflect light. The second lens 2 is an aspherical lens with negative optical power, its object-side surface S3 is concave, and its image-side surface S4 is concave. The aspherical surface shape can effectively correct optical distortion and reduce the front aperture of the lens. In addition, the second lens 2 is made of glass, which can effectively improve back focus shift caused by temperature and improve temperature stability.

[0078] It should be noted that the first lens group includes not only two lenses with negative optical power, but also three or four lenses with negative optical power. In this first lens group, the lens furthest from the magnification side is an aspherical lens. Alternatively, the first lens group may also include lenses with positive optical power, for example, a lens with positive optical power located between two lenses with negative optical power, where the lens furthest from the magnification side in the first lens group is an aspherical lens.

[0079] In one embodiment, the optical Abbe number of the second lens 2 is greater than 60.

[0080] In this embodiment, the second lens 2 is made of a lens material with an optical Abbe number Vd>60, which helps to reduce chromatic aberration.

[0081] In one embodiment, refer to Figure 1 , Figure 6 and Figure 11 From the magnifying side to the reducing side, the second lens group 200 includes a third lens 3 and a fourth lens 4, both of which have positive optical power.

[0082] In this embodiment, the second lens group 200 includes a third lens 3 and a fourth lens 4. The third lens 3 is a spherical lens with positive optical power, its object-side surface is S5, and its image-side surface is S6. The fourth lens 4 is a spherical lens with positive optical power, its object-side surface is S7, and its image-side surface is S8. The second lens group 200 can compensate for field curvature astigmatism caused by the first lens group 100 and introduce compensation for spherical aberration.

[0083] It should be noted that the second lens group includes not only two lenses with positive optical power, but also three or four lenses with positive optical power; or the second lens group may also include lenses with negative optical power, for example, a lens with negative optical power located between two lenses with positive optical power.

[0084] In one embodiment, refer to Figure 1 , Figure 6 and Figure 11 From the magnifying side to the reducing side, the third lens group 300 includes a first cemented lens and a second cemented lens, wherein at least one of the first cemented lens and the second cemented lens has a positive optical power.

[0085] In this embodiment, the projection lens provided by this application uses a combination of spherical lenses, aspherical lenses, and cemented lenses to effectively improve the image quality, reduce tolerance sensitivity, and increase manufacturing yield while meeting optical performance requirements.

[0086] In the first and second cemented lenses, at least one set of cemented lenses has a positive optical power. In this way, the optical power distribution between the first and second sets of cemented lenses can effectively reduce the tolerance sensitivity of the cemented lenses and improve the production yield.

[0087] In one embodiment, refer to Figure 1 , Figure 6 and Figure 11 From the magnifying side to the reducing side, the first cemented lens includes a fifth lens 5 and a sixth lens 6, and the second cemented lens includes a seventh lens 7 and an eighth lens 8.

[0088] In this embodiment, the third lens group 300 includes a fifth lens 5, a sixth lens 6, a seventh lens 7, and an eighth lens 8. The fifth lens 5 is a spherical lens with an object-side surface S9 and an image-side surface S10; the sixth lens 6 is a spherical lens with an object-side surface S10 and an image-side surface S11; the fifth lens 5 and the sixth lens 6 form a first cemented lens L1 on the S10 surface. The seventh lens 7 is a spherical lens with an object-side surface S12 and an image-side surface S13; the eighth lens 8 is a spherical lens with an object-side surface S13 and an image-side surface S14; the seventh lens 7 and the eighth lens 8 form a second cemented lens L2 on the S13 surface.

[0089] In one embodiment, at least two lenses in the third lens group 300 have an optical Abbe number greater than 60.

[0090] In this embodiment, at least two of the first and second cemented lens groups have an optical Abbe number >60, which can effectively improve the axial and transverse chromatic aberration of the projection lens and correct part of the residual spherical aberration introduced by the second lens group 200.

[0091] In one embodiment, refer to Figure 1 , Figure 6 and Figure 10 From the magnifying side to the reducing side, the fourth lens group 400 includes a ninth lens 9 and a tenth lens 10, both of which have positive optical power.

