Projection lens and projection system

Abstract

The invention discloses a projection lens and a projection system. The projection lens comprises a variable aperture, and a front group lens group and a rear group lens group which are respectively positioned on two sides of the variable aperture, the front group lens group, the variable aperture and the rear group lens group are coaxially arranged; wherein the front lens group comprises an aspherical lens, and the rear lens group comprises an aspherical lens and a balsaming lens group. The projection lens can be matched with the variable aperture to realize clear imaging under different F numbers only by arranging two aspheric lenses and one balsaming lens, and the relative illumination and contrast can be controlled by adjusting the F number of the variable aperture.

Description

Technical Field

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

[0002] As a product that meets the needs of scenarios, intelligent projection products need to cover more functions in the usage scenarios. Different from products such as laser TVs and LCD TVs, projection products have poor anti - ambient light ability. Users' usage habits are mostly in a dark ambient light environment, even at night. When used in a night scene, the indicators that users are more concerned about are no longer brightness, but image quality performance. Therefore, the contrast and uniformity indicators will directly affect the user's viewing experience. Summary of the Invention

[0003] In a first aspect of an embodiment of the present invention, a projection lens is provided, including: a variable aperture, a front lens group and a rear lens group respectively located on both sides of the variable aperture; the front lens group, the variable aperture and the rear lens group are coaxially arranged;

[0004] Wherein, the front lens group includes an aspherical lens, and the rear lens group includes an aspherical lens and a cemented lens group.

[0005] In some embodiments of the present invention, the front lens group includes: a first lens, a second lens, a third lens and a fourth lens arranged in sequence along the direction gradually approaching the variable aperture;

[0006] The diopter of the first lens is positive, the diopter of the second lens is negative, the diopter of the third lens is positive, and the diopter of the fourth lens is positive.

[0007] In some embodiments of the present invention, the first lens is an aspherical lens, and the second lens, the third lens and the fourth lens are all spherical lenses.

[0008] In some embodiments of the present invention, the rear lens group includes: a fifth lens, a sixth lens, a seventh lens and an eighth lens arranged in sequence along the direction gradually away from the variable aperture;

[0009] The diopter of the fifth lens is positive, the diopter of the sixth lens is negative, the diopter of the seventh lens is positive, and the diopter of the eighth lens is positive.

[0010] In some embodiments of the present invention, the fifth lens and the sixth lens are mutually cemented to form a cemented lens group.

[0011] In some embodiments of the present invention, the seventh lens is an aspherical lens, and the fifth lens, the sixth lens and the eighth lens are all spherical lenses.

[0012] In some embodiments of the present invention, the variation range of the F-number of the variable aperture is 2.0 to 2.3.

[0013] In some embodiments of the present invention, the relative illumination of the projection lens increases as the F-number of the variable aperture increases;

[0014] The contrast of the projection lens increases as the F-number of the variable aperture increases.

[0015] In some embodiments of the present invention, the projection ratio of the projection lens is 1.2, and the total length of the projection lens is less than or equal to 55 mm.

[0016] In a second aspect of the embodiments of the present invention, a projection system is provided, including:

[0017] A projection light source for emitting projection light;

[0018] An illumination system located on the light-emitting side of the projection light source; the illumination system includes a light modulator;

[0019] A projection lens, where the projection lens is any of the above projection lenses; the projection lens is located on the light-emitting side of the light modulator.

[0020] The projection lens and the projection system provided by the embodiments of the present invention include a variable aperture, and a front lens group and a rear lens group respectively located on both sides of the variable aperture; the front lens group, the variable aperture, and the rear lens group are coaxially arranged; wherein, the front lens group includes an aspherical lens, and the rear lens group includes an aspherical lens and a cemented lens group. The projection lens only needs to be provided with two aspherical lenses and one cemented lens, and can cooperate with the variable aperture to achieve clear imaging at different F-numbers. By adjusting the F-number of the variable aperture, the relative illumination and the contrast can be controlled. Description of the Drawings

[0021] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required to be used in the embodiments of the present invention. Obviously, the following introduced drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0022] Figure 1 It is a schematic structural diagram of the projection system provided by the embodiments of the present invention;

[0023] Figure 2 It is a schematic diagram of the imaging principle of the projection device provided by the embodiments of the present invention;

[0024] Figure 3 It is a schematic structural diagram of the projection lens provided by the embodiments of the present invention;

[0025] Figure 4 The ray tracing diagram of the projection lens provided by the embodiment of the present invention;

