Projection lens and projection device

Abstract

The embodiments of the present application provide a projection lens and a projection device; wherein the projection lens includes a front lens group, a rear lens group, and an aperture along the same optical axis from the object side to the image side, wherein the aperture is located between the front lens group and the rear lens group; the front lens group includes a first lens closest to the object side; the rear lens group includes a seventh lens closest to the image side; the distance from the object-side surface of the first lens to the image-side surface of the seventh lens is L1, and the distance from the object-side surface of the first lens to the imaging plane is L2, and the ratio of L1 to L2 satisfies: L1 / L2≤0.6. The projection lens provided in the embodiments of the present application has the characteristics of small size, small distortion, and high resolution, which is conducive to miniaturization of the entire projection device, and can have a large back focal length when the projection lens size is small.

Description

Technical Field

[0001] The embodiments of the present application relate to the field of projection imaging technology, and more specifically, to a projection lens and a projection device. Background Art

[0002] As the market environment continues to change, projectors of various shapes are constantly emerging. While improving performance, projectors are becoming smaller and more compact, which poses new challenges to the projection lenses.

[0003] Traditional projection lenses, due to their large size, generally have a long optical length, making them unsuitable for the current design requirements of micro / mini projectors. Furthermore, to improve projection resolution, a galvanometer mirror is added between the lens assembly and the beam splitter, resulting in improved resolution. However, the addition of the galvanometer mirror requires more structural space for the back focus of the projection lens, increasing the back focal length of the lens, which in turn increases the size of the projection lens and the difficulty of miniaturizing the projection lens. Summary of the Invention

[0004] The purpose of this application is to provide a new technical solution for a projection lens and a projection device.

[0005] In a first aspect, an embodiment of the present application provides a projection lens, comprising a front lens group, a rear lens group, and an aperture along the same optical axis from the object side to the image side, wherein the aperture is located between the front lens group and the rear lens group;

[0006] The front lens group includes a first lens closest to the object side;

[0007] The rear lens group includes a seventh lens closest to the image side;

[0008] The distance between the object-side surface of the first lens and the image-side surface of the seventh lens is L1, and the distance between the object-side surface of the first lens and the imaging plane is L2. The ratio of L1 to L2 satisfies: L1 / L2≤0.6.

[0009] Optionally, the projection lens satisfies: H / L2>0.165, where H is the diameter of the imaging circle of the projection lens.

[0010] Optionally, the projection lens satisfies: L2 / F<7.5, where F is the effective focal length of the projection lens.

[0011] Optionally, the projection lens satisfies: D / L2<0.3, where D is the effective optical aperture of the first lens.

[0012] Optionally, the aperture value FNO of the projection lens is set to: FNO≤1.8.

[0013] Optionally, surfaces of the first lens and the seventh lens are set to be aspherical.

[0014] Optionally, the front lens group further includes a second lens and a third lens arranged adjacent to each other;

[0015] Two adjacent surfaces of the second lens and the third lens are cemented together to form a first cemented lens group, and the optical power of the first cemented lens group is positive;

[0016] The first cemented lens group is located between the first lens and the aperture.

[0017] Optionally, the optical power of the first lens is negative, two surfaces of the first lens are even aspheric surfaces, and the optical Abbe number of the first lens is greater than 50.

[0018] Optionally, the optical power of the second lens is negative, and the optical power of the third lens is positive.

[0019] Optionally, the rear lens group further includes a fourth lens, a fifth lens and a sixth lens;

[0020] The fourth lens is disposed near the aperture stop, the fourth lens and the fifth lens are adjacent and cemented together, two adjacent surfaces of the fourth lens and the fifth lens are cemented together to form a second cemented lens group, and the optical power of the second cemented lens group is positive;

[0021] The sixth lens is located between the second cemented lens group and the seventh lens, and the sixth lens is a biconvex lens.

[0022] Optionally, the optical power of the seventh lens is positive, two surfaces of the seventh lens are even aspheric surfaces, and the optical Abbe number of the seventh lens is greater than 50.

[0023] Optionally, the fourth lens has a positive optical power, and the fifth lens has a negative optical power;

[0024] The refractive power of the sixth lens is positive.

[0025] Optionally, the projection lens further includes an optical jitter device and a spectrometer, and the optical jitter device and the spectrometer are sequentially arranged between the rear lens group and the imaging surface along the optical axis; wherein the optical jitter device includes a galvanometer.

[0026] In a second aspect, the present application provides a projection device. The projection device includes:

[0027] a housing; and

[0028] As described above, the projection lens is disposed on the housing.

[0029] According to an embodiment of the present application, a projection lens is provided. The optical structure design of the projection lens is relatively simple, the entire projection lens is small in size and has high resolution, which effectively solves the problem of the projection lens of the existing projector being too large in size; moreover, when the projection lens size is small, the back focus length of the projection lens can be made larger, and optical elements such as a galvanometer can be added to the back focus of the projection lens.

[0030] Other features and advantages of the present specification will become apparent from the following detailed description of exemplary embodiments of the present specification with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the specification and, together with the description, serve to explain the principles of the specification.

