Projection lens and projection system

Abstract

The invention discloses a projection lens and a projection system, and the projection lens comprises two lens groups which are respectively located at two sides of a diaphragm, the first lens group comprises six lenses, and the second lens group comprises five lenses. The length of the projection lens can be controlled within 200mm by reasonably optimizing the surface type of each lens, and the size of an optical engine is greatly reduced. Meanwhile, the projection ratio of the projection lens is 0.5, large-angle projection can be achieved, the chromatic aberration is smaller than 0.3 pixel, a picture still has small distortion under the large size, and the resolution range of 80-200 inches can be achieved while other optical performance is kept.

Description

Technical Field

[0001] The present invention relates to the field of projection technology, and in particular to a projection lens and a projection system. Background Art

[0002] Projection display technology is a technology that uses optical systems and projection space to magnify and display image information. The projection system uses an optical imaging system to display images. The projection lens greatly affects the application scenario and imaging quality of the projection system. The size of the projection lens also affects the volume of the optical engine.

[0003] With the rapid development of projection technology, its application demand patterns are becoming more and more diverse. In order to meet the needs of different application scenarios, in some cases it is necessary to reduce the size of the projection lens, thereby reducing the overall volume of the optical engine. For projection display products, how to maintain a better resolution while displaying large-size images is a problem worthy of attention. Summary of the invention

[0004] According to a first aspect of an embodiment of the present invention, there is provided a projection lens comprising: an aperture, and a first lens group and a second lens group respectively located on both sides of the aperture; the first lens group comprises six lenses, and the second lens group comprises five lenses;

[0005] The projection lens meets the following requirements:

[0006] 2 <f / tan(Semi-FOV)<3;

[0007] Wherein, f represents the effective focal length of the projection lens, and Semi-FOV represents the maximum half field of view angle of the projection lens.

[0008] In some embodiments of the present invention, the first lens group includes: a first lens, a second lens, a third lens, a fourth lens, a fifth lens and a sixth lens coaxially arranged in a direction gradually approaching the aperture stop;

[0009] The refractive power of the first lens is negative, the refractive power of the second lens is negative, the refractive power of the third lens is negative, the refractive power of the fourth lens is positive, the refractive power of the fifth lens is positive, and the refractive power of the sixth lens is negative;

[0010] The first lens is a non-lens surface lens, and the second lens, the third lens, the fourth lens, the fifth lens and the sixth lens are all spherical lenses.

[0011] In some embodiments of the present invention, the curvature radii of the first lens and the second lens satisfy:

[0012] 0.3 <R2 / (R1+R3)<0.7;

[0013] Wherein, R2 represents the curvature radius of the object-side surface of the first lens, R1 represents the curvature radius of the image-side surface of the first lens, and R3 represents the curvature radius of the image-side surface of the second lens.

[0014] In some embodiments of the present invention, the first lens satisfies:

[0015] 50≤sd≤58;

[0016] Wherein, sd represents the maximum aperture of the first lens.

[0017] The second lens satisfies:

[0018] 0.2≤|ct45 / et45|≤0.5;

[0019] f45≤-30;

[0020] Among them, ct45 represents the center thickness of the second lens along the optical axis, et45 represents the edge thickness of the second lens along the optical axis, and f45 represents the focal length of the second lens.

[0021] In some embodiments of the present invention, the refractive powers of adjacent surfaces of the second lens and the third lens are symmetrically arranged; and the refractive powers of adjacent surfaces of the fourth lens and the fifth lens are symmetrically arranged.

[0022] In some embodiments of the present invention, the second lens group includes: a seventh lens, an eighth lens, a ninth lens, a tenth lens and an eleventh lens coaxially arranged along a direction in which the aperture stops away from the first lens group;

[0023] The refractive power of the seventh lens is negative, the refractive power of the eighth lens is positive, the refractive power of the ninth lens is negative, the refractive power of the tenth lens is positive, and the refractive power of the eleventh lens is positive;

[0024] The tenth lens is a non-lens surface lens, and the seventh lens, the eighth lens, the ninth lens and the eleventh lens are all spherical lenses.

[0025] In some embodiments of the present invention, the seventh lens, the eighth lens and the ninth lens are glued to each other;

[0026] The refractive index of the seventh lens is greater than that of the eighth lens, and the refractive index of the eighth lens is less than that of the ninth lens.

[0027] In some embodiments of the present invention, the refractive index of the second lens and the third lens is greater than the refractive index of other lenses in the projection lens.

[0028] In some embodiments of the present invention, the projection lens satisfies:

[0029] 0.2≤(CTmin+CTmax) / ∑CT≤0.4;

[0030] Wherein, CTmin represents the minimum value of the center thickness of the lenses from the first lens to the eleventh lens, CTmax represents the maximum value of the center thickness of the lenses from the first lens to the eleventh lens, and ΣCT represents the sum of the center thicknesses of all lenses in the projection lens.