[0092] In this embodiment, the fourth lens group 400 includes a ninth lens 9 and a tenth lens 10. The ninth lens 9 is a spherical lens with positive optical power, its object-side surface is S15, and its image-side surface is S16. The tenth lens 10 is a spherical lens with positive optical power, its object-side surface is S17, and its image-side surface is S18. The fourth lens group 400 can refract and converge light rays, reduce the angle of light rays exiting the lens, increase telecentrism, and correct residual spherical aberration, coma, and astigmatism.

[0093] It should be noted that the second lens group includes not only two lenses with positive optical power, but also three or four lenses with positive optical power; or the second lens group may also include lenses with negative optical power, for example, a lens with negative optical power located between two lenses with positive optical power.

[0094] In one embodiment, the optical Abbe number of the tenth lens 10 is less than 25.

[0095] In this embodiment, the optical Abbe number of the tenth lens 10 in the fourth lens group 400 is less than 25, which can effectively compensate for the remaining chromatic aberration.

[0096] In this embodiment, the fourth lens group 400 includes two lenses, and the tenth lens 10 is the lens furthest from the first lens group 100. Therefore, limiting the optical Abbe number of the tenth lens 10 to less than 25 can effectively compensate for residual chromatic aberration. When the fourth lens group 400 includes more than two lenses, the optical Abbe number of the lens furthest from the first lens group 100 in the fourth lens group 400 is limited to less than 25 to effectively compensate for residual chromatic aberration.

[0097] In one embodiment, refer to Figure 1 , Figure 6 and Figure 11 The center thickness of the first lens 1 ranges from 3mm to 3.5mm; the center thickness of the second lens 2 ranges from 1.5mm to 2mm; the center thickness of the third lens 3 ranges from 4mm to 4.5mm; the center thickness of the fourth lens 4 ranges from 4.1mm to 4.7mm; the center thickness of the fifth lens 5 ranges from 3.3mm to 3.8mm; the center thickness of the sixth lens 6 ranges from 1.2mm to 1.6mm; the center thickness of the seventh lens 7 ranges from 4.5mm to 5mm; the center thickness of the eighth lens 8 ranges from 5mm to 5.5mm; the center thickness of the ninth lens ranges from 4mm to 4.5mm; and the center thickness of the tenth lens ranges from 3mm to 3.5mm. For example, the center thickness of the first lens 1 is 3.2905 mm, the center thickness of the second lens 2 is 1.999 mm, the center thickness of the third lens 3 is 4.0448 mm, the center thickness of the fourth lens 4 is 4.6980 mm, the center thickness of the fifth lens 5 is 3.5844 mm, the center thickness of the sixth lens 6 is 1.5000 mm, the center thickness of the seventh lens 7 is 4.9569 mm, the center thickness of the eighth lens 8 is 5.3535 mm, the center thickness of the ninth lens 9 is 4.3415 mm, and the center thickness of the tenth lens 10 is 3.4434 mm. In this embodiment, by optimizing the material and center thickness of all lenses, the average transmittance of the lens at the center of the optical axis in the 450 nm to 650 nm wavelength band is >85%.

[0098] In one specific embodiment, the projection lens, from the magnification side to the reduction side, includes a first lens group 100, a second lens group 200, a third lens group 300, and a fourth lens group 400. The first lens group 100 includes a first lens 1 and a second lens 2, both with negative optical power, and the second lens 2 is an aspherical lens. The second lens group 200 includes a third lens 3 and a fourth lens 4, both with positive optical power. The third lens group 300 includes two cemented lenses: the first cemented lens includes a fifth lens 5 and a sixth lens 6, and the second cemented lens includes a seventh lens 7 and an eighth lens 8. The fourth lens group 400 includes a ninth lens 9 and a tenth lens 10, both with positive optical power. In this embodiment, except for the second lens 2, all other lenses are spherical lenses. In this embodiment, all lenses are made of glass. Therefore, in this embodiment of the application, through optimized design, using only one glass aspherical lens and two sets of cemented doublet lenses for a total of 10 lenses, the lens MTF, chromatic aberration, distortion and other indicators are improved and the product cost is reduced by reasonable optical power distribution and material matching, making it more suitable for the laser projection market.