[0032] Figure 1 This is one of the structural schematic diagrams of the projection lens provided in an embodiment of the present application;

[0033] Figure 2 The second structural diagram of the projection lens provided in the embodiment of the present application;

[0034] Figure 3 A modulation transfer function diagram of the projection lens provided in Example 1;

[0035] Figure 4 A spot diagram of the projection lens provided in Example 1;

[0036] Figure 5 Field curvature and distortion diagram of the projection lens provided in Example 1;

[0037] Figure 6 A diagram of vertical axis chromatic aberration of the projection lens provided in Example 1;

[0038] Figure 7 A modulation transfer function diagram of the projection lens provided in Example 2;

[0039] Figure 8 A spot diagram of the projection lens provided in Example 2;

[0040] Figure 9 Field curvature and distortion diagram of the projection lens provided in Example 2;

[0041] Figure 10 A diagram of vertical axis chromatic aberration of the projection lens provided in Example 2;

[0042] Figure 11A modulation transfer function diagram of the projection lens provided in Example 3;

[0043] Figure 12 A spot diagram of the projection lens provided in Example 3;

[0044] Figure 13 Field curvature and distortion diagram of the projection lens provided in Example 3;

[0045] Figure 14 This is a diagram of vertical axis chromatic aberration of the projection lens provided in Example 3.

[0046] Description of reference numerals:

[0047] 10. Front lens group; 11. First lens; 12. Second lens; 13. Third lens; 20. Rear lens group; 21. Fourth lens; 22. Fifth lens; 23. Sixth lens; 24. Seventh lens; 30. Aperture; 40. Optical dithering device; 50. Spectral device; 60. Light-transmitting protection device; 70. Image source; S1. First surface; S2. Second surface; S3. Third surface; S4. Fourth surface; S5. Fifth surface; S6. Sixth surface; S7. Seventh surface; S8. Eighth surface; S9. Ninth surface; S10. Tenth surface; S11. Eleventh surface; S12. Twelfth surface. DETAILED DESCRIPTION

[0048] 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 arrangements of components and steps, numerical expressions and numerical values set forth in these embodiments do not limit the scope of the present application.

[0049] The following description of at least one exemplary embodiment is merely illustrative in nature and is in no way intended to limit the present disclosure, its application, or uses.

[0050] Techniques and equipment known to ordinary technicians in the relevant art may not be discussed in detail, but where appropriate, the techniques and equipment should be considered part of the specification.

[0051] In all examples shown and discussed herein, any specific values should be interpreted as merely exemplary and not limiting. Therefore, other examples of the exemplary embodiments may have different values.

[0052] It should be noted that like reference numerals and letters refer to like items in the following figures, and therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures.

[0053] The embodiments of the present application provide a projection lens, which can be applied to a projection device. The projection lens has a small volume and size and a high resolution, meeting the development trend of miniaturization of projection devices.

[0054] In the embodiments of the present application, Figure 1 and Figure 2 As shown, the projection lens includes, from the object side to the image side, along the same optical axis: a front lens group 10, a rear lens group 20, and an aperture 30, wherein the aperture 30 is located between the front lens group 10 and the rear lens group 20;

[0055] The front lens group 10 includes a first lens 11 closest to the object side;

[0056] The rear lens group 20 includes a seventh lens 24 closest to the image side;

[0057] The distance between the object-side surface of the first lens 11 and the image-side surface of the seventh lens 24 is L1, and the distance between the object-side surface of the first lens 11 and the imaging plane is L2. The ratio of L1 to L2 is set to satisfy: L1 / L2≤0.6.

[0058] The projection lens provided in the above embodiment has a corresponding optical structure designed with the aperture 30 as the boundary, and can include two lens groups: one lens group is the front lens group 10, which is set close to the object side; and the other lens group is the rear lens group 20, which is set close to the image side.

[0059] Of course, other optical elements such as galvanometer mirrors, prisms, etc. may also be provided in the projection lens.

[0060] It should be noted that, in the above embodiments, the image side refers to the side where the light source of the projected image (or projection screen) is located during the projection process. Figure 1 and Figure 2 The image source 70 is shown on the right side of the figure. The object side refers to the side where the projected image is imaged on the projection surface (such as a wall). Figure 1 and Figure 2 The leftmost one.

[0061] In the projection lens of the embodiment of the present application, a light source, such as a display / display screen, can be further provided on the side of the rear lens group 20 away from the aperture 30 , which can emit projection light.

[0062] The stop 30 in the above-mentioned embodiment is, for example, an aperture stop. The stop 30 can be used to control the aperture of the projection lens. Specifically, in the embodiment of the present application, the stop 30 (STOP) is positioned at a suitable position between the front lens group 10 and the rear lens group 20. This effectively reduces the aperture of the first lens 11 in the projection lens while maximizing the amount of light passing through, thereby achieving a clearer image of the projected light. Furthermore, reducing the aperture of the first lens 11 also helps reduce the volume and weight of the resulting projection lens, and can also reduce the cost of the projection lens to a certain extent.