[0026] Figure 5 The comparison diagram of the projection lens provided by the embodiment of the present invention at different F-numbers;

[0027] Figure 6 The planar schematic diagram of the variable aperture provided by the embodiment of the present invention;

[0028] Figure 7 The change curves of the contrast and relative illuminance with respect to the F-number provided by the embodiment of the present invention;

[0029] Figure 8 The modulation transfer function curve diagram of the projection lens provided by the embodiment of the present invention;

[0030] Figure 9 The lateral chromatic aberration diagram of the projection lens provided by the embodiment of the present invention;

[0031] Figure 10 The spot diagram of the projection lens provided by the embodiment of the present invention;

[0032] Figure 11 The schematic diagram of the field curvature curve of the projection lens provided by the embodiment of the present invention;

[0033] Figure 12 The schematic diagram of the distortion curve of the projection lens provided by the embodiment of the present invention. Detailed implementation manners

[0034] To make the above objects, features, and advantages of the present invention more obvious and understandable, the present invention will be further described below with reference to the drawings and embodiments. However, the exemplary embodiments can be implemented in various forms and should not be construed as 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 concept of the exemplary embodiments to those skilled in the art. The same reference numerals in the drawings represent the same or similar structures, and thus their repeated description will be omitted. The words expressing positions and directions described in the present invention are all illustrated by taking the drawings as examples, but can be changed according to needs, and all the changes are included in the protection scope of the present invention. The drawings of the present invention are only used to illustrate the relative positional relationship and do not represent the actual proportion.

[0035] Projection display technology is a technology that uses an optical system and a projection space to magnify and display image information. The projection system finally completes the display of the image by the optical imaging system. A projection lens is provided in the projection system, and the specifications of the projection lens will affect the size of the projection screen and the projection distance. In practical applications, ultra-short focus, short focus or long focus projection lenses are used according to different application scenarios.

[0036] The projection system is divided into a front projection system and a rear projection system. For the front projection system, the audience and the projection device are on the same side of the projection screen. For the rear projection system, the audience and the projection device are on both sides of the projection screen. The embodiments of the present invention will be specifically described by taking the front projection system as an example. Figure 1 It is a schematic structural diagram of the projection system provided by the embodiments of the present invention.

[0037] As Figure 1 shown, the front projection system may include: a projection device 100 and a projection screen 200.

[0038] 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, and the projection light is incident on the projection screen 200 and is reflected to the position where the audience is located through the projection screen 200, so that the audience can view the projection image.

[0039] Figure 2 It is a schematic diagram of the imaging principle of the projection device provided by the embodiments of the present invention.

[0040] As Figure 2 shown, the projection device includes: a projection light source 1, an illumination system 2 and a projection lens 3. Among them, the illumination system 2 is located on the light-emitting side of the projection light source 1. A light modulator 21 is provided in the illumination system 2. The light modulator 21 is used to modulate the incident light and then emit it. The projection lens 3 is located on the light-emitting side of the light modulator 21.

[0041] The projection light source 1 can adopt a light-emitting diode (LED) light source or a laser light source. The LED light source has the advantages of low power consumption, small volume, long life, etc., and is suitable for application scenarios such as small-size projection. The laser light source has higher brightness and better color saturation, and can optimize the display effect of the projection image.

[0042] The projection light source 1 can also use a laser light source. The laser light source can use a single-color laser, a laser that can emit multiple colors of laser, or multiple lasers that emit different colors of laser. When the laser light source uses a single-color laser, the laser display device also needs to be provided with a color wheel for color conversion. The single-color laser and the color wheel can be used to achieve the purpose of emitting primary color lights of different colors in sequence. When the laser light source uses a laser that can emit multiple colors of laser, it is necessary to control the laser light source to emit lasers of different colors in sequence as primary color lights. Using a three-color laser light source is beneficial to improving the color gamut of the projection image, has better color expressiveness, and can accurately reproduce the input image.

[0043] The illumination system 2 is located on the light-emitting side of the projection light source 1. On the one hand, the illumination system 2 collimates and homogenizes the light emitted by the projection light source 1. On the other hand, it can make the light emitted by the projection light source 1 enter the light modulator 21 at an appropriate angle. The illumination system 2 can include multiple lenses or lens groups, light guide tubes, diffuser sheets, diffuser wheels and other components, which are not limited here.