[0099] This application also provides a projection device, which includes the projection lens described above. The projection device can be a projector, such as a laser projector.

[0100] The optical module provided in this application will be described below through three embodiments.

[0101] Example 1

[0102] This application provides a projection lens. (Refer to...) Figure 1 The projection lens, from the magnification side to the reduction side, includes: a first lens group 100, a second lens group 200, an aperture 11, a third lens group 300, a fourth lens group 400, a dithering device 12, a beam splitter 13, and a display chip 14.

[0103] The first lens group 100 includes a first lens 1 and a second lens 2 sequentially from the magnifying side to the reducing side. The surface S1 of the first lens 1 away from the second lens 2 is convex, and the surface S2 of the first lens 1 close to the second lens 2 is concave. The surface S3 of the second lens 2 close to the first lens 1 is convex, and the surface S4 of the second lens 2 away from the first lens 1 is concave.

[0104] The second lens group 200 includes a third lens 3 and a fourth lens 4 sequentially from the magnifying side to the reducing side. The surface S5 of the third lens 3 away from the fourth lens 4 is concave, and the surface S6 of the third lens 3 close to the fourth lens 4 is convex. The surface S7 of the fourth lens 4 close to the third lens 3 is convex, and the surface S8 of the fourth lens 4 away from the third lens 3 is concave.

[0105] The third lens group 300 includes, from the magnifying side to the reducing side, a fifth lens 5, a sixth lens 6, a seventh lens 7, and an eighth lens 8. The fifth lens 5 and the sixth lens 6 are cemented together, and the seventh lens 7 and the eighth lens 8 are cemented together.

[0106] The surface S9 of the fifth lens 5 that is far from the sixth lens 6 is flat, and the surface S10 of the fifth lens 5 that is close to the sixth lens 6 is concave; the surface S10 of the sixth lens 6 that is close to the fifth lens 5 is convex, and the surface S11 of the sixth lens 6 that is far from the fifth lens 5 is convex.

[0107] The surface S12 of the seventh lens 7 that is far from the eighth lens 8 is concave, and the surface S13 of the seventh lens 7 that is close to the eighth lens 8 is concave; the surface S13 of the eighth lens 8 that is close to the seventh lens 7 is convex, and the surface S14 of the eighth lens 8 that is far from the seventh lens 7 is convex.

[0108] The fourth lens group 400 includes a ninth lens 9 and a tenth lens 10 from the magnification side to the reduction side. The surface S15 of the ninth lens 9 away from the tenth lens 10 is convex. The surface S16 of the ninth lens 9 close to the tenth lens 10 is convex. The surface S17 of the tenth lens 10 close to the ninth lens 9 is convex. The surface S18 of the tenth lens 10 away from the ninth lens 9 is convex.

[0109] The second lens 2 is a glass aspherical lens, while the other lenses are all glass spherical lenses.

[0110] Therefore, this embodiment 1 provides a method using an optical power of "negative" - just - burden - The projection lens features a four-group "positive" structure. This lens comprises 10 lenses, with carefully designed optical power, object-side and image-side shapes, and aspherical elements.

[0111] The number of surface lenses and spherical lenses can stabilize the light path of the entire optical system of the projection lens, enabling the projection lens to achieve high resolution while also achieving small size and low cost.

[0112] The relevant parameters of each device in Embodiment 1 of this application are shown in Table 1:

[0113] Table 1:

[0114]

[0115] The second lens has an even-numbered aspherical surface profile, which satisfies the following formula:

[0116] Z = cy 2 / {1+[1-(1+k)c 2 y2 ] 1 / 2}+a1y 2 +a2y 4 +a3y 6 +a4y 8 +a5y 10 +a6y 12 +a7y 14 +a8y 16

[0117] Wherein, parameter c is the curvature corresponding to the radius, y is the radial coordinate (its unit is the same as the lens length unit), and k is the conic conic coefficient. When k is less than -1, the surface curve is a hyperbola; when k equals -1, the surface curve is a parabola; when k is between -1 and 0, the surface curve is an ellipse; when k equals 0, the surface is a circle; and when k is greater than 0, the surface is an oval curve. a1 to a8 represent the coefficients corresponding to each radial coordinate. These parameters allow for precise setting of the shape and dimensions of the aspherical surface of the lens imaging optical surface. The aspherical coefficients of the second lens 2 are shown in Table 2.

