Projection lens and projection system

Abstract

The invention discloses a projection lens and a projection system. The projection lens comprises a front lens group, a middle lens group and a rear lens group which are sequentially arranged in the emergent direction of projection light. Wherein the front group lens group and the middle group lens group respectively comprise a balsaming lens, and the rear working distance and the equivalent focal length of the projection lens meet BFL / Fgt, and 1.6. On the premise that the total length of the projection lens is controlled to be smaller than 55.5 mm, the chromatic aberration is suppressed to 0.15 Pixel; by adjusting the middle group structure and cooperating with the adjustment of the projection distance, 40-120 inch picture display can be realized, and the picture quality is excellent under different sizes.

Description

TECHNICAL FIELD

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

[0002] Projection display technology is a technology of enlarging and displaying image information by using optical system and projection space. The projection system is to complete the display of image by optical imaging system, and the projection lens greatly affects the application scene and imaging quality of the projection system. And the size of the projection lens also affects the volume of the optical engine.

[0003] The laser light source has a high color gamut, and the projection system matched with the laser light source can have higher color performance and color restoration. However, at the same time, the projection system matched with the three-color laser light source also has the problem of too large color difference, which causes the color trailing problem at the edge of the display picture, affecting the viewing experience. SUMMARY

[0004] The first aspect of the embodiment of the present application provides a projection lens, comprising:

[0005] In some embodiments of the present application,

[0006] The second aspect of the embodiment of the present application provides a projection system, comprising:

[0007] A projection light source;

[0008] An illumination system located on the light exit side of the projection light source; the illumination system comprises a light modulator;

[0009] A projection lens, the projection lens is any of the above projection lenses; the projection lens is located on the light exit side of the light modulator.

[0010] The projection lens and the projection system provided by the embodiment of the present application comprise a front group lens, a middle group lens and a rear group lens arranged in sequence along the exit direction of the projection light; wherein the front group lens and the middle group lens each comprise a cemented lens, and the back working distance and the equivalent focal length of the projection lens satisfy: BFL / F>1.6. Under the premise of controlling the total length of the projection lens to be less than 55.5mm, the color difference is suppressed to 0.15Pixel; by adjusting the middle group structure and cooperating with the adjustment of the projection distance, the picture display of 40 inches to 120 inches can be realized, and the picture quality is excellent under different sizes. BRIEF DESCRIPTION OF DRAWINGS

[0011] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed to be used in the embodiments of the present application will be briefly introduced as follows. Obviously, the drawings to be introduced below are only some of the embodiments of the present application, and other drawings can also be obtained by those skilled in the art without any creative effort on the basis of these drawings.

[0012] Figure 1 The structural schematic diagram of the projection system provided by the embodiments of the present application is shown in the figure.

[0013] Figure 2 The imaging principle schematic diagram of the projection device provided by the embodiments of the present application is shown in the figure.

[0014] Figure 3 The optical architecture schematic diagram of the projection lens provided by the embodiments of the present application is shown in the figure.

[0015] Figure 4 The ray tracing diagram provided by the embodiments of the present application is shown in the figure.

[0016] Figure 5 The axial chromatic aberration diagram provided by the embodiments of the present application is shown in the figure.

[0017] Figure 6 The modulation transfer function curve diagram provided by the embodiments of the present application is shown in the figure.

[0018] Figure 7 The modulation transfer function curve diagram provided by the embodiments of the present application is shown in the figure.

[0019] Figure 8 The light fan diagram provided by the embodiments of the present application is shown in the figure.

[0020] Figure 9 The point column diagram provided by the embodiments of the present application is shown in the figure.

[0021] Figure 10 The field curvature curve schematic diagram provided by the embodiments of the present application is shown in the figure.

[0022] Figure 11 The distortion curve schematic diagram provided by the embodiments of the present application is shown in the figure.

[0023] Figure 12 The relative luminance schematic diagram provided by the embodiments of the present application is shown in the figure.