[0044] The light modulator 21 is used to modulate the incident light to form an image. In specific implementation, the light modulator 21 can use a transmissive light modulator or a reflective light modulator. Figure 2 The shown light modulator 21 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 turns back through the reflective light modulator, the volume of the projection device can be reduced.

[0045] In specific implementation, the light modulator 21 can use Liquid Crystal on Silicon (LCoS) or Digital Micromirror Device (DMD).

[0046] LCoS is formed by laminating a Complementary Metal Oxide Semiconductor (CMOS) substrate and a glass substrate with a transparent electrode, and then injecting liquid crystal based on semiconductor technology. LCoS has the characteristics of high aperture ratio and high resolution of each pixel, and can form high-resolution images.

[0047] DMD includes a large number of tiny mirrors, and each tiny mirror can be individually driven to deflect. By controlling the deflection angle of the DMD, the brightness of the light incident on the projection lens 3 is controlled.

[0048] The beam splitter prism P is used to separate the illumination beam and the imaging beam. Since the beam emitted by the projection light source undergoes processes such as shaping and homogenization and is finally reflected by the beam splitter prism P towards the light modulator 21, and the light emitted after being modulated by the light modulator 21 will pass through the beam splitter prism P and enter the projection lens 3 for emission.

[0049] In specific implementation, an image shift component Z can also be provided on the light-emitting side of the light modulator 21. The image polarization component Z can generally adopt a flat glass, and high-frequency vibration can be used to achieve image shift so as to achieve high-resolution image display.

[0050] After the light modulator 21 modulates the incident light to form an image, the light is reflected towards the projection lens 3, and the projection lens 3 performs imaging, so as to project the image onto a suitable size for viewing.

[0051] With the continuous development of computer technology, projection products are also constantly progressing towards intelligent projection products. However, projection products are different from products such as laser TVs and LCD TVs, and their ability to resist ambient light is relatively poor. Users' usage habits are mostly in a dark ambient light environment or even at night. When used in a night scene, the index that users are more concerned about is no longer brightness, but image quality performance. Therefore, the contrast and uniformity indexes will directly affect the viewing experience of users.

[0052] In view of this, an embodiment of the present invention provides a projection lens provided with a variable aperture, which can control parameters such as brightness, relative illuminance, and contrast.

[0053] Figure 3 It is a schematic structural diagram of the projection lens provided by the embodiment of the present invention. Figure 4 It is a ray tracing diagram of the projection lens provided by the embodiment of the present invention.

[0054] As Figure 3 and Figure 4 shown, the projection lens includes: a variable aperture s, and a front group lens 31 and a rear group lens 32 respectively located on both sides of the variable aperture s; the front group lens 31, the variable aperture s, and the rear group lens 32 are coaxially arranged; wherein, the front group lens 31 includes an aspherical lens, and the rear group lens 32 includes an aspherical lens and a cemented lens group.

[0055] The projection lens provided by the embodiment of the present invention only needs to be provided with two aspherical lenses and one cemented lens, and can cooperate with the variable aperture to achieve clear imaging at different F numbers.

[0056] Specifically, the front lens group 31 includes: a first lens l1, a second lens l2, a third lens l3, and a fourth lens l4 sequentially arranged along the direction gradually approaching the variable aperture s; among them, the diopter of the first lens l1 is positive, the diopter of the second lens l2 is negative, the diopter of the third lens l3 is positive, and the diopter of the fourth lens l4 is positive. The rear lens group 32 includes: a fifth lens l5, a sixth lens l6, a seventh lens l7, and an eighth lens l8 sequentially arranged along the direction gradually away from the variable aperture s; among them, the diopter of the fifth lens l5 is positive, the diopter of the sixth lens l6 is negative, the diopter of the seventh lens l7 is positive, and the diopter of the eighth lens l8 is positive.

[0057] According to the propagation direction of light, the light modulated by the light modulator 21 passes through the beam splitting prism P and then enters from the side of the eighth lens l8, and exits from the side of the first lens l1 after passing through the eight lenses in sequence. Therefore, when the projection lens is applied, 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 property of the reversibility of the optical path is used to achieve projection imaging.

[0058] The projection lens provided by the embodiment of the present invention only includes eight lenses and a variable aperture. The eight lenses and the variable aperture are coaxially arranged. The total length of the projection lens can be less than 55 mm, having the advantage of a small size, and can be applied to various scenarios such as household, office, and vehicle-mounted.