[0118] Table 2:

[0119]

[0120] In this embodiment 1, the main parameters are shown in Table 3: F1 is the focal length of the first lens group 100, F2 is the focal length of the second lens group 200, and EFL is the effective focal length of the projection lens. L1 is the first cemented lens formed by cementing the fifth lens 5 and the sixth lens 6 together, and L2 is the second cemented lens formed by cementing the seventh lens 7 and the eighth lens 8 together.

[0121] Table 3:

[0122]

[0123] The image source pixel size used in Embodiment 1 of this application is 5.4*5.4um, and the corresponding design resolution is 93lp / mm.

[0124] from Figure 2 It can be seen that the entire field of view of the projection lens in this embodiment 1 has an MTF > 0.6 at 93 lp / mm, which indicates that it has very high resolution.

[0125] Figure 3 The image is a dot matrix plot with an RMS radius of 3.7µm, which is within 0.8 pixels to ensure sharp resolution.

[0126] Figure 4 In field curvature distortion, optical distortion is ≤0.6%, resulting in extremely small distortion in the image that is difficult to detect with the naked eye.

[0127] Figure 5 The maximum vertical color difference is <0.8um, which is within 0.2 pixels. The vertical color difference is well corrected, ensuring that the image has no color fringing.

[0128] Embodiment 1 of this application is applicable to a laser projector with a 0.47” DMD (0.47-inch DMD) display chip 14, a lens throw ratio of 1.2, and an aperture Fn0. of 2.4.

[0129] Example 2

[0130] This application provides a projection lens. (Refer to...) Figure 6 The projection lens, from the magnification side to the reduction side, includes: a first lens group 100, a second lens group 200, an aperture 11, a third lens group 300, a fourth lens group 400, a dithering device 12, a beam splitter 13, a protective glass, and a display chip 14.

[0131] The first lens group 100 includes a first lens 1 and a second lens 2 sequentially from the magnifying side to the reducing side. The surface S1 of the first lens 1 away from the second lens 2 is convex, and the surface S2 of the first lens 1 close to the second lens 2 is concave. The surface S3 of the second lens 2 close to the first lens 1 is convex, and the surface S4 of the second lens 2 away from the first lens 1 is concave.

[0132] The second lens group 200 includes a third lens 3 and a fourth lens 4 sequentially from the magnifying side to the reducing side. The surface S5 of the third lens 3 away from the fourth lens 4 is concave, and the surface S6 of the third lens 3 close to the fourth lens 4 is convex. The surface S7 of the fourth lens 4 close to the third lens 3 is convex, and the surface S8 of the fourth lens 4 away from the third lens 3 is concave.

[0133] The third lens group 300 includes, from the magnifying side to the reducing side, a fifth lens 5, a sixth lens 6, a seventh lens 7, and an eighth lens 8. The fifth lens 5 and the sixth lens 6 are cemented together, and the seventh lens 7 and the eighth lens 8 are cemented together.

[0134] The surface S9 of the fifth lens 5 that is far from the sixth lens 6 is convex, and the surface S10 of the fifth lens 5 that is close to the sixth lens 6 is convex; the surface S10 of the sixth lens 6 that is close to the fifth lens 5 is concave, and the surface S11 of the sixth lens 6 that is far from the fifth lens 5 is concave.

[0135] The surface S12 of the seventh lens 7 that is far from the eighth lens 8 is flat, and the surface S13 of the seventh lens 7 that is close to the eighth lens 8 is concave; the surface S13 of the eighth lens 8 that is close to the seventh lens 7 is convex, and the surface S14 of the eighth lens 8 that is far from the seventh lens 7 is convex.