[0031] According to a second aspect of an embodiment of the present invention, a projection system is provided, comprising:

[0032] Projection light source;

[0033] An illumination system, located at the light-emitting side of the projection light source; the illumination system comprises a light modulator;

[0034] A projection lens, wherein the projection lens is any of the above-mentioned projection lenses; the projection lens is located at the light-emitting side of the light modulator.

[0035] The projection lens and projection system provided by the embodiment of the present invention include two lens groups respectively located on both sides of the aperture, the first lens group includes six lenses, and the second lens group includes five lenses. By reasonably optimizing the surface shape of each lens, the length of the projection lens can be controlled within 200 mm, greatly reducing the size of the optical engine. At the same time, the projection ratio of the projection lens is 0.5, which can achieve large-angle projection, the chromatic aberration is less than 0.3 pixel, and the picture still has small distortion at a large size. While maintaining other optical properties, the resolution range of 80-200 inches can be achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for use in the embodiments of the present invention will be briefly introduced below. Obviously, the accompanying drawings introduced below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0037] Figure 1 A schematic diagram of the structure of a projection system provided by an embodiment of the present invention;

[0038] Figure 2 A schematic diagram of the imaging principle of a projection device provided by an embodiment of the present invention;

[0039] Figure 3 A schematic diagram of the structure of a projection lens provided in an embodiment of the present invention;

[0040] Figure 4 An optical path diagram of a projection lens provided by an embodiment of the present invention;

[0041] Figure 5 A modulation transfer function curve diagram of a projection lens provided by an embodiment of the present invention;

[0042] Figure 6 A defocus curve diagram of a projection lens provided by an embodiment of the present invention;

[0043] Figure 7 A spot diagram of a projection lens provided by an embodiment of the present invention;

[0044] Figure 8 A vertical axis chromatic aberration diagram of the projection lens provided by an embodiment of the present invention;

[0045] Fig. 9 Axial chromatic aberration diagram of the projection lens provided by an embodiment of the present invention;

[0046] Fig.10 A schematic diagram of a field curvature curve of a projection lens provided by an embodiment of the present invention;

[0047] Fig.11 A schematic diagram of a distortion curve of a projection lens provided by an embodiment of the present invention;

[0048] Fig.12 A schematic diagram of a telecentricity curve provided by an embodiment of the present invention;

[0049] Fig.13 One of the aberration curve diagrams of the projection lens provided by the embodiment of the present invention;

[0050] Fig.14 A second aberration curve diagram of the projection lens provided by an embodiment of the present invention;

[0051] Fig.15 The third aberration curve diagram of the projection lens provided by the embodiment of the present invention. DETAILED DESCRIPTION

[0052] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and understandable, the present invention will be further described below with reference to the accompanying drawings and examples. However, the exemplary embodiments can be implemented in various forms and should not be understood as being limited to the embodiments described herein; on the contrary, these embodiments are provided to make the present invention more comprehensive and complete, and to fully convey the concepts of the exemplary embodiments to those skilled in the art. The same figure marks in the figures represent the same or similar structures, and thus their repeated descriptions will be omitted. The words expressing position and direction described in the present invention are all explained using the accompanying drawings as examples, but changes can be made as needed, and the changes made are all included in the scope of protection of the present invention. The drawings of the present invention are only used to illustrate the relative position relationship and do not represent the true proportions.

[0053] Projection display technology is a technology that uses optical systems and projection space to magnify and display image information. The projection system is an optical imaging system that ultimately displays the image. With the continuous development of projection technology, laser projection systems have been widely used in large-screen displays, laser TVs, digital cinemas, portable projection displays, and other fields due to their unique advantages. Laser projection display can display more realistic and gorgeous dynamic images on ultra-large screens, achieving visual shock effects that other display technologies cannot achieve.

[0054] Figure 1 A schematic diagram of the structure of a projection system provided by an embodiment of the present invention.

[0055] like Figure 1 As shown, in actual application, the front projection system may include: a projection device 100 and a projection screen 200 .

[0056] The projection screen 200 is located on the light emitting side of the projection device 100. The audience faces the projection screen 200. The projection device 100 emits projection light, which is incident on the projection screen 200 and reflected toward the audience's position through the projection screen 200, so that the audience can view the projected image.

[0057] The projection device is provided with a projection lens, and the specifications of the projection lens will affect the size of the projection image and the projection distance. In actual applications, ultra-short-throw, short-throw or long-throw projection lenses are used according to different application scenarios.

[0058] Figure 2 A schematic diagram of the imaging principle of a projection device provided in an embodiment of the present invention.

[0059] like Figure 2 As shown, the projection device includes: a projection light source 1, an illumination system 2 and a projection lens 3. The illumination system 2 is located at the light-emitting side of the projection light source 1, and a light modulator 21 is provided in the illumination system 2. The light modulator 21 is used to modulate the incident light before emitting it, and the projection lens 3 is located at the light-emitting side of the light modulator 21.