[0063] Typically, the aperture of the diaphragm 30 is a fixed value. Of course, in order to flexibly adjust the imaging clarity and enable the projection lens to better adapt to the switching between high and low resolutions, the diaphragm 30 can also be set to have an adjustable aperture.

[0064] The projection light is emitted by a display, for example, and can be emitted from the image side toward the object side. After passing through the rear lens group 20, the aperture 30 and the front lens group 10 in sequence, it is finally output to the projection surface of the object side, thereby presenting a projected image.

[0065] According to an embodiment of the present application, a projection lens is provided. The optical structure design of the projection lens is relatively simple, the entire projection lens is compact, and the resolution is high, effectively solving the problem of oversized projection lenses in existing projectors. Furthermore, with a smaller projection lens size, the back focal length of the projection lens can be increased, and optical elements such as a galvanometer can be added to the back focal length of the projection lens. This can reduce the size and weight of the entire projection lens.

[0066] The projection lens provided in the embodiments of the present application can be designed to have a relatively small volume / size by adjusting optical parameters, for example, by controlling the ratio of the distance L1 from the object-side surface of the first lens 11 to the image-side surface of the seventh lens 24 to the distance L2 from the object-side surface of the first lens 11 to the imaging plane to satisfy the relationship L1 / L2≤0.6, thereby controlling the formed projection lens to have a sufficiently large back focal length within a limited volume. This allows additional optical elements such as a galvanometer mirror to be accommodated within the limited size. Adding a galvanometer mirror to a projection lens can improve resolution.

[0067] It should be noted that if the value of L1 / L2 exceeds the above range, for example, L1 / L2 is 0.7 or 0.8, or even larger, the back focal length of the projection lens formed will be relatively small, and there will not be enough structural space to accommodate the above-mentioned galvanometer and other optical components.

[0068] As can be seen, the optical parameters designed in the embodiments of the present application enable the projection lens to have a large back focal length while maintaining a small size. This allows the introduction of a galvanometer mirror to improve the resolution of the projection lens without affecting the small size of the projection lens. The resulting projection lens has the advantages of being small in size, light in weight, and having high resolution.

[0069] In some examples of the present application, the projection lens satisfies: H / L2>0.165, where H is the diameter of the imaging circle of the projection lens.

[0070] Generally, as the size / volume of a projection lens decreases, the size of the accompanying microdisplay chip (i.e., light-emitting chip) will also be smaller, such as below 0.2 inches. This may result in a smaller diameter H of the image circle of the projection lens, thereby affecting the field of view and imaging quality of the projection lens.

[0071] In the above example of the present application, through the new design of optical parameters, when the size of the projection lens is limited, the diameter H of the imaging circle of the projection lens can be designed to be as large as possible, so that it can match, for example, a 0.2-inch to 0.3-inch digital micromirror device (DMD) or other light-emitting chip, which is conducive to expanding the field of view and imaging quality of the projection lens.

[0072] The projection lens may further include an image source 70 (IMAGE), which may be a microdisplay chip such as a DMD or LCOS. Specifically, the image source 70 is located on a side of the rear lens group 20 facing away from the aperture 30, and may be used to project projection light.

[0073] The projection lens of the present embodiment has an optical structure that can be used with a 0.2-inch to 0.3-inch digital micromirror device (DMD). This ensures excellent projection display effects without increasing the size of the entire projection lens. This results in a smaller and more compact projection lens, which facilitates the miniaturization of projection devices.

[0074] A DMD is composed of numerous digital micromirrors arranged in a matrix. Each micromirror can be deflected and locked in both positive and negative directions during operation, projecting light in a predetermined direction. The micromirrors oscillate at a frequency of tens of kilohertz, reflecting the light beam from the illumination source into the projection lens and forming an image on the screen. DMDs offer advantages such as high resolution and the elimination of the need for digital-to-analog conversion.

[0075] In some examples of the present application, the projection lens satisfies: L2 / F<7.5, where F is the effective focal length of the projection lens.

[0076] By controlling the object side surface of the first lens 11 in the projection lens (see Figure 2 When the ratio of the distance L2 from the first surface S1 shown in FIG4 to the imaging plane to the effective focal length F of the projection lens is within the above range, the curvature radius and focal length of the first lens 11 can be controlled to be reduced, thereby appropriately reducing the size and weight of the first lens 11, thereby facilitating a reduction in the volume and weight of the entire projection lens while ensuring better quality of the projection image.

[0077] For example, the first lens 11 is designed as a meniscus aspheric lens. The first lens 11 is a negative lens, which can effectively reduce distortion and field curvature aberration when used in the projection lens of the embodiment of the present application.

[0078] When the projection lens is in use, the first lens 11 is the frontmost lens of the projection lens. As the size of the first lens 11 decreases, the front diameter of the projection lens is compressed.

[0079] In some examples of the present application, the projection lens satisfies: D / L2<0.3, where D is the effective optical aperture of the first lens 11 .