[0024] Figure 13 The telecentricity curve diagram provided by the embodiments of the present application is shown in the figure. DETAILED DESCRIPTION

[0025] In order to make the above objectives, characteristics and advantages of the present application more apparent, comprehensible and easier to understand, the present application will be further described below in conjunction with the accompanying drawings and embodiments. However, the example embodiments can be implemented in various forms, and should not be understood as being limited to the embodiments set forth herein; on the contrary, these embodiments are provided so as to make the present application more comprehensive and complete, and to fully convey the concept of the example embodiments to those skilled in the art. Identical reference numerals in the drawings represent identical or similar structures, and thus repeated description thereof will be omitted. The words expressing position and direction described in the present application are described with reference to the drawings, but can be changed as needed, and the changes made are included in the scope of protection of the present application. The drawings of the present application are only used to illustrate the relative positional relationship and do not represent the true proportions.

[0026] The projection display technology is a technology of magnifying and displaying image information by using an optical system and a projection space. The projection system is ultimately completed by the optical imaging system to display the image. With the continuous development of projection technology, the laser projection system has unique advantages and is widely used in large-screen display, laser television, digital cinema, portable projection display and other fields. Laser projection display can display more realistic and more magnificent dynamic images on an ultra-large screen, and achieve a visual stunning effect that cannot be achieved by other display technologies.

[0027] In actual application, the projection system can be divided into a front projection type projection system and a back projection type projection system, Figure 1 The structure schematic diagram of the projection system provided by the embodiment of the present application is shown.

[0028] As shown in the drawings, Figure 1 The front projection type projection system can include a projection device 100 and a projection screen 200.

[0029] The projection screen 200 is located on the light exit side of the projection device 100, the audience faces the projection screen 200, the projection device 100 emits projection light, the projection light is incident to the projection screen 200, and the projection screen 200 reflects the projection light to the position where the audience is located, so that the audience can watch the projection image.

[0030] A projection lens is arranged in the projection device, and the specification of the projection lens will affect the size of the projection picture and the projection distance. In actual application, different projection lenses such as ultra-short focus, short focus or long focus can be used according to different application scenarios.

[0031] Figure 2 The imaging principle schematic diagram of the projection device provided by the embodiment of the present application is shown.

[0032] As shown in the drawings, Figure 2As shown, the projection device comprises a projection light source 1, an illumination system 2 and a projection lens 3. The illumination system 2 is located on the light exit side of the projection light source 1, and the illumination system 2 is provided with a light modulator 21 for modulating the incident light and emitting, and the projection lens 3 is located on the light exit side of the light modulator 21.

[0033] 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 small power consumption, small size and long service life, and is suitable for small size projection and other application scenarios. The laser light source has higher brightness and better color saturation, which can optimize the display effect of the projection image.

[0034] In the embodiment of the application, the projection light source can adopt a laser light source, which can adopt a single-color laser or a laser that can emit multiple colors of laser light or multiple lasers that emit different colors of laser light. When the laser light source adopts a single-color laser, the laser display device also needs to be provided with a color wheel for color conversion. The single-color laser cooperates with the color wheel to achieve the purpose of emitting different color primary light in time sequence. When the laser light source adopts a laser that can emit multiple colors of laser light, the laser light source needs to be controlled to emit different colors of laser light as primary light in time sequence. Adopting a three-color laser light source is beneficial to improve the color gamut of the projection image and has better color performance, which can accurately reproduce the input image.

[0035] The illumination system 2 is located on the light exit side of the projection light source 1, which can collimate and homogenize the emitted light of the projection light source 1 on the one hand, and can make the emitted light of the projection light source 1 incident to the light modulator 21 at a suitable angle on the other hand. The illumination system 2 can include multiple lenses or lens groups 22, light guide pipes, diffusion sheets, diffusion wheels and other components, which are not limited here.