[0060] The projection light source 1 can be a light emitting diode (LED) light source or a laser light source. LED light sources have the advantages of low power consumption, small size, and long life, and are suitable for application scenarios such as small-size projection. Laser light sources have higher brightness and better color saturation, and can optimize the display effect of the projected image.

[0061] In an embodiment of the present invention, a laser light source may be used as a projection light source. The laser light source may be a monochromatic laser or a laser that can emit lasers of multiple colors or multiple lasers that emit lasers of different colors. When a monochromatic laser is used as the laser light source, the laser display device also needs to be provided with a color wheel, which is used for color conversion. The monochromatic laser cooperates with the color wheel to achieve the purpose of emitting primary color lights of different colors in a time sequence. When a laser light source is used that can emit lasers of multiple colors, it is necessary to control the laser light source to emit lasers of different colors as primary color lights in a time sequence. The use of a three-color laser light source is conducive to improving the color gamut of the projected image, has better color expression, and can accurately reproduce the input image.

[0062] The illumination system 2 is located at the light-emitting side of the projection light source 1. On the one hand, the illumination system 2 collimates and homogenizes the emitted light of the projection light source 1, and on the other hand, it enables the emitted light of the projection light source 1 to be incident on the light modulator 21 at a suitable angle. The illumination system 2 may include a plurality of lenses or lens groups, light guides, diffusers, diffuser wheels and other components, which are not limited here.

[0063] The light modulator 21 is used to modulate the incident light to form an image. In a specific implementation, the light modulator 21 can be a transmission light modulator or a reflection light modulator. Figure 2 The light modulator 21 shown is a reflective light modulator. The light modulator 21 receives the light reflected by the beam splitter prism P, modulates the incident light, and reflects the modulated light. Since the light path is folded back through the reflective light modulator, the volume of the projection device can be reduced.

[0064] In the embodiment of the present invention, the light modulator 21 may be Liquid Crystal on Silicon (LCoS) or a Digital Micromirror Device (DMD).

[0065] LCoS is based on semiconductor technology, which combines a complementary metal oxide semiconductor (CMOS) substrate with a glass substrate containing transparent electrodes, and then injects liquid crystal packaging. LCoS has the characteristics of high aperture ratio and high resolution of each pixel, and can form high-resolution images.

[0066] The DMD includes a large number of tiny reflectors, each of which can be driven individually to deflect. By controlling the deflection angle of the DMD, the brightness of the light incident on the projection lens 3 is controlled.

[0067] The beam splitter P is used to separate the illumination beam and the imaging beam. The beam emitted by the projection light source is shaped and homogenized and finally reflected toward the light modulator 21 by the beam splitter P. The light emitted after being modulated by the light modulator 21 passes through the beam splitter P and enters the projection lens 3 and is emitted.

[0068] In a specific implementation, an image shift component Z may be further provided on the light output side of the light modulator 21. The image polarization component Z may generally be made of flat glass. Image shift may be achieved through high-frequency vibration, thereby realizing high-resolution image display.

[0069] After the light modulator 21 modulates the incident light to form an image, the light is reflected toward the projection lens 3, which forms an image, thereby projecting the image to a suitable size for viewing.

[0070] The spectral range of the projection system using a three-color laser light source as the projection light source becomes larger. Under the premise of ensuring the image quality, it becomes increasingly important to achieve small chromatic aberration. At the same time, for large-size projected images, keeping their distortion within a smaller range can effectively improve the viewing experience.

[0071] Figure 3 A schematic diagram of the structure of a projection lens provided in an embodiment of the present invention; Figure 4 This is a light path diagram of a projection lens provided in an embodiment of the present invention.

[0072] like Figure 3 As shown, the projection lens includes a first lens group 31, an aperture s, and a second lens group 32 arranged coaxially; wherein the first lens group 31 and the second lens group 32 are respectively located on both sides of the aperture s. The first lens group 31 includes six lenses, and the second lens group 32 includes five lenses; and the projection lens satisfies:

[0073] 2 <f / tan(Semi-FOV)<3;

[0074] Wherein, f represents the effective focal length of the projection lens, and Semi-FOV represents the maximum half field of view angle of the projection lens.

[0075] The projection lens provided in the embodiment of the present invention includes only two lens groups. By limiting the focal length and the field of view angle within the above range, the contribution of each lens to the optical focal length can be effectively distributed, which is conducive to balancing aberrations and meeting the requirements of both wide angle and high image quality. At the same time, a smaller lens size can be ensured to meet the requirements of lens miniaturization.

[0076] Specifically, Figure 3As shown, the first lens group 31 includes: a first lens l1, a second lens l2, a third lens l3, a fourth lens l4, a fifth lens l5 and a sixth lens l6 coaxially arranged along a direction gradually approaching the aperture s. The second lens group 32 includes: a seventh lens l7, an eighth lens l8, a ninth lens l9, a tenth lens l10 and an eleventh lens l11 coaxially arranged along a direction away from the aperture s from the first lens group 31.