[0080] The optical parameter design ranges in the above examples also control and reduce the aperture and focal length of the first lens 11 to a certain extent, while ensuring the resolution of the final projected image. This helps to achieve a projection lens that is both compact and lightweight while still achieving excellent imaging results.

[0081] In some examples of the present application, the aperture value FNO of the projection lens is set to: FNO≤1.8.

[0082] The aperture value FNO of the projection lens is used to control the amount of light passing through.

[0083] Specifically, the smaller the FNO value, the more light passes through. In other words, the aperture value FNO will affect the imaging brightness of the projection lens.

[0084] In the example of this application, the aperture value FNO of the projection lens is designed to be no greater than 1.8, which can ensure that the light output brightness of the entire projection lens is high and the light energy loss is small. The final projected image is brighter and the visual experience is better.

[0085] It should be noted that if the aperture value FNO of the projection lens is designed to be relatively large, for example, 2.0, the brightness of the projected image will be very low, which cannot meet the imaging quality requirements of the projected image.

[0086] In some examples of this application, such as Figure 1 and Figure 2 As shown, the surfaces of the first lens 11 and the seventh lens 24 are set to be aspherical.

[0087] In the projection lens, the first lens 11 is designed to be the lens closest to the object side. The first lens 11 can be designed as an aspheric negative lens, which can effectively reduce distortion and field curvature aberration and compress the front port diameter of the projection lens.

[0088] In the projection lens, the seventh lens 24 is designed as the lens closest to the image side. The aspherical surface design can effectively correct the residual aberration, shorten the total optical length of the projection lens, and ensure the image quality of the projected picture.

[0089] Optionally, see Figure 2 , the two surfaces of the first lens 11, for example: the first surface S1 and the second surface S2 are both set to be even aspheric surfaces; wherein the first surface S1 is the object side surface of the first lens 11, and the second surface S2 is the image side surface of the first lens 11.

[0090] Optionally, see Figure 2 , two surfaces of the seventh lens 24, for example: the eleventh surface S11 and the twelfth surface S12 are both set to be even aspheric surfaces; wherein the eleventh surface S11 is the object side surface of the seventh lens 24, and the twelfth surface S12 is the image side surface of the seventh lens 24.

[0091] The surface shapes of the first lens 11 and the seventh lens 24 are even aspheric surfaces, which satisfy the following formula:

[0092] 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 ;

[0093] Where: 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 quadratic curve coefficient.

[0094] When k < -1, the surface curve is a hyperbola. When k = -1, the surface curve is a parabola. When k is between -1 and 0, the surface curve is an ellipse. When k = 0, the surface curve is a circle. When k > 0, the surface curve is an oblate curve. a1 to a8 represent the coefficients corresponding to each radial coordinate. These parameters can be used to accurately set the shape and dimensions of the aspheric surface of the lens imaging optical surface.

[0095] In some examples of this application, see Figure 1 and Figure 2 In addition to the above-mentioned first lens 11, the front lens group 10 may also include a second lens 12 and a third lens 13 arranged adjacent to each other; the two adjacent surfaces of the second lens 12 and the third lens 13 are glued together to form a first glued lens group, and the optical focal length of the first glued lens group is positive; the first glued lens group is located between the first lens 11 and the aperture 30.

[0096] That is to say, in the example of the present application, the front lens group 10 may include three lenses, namely a first lens 11, a second lens 12 and a third lens 13 which are sequentially arranged along the same optical axis.

[0097] In the front lens group 10 of the above example: the second lens 12 and the third lens 13 are glued together to form a first glued lens group designed to be placed on one side of the aperture 30. The second lens 12 and the third lens 13 cooperate with each other to adjust the optical incident angle and reduce optical distortion. At the same time, the glueing of the two can also effectively reduce chromatic aberration.

[0098] See also Figure 2 The surface where the second lens 12 and the third lens 13 are cemented together forms a fourth surface S4, and the two lenses together form a first cemented lens group with positive optical power. For example, if the second lens 12 is a negative lens, it can further correct for incident light distortion; if the third lens 13 is a positive lens, it can correct for field curvature aberration. In this way, the second lens 12 and the third lens 13 are cemented together using positive and negative lenses, and the materials used can be a combination of high and low optical Abbe numbers to reduce vertical and axial chromatic aberration of the projection lens.

[0099] In addition, lens bonding can effectively reduce the required structural space and the volume of the projection lens.

[0100] Optionally, see Figure 1 The optical power of the first lens 11 is negative, two surfaces of the first lens 11 are even aspheric surfaces, and the optical Abbe number of the first lens 11 is greater than 50.

[0101] For example, see Figure 2The first lens 11 is a meniscus-shaped aspherical lens with negative optical power, whose first surface S1 is convex and whose second surface S2 is concave. The use of a negative meniscus lens in the first lens 11 allows for rapid light deflection. Using a lens material with an optical Abbe number greater than 50 helps reduce chromatic aberration. The aspherical surface shape effectively corrects optical distortion and reduces the front diameter of the projection lens.