[0036] The light modulator 21 is used for modulating the incident light to form an image. In specific implementation, the light modulator 21 can adopt a transmissive light modulator or a reflective light modulator. Figure 2 The light modulator 21 shown is a reflective light modulator. The light modulator 21 receives the light reflected by the light splitting prism P and modulates the incident light, and reflects the modulated light. Since the light path is folded back by the reflective light modulator, the volume of the projection device can be reduced.

[0037] In the embodiment of the application, the light modulator 21 can adopt a liquid crystal on silicon (LCoS) or a digital micromirror device (DMD).

[0038] LCoS is based on semiconductor technology to paste the complementary metal oxide semiconductor (CMOS) substrate with the glass substrate containing transparent electrode, and then inject liquid crystal encapsulation.

[0039] DMD includes many micro-mirrors, each of which can be driven to deflect individually, and by controlling the deflection angle of the DMD, the brightness of the light incident to the projection lens 3 can be controlled.

[0040] The light splitting prism P is used to separate the illumination beam and the imaging beam.

[0041] In a specific implementation, the light-emitting side of the light modulator 21 can also be provided with an image offset component Z, which can usually be a flat glass.

[0042] After the light modulator 21 modulates the incident light to form an image, the light is reflected to the projection lens 3 for imaging, so that the image is projected to a suitable size for viewing.

[0043] The spectral range of the projection system using a three-color laser light source as the projection light source becomes larger, and under the premise of ensuring the imaging quality, it becomes more and more important to realize small chromatic aberration.

[0044] The embodiment of the present application provides a projection lens, as shown in the accompanying drawings, comprising: a front group lens set 31, a middle group lens set 32 and a rear group lens set 33 arranged in sequence along the projection light emitting direction; the front group lens set 31, the middle group lens set 32 and the rear group lens set 33 are coaxially arranged; wherein the front group lens set 31 comprises one cemented lens, and the middle group lens set 32 comprises one cemented lens. Figure 3

[0045] Figure 3 ​​As shown in the figure, the front group lens set 31 includes: a first lens l1, a second lens l2, a third lens l3, a fourth lens l4 and a fifth lens l5 arranged in sequence along the outgoing direction of the projection light. The refractive power of the first lens l1 is positive, the refractive power of the second lens l2 is positive, the refractive power of the third lens l3 is positive, the refractive power of the fourth lens l4 is negative, and the refractive power of the fifth lens l5 is positive. The first lens l1, the second lens l2, the third lens l3, the fourth lens l4 and the fifth lens l5 are all spherical lenses.

[0046] Among them, the third lens l3, the fourth lens l4 and the fifth lens l5 are mutually cemented to form a first cemented lens. The Abbe number of the third lens l3 satisfies: 35 < Vd3 < 90, the refractive index of the third lens l3 satisfies: Nd3 > 1.4, the refractive index of the fourth lens l4 is greater than that of the third lens l3, the Abbe number of the fourth lens l4 is less than that of the third lens l3, the refractive index of the fifth lens l5 is less than that of the fourth lens l4, and the Abbe number of the fifth lens l5 is greater than that of the fourth lens l4. The first cemented lens can effectively improve the spherical aberration and the sagittal chromatic aberration, improve the coma of different spectra of the lens, and correct the astigmatism of the lens.

[0047] As shown in the figure, Figure 3 The middle group lens set 32 includes: a sixth lens l6 and a seventh lens l7 arranged in sequence along the outgoing direction of the projection light. The refractive power of the sixth lens l6 is negative, and the refractive power of the seventh lens l7 is positive. The sixth lens l6 and the seventh lens l7 are both spherical lenses.

[0048] Among them, the sixth lens l6 and the seventh lens l7 are mutually cemented to form a second cemented lens. The Abbe number of the sixth lens l6 satisfies: 15 < Vd6 < 300, the refractive index of the sixth lens l6 satisfies: Nd6 > 1.85, the refractive index of the seventh lens l7 is less than that of the sixth lens l6, and the Abbe number of the seventh lens l7 is greater than that of the sixth lens l6. The second cemented lens can correct the system residual sagittal chromatic aberration and spherical aberration.