[0077] According to the propagation direction of the light, the light modulated by the light modulator 21 passes through the dichroic prism P, enters from the side of the eleventh lens l11, and exits from the side of the first lens l1 after passing through eleven lenses in sequence. Therefore, when the projection lens is used, the side close to the light modulator 21 is the object side, and the side close to the projection screen is the image side. When performing optical design, the final imaging position is used as the object plane, and the light exit surface of the light modulator 21 is used as the image plane to optimize the design of each lens in the projection lens, and then the reversible nature of the optical path is used to achieve projection imaging.

[0078] In the following, the surface of the lens close to the light modulator 21 is referred to as the object side surface, and the surface of the lens close to the projection screen is referred to as the image side surface. The overall refractive power of the first lens L1 is negative, the refractive power of the image-side surface of the first lens L1 is negative, and the refractive power of the object-side surface of the first lens L1 is positive; the overall refractive power of the second lens L2 is negative, the refractive power of the image-side surface of the second lens L2 is negative, and the refractive power of the object-side surface of the second lens L2 is negative; the overall refractive power of the third lens L3 is negative, the refractive power of the image-side surface of the third lens L3 is negative, and the refractive power of the object-side surface of the third lens L3 is negative; the overall refractive power of the fourth lens L4 is positive, the refractive power of the image-side surface of the fourth lens L4 is negative, and the refractive power of the object-side surface of the fourth lens L4 is positive; the overall refractive power of the fifth lens L5 is positive, the refractive power of the image-side surface of the fifth lens L5 is positive, and the refractive power of the object-side surface of the fifth lens L5 is positive; the overall refractive power of the sixth lens L6 is negative, and the refractive power of the image-side surface of the sixth lens L6 is negative. is positive, and the object-side surface of the sixth lens element l6 is negative; the overall refractive power of the seventh lens element l7 is negative, the image-side surface of the seventh lens element l7 is positive, and the object-side surface of the seventh lens element l7 is negative; the overall refractive power of the eighth lens element l8 is positive, the image-side surface of the eighth lens element l8 is positive, and the object-side surface of the eighth lens element l8 is positive; the overall refractive power of the ninth lens element l9 is negative, the image-side surface of the ninth lens element l9 is negative, and the object-side surface of the ninth lens element l9 is negative; the overall refractive power of the tenth lens element l10 is positive, the image-side surface of the tenth lens element l10 is positive, and the object-side surface of the tenth lens element l10 is positive; the overall refractive power of the eleventh lens element l11 is positive, the image-side surface of the eleventh lens element l11 is positive, and the object-side surface of the eleventh lens element l11 is positive.

[0079] Among them, the first lens l1 and the tenth lens l10 are non-lens surface lenses, and the second lens l2, the third lens l3, the fourth lens l4, the fifth lens l5, the sixth lens l6, the seventh lens l7, the eighth lens l8, the ninth lens l9 and the eleventh lens l11 are all spherical lenses.

[0080] The projection lens only needs two aspherical lenses, and both aspherical lenses can be glass aspherical lenses. By optimizing the surface of each lens, the length of the projection lens can be controlled within 200mm, greatly reducing the size of the optical engine. At the same time, the projection ratio of the projection lens is 0.5, which can achieve large-angle projection, and the chromatic aberration is less than 0.3pixel. The picture still has small distortion at a large size, and the resolution range of 80-200 inches can be achieved while maintaining other optical properties.

[0081] Specifically, the first lens l1 satisfies:

[0082] 50≤sd≤58;

[0083] Wherein, sd represents the maximum aperture of the first lens l1.

[0084] Since the design specification of the projection ratio of the projection lens provided by the embodiment of the present invention is 0.5 and the angle of the emitted light is relatively large, the first lens l1 plays the role of expanding the angle of the emitted light, thereby achieving the projection ratio specification of 0.5 while maintaining a relatively small aperture.

[0085] The second lens l2 satisfies:

[0086] 0.2≤|ct45 / et45|≤0.5;

[0087] f45≤-30;

[0088] Wherein, ct45 represents the center thickness of the second lens L2 along the optical axis, et45 represents the edge thickness of the second lens L2 along the optical axis, and f45 represents the focal length of the second lens L2.

[0089] In the embodiment of the present invention, the refractive index of the second lens 12 and the third lens 13 is greater than the refractive index of other lenses in the projection lens, and is used to deflect the angle of light to avoid the angle of light in the optical system being too large, which causes the first lens to be too large and causes processing difficulties. At the same time, the second lens 12 and the third lens 13 also play a role of a certain negative focal length, which is conducive to the projection lens to achieve a larger field of view. The refractive index of the second lens 12 is relatively large, which can effectively control the angle of light emission and reduce the height of the light. By limiting the parameters of the second lens 12 within the above range, the aperture of the second lens 12 will not be too large, which will cause processing difficulties.