[0102] The material of the first lens 11 can be glass, for example, which is beneficial to further reduce distortion, improve the scratch resistance of the lens, and improve temperature stability.

[0103] Optionally, the optical power of the second lens 12 is negative, and the optical power of the third lens 13 is positive.

[0104] For example, see Figure 2 The second lens 12 is a spherical lens with negative optical power, the surface of which close to the object side is the third surface S3, and the surface of which close to the image side is the fourth surface S4.

[0105] Specifically, see Figure 2 The third lens 13 is a spherical lens with positive refractive power. Its object-side surface is cemented to the fourth surface S4 of the second lens 12, and its image-side surface is the fifth surface S5. It can also be understood that the cemented surface of the second lens 12 and the third lens 13 forms the fourth surface S4.

[0106] In the projection lens provided in the embodiments of the present application, the second lens 12 and the third lens 13 can form a first cemented lens group with positive optical power. The second lens 12 is a negative lens, which can further correct for incident light distortion. The third lens 13 is a positive lens, which can correct for field curvature aberration. Thus, the second lens 12 and the third lens 13 are cemented together using positive and negative lenses. The materials used can be a combination of high and low optical Abbe numbers, thereby reducing vertical and axial chromatic aberration of the projection lens.

[0107] In some examples of this application, see Figure 1 and Figure 2 In addition to the aforementioned seventh lens 24, the rear lens group 20 also includes a fourth lens 21, a fifth lens 22 and a sixth lens 23; wherein the fourth lens 21 is arranged close to the aperture 30, the fourth lens 21 and the fifth lens 22 are adjacent and glued together, and the two adjacent surfaces of the fourth lens 21 and the fifth lens 22 are glued together to form a second glued lens group, and the optical power of the second glued lens group is positive; the sixth lens 23 is located between the second glued lens group and the seventh lens 24, and the sixth lens 23 is a biconvex lens.

[0108] In the projection lens, the aperture 30 is positioned between the third lens 13 and the fourth lens 21, reducing the effective optical aperture of the first lens 11 while maintaining a large aperture. Cemented lens groups are located on either side of the aperture 30. Specifically, a first cemented lens group formed by cementing the second lens 12 and the third lens 13 is located on one side of the aperture 30, and a second cemented lens group formed by cementing the fourth lens 21 and the fifth lens is located on the other side of the aperture 30.

[0109] The fourth lens 21 and the fifth lens 22 are glued together to effectively reduce optical spherical aberration and axial chromatic aberration.

[0110] For example, the sixth lens 23 is a biconvex positive lens, which folds the light so that the light emitted from the projection lens is a telecentric light path, which can meet the projection light output requirements.

[0111] For example, the seventh lens 24 is an aspherical lens, which can effectively correct the residual aberration and compress the total optical length of the projection lens, thereby ensuring the image quality of the projected image.

[0112] Through the above combination, the projection lens formed can effectively reduce the total optical length of the projection lens while meeting the requirements of high resolution and small distortion, thus meeting the design trend of miniaturization and lightweight projectors.

[0113] Optionally, the optical power of the seventh lens 24 is positive, two surfaces of the seventh lens 24 are even aspheric surfaces, and the optical Abbe number of the seventh lens 24 is greater than 50.

[0114] See also Figure 2 The seventh lens element 24 is, for example, a biconvex aspheric lens with positive refractive power. Its object-side surface is a convex eleventh surface S11, and its image-side surface is a convex twelfth surface S12. The seventh lens element 24 can be used to converge light, correct residual aberrations, and reduce the size of the projection lens. Using an aspheric surface significantly enhances correction capabilities.

[0115] The seventh lens 24 is made of a lens material with an optical Abbe number greater than 50 to further reduce chromatic aberration.

[0116] In addition, the seventh lens 24 is made of, for example, glass, which can further improve the aberration correction capability, significantly increase the temperature stability of the lens, and alleviate the thermal defocus phenomenon.

[0117] Optionally, the optical focal power of the fourth lens 21 is positive, the optical focal power of the fifth lens 22 is negative, and the optical focal power of the sixth lens 23 is positive.

[0118] See also Figure 2 The fourth lens 21 is, for example, a meniscus spherical lens with positive power, which includes a sixth surface S6 close to the object side and a seventh surface S7 close to the image side. The sixth surface S6 may be a concave surface, and the seventh surface S7 may be a convex surface.

[0119] The fifth lens 22 is, for example, a meniscus spherical lens with negative optical power, which includes a surface close to the object side, which is a concave surface glued together with the seventh surface S7 of the fourth lens 21. The fifth lens 22 also includes an eighth surface S8 close to the image side, which is a convex surface.

[0120] The fourth lens 21 and the fifth lens 22 are cemented together to form a cemented lens with positive refractive power, which can effectively reduce spherical aberration and axial chromatic aberration, and reduce field curvature aberration.