[0059] In specific implementation, the first lens l1 is an aspherical lens, and the second lens l2, the third lens l3, and the fourth lens l4 are all spherical lenses. That is, only one aspherical lens is provided in the front lens group 31, and this aspherical lens is the lens farthest from the light modulator 21. In specific implementation, a plastic aspherical lens can be used, and the first lens l1 can play a role in compressing the light angle, balancing the field curvature and aberration.

[0060] In the rear lens group 32, the seventh lens l7 is an aspherical lens, and the fifth lens l5, the sixth lens l6, and the eighth lens l8 are all spherical lenses. Only one aspherical lens is provided in the rear lens group 32. Since the seventh lens l7 is closer to the light modulator 21 and needs to have better light resistance, in specific implementation, the seventh lens l7 can be made of a glass aspherical lens.

[0061] The fifth lens l5 and the sixth lens l6 are glued together to form a glued lens group. The refractive index of the fifth lens l5 is less than that of the sixth lens l6, and the Abbe number of the fifth lens l5 is greater than that of the sixth lens l6. The doublet lens group composed of the fifth lens l5 and the sixth lens l6 can effectively reduce the chromatic aberration of the optical system.

[0062] In an embodiment of the present invention, based on the above optical architecture, the variation range of the F-number of the variable aperture s can be 2.0 to 2.3. The F-number characterizes the light-gathering ability of the projection lens. The larger the F-number value, the smaller the aperture diameter and the smaller the light-gathering range; the smaller the F-number value, the larger the aperture diameter and the larger the light-gathering range. In the present invention patent, the F-number range of the lens is 2.0 - 3.2, and it has the ability to change the contrast, brightness, and relative illumination.

[0063] Figure 5 It is a comparison chart of the projection lens provided by the embodiment of the present invention at different F-numbers; Figure 6 It is a schematic plan view of the variable aperture provided by the embodiment of the present invention; Figure 7 It is a change curve of the contrast and relative illumination with respect to the F-number provided by the embodiment of the present invention.

[0064] As Figure 5 and Figure 6 shown, when the F-number of the variable aperture is 2.0, the light-passing aperture of the variable aperture is relatively large, and the light-gathering range at this time is larger; when the F-number of the variable aperture is 3.2, the light-passing aperture of the variable aperture is relatively small, and the light-gathering range at this time is smaller. In the embodiment of the present invention, the F-number of the variable aperture can vary within the range of 2.0 to 3.2, so as to achieve the control of the relative illumination and contrast. As Figure 7 shown, where the abscissa represents the F-number and the ordinate represents the relative value of the relative illumination / contrast. It can be seen from Figure 7 that as the F-number gradually increases, the relative illumination and contrast of the projection lens also increase, and the F-number of the variable aperture can control the illumination uniformity.

[0065] The surface shape parameters of each optical component in the projection lens provided by the embodiment of the present invention and the distances between the optical components are shown in the following table:

[0066] Serial number Radius of curvature Thickness Material Semi-aperture Conic coefficient Infinity / 2018.0 0 C1 -25.5 3.0 1.54,55.7 11.0 -54.5 16.8 5.5 8.0 0.7 C2 -15.6 0.8 1.5,81.6 8.0 0 23.9 2.1 8.2 0 C3 -202.7 4.3 1.9,31.3 8.4 0 26.7 0.1 8.9 0 C4 15.6 4.0 1.62,36.3 8.9 0 -164.9 10.0 8.6 0 Infinity 5.0 4.1 0 C5 45.3 3.6 1.49,70.4 4.9 0 C6 -7.1 1.2 1.85,23.8 5.0 0 -62.1 2.3 5.7 0 C7 39.4 4.8 1.5,81.6 7.2 -1.1 -10.8 1.1 7.9 0.4 C8 237.6 3.5 1.92,20.9 8.8 0 -28.3 0.0 8.9 0 Infinity 2.8 8.7 0 TSP Infinity 2.0 1.52,58.6 8.3 0 Infinity 6.4 8.0 0 TIR Infinity 13.0 1.72,29.5 7.0 0 Infinity 0.5 5.9 0 CG Infinity 1.1 1.52,64.2 5.8 0 Infinity 0.8 5.7 0 DMD Infinity 0.0 5.7 0

[0067] The coefficients of the aspherical lens are:

[0068]

[0069]

[0070] Based on the above parameters, the projection lens is a telephoto lens, the projection ratio is 1.2, the total length of the projection lens is less than or equal to 55 mm, and the chromatic aberration < 2.4 μm.