[0090] The curvature radius of the first lens l1 and the second lens l2 satisfy:

[0091] 0.3 <R2 / (R1+R3)<0.7;

[0092] Wherein, R2 represents the curvature radius of the object-side surface of the first lens l1, R1 represents the curvature radius of the image-side surface of the first lens l1, and R3 represents the curvature radius of the image-side surface of the second lens l2.

[0093] By controlling the curvature radius of the image side surface of the first lens L1, the curvature radius of the object side surface, and the curvature radius of the image side surface of the second lens within the above range, it is helpful to increase the light emission angle. With the combination of the low refractive index of the first lens L1 and the high refractive index of the second lens L2, the projection lens can have a larger field of view, achieve a smaller projection ratio of the projection lens, and reduce the aberration of the edge field of view, thereby improving the image quality.

[0094] In the embodiment of the present invention, the diopter of the adjacent surfaces of the second lens 12 and the third lens 13 is symmetrically arranged; the diopter of the adjacent surfaces of the fourth lens 14 and the fifth lens 15 is symmetrically arranged. In this way, when the light enters the second lens 12 and the third lens 13, the fourth lens 14 and the fifth lens 15, it will not be sharply deflected, which is conducive to the control of the height of the light, and the angle of the light will not be too large, which can avoid the problems of stray light ghost image caused by the excessively large angle of the light.

[0095] The seventh lens 17, the eighth lens 18 and the ninth lens 19 are cemented together to form a triplet lens, and the refractive index of the seventh lens 17 is greater than the refractive index of the eighth lens 18, and the refractive index of the eighth lens 18 is less than the refractive index of the ninth lens 19. The triplet lens can effectively reduce the chromatic aberration of the optical system, balance the field curvature, and improve the overall performance of the optical system.

[0096] Projection lens meets:

[0097] 0.2≤(CTmin+CTmax) / ∑CT≤0.4;

[0098] Wherein, CTmin represents the minimum value of the center thickness of all lenses in the projection lens, CTmax represents the maximum value of the center thickness of all lenses in the projection lens, and ΣCT represents the sum of the center thickness of all lenses in the projection lens.

[0099] Limiting the center thickness of each lens in the projection lens within the above range can control the overall uniformity of each lens, so that the center thickness of each lens can be reasonably distributed, and the phenomenon of a certain lens being too thick or too thin will not occur. At the same time, the chromatic aberration and distortion of the optical system can also be effectively balanced, and the problem of processing difficulties caused by lenses being too thin or too thick can also be avoided.

[0100] By designing the surface shapes and combinations of eleven lenses in the projection lens, the embodiment of the present invention can make the projection ratio of the projection lens 0.5, the total length of the projection lens only 200 mm, the F.NO of the projection lens 2.0, and have a strong light-collecting ability and a large luminous flux.

[0101] The surface parameters of each optical component in the projection lens provided by the embodiment of the present invention and the spacing between the optical components are shown in the following table:

[0102] Face number Face type Radius of curvature thickness Material Semi-aperture Spherical 1.00E+18 1550 refraction Spherical 1.00E+18 1 refraction 40.28867 L1 Aspheric -20.7465 12 496998.8159 refraction 57.99999 Aspheric -70.3575 21.40367 refraction 24.96678 L2 Spherical -154.644 2 922866.2088 refraction 14.9984 Spherical 39.70368 17.9298 refraction 13.77476 L3 Spherical -38.2451 2 743972.4485 refraction 12.94702 Spherical 108.0372 12.02679 refraction 13.59412 L4 Spherical -546.544 9.696264 805201.2558 refraction 17.26053 Spherical -46.1404 0.2 refraction 26.41101 L5 Spherical 59.54968 8.975024 672887.319 refraction 18.46916 Spherical -348.786 0.2 refraction 17.75518 L6 Spherical 48.35828 2 755201.2758 refraction 16.80643 Spherical 32.29066 80.57605 refraction 15.84601 Spherical 1.00E+18 10.22865 refraction 6.199091 L7 Spherical 22.17664 2 647693.3384 refraction 7.2065 L8 Spherical 14.00657 5.723098 496998.8159 refraction 7.031687 L9 Spherical -14.1205 3.862302 799519.4225 refraction 7.009371 Spherical 35.01856 0.327909 refraction 7.743556 L10 Spherical 55.89885 3.199314 497103.8156 refraction 7.743543 Aspheric -39.9955 0.3 refraction 8.184074 L11 Spherical 51.62656 5.351135 670031.472 refraction 8.670356 Spherical -19.7102 1 refraction 8.917412 Spherical 1.00E+18 2 523014.5859 refraction 8.34251 Spherical 1.00E+18 4 refraction 8.104096 Spherical 1.00E+18 21.8 516800.6417 refraction 7.369281 Spherical 1.00E+18 2 refraction 4.759213 Spherical 1.00E+18 1.1 516797.6421 refraction 4.391806 Spherical 1.00E+18 0.705151 refraction 4.260105 Spherical 1.00E+18 0 refraction 4.130566

[0103] Based on the above parameters, the projection lens is a short-focus lens with a projection ratio of 0.5, an effective focal length of 3.88mm, an offset of 100% to 102%, a resolution of 93lp / mm, a projection size of 80 inches to 200 inches, and a color difference of <0.3pixel.