[0121] The sixth lens element 23 is, for example, a biconvex spherical lens with positive optical power. It includes a ninth surface S9 on the object side and a tenth surface S10 on the image side, both of which are convex. The sixth lens element 23 can fold and converge light, reducing the angle of light emitted from the projection lens, improving telecentricity, and correcting coma and astigmatism. Furthermore, the sixth lens element 23 is made of a material with an Abbe number greater than 50 to reduce chromatic aberration.

[0122] In some examples of the present application, the projection lens further includes an optical jitter device 40 and a spectrometer 50, and the optical jitter device 40 and the spectrometer 50 are sequentially arranged along the optical axis between the rear lens group 20 and the imaging surface; wherein the optical jitter device 40 includes a galvanometer.

[0123] The projection lens provided in the embodiments of the present application has ample structural space in the back-focus portion, where an optical dither device 40 is incorporated. This optical dither device 40, when in operation, can improve the resolution of the projection lens. It should be noted that the optical solution of the present application, by adding the optical dither device 40, can reduce the size of the projection lens while maintaining good projection image quality.

[0124] In addition, the optical splitter 50 (PRISM) is, for example, a TIR or RTIR prism, which has an equal optical path length.

[0125] See also Figure 1 and Figure 2 A light-transmitting protective device 60 may be further provided between the light-splitting device 50 and the image source 70. Optionally, the light-transmitting protective device 60 is a protective glass.

[0126] The image source 70 (IMAGE) is, for example, a micro display chip such as DMD or LCOS.

[0127] In a specific example of the present application, the projection lens includes, from the object side to the image side, along the same optical axis, in order: a first lens 11, a second lens 12, a third lens 13, an aperture 30, a fourth lens 21, a fifth lens 22, a sixth lens 23, a seventh lens 24, an optical dither device 40, a spectrometer 50, a light transmission protection device 60, and an image source 70; wherein:

[0128] The first lens 11 is a meniscus aspheric lens with negative optical power and an optical Abbe number greater than 50;

[0129] The second lens 12 is a spherical glass lens with negative optical power and an optical Abbe number greater than 50;

[0130] The third lens 13 is a spherical glass lens with positive refractive power and an optical Abbe number <35;

[0131] The fourth lens 21 is a meniscus spherical glass lens with positive optical power and an optical Abbe number greater than 50;

[0132] The fifth lens 22 is a meniscus spherical glass lens with negative optical power;

[0133] The sixth lens 23 is a biconvex spherical glass lens with positive optical power and an optical Abbe number greater than 50;

[0134] The seventh lens 24 is a biconvex aspheric lens with positive optical power and an optical Abbe number greater than 50;

[0135] The second lens 12 and the third lens 12 are cemented together to form a first cemented lens group with positive refractive power; the fourth lens 21 and the fifth lens 22 are cemented together to form a second cemented lens group with positive refractive power;

[0136] The optical jitter device 40 is a galvanometer;

[0137] The distance between the object-side surface of the first lens 11 and the image-side surface of the seventh lens 24 is L1, and the distance between the object-side surface of the first lens 11 and the imaging plane is L2. The ratio of L1 to L2 satisfies: L1 / L2≤0.6;

[0138] The projection lens satisfies: H / L2>0.165, where H is the diameter of the image circle of the projection lens;

[0139] The projection lens satisfies: L2 / F<7.5, where F is the effective focal length of the projection lens;

[0140] The projection lens satisfies: D / L2<0.3, where D is the effective optical aperture of the first lens;

[0141] The aperture value FNO of the projection lens is set to: FNO≤1.8.

[0142] The projection lens provided in the present application uses spherical lenses, aspherical lenses and cemented lenses that are matched with each other. While meeting the requirements of optical performance, the total length of the projection lens is effectively reduced, and the entire projection lens formed has the characteristics of small size, small distortion and high resolution.

[0143] In order to further optimize the performance of the projection lens, three examples are used below for illustration.

[0144] Example 1

[0145] The projection lens provided in Example 1 of the present application includes, from the object side to the image side, along the same optical axis, a first lens 11, a second lens 12, a third lens 13, an aperture 30, a fourth lens 21, a fifth lens 22, a sixth lens 23, a seventh lens 24, an optical dithering device 40, a beam splitter 50, a light transmission protection device 60, and an image source 70. The relevant parameters of each lens are shown in Table 1:

[0146] Table 1

[0147]

[0148] The aspheric coefficients of the first lens 11 and the seventh lens 24 in Example 1 are shown in Table 2:

[0149] Table 2

[0150]

[0151] The main parameters in Example 1 are shown in Table 3:

[0152] Table 3

[0153] L1(mm) L2(mm) H(mm) F(mm) D(mm) FNO. L1 / L2 H / L2 L2 / F D / L2 25.51 43.813 8 6.3 11.6 1.7 0.58 0.182 6.95 0.265

[0154] The MTF curve, spot diagram, field curvature distortion, and vertical axis chromatic aberration of the projection lens provided in this embodiment 1 are shown as follows: Figure 3 、 Figure 4 、 Figure 5 and Figure 6 shown.

[0155] The image source pixel size used in this embodiment 1 is 5.4 μm, and the corresponding design resolution is 93 lp / mm.