[0136] The fourth lens group 400 includes a ninth lens 9 and a tenth lens 10 from the magnification side to the reduction side. The surface S15 of the ninth lens 9 away from the tenth lens 10 is convex. The surface S16 of the ninth lens 9 close to the tenth lens 10 is convex. The surface S17 of the tenth lens 10 close to the ninth lens 9 is convex. The surface S18 of the tenth lens 10 away from the ninth lens 9 is convex.

[0137] The relevant parameters of each device in Embodiment 2 of this application are shown in Table 4:

[0138] Table 4:

[0139]

[0140] In this embodiment 2, except for the second lens 2, whose surface is aspherical, all other lenses have spherical surfaces. The second lens 2 has an even-numbered aspherical surface shape, which satisfies the following formula:

[0141] Z = cy 2 / {1+[1-(1+k)c 2 y 2 ] 1 / 2}+a1y 2 +a2y 4 +a3y 6 +a4y 8 +a5y 10 +a6y 12 +a7y 14 +a8y 16

[0142] Wherein, parameter c is the curvature corresponding to the radius, y is the radial coordinate (its unit is the same as the lens length unit), and k is the conic conic coefficient. When k is less than -1, the surface curve is a hyperbola; when k equals -1, the surface curve is a parabola; when k is between -1 and 0, the surface curve is an ellipse; when k equals 0, the surface is a circle; and when k is greater than 0, the surface is an oval curve. a1 to a8 represent the coefficients corresponding to each radial coordinate. These parameters allow for precise setting of the shape and dimensions of the aspherical surface of the lens imaging optical surface. The aspherical coefficients of the second lens 2 are shown in Table 5.

[0143] Table 5:

[0144]

[0145] In this embodiment 2, the main parameters are shown in Table 6: F1 is the focal length of the first lens group 100, F2 is the focal length of the second lens group 200, and EFL is the effective focal length of the projection lens. L1 is the first cemented lens formed by cementing the fifth lens 5 and the sixth lens 6 together, and L2 is the second cemented lens formed by cementing the seventh lens 7 and the eighth lens 8 together.

[0146] Table 6:

[0147]

[0148] The image source pixel size used in Embodiment 2 of this application is 5.4um, and the corresponding design resolution is 93lp / mm.

[0149] from Figure 7 It can be seen that the entire field of view of the lens in this embodiment 2 has an MTF > 0.6 at 93 lp / mm, which indicates that it has very high resolution.

[0150] Figure 8 The image is a dot matrix plot with an RMS radius of 4.1µm, which is within 0.8 pixels to ensure sharp resolution.

[0151] Figure 9 In field curvature distortion, optical distortion is ≤0.6%, resulting in extremely small distortion in the image, which is difficult to detect with the naked eye.

[0152] Figure 10 The maximum vertical color difference is <0.8um, which is within 0.2 pixels. The vertical color difference is well corrected, ensuring that the image has no color fringing.

[0153] Embodiment 2 of this application is applicable to a laser projector with a 0.47” DMD (0.47-inch DMD) display chip 14, a lens throw ratio of 1.2, and an aperture Fn0. of 2.4.

[0154] Example 3

[0155] This application provides a projection lens. (Refer to...) Figure 11 The projection lens, from the magnification side to the reduction side, includes: a first lens group 100, a second lens group 200, an aperture 11, a third lens group 300, a fourth lens group 400, a dithering device 12, a beam splitter 13, a protective glass, and a display chip 14.

[0156] The first lens group 100 includes a first lens 1 and a second lens 2 sequentially from the magnifying side to the reducing side. The surface S1 of the first lens 1 away from the second lens 2 is convex, and the surface S2 of the first lens 1 close to the second lens 2 is concave. The surface S3 of the second lens 2 close to the first lens 1 is convex, and the surface S4 of the second lens 2 away from the first lens 1 is concave.