[0104] The embodiment of the present invention also evaluates the image quality of the projection lens based on the above parameter optimization results.

[0105] Figure 5 A modulation transfer function curve diagram of the projection lens provided by an embodiment of the present invention.

[0106] Figure 5 The figure shows the Modulation Transfer Function (MTF) curves of light with wavelengths of 643nm, 525nm, and 465nm in different fields of view, where the horizontal axis represents the spatial frequency, expressed in cycles per millimeter in the image space, and the unit is cycles / mm, and the vertical axis represents the MTF value (Modulation). MTF can characterize the resolution of the resolution lens. Figure 5 It can be seen that the MTF values ​​of the light are all above 0.6 and the curve is relatively flat, indicating that the imaging difference between the edge and the center of the projection lens is small and the imaging quality is good.

[0107] Figure 6 This is a defocus curve diagram of the projection lens provided by an embodiment of the present invention.

[0108] Figure 6 The defocus curves of light with wavelengths of 643nm, 525nm, and 465nm in different fields of view when the spatial frequency is 93.0 cycles / mm are shown, where the abscissa represents the defocusing position (Defocusing Position), in mm, and the ordinate represents the MTF value (Modulation). Figure 6It can be seen that the MTF values ​​of the light at the optical axis are all above 0.6, and the image plane shift degree is within a reasonable range.

[0109] Figure 7 A spot diagram of a projection lens provided by an embodiment of the present invention.

[0110] The spot diagram can reflect the clarity of the image. The more concentrated the points in the diagram are, the less smear and the better the sharpness of the projection lens. Figure 7 It can be seen that the image formed by the projection lens in different fields of view can be within a reasonable range. Figure 7 The data on the left side are different fields of view, the middle is the spot size diagram corresponding to different fields of view, and the data on the right are the imaging radius corresponding to each spot size diagram, where RMS represents the root mean square radius, and 100% represents the imaging radius when the image is fully displayed.

[0111] Figure 8 A diagram of vertical axis chromatic aberration of the projection lens provided by an embodiment of the present invention.

[0112] Figure 8 The figure shows the lateral chromatic aberration of light with wavelengths of 643nm, 525nm and 465nm at different imaging sizes within a certain field of view, where the horizontal axis represents the lateral chromatic aberration (Lateral colour) in μm and the vertical axis represents the actual imaging size (Image real size) in mm. The maximum lateral chromatic aberration of the projection lens is 1.85μm.

[0113] Fig. 9 Axial chromatic aberration diagram of the projection lens provided by an embodiment of the present invention.

[0114] Fig. 9 The axial chromatic aberration of light with wavelengths of 643nm, 525nm and 465nm is shown. Fig. 9 It can be seen that the intervals between the curves corresponding to the three wavelengths are small, indicating that the axial chromatic aberration of the projection lens is small and meets the requirements.

[0115] Fig.10 A schematic diagram of a field curvature curve of a projection lens provided by an embodiment of the present invention.

[0116] Fig.10 The figure shows the field curvature curves of the projection lens in the meridian direction (T) and the sagittal direction (S) under different fields of view, where the horizontal axis represents the field curvature size in mm, and the vertical axis represents the image height (field of view). Fig.10 It can be seen that the field curvature of the projection lens is controlled within 0.025mm.

[0117] Fig.11 A schematic diagram of a distortion curve of a projection lens provided by an embodiment of the present invention.

[0118] Fig.11 The distortion curve of the projection lens under different fields of view is shown in FIG. 1 , where the horizontal axis represents the distortion percentage of the image and the vertical axis represents the image height (field of view). Fig.10 It can be seen that the distortion of the projection lens is controlled within 0.5%.

[0119] Fig.12 A schematic diagram of a telecentricity curve provided in an embodiment of the present invention.

[0120] Fig.12 The telecentricity bar graph of the DMD outgoing light under different fields of view is shown, where the horizontal axis represents the size of the field of view, and the vertical axis represents the angle of the outgoing light corresponding to different fields of view, i.e., the telecentricity. The specific data are shown in the following table. It can be seen that the telecentricity is less than 0.8 degrees and increases evenly without recurvature, and the system performance is good.

[0121] Field of view (Y) 0.00Y 0.10Y 0.20Y 0.30Y 0.40Y 0.50Y 0.60Y 0.70Y 0.80Y 0.90Y 1.00Y Telecentricity 0.00 0.08 0.17 0.25 0.33 0.41 0.48 0.56 0.63 0.70 0.78

[0122] Figure 13 to Figure 15 The aberration curve of the projection lens provided by the embodiment of the present invention.