[0156] from Figure 3It can be seen from the MTF curve that the projection lens proposed in Example 1 has an MTF greater than 0.6 at a center field of view of 93 lp / mm and an MTF greater than 0.4 at the maximum field of view, which can meet the design requirement of an MTF greater than 0.3 for the light emitting chip.

[0157] Figure 4 This is the spot diagram of the projection lens proposed in Example 1, where the RMS radius is 4.1 μm, which is within 1 pixel, ensuring sharp resolution.

[0158] Figure 5 This is a field curvature distortion diagram of the projection lens proposed in Example 1. The optical distortion in the field curvature distortion is ≤1%, and the image is not significantly deformed.

[0159] Figure 6 This is the vertical axis chromatic aberration diagram of the projection lens proposed in Example 1. The maximum vertical chromatic aberration is 3 μm, which is within 1 pixel, and the image has no color fringing phenomenon.

[0160] The first embodiment is applicable to an image source 70 of a 0.23-inch digital micromirror device (DMD), a projection lens with a throw ratio of 1.2, and an aperture value FNO of 1.7.

[0161] Example 2

[0162] The projection lens provided in Example 2 of the present application includes, from the object side to the image side, along the same optical axis, a first lens 11, a second lens 12, a third lens 13, an aperture 30, a fourth lens 21, a fifth lens 22, a sixth lens 23, a seventh lens 24, an optical dithering device 40, a beam splitter 50, a light transmission protection device 60, and an image source 70. The relevant parameters of each lens are shown in Table 4:

[0163] Table 4

[0164]

[0165]

[0166] The aspheric coefficients of the first lens 11 and the seventh lens 24 in Example 2 are shown in Table 5:

[0167] Table 5

[0168]

[0169] The main parameters in Example 2 are shown in Table 6:

[0170] Table 6

[0171] L1(mm) L2(mm) H(mm) F(mm) D(mm) FNO L1 / L2 H / L2 L2 / F D / L2 22.59 40.343 7 5.66 10 1.7 0.56 0.173 7.13 0.247

[0172] The MTF curve, spot diagram, field curvature distortion, and vertical axis chromatic aberration of the projection lens provided in this embodiment 2 are shown as follows: Figure 7 、 Figure 8 、 Figure 9 and Figure 10 shown.

[0173] The image source pixel size used in this embodiment 2 is 5.4 μm, and the corresponding design resolution is 93 lp / mm.

[0174] from Figure 7 It can be seen from the MTF curve that the projection lens proposed in Example 2 has an MTF greater than 0.55 at a center field of view of 93 lp / mm and an MTF greater than 0.4 at the maximum field of view, which can meet the design requirement of an MTF greater than 0.3 for the light emitting chip.

[0175] Figure 8 This is the spot diagram of the projection lens proposed in Example 2, where the RMS radius is 3.7 μm, which is within 1 pixel, ensuring sharp resolution.

[0176] Figure 9 This is a field curvature distortion diagram of the projection lens proposed in Example 2. The optical distortion in the field curvature distortion is ≤1%, and the image is not significantly deformed.

[0177] Figure 10 This is the vertical chromatic aberration diagram of the projection lens proposed in Example 2. The maximum vertical chromatic aberration is 3.3 μm, which is within 1 pixel and there is no color fringing in the image.

[0178] The second embodiment is applicable to an image source 70 of a 0.2-inch digital micromirror device (DMD), a projection lens with a throw ratio of 1.2, and an aperture value FNO of 1.7.

[0179] Example 3

[0180] The projection lens provided in Example 3 of the present application includes, from the object side to the image side, along the same optical axis, a first lens 11, a second lens 12, a third lens 13, an aperture 30, a fourth lens 21, a fifth lens 22, a sixth lens 23, a seventh lens 24, an optical dither device 40, a beam splitter 50, a light transmission protection device 60, and an image source 70. The relevant parameters of each lens are shown in Table 7:

[0181] Table 7

[0182]

[0183]

[0184] The aspheric coefficients of the first lens 11 and the seventh lens 24 in Example 3 are shown in Table 8:

[0185] Table 8

[0186]

[0187] The main parameters in Example 3 are shown in Table 9:

[0188] Table 9

[0189] L1(mm) L2(mm) H(mm) F(mm) D(mm) FNO L1 / L2 H / L2 L2 / F D / L2 25.97 44.26 8 5.96 11.5 1.8 0.587 0.181 7.43 0.26

[0190] The MTF curve, spot diagram, field curvature distortion, and vertical axis chromatic aberration of the projection lens provided in this embodiment 3 are shown as follows: Figure 11 、 Figure 12 、 Figure 13 and Figure 14 shown.

[0191] The image source pixel size used in this embodiment 3 is 5.4 μm, and the corresponding design resolution is 93 lp / mm.

[0192] from Figure 11 It can be seen from the MTF curve that the projection lens proposed in Example 3 has an MTF greater than 0.58 at a center field of view of 93 lp / mm and an MTF greater than 0.4 at the maximum field of view, which can meet the design requirement of an MTF greater than 0.3 for the light emitting chip.