[0049] As shown in the figure, Figure 3 The rear group lens set 33 includes: an eighth lens l8, a ninth lens l9, a tenth lens l10 and an eleventh lens l11 arranged in sequence along the outgoing direction of the projection light. The refractive power of the eighth lens l8 is positive, the refractive power of the ninth lens l9 is positive, the refractive power of the tenth lens l10 is negative, and the refractive power of the eleventh lens l11 is negative. The eighth lens l8, the ninth lens l9 and the tenth lens l10 are all spherical lenses, and the eleventh lens l11 is an aspherical lens. The eleventh lens l11 can be an axially symmetric aspherical lens, which can effectively improve the astigmatism and the field curvature.

[0050] The eleventh aspheric lens, the first cemented lens and the second cemented lens correct large field aberration, improve the resolving power of the lens, and thus realize high-resolution imaging quality.

[0051] The focal length of the projection lens satisfies:

[0052] BFL / F>1.6;

[0053] 1<|FB / F|<15;

[0054] 5<|FM / F|<150;

[0055] 5<|FF / F|<100;

[0056] Wherein, BFL represents the back working distance of the projection lens, F represents the equivalent focal length of the projection lens, FF represents the equivalent focal length of the front group lens set, FM represents the equivalent focal length of the middle group lens set, and FB represents the equivalent focal length of the rear group lens set.

[0057] Controlling the equivalent focal lengths of the front group lens set, the middle group lens set and the rear group lens set of the projection lens within the above range can balance the focal lengths of the front group lens set, the middle group lens set and the rear group lens set, and avoid excessively concentrating the optical power on one lens set. In addition, the total length of the lens can be reduced, and the total length of the projection lens provided by the embodiment of the application is less than 55.5mm.

[0058] The projection lens provided by the embodiment of the application can also change the size of the projected image by moving the middle group lens set. When adjusting the size of the picture, the positions of the front group lens set and the rear group lens set remain unchanged, the middle group lens set is moved along the optical axis, and the distance from the projection lens to the projection surface is changed. The size of the projected picture is optimized to 40 inches to 120 inches without changing the focal length, and the picture quality is excellent at different sizes, so as to meet the gradually increasing demand for display pictures.

[0059] In some embodiments, the surface parameters of each optical component in the projection lens and the spacing between the optical components are shown in the following table. It should be noted that, when the optical design of the projection lens is performed, the imaging position (projection surface, projection screen) is taken as the object surface, and the display surface of the light modulator is taken as the image surface for optical design. According to the principle of reversible optical path, the projection display conforming to the design size and image quality can be realized at the object surface in the design.

[0060]

[0061]

[0062] The aspheric coefficients of the eleventh lens are shown in the following table:

[0063]

[0064] Based on the above parameters, the projection lens is a long-focus lens, and the parameters satisfy: F.NO=2.2, effective focal length (EFL)=10.5mm, image plane relative optical axis offset is offset=100%, resolving power is 111lp / mm, projection picture is 40-120 inches, and projection ratio is 1.18-1.22.

[0065] The embodiment of the present application also performs image quality evaluation on the projection lens based on the above parameter optimization results.

[0066] Figure 4 The ray tracing diagram provided by the embodiment of the present application.

[0067] As shown in Figure 3 and Figure 4 , the light modulator 21 is located at the light entrance side of the projection lens, and the first lens l1 in the projection lens is arranged adjacent to the light modulation component 21. The embodiment of the present application takes the 0.39-inch DMD as an example to illustrate the light modulator 21, and the light exit side of the light modulator 21 is also provided with a protective glass G. The modulated light emitted from the display surface of the light modulator 21 first passes through the protective glass G, then passes through the image offset component Z and the light splitting prism P, and is incident on the projection lens from the side of the first lens l1 of the projection lens. As shown in Figure 4 It can be seen that the projection light can pass through the entire projection lens well.

[0068] Figure 5 The axial chromatic aberration diagram provided by the embodiment of the present application.