[0123] Figure 13 to Figure 15 The aberration curves of the light with wavelengths of 643nm, 525nm, and 465nm in 12 normalized fields of view along the tangential and sagittal directions are shown. The smaller the fluctuation of the curve and the closer it is to the horizontal line, the smaller the aberration. Figure 13 to Figure 15 It can be seen that the projection lens has small aberration and good imaging quality.

[0124] Based on the same inventive concept, an embodiment of the present invention further provides a projection system, such as Figure 1 As shown, the projection system may include a projection device 100 and a projection screen 200, and the projection device may include any of the above-mentioned projection lenses. The projection lens may be applied to a three-color laser projection system, and under the premise of ensuring that the total length of the lens is 200 mm, the design indicator of a color difference of less than 0.3 pixel is achieved, and the projection picture still has small distortion at a large size.

[0125] According to the first invention concept, the projection lens includes two lens groups located on both sides of the aperture, the first lens group includes six lenses, and the second lens group includes five lenses. By reasonably optimizing the surface of each lens, the length of the projection lens can be controlled within 200mm, greatly reducing the size of the optical engine. At the same time, the projection ratio of the projection lens is 0.5, which can achieve large-angle projection, the chromatic aberration is less than 0.3pixel, and the picture still has small distortion at a large size. While maintaining other optical properties, it can achieve a resolution range of 80-200 inches.

[0126] According to the second inventive concept, the projection lens satisfies: 2 < f / tan(Semi-FOV) < 3; where f represents the effective focal length of the projection lens, and Semi-FOV represents the maximum semi-field angle of the projection lens. By limiting the focal length and the field angle within the above ranges, the contribution of each lens to the optical power can be effectively distributed, which is beneficial to balancing aberrations, meeting the requirements of both wide angle and high image quality, and at the same time ensuring a smaller lens size to meet the requirement of lens miniaturization.

[0127] According to the third inventive concept, the first lens group includes: a first lens, a second lens, a third lens, a fourth lens, a fifth lens, and a sixth lens coaxially arranged along the direction gradually approaching the aperture. The second lens group includes: a seventh lens, an eighth lens, a ninth lens, a tenth lens, and an eleventh lens coaxially arranged along the direction in which the aperture is away from the first lens group.

[0128] According to the fourth inventive concept, the first lens and the tenth lens are aspherical lenses, and the second lens, the third lens, the fourth lens, the fifth lens, the sixth lens, the seventh lens, the eighth lens, the ninth lens, and the eleventh lens are all spherical lenses.

[0129] According to the fifth inventive concept, the first lens satisfies: 50 ≤ sd ≤ 58; where sd represents the maximum aperture of the first lens. The first lens plays the role of expanding the angle of the outgoing light, and realizes a projection ratio specification of 0.5 while maintaining a smaller aperture.

[0130] According to the sixth inventive concept, the second lens satisfies: 0.2 ≤ |ct45 / et45| ≤ 0.5; f45 ≤ -30; where ct45 represents the central thickness of the second lens along the optical axis direction, et45 represents the edge thickness of the second lens along the optical axis direction, and f45 represents the focal length of the second lens. By limiting the parameters of the second lens within the above ranges, the aperture of the second lens can be prevented from being too large, which may cause processing difficulties.

[0131] According to the seventh inventive concept, the refractive indices of the second lens and the third lens are greater than those of the other lenses in the projection lens, which are used to deflect the light angle, avoiding the first lens being too large due to too large light angles in the optical system, resulting in processing difficulties. At the same time, the second lens and the third lens also play a role in bearing a certain amount of negative optical power, which is beneficial to the projection lens to achieve a larger field angle.

[0132] According to the eighth inventive concept, the radii of curvature of the first lens and the second lens satisfy: 0.3 < R2 / (R1 + R3) < 0.7; where, R2 represents the radius of curvature of the object-side surface of the first lens, R1 represents the radius of curvature of the image-side surface of the first lens, and R3 represents the radius of curvature of the image-side surface of the second lens. By controlling the radius of curvature of the image-side surface, the radius of curvature of the object-side surface of the first lens, and the radius of curvature of the image-side surface of the second lens within the above range, it helps to increase the light-emitting angle. Combining the low refractive index of the first lens and the high refractive index of the second lens can enable the projection lens to have a larger field of view angle, achieve a smaller projection ratio of the projection lens, and at the same time reduce the aberration of the marginal field of view and improve the image quality.

[0133] According to the ninth inventive concept, the diopters of the adjacent surfaces of the second lens and the third lens are symmetrically arranged; the diopters of the adjacent surfaces of the fourth lens and the fifth lens are symmetrically arranged. This is beneficial to the control of the light height, and the light angle will not be too large, which can avoid problems such as stray light ghosts caused by too large light angles.

[0134] According to the tenth inventive concept, the seventh lens, the eighth lens, and the ninth lens are mutually cemented to form a triple cemented lens, and the refractive index of the seventh lens is greater than that of the eighth lens, and the refractive index of the eighth lens is less than that of the ninth lens. The triple cemented lens can effectively reduce the chromatic aberration of the optical system, balance the field curvature, and improve the overall performance of the optical system.