[0157] The second lens group 200 includes a third lens 3 and a fourth lens 4 sequentially from the magnifying side to the reducing side. The surface S5 of the third lens 3 away from the fourth lens 4 is concave, and the surface S6 of the third lens 3 close to the fourth lens 4 is convex. The surface S7 of the fourth lens 4 close to the third lens 3 is convex, and the surface S8 of the fourth lens 4 away from the third lens 3 is concave.

[0158] The third lens group 300 includes, from the magnifying side to the reducing side, a fifth lens 5, a sixth lens 6, a seventh lens 7, and an eighth lens 8. The fifth lens 5 and the sixth lens 6 are cemented together, and the seventh lens 7 and the eighth lens 8 are cemented together.

[0159] The surface S9 of the fifth lens 5 that is far from the sixth lens 6 is convex, and the surface S10 of the fifth lens 5 that is close to the sixth lens 6 is convex; the surface S10 of the sixth lens 6 that is close to the fifth lens 5 is concave, and the surface S11 of the sixth lens 6 that is far from the fifth lens 5 is concave.

[0160] The surface S12 of the seventh lens 7 that is far from the eighth lens 8 is flat, and the surface S13 of the seventh lens 7 that is close to the eighth lens 8 is convex; the surface S13 of the eighth lens 8 that is close to the seventh lens 7 is concave, and the surface S14 of the eighth lens 8 that is far from the seventh lens 7 is convex.

[0161] The fourth lens group 400 includes a ninth lens 9 and a tenth lens 10 from the magnification side to the reduction side. The surface S15 of the ninth lens 9 away from the tenth lens 10 is a plane, the surface S16 of the ninth lens 9 close to the tenth lens 10 is a convex surface, the surface S17 of the tenth lens 10 close to the ninth lens 9 is a convex surface, and the surface S18 of the tenth lens 10 away from the ninth lens 9 is a plane.

[0162] The relevant parameters of each device in Embodiment 3 of this application are shown in Table 7:

[0163] Table 7:

[0164]

[0165]

[0166] In this embodiment 3, except for the second lens 2, whose surface is aspherical, all other lenses have spherical surfaces. The second lens 2 has an even-numbered aspherical surface shape, which satisfies the following formula:

[0167] Z = cy 2 / {1+[1-(1+k)c 2 y 2 ] 1 / 2}+a1y 2 +a2y 4 +a3y6 +a4y 8 +a5y 10 +a6y 12 +a7y 14 +a8y 16

[0168] Wherein, parameter c is the curvature corresponding to the radius, y is the radial coordinate (its unit is the same as the lens length unit), and k is the conic conic coefficient. When k is less than -1, the surface curve is a hyperbola; when k equals -1, the surface curve is a parabola; when k is between -1 and 0, the surface curve is an ellipse; when k equals 0, the surface is a circle; and when k is greater than 0, the surface is an oval curve. a1 to a8 represent the coefficients corresponding to each radial coordinate. These parameters allow for precise setting of the shape and dimensions of the aspherical surface of the lens imaging optical surface. The aspherical coefficients of the second lens 2 are shown in Table 8.

[0169] Table 8:

[0170]

[0171] In this embodiment 3, the main parameters are shown in Table 9: F1 is the focal length of the first lens group 100, F2 is the focal length of the second lens group 200, and EFL is the effective focal length of the projection lens. L1 is the first cemented lens formed by cementing the fifth lens 5 and the sixth lens 6 together, and L2 is the second cemented lens formed by cementing the seventh lens 7 and the eighth lens 8 together.

[0172] Table 9:

[0173]

[0174] The image source pixel size used in Embodiment 3 of this application is 5.4um, and the corresponding design resolution is 93lp / mm.

[0175] As can be seen from 12, the entire field of view of lens 3 in this embodiment has an MTF > 0.6 at 93 lp / mm, which indicates high resolution.

[0176] Figure 13 The image is a dot matrix plot with an RMS radius of 3.7µm, which is within 1 pixel to ensure sharp resolution.

[0177] Figure 14 In field curvature distortion, optical distortion is ≤0.6%, resulting in extremely small distortion in the image, which is difficult to detect with the naked eye.