[0069] Figure 5 The axial chromatic aberration when the light with wavelengths of 0.650μm, 0.525μm and 0.450μm is imaged in the range of the maximum field of view of 6.5684mm is shown, wherein the abscissa represents the size of the axial chromatic aberration, the unit is μm, the ordinate is the field of view, the unit is mm, and the dotted line in the figure is the range of the Airy disk, as shown in Figure 5 It can be seen that, within the range of the Airy disk, the axial chromatic aberration imaged by the projection lens is within a reasonable range.

[0070] Figure 6 One of the modulation transfer function curve diagrams provided by the embodiment of the present application.

[0071] Figure 6 The modulation transfer function (Modulation Transfer Function, MTF) curve diagram of the light with wavelengths of 0.650μm, 0.525μm and 0.450μm in different fields of view is shown, wherein the abscissa represents the spatial frequency, the unit is cycle / mm, and the ordinate represents the MTF value. The MTF value can represent the resolving power of the projection lens. As shown in Figure 6It can be seen that the MTF values of the light rays are all above 0.5 and the curves are relatively flat, which indicates that the imaging difference between the edge and the center of the projection lens is small, and the projection lens can better feedback the details of the picture, and the imaging quality reaches the design standard.

[0072] Figure 7 The modulation transfer function curve diagram two provided by the embodiment of the application.

[0073] Figure 7 The modulation transfer function (MTF) curve diagrams of light rays with wavelengths of 0.650 μm, 0.525 μm and 0.450 μm in different fields of view are shown, wherein the abscissa represents the field of view in mm, and the ordinate represents the MTF value. Figure 7 It can be seen that the MTF values of the projection lens in the full field of view are all above 0.5, and the imaging of the full picture has better resolution.

[0074] Figure 8 The light fan diagram provided by the embodiment of the application.

[0075] The figure shows the aberration values of the main light rays with wavelengths of 0.650 μm, 0.525 μm and 0.450 μm between the x-axis and the y-axis under the condition of 10 normalized fields of view. The two graphs in each field of view are the x-axis and the y-axis respectively symmetrically centered on the optical axis of the projection lens; the horizontal axis direction in each graph is the pupil height position under the field of view condition, and the vertical axis direction is the error between the light rays of different wavelengths and the main light ray. From the figure, Figure 8 It can be seen that the separation degree between the light rays of different wavelengths and the main light ray is very small under each field of view, which means that the aberration is small.

[0076] Figure 9 The spot diagram provided by the embodiment of the application.

[0077] The spot diagram can reflect the clarity of the imaging of the projection lens, and the more concentrated the points in the figure are, the less the trailing of the projection lens is when imaging, and the better the sharpness is, Figure 9 The imaging spot size diagrams (Spot Size diagrams) of light rays with wavelengths of 0.650 μm, 0.525 μm and 0.450 μm in 10 fields of view are shown, from which Figure 9 It can be seen that the images formed by the projection lens in different fields of view can be within a reasonable range. The root mean square (RNS) radius and the geometric (GEO) radius data corresponding to the images formed by the 10 fields of view simulated by the embodiment of the application are shown in the following table:

[0078] Field of view 1 2 3 4 5 6 7 8 9 10 RNS radius (pm) 2.154 2.412 2.368 2.053 1.590 1.196 1.019 1.037 1.370 1.994 GEO radius (pm) 4.877 6.314 6.986 6.218 4.666 3.285 3.652 2.679 8.258 18.743

[0079] From the above table and Figure 9It can be seen that the root mean square radius is less than 2.4 μm, and the light rays are well converged.

[0080] Figure 10 A field curvature curve diagram provided for the embodiment of the present application is shown.

[0081] Figure 10 The meridional and sagittal field curvature curves of images formed by light rays with wavelengths of 0.650 μm, 0.525 μm and 0.450 μm under different fields of view are shown, wherein the abscissa represents the field curvature size in mm, and the ordinate represents the image height (field of view), Figure 10 The maximum field of view is 6.568 mm, the sagittal field curvature is 0.0422 mm, the meridional field curvature is 0.0476 mm, the field curvatures in different directions are all less than 0.05 mm, and the field curvature of the projection lens is within a reasonable range.