[0135] According to the eleventh inventive concept, the projection lens satisfies: 0.2 ≤ (CTmin + CTmax) / ∑CT ≤ 0.4; where, CTmin represents the minimum value of the center thickness among all the lenses of the projection lens, CTmax represents the maximum value of the center thickness among all the lenses of the projection lens, and ∑CT represents the sum of the center thicknesses of all the lenses in the projection lens. Limiting the center thicknesses of the lenses in the projection lens within the above range can control the overall uniformity of each lens, make the center thicknesses of each lens be reasonably distributed, and prevent the phenomenon that a certain lens is too thick or too thin. At the same time, the chromatic aberration and distortion of the optical system can also be effectively balanced, and the problem of difficult processing caused by too thin or too thick lenses is also avoided.

[0136] According to the twelfth inventive concept, in the embodiment of the present invention, by designing the surface types and their combination modes of the eleven lenses in the projection lens, the projection ratio of the projection lens can be 0.5, the total length of the projection lens is only 200 mm, and the F.NO of the projection lens is 2.0, having a strong light-gathering ability and a large light flux.

[0137] Although the preferred embodiments of the present invention have been described, those skilled in the art may make other changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0138] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A projection lens, It is characterized in that include: An aperture, and a first lens group and a second lens group respectively located on both sides of the aperture; The first lens group includes six lenses, and the second lens group includes five lenses; The projection lens meets the following requirements: 2 <f / tan(Semi-FOV)<3; Wherein, f represents the effective focal length of the projection lens, and Semi-FOV represents the maximum half field of view angle of the projection lens.

2. The projection lens according to claim 1, It is characterized in that The first lens group comprises: a first lens, a second lens, a third lens, a fourth lens, a fifth lens and a sixth lens coaxially arranged in a direction gradually approaching the aperture stop; The refractive power of the first lens is negative, the refractive power of the second lens is negative, the refractive power of the third lens is negative, the refractive power of the fourth lens is positive, the refractive power of the fifth lens is positive, and the refractive power of the sixth lens is negative; The first lens is a non-lens surface lens, and the second lens, the third lens, the fourth lens, the fifth lens and the sixth lens are all spherical lenses.

3. The projection lens according to claim 2, It is characterized in that The curvature radii of the first lens and the second lens satisfy: 0.3 <R2 / (R1+R3)<0.7; Wherein, R2 represents the curvature radius of the object-side surface of the first lens, R1 represents the curvature radius of the image-side surface of the first lens, and R3 represents the curvature radius of the image-side surface of the second lens.

4. The projection lens according to claim 2, It is characterized in that The first lens satisfies: 50≤sd≤58; Wherein, sd represents the maximum aperture of the first lens; The second lens satisfies: 0.2≤|ct45 / et45|≤0.5; f45≤-30； Among them, ct45 represents the center thickness of the second lens along the optical axis, et45 represents the edge thickness of the second lens along the optical axis, and f45 represents the focal length of the second lens.

5. The projection lens according to claim 2, It is characterized in that The refractive powers of adjacent surfaces of the second lens and the third lens are symmetrically arranged; the refractive powers of adjacent surfaces of the fourth lens and the fifth lens are symmetrically arranged.

6. The projection lens according to claim 2, It is characterized in that The second lens group comprises: a seventh lens, an eighth lens, a ninth lens, a tenth lens and an eleventh lens coaxially arranged along a direction in which the aperture stops away from the first lens group; The refractive power of the seventh lens is negative, the refractive power of the eighth lens is positive, the refractive power of the ninth lens is negative, the refractive power of the tenth lens is positive, and the refractive power of the eleventh lens is positive; The tenth lens is a non-lens surface lens, and the seventh lens, the eighth lens, the ninth lens and the eleventh lens are all spherical lenses.

7. The projection lens according to claim 6, It is characterized in that The seventh lens, the eighth lens and the ninth lens are glued to each other; The refractive index of the seventh lens is greater than that of the eighth lens, and the refractive index of the eighth lens is less than that of the ninth lens.

8. The projection lens according to claim 6, It is characterized in that The refractive indexes of the second lens and the third lens are greater than the refractive indexes of other lenses in the projection lens.

9. The projection lens according to claim 7, It is characterized in that The projection lens meets the following requirements: 0.2≤(CTmin+CTmax) / ∑CT≤0.4; Wherein, CTmin represents the minimum value of the center thickness of the lenses from the first lens to the eleventh lens, CTmax represents the maximum value of the center thickness of the lenses from the first lens to the eleventh lens, and ΣCT represents the sum of the center thicknesses of all lenses in the projection lens.

10. A projection system, It is characterized in that include: Projection light source; An illumination system, located at the light-emitting side of the projection light source; the illumination system comprises a light modulator; A projection lens, wherein the projection lens is the projection lens according to any one of claims 1 to 9; the projection lens is located on the light output side of the light modulator.

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