[0071] The embodiment of the present invention also performs an image quality evaluation on the projection lens based on the above parameter optimization results.

[0072] Figure 8It is the modulation transfer function curve graph of the projection lens provided by the embodiment of the present invention.

[0073] Figure 8 It shows the modulation transfer function (MTF) curve graphs of light rays with wavelengths of 647nm, 525nm, and 455nm in different fields of view. Among them, the abscissa represents the spatial frequency, expressed as the number of cycles per millimeter in the image space, with the unit of cycles / mm, and the ordinate represents the OTF value (Modulation). MTF can characterize the resolution of the lens. From Figure 8 It can be seen that the MTF values of the light rays are all above 0.6 and the curves are 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.

[0074] Figure 9 It is the lateral chromatic aberration graph of the projection lens provided by the embodiment of the present invention.

[0075] Figure 9 It shows the lateral chromatic aberration of light rays with wavelengths of 647nm, 525nm, and 455nm in the maximum field of view of 5.6mm. Among them, the abscissa represents the lateral chromatic aberration, with the unit of μm, and the ordinate is the field of view, with the unit of mm. From Figure 9 It can be seen that the maximum value of the lateral chromatic aberration of the projection lens is 2.4μm.

[0076] Figure 10 It is the spot diagram of the projection lens provided by the embodiment of the present invention.

[0077] The spot diagram can reflect the clarity of imaging. The more concentrated the illustrated points are, the less smear and better sharpness there are when the projection lens forms an image. Figure 10 It shows the spot diagrams (Spot Size diagrams) of light rays with wavelengths of 0.647μm, 0.525μm, and 0.455μm in ten fields of view. From Figure 10 It can be known that the images formed by the projection lens in different fields of view can be within a reasonable range. The root mean square (RMS) radius and geometric (GEO) radius data corresponding to the images formed in the ten fields of view simulated by the embodiment of the present invention are shown in the following table, where the global RMS is less than 2.5μm:

[0078]

[0079]

[0080] Figure 11 It is the schematic diagram of the field curvature curve of the projection lens provided by the embodiment of the present invention.

[0081] Figure 11 The field curvature curves in the meridional direction (T) and the sagittal direction (S) of the projection lens at different fields of view are shown, where the abscissa represents the magnitude of the field curvature in mm and the ordinate represents the image height (field of view). Figure 11 The maximum field of view is 32.234 degrees. The field curvature in the meridional direction is within 0.03 mm, and the field curvature in the sagittal direction is within 0.025 mm. The field curvature of the projection lens is within a reasonable range.

[0082] Figure 12 It is a schematic diagram of the distortion curve of the projection lens provided by the embodiment of the present invention.

[0083] Figure 12 The distortion curves of the projection lens at different fields of view are shown, where the abscissa represents the percentage of distortion of the imaging and the ordinate represents the image height (field of view). Figure 12 It can be seen that the distortion of the projection lens is controlled within 0.5%.

[0084] Comprehensively Figures 8 - 12 Based on the results of the image quality evaluation, it can be known that various aberrations during the imaging of the projection lens provided by the embodiment of the present invention are small, and it can have good imaging quality.

[0085] Based on the same inventive concept, the embodiment of the present invention also provides a projection system, as Figure 2 shown. The projection system includes: a projection light source 1, an illumination system 2, and a projection lens 3. Among them, the projection light source 1 is used to emit projection light; the illumination system 2 is located on the light-emitting side of the projection light source 1, and the illumination system 2 includes a light modulator 21; the projection lens 3 is any of the above projection lenses and is located on the light-emitting side of the light modulator 21. A variable aperture is provided in the projection lens 3 provided by the embodiment of the present invention, and the relative illuminance and contrast of the projection lens can be controlled.

[0086] According to the first inventive concept, the projection lens includes a variable aperture, and a front group lens and a rear group lens respectively located on both sides of the variable aperture; the front group lens, the variable aperture, and the rear group lens are coaxially arranged; among them, the front group lens includes an aspherical lens, and the rear group lens includes an aspherical lens and a cemented lens group. The projection lens only needs to be provided with two aspherical lenses and one cemented lens, and can achieve clear imaging at different F-numbers in cooperation with the variable aperture.