[0082] Figure 11 A distortion curve diagram provided for the embodiment of the present application is shown.

[0083] Figure 11 The distortion curves of images formed by light rays with wavelengths of 0.650 μm, 0.525 μm and 0.450 μm within a maximum field of view of 6.568 mm are shown, wherein the abscissa represents the distortion percentage, and the ordinate represents the image height (field of view), Figure 11 The maximum distortion is 1.2298%, and the distortion of the projection lens is within a reasonable range, avoiding too large picture deformation.

[0084] Figure 12 A relative luminance diagram provided for the embodiment of the present application is shown, wherein the abscissa represents the field of view in mm, and the ordinate represents the relative luminance. Figure 12 It can be seen that the relative luminance of the full field of view is close to 100%, and the projection picture uniformity is good.

[0085] Figure 13 A telecentricity curve diagram provided for the embodiment of the present application is shown.

[0086] Figure 13 The telecentricity histograms of chief rays under different fields of view are shown, wherein the abscissa represents the field of view size, and the ordinate represents the angle of the chief ray corresponding to different fields of view, i.e. the telecentricity, and the specific data are shown in the following table:

[0087] Field of view (Y) 0.00Y 0.02Y 0.10Y 0.15Y 0.20Y 0.25Y 0.30Y 0.35Y 0.40Y 0.45Y 0.50Y Telecentricity 0.00 0.08 0.17 0.26 0.34 0.42 0.50 0.58 0.65 0.71 0.77 Field of view (Y) 0.55Y 0.60Y 0.65Y 0.70Y 0.75Y 0.80Y 0.85Y 0.90Y 0.95Y 1.00Y Telecentricity 0.82 0.87 0.91 0.93 0.95 0.96 0.95 0.94 0.90 0.86

[0088] From the above table and Figure 13 It can be seen that the angles of the chief rays of the full field of view are all less than 1°, the angles of the chief rays of different fields of view are basically parallel, and the requirements of the image-side telecentric optical path are met.

[0089] Based on the same inventive concept, the embodiment of the present application further provides a projection system, such as Figure 1As shown, the projection system can include a projection device 100 and a projection screen 200, the projection device can include any of the above projection lenses. The projection lens can be applied to a three-color laser projection system, under the premise of ensuring the total length of the lens is less than 55.5mm, the chromatic aberration is less than 0.15pixel, by adjusting the middle group lens and cooperating with the adjustment of the projection distance, the 4inch-120inch picture display can be realized.

[0090] According to the first inventive concept, the projection lens comprises a front group lens, a middle group lens and a rear group lens arranged in sequence along the projection light ray exit direction; wherein the front group lens and the middle group lens respectively comprise a cemented lens, and the chromatic aberration is suppressed to 0.15pixel.

[0091] According to the second inventive concept, the front group lens comprises five lenses, the middle group lens comprises two lenses, and the rear group lens comprises four lenses. The last lens in the rear group lens is a non-spherical lens, and the rest of the lenses are spherical lenses. Only one non-spherical lens is included in the projection lens, which can effectively improve the astigmatism and field curvature.

[0092] According to the third inventive concept, the third lens, the fourth lens and the fifth lens in the front group lens are cemented to form a first cemented lens. The spherical aberration and the axial chromatic aberration can be effectively improved, the coma of different spectra of the lens can be improved, and the astigmatism of the lens can be corrected.

[0093] According to the fourth inventive concept, the sixth lens and the seventh lens in the middle group lens are cemented to form a second cemented lens, which can correct the residual axial chromatic aberration and spherical aberration of the system.