[0178] Figure 15 The maximum vertical color difference is 1µm, which is within 0.2 pixels. The vertical color difference is well corrected, ensuring that the image has no color fringing.

[0179] Embodiment 3 of this application is applicable to a laser projector with a 0.47” DMD (0.47-inch DMD) display chip 14, a lens throw ratio of 1.3, and an aperture Fn0. of 2.4.

[0180] The above embodiments mainly describe the differences between the various embodiments. As long as the different optimization features between the various embodiments are not contradictory, they can be combined to form a better embodiment. For the sake of brevity, they will not be elaborated here.

[0181] While specific embodiments of this application have been described in detail by way of examples, those skilled in the art should understand that the above examples are for illustrative purposes only and are not intended to limit the scope of this application. Those skilled in the art should understand that modifications can be made to the above embodiments without departing from the scope and spirit of this application. The scope of this application is defined by the appended claims.

Claims

1. A projection lens, characterized in that, The projection lens, from the magnification side to the reduction side, includes: a first lens group (100) with negative optical power, a second lens group (200) with positive optical power, an aperture, a third lens group (300) with negative optical power, and a fourth lens group (400) with positive optical power. From the magnifying side to the reducing side, the first lens group (100) includes a first lens (1) and a second lens (2), both of which have negative optical power; the second lens group (200) includes a third lens (3) and a fourth lens (4), both of which have positive optical power; the third lens group (300) includes a first cemented lens and a second cemented lens, wherein at least one of the first and second cemented lenses has positive optical power; the fourth lens group (400) includes a ninth lens (9) and a tenth lens (10), both of which have positive optical power; the projection lens has ten lenses with optical power. Only the second lens (2) in the projection lens is an aspherical lens, and all the lenses included in the projection lens are made of glass. Wherein, the focal length of the first lens group (100) is F1, the effective focal length of the projection lens is EFL, and the projection lens satisfies: 1.2 < |F1 / EFL| < 1.6; The second lens group (200) has a focal length of F2, the effective focal length of the projection lens is EFL, and the projection lens satisfies: 1.8 < |F2 / EFL| < 2.4; The focal length of the third lens group (300) is F3, the effective focal length of the projection lens is EFL, and the projection lens satisfies: 4.2 < |F3 / EFL| < 4.8; The focal length of the fourth lens group (400) is F4, the effective focal length of the projection lens is EFL, and the projection lens satisfies: 1.6 < |F4 / EFL| < 2.

0.

2. The projection lens according to claim 1, characterized in that, The projection lens has an aperture value FNO. ≤ 2.4 and an image circle diameter D ≥ 16mm.

3. The projection lens according to claim 1, characterized in that, The optical Abbe number of the second lens (2) is greater than 60.

4. The projection lens according to claim 1, characterized in that, From the magnifying side to the reducing side, the first cemented lens includes a fifth lens (5) and a sixth lens (6), and the second cemented lens includes a seventh lens (7) and an eighth lens (8).

5. The projection lens according to claim 4, characterized in that, At least two lenses in the third lens group (300) have an optical Abbe number greater than 60.

6. The projection lens according to claim 1, characterized in that, The optical Abbe number of the tenth lens (10) is less than 25.

7. The projection lens according to claim 4, characterized in that, The center thickness of the first lens ranges from 3mm to 3.5mm; The center thickness of the second lens ranges from 1.5mm to 2mm; The center thickness of the third lens ranges from 4mm to 4.5mm. The center thickness of the fourth lens ranges from 4.1 mm to 4.7 mm. The center thickness of the fifth lens ranges from 3.3mm to 3.8mm. The center thickness of the sixth lens ranges from 1.2mm to 1.6mm. The center thickness of the seventh lens ranges from 4.5mm to 5mm. The center thickness of the eighth lens ranges from 5mm to 5.5mm. The center thickness of the ninth lens ranges from 4mm to 4.5mm. The center thickness of the tenth lens ranges from 3mm to 3.5mm.

8. A projection device, characterized in that, The projection device includes a projection lens as described in any one of claims 1-7.

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