[0087] According to the second inventive concept, the front lens group includes: a first lens, a second lens, a third lens, and a fourth lens sequentially arranged along a direction gradually approaching the variable aperture. The rear lens group includes: a fifth lens, a sixth lens, a seventh lens, and an eighth lens sequentially arranged along a direction gradually moving away from the variable aperture. The projection lens only includes eight lenses and a variable aperture, and the eight lenses and the variable aperture are coaxially arranged. The total length of the projection lens can be below 55 mm, having the advantage of a small size, and can be applied to various scenarios such as home, office, and vehicle-mounted.

[0088] According to the third inventive concept, the first lens is an aspherical lens, and the second lens, the third lens, and the fourth lens are all spherical lenses. Only one aspherical lens is provided in the front lens group, and this aspherical lens is the lens farthest from the light modulator. A plastic aspherical lens can be used, and the first lens can play a role in compressing the light angle, balancing the field curvature and aberration.

[0089] According to the fourth inventive concept, the seventh lens is an aspherical lens, and the fifth lens, the sixth lens, and the eighth lens are all spherical lenses. Only one aspherical lens is provided in the rear lens group. Since the seventh lens is closer to the light modulator and needs to have better light resistance, the seventh lens can be made of a glass aspherical lens.

[0090] According to the fifth inventive concept, the fifth lens and the sixth lens are mutually cemented to form a cemented lens group. The refractive index of the fifth lens is less than that of the sixth lens, and the Abbe number of the fifth lens is greater than that of the sixth lens. The doublet lens group formed by the fifth lens and the sixth lens can effectively reduce the chromatic aberration of the optical system, reducing the chromatic aberration of the optical system to below 2.4 μm.

[0091] According to the sixth inventive concept, the change range of the F-number of the variable aperture can be 2.0 to 2.3, having the ability to change the contrast, brightness, and relative illuminance.

[0092] According to the seventh inventive concept, as the F-number gradually increases, the relative illuminance and contrast of the projection lens also increase, and the F-number of the variable aperture can control the illuminance uniformity.

[0093] Although the preferred embodiments of the present invention have been described, those skilled in the art can make additional changes and modifications to these embodiments once they learn the basic creative concept. Therefore, the appended claims are intended to be construed to include the preferred embodiments as well as all changes and modifications falling within the scope of the present invention.

[0094] 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 equivalent technologies, the present invention is also intended to include these modifications and variations.

Claims

1. A projection lens, characterized in that, Comprising: A variable aperture, a front lens group and a rear lens group respectively located on both sides of the variable aperture; the front lens group, the variable aperture and the rear lens group are coaxially arranged; Wherein, the front lens group includes an aspherical lens, and the rear lens group includes an aspherical lens and a cemented lens group.

2. The projection lens according to claim 1, characterized in that, The front lens group includes: a first lens, a second lens, a third lens and a fourth lens arranged in sequence along the direction gradually approaching the variable aperture; The diopter of the first lens is positive, the diopter of the second lens is negative, the diopter of the third lens is positive, and the diopter of the fourth lens is positive.

3. The projection lens according to claim 2, characterized in that, The first lens is an aspherical lens, and the second lens, the third lens and the fourth lens are all spherical lenses.

4. The projection lens according to claim 1, characterized in that, The rear lens group includes: a fifth lens, a sixth lens, a seventh lens and an eighth lens arranged in sequence along the direction gradually away from the variable aperture; The diopter of the fifth lens is positive, the diopter of the sixth lens is negative, the diopter of the seventh lens is positive, and the diopter of the eighth lens is positive.

5. The projection lens according to claim 4, wherein The fifth lens and the sixth lens are mutually cemented to form a cemented lens group.

6. The projection lens according to claim 4, wherein The seventh lens is an aspherical lens, and the fifth lens, the sixth lens and the eighth lens are all spherical lenses.

7. The projection lens according to any one of claims 1 to 6, characterized in that, The change range of the F-number of the variable aperture is 2.0 to 2.

3.

8. The projection lens according to claim 7, wherein, The relative illumination of the projection lens increases with the increase of the F-number of the variable aperture; The contrast of the projection lens increases with the increase of the F-number of the variable aperture.

9. The projection lens according to any one of claims 1 to 6, characterized in that, The projection ratio of the projection lens is 1.2, and the total length of the projection lens is less than or equal to 55 mm.

10. A projection system, characterized in that, Comprising: A projection light source for emitting projection light; An illumination system located on the light-emitting side of the projection light source; the illumination system includes a light modulator; A projection lens, where the projection lens is the projection lens according to any one of claims 1 to 9; the projection lens is located on the light-emitting side of the light modulator.

Images