[0094] According to the fifth inventive concept, the focal length of the projection lens satisfies: BFL / F>1.6; 1<|FB / F|<15; 5<|FM / F|<150; 5<|FF / F|<100. By balancing the focal length of the front group lens, the middle group lens and the rear group lens, the optical power is avoided to be excessively concentrated on one lens group. In addition, the total length of the lens can be reduced, and the total length of the projection lens provided by the embodiment of the present application is less than 55.5mm.

[0095] According to the sixth inventive concept, the positions of the front group lens and the rear group lens are kept unchanged, the middle group lens is moved along the optical axis, and the distance between the projection lens and the projection surface is changed, so that the size of the projection picture is optimized to 40inch-120inch without changing the focal length, and the picture quality is excellent at different sizes, so as to meet the gradually increasing demand of the display picture.

[0096] Although the preferred embodiments of the present application have been described, those skilled in the art can make further changes and modifications to the embodiments once they know the basic inventive concept. Therefore, the appended claims are intended to be interpreted as including all the preferred embodiments and all the changes and modifications falling within the scope of the present application.

[0097] Obviously, many modifications and variations of the present application are possible in light of the above teachings. It is, therefore, to be understood that within the scope of the appended claims and their equivalents, the application can be practiced otherwise than as specifically described.

Claims

1. A projection lens, characterized in that, The projection lens comprises: a front group, a middle group and a rear group of lens sets arranged in sequence along the exit direction of the projection light; the front group, the middle group and the rear group of lens sets are coaxially arranged; the front group of lens sets comprises one cemented lens, and the middle group of lens sets comprises one cemented lens; the projection lens satisfies: BFL / F>1.6; wherein, BFL represents the back working distance of the projection lens, and F represents the equivalent focal length of the projection lens.

2. The projection lens of claim 1, wherein, The front group of lens sets comprises: a first lens, a second lens, a third lens, a fourth lens and a fifth lens arranged in sequence along the exit direction of the projection light; the first lens has positive refractive power, the second lens has positive refractive power, the third lens has positive refractive power, the fourth lens has negative refractive power, and the fifth lens has positive refractive power; the first lens, the second lens, the third lens, the fourth lens and the fifth lens are all spherical lenses.

3. The projection lens of claim 2, wherein, The third lens, the fourth lens and the fifth lens are cemented to form a first cemented lens.

4. The projection lens of claim 2, wherein, The middle group of lens sets comprises: a sixth lens and a seventh lens arranged in sequence along the exit direction of the projection light; the sixth lens has negative refractive power, and the seventh lens has positive refractive power; the sixth lens and the seventh lens are both spherical lenses.

5. The projection lens of claim 4, wherein, The sixth lens and the seventh lens are cemented to form a second cemented lens.

6. The projection lens of claim 4, wherein, The rear group of lens sets comprises: an eighth lens, a ninth lens, a tenth lens and an eleventh lens arranged in sequence along the exit direction of the projection light; the eighth lens has positive refractive power, the ninth lens has positive refractive power, the tenth lens has negative refractive power, and the eleventh lens has negative refractive power.

7. The projection lens of claim 6, wherein, The eighth lens, the ninth lens and the tenth lens are all spherical lenses; and the eleventh lens is an aspherical lens.

8. The projection lens of claim 1, wherein, The focal length of the projection lens satisfies: 1<|FB / F|<15; 5<|FM / F|<150; 5<|FF / F|<100; wherein, F represents the equivalent focal length of the projection lens, FF represents the equivalent focal length of the front group of lens sets, FM represents the equivalent focal length of the middle group of lens sets, and FB represents the equivalent focal length of the rear group of lens sets.

9. The projection lens of claim 1, wherein, When the size of the projection image is changed, the positions of the front group of lens sets and the rear group of lens sets are kept unchanged, the middle group of lens sets is moved along the optical axis, and the distance between the projection lens and the projection plane is changed.

10. A projection system, characterized by The projection system comprises: a projection light source; an illumination system located on the light exit side of the projection light source; the illumination system comprises a light modulator; a projection lens, which is the projection lens according to any one of claims 1-9; the projection lens is located on the light exit side of the light modulator.

Images