[0193] Figure 12 This is the spot diagram of the projection lens proposed in Example 3, where the RMS radius is 5 μm, ensuring sharp resolution within 1 pixel.

[0194] Figure 13 This is a field curvature distortion diagram of the projection lens proposed in Example 3. The optical distortion in the field curvature distortion is ≤1%, and the image is not significantly deformed.

[0195] Figure 14 This is the vertical chromatic aberration diagram of the projection lens proposed in Example 3. The maximum vertical chromatic aberration is 2.9 μm, which is within 1 pixel and the image has no color fringing.

[0196] The third embodiment is applicable to an image source 70 having a 0.23-inch digital micromirror device (DMD), a projection lens with a throw ratio of 1.15, and an aperture value FNO of 1.8.

[0197] An embodiment of the present application further provides a projection device, which includes a housing and the projection lens as described above, wherein the projection lens is disposed in the housing.

[0198] The specific structure of the projection lens can be found in the above embodiments.

[0199] Since the projection device of the present application adopts the projection lenses of all the above embodiments, it has at least all the beneficial effects brought by the technical solutions of the above embodiments, which will not be described one by one here.

[0200] The above embodiments focus on 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. Considering the simplicity of the text, they will not be repeated here.

[0201] Although some specific embodiments of the present application have been described in detail by way of example, it should be understood by those skilled in the art that the above examples are for illustration only and are not intended to limit the scope of the present application. It should be understood by those skilled in the art that the above examples may be modified without departing from the scope and spirit of the present application. The scope of the present application is defined by the appended claims.

Claims

1. A projection lens, characterized in that: The projection lens comprises a front lens group (10), a rear lens group (20) and an aperture (30) along the same optical axis from the object side to the image side, wherein the aperture (30) is located between the front lens group (10) and the rear lens group (20); The front lens group (10) includes a first lens (11) closest to the object side, the optical power of the first lens (11) is negative, the front lens group (10) also includes a second lens (12) and a third lens (13) arranged adjacent to each other, two adjacent surfaces of the second lens (12) and the third lens (13) are glued together to form a first glued lens group, and the optical power of the first glued lens group is positive; The rear lens group (20) includes a seventh lens (24) closest to the image side, the optical power of the seventh lens (24) is positive, the rear lens group (20) also includes a fourth lens (21), a fifth lens (22) and a sixth lens (23), the fourth lens (21) and the fifth lens (22) are adjacent and glued together, the two adjacent surfaces of the fourth lens (21) and the fifth lens (22) are glued together to form a second glued lens group, the optical power of the second glued lens group is positive, and the sixth lens (23) is a biconvex lens; The distance between the object side surface of the first lens (11) and the image side surface of the seventh lens (24) is L1, and the distance between the object side surface of the first lens (11) and the imaging surface is L2, and the ratio of L1 to L2 satisfies: L1 / L2≤0.6; The projection lens satisfies: D / L2<0.3, wherein D is the effective optical aperture of the first lens (11).

2. The projection lens according to claim 1, wherein: The projection lens satisfies: H / L2>0.165, where H is the diameter of the imaging circle of the projection lens.

3. The projection lens according to claim 1, wherein: The projection lens satisfies: L2 / F<7.5, where F is the effective focal length of the projection lens.

4. The projection lens according to claim 1, wherein: The aperture value FNO of the projection lens is set to: FNO≤1.

8.

5. The projection lens according to claim 1, wherein: The surfaces of the first lens (11) and the seventh lens (24) are configured as aspherical surfaces.

6. The projection lens according to claim 1, wherein: The first cemented lens group is located between the first lens (11) and the aperture (30).

7. The projection lens according to any one of claims 1 to 6, wherein: Two surfaces of the first lens (11) are even aspheric surfaces, and the optical Abbe number of the first lens (11) is greater than 50.

8. The projection lens according to claim 1, wherein: The optical power of the second lens (12) is negative, and the optical power of the third lens (13) is positive.

9. The projection lens according to claim 1, wherein: The fourth lens (21) is arranged close to the aperture (30), and the sixth lens (23) is located between the second cemented lens group and the seventh lens (24).

10. The projection lens according to claim 1, wherein: Two surfaces of the seventh lens (24) are even aspheric surfaces, and the optical Abbe number of the seventh lens (24) is greater than 50.

11. The projection lens according to claim 1, wherein: The optical power of the fourth lens (21) is positive, and the optical power of the fifth lens (22) is negative; The optical power of the sixth lens (23) is positive.

12. The projection lens according to claim 1, wherein: The projection lens further comprises an optical jitter device (40) and a spectrometer (50), wherein the optical jitter device (40) and the spectrometer (50) are sequentially arranged between the rear lens group and the imaging surface along the optical axis; Wherein, the optical jitter device (40) includes a galvanometer mirror.

13. A projection device, characterized in that: The projection device comprises: a housing; and The projection lens according to any one of claims 1 to 12, wherein the projection lens is disposed in the housing.

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