CN112578610B

CN112578610B - Projection lens and laser projection equipment

Info

Publication number: CN112578610B
Application number: CN201910938956.9A
Authority: CN
Inventors: 李晓平
Original assignee: Qingdao Hisense Laser Display Co Ltd
Current assignee: Qingdao Hisense Laser Display Co Ltd
Priority date: 2019-09-30
Filing date: 2019-09-30
Publication date: 2022-04-26
Anticipated expiration: 2039-09-30
Also published as: CN112578610A

Abstract

The invention discloses a projection lens and laser projection equipment, and belongs to the field of optical equipment. The projection lens includes: a refractor set and a reflector. The refracting lens group comprises a first lens group, a second lens group, a third lens group and a fourth lens group. The third lens group comprises at least one sub lens group, each sub lens group can move along the light emitting direction or the reverse direction of the light emitting direction, the projection size of the projection lens can be adjusted, and the projection size of the projection lens is effectively simplified.

Description

Projection lens and laser projection equipment

Technical Field

The invention relates to the field of optical equipment, in particular to a projection lens and laser projection equipment.

Background

With the improvement of scientific technology, the application of the projection lens in the work and life of people is more and more extensive, such as education, office, household or entertainment, for example, for the projection lens used in a home theater, the higher the resolution of the projection lens is, the higher the user viewing experience is. Therefore, the demand for projection lenses is also increasing.

In the related art, there is a trend toward a laser projection apparatus using ultra-short focus in a home projection apparatus, the laser projection apparatus including: a light valve and a projection lens. The projection lens includes: a refractor set and a reflector. The light valve is used for generating image beams, the image beams firstly enter the refractor set, the refractor set images the image beams, then secondary imaging is carried out through the reflector, the images are reflected to the screen, and the projection is finished by displaying the images through the screen. In order to enable projection of different sizes of the projection lens, the focal plane of the projection device can be adjusted by adjusting the distance between the refractive lens group and the reflecting mirror to adjust the projection size of the projection lens.

At present, in the process of adjusting the distance between the refractive lens group and the reflecting mirror, the reflecting mirror is usually required to be detached from the laser projection equipment, and after the distance between the refractive lens group and the reflecting mirror is determined again, the reflecting mirror is installed in the laser projection equipment again. Therefore, the complexity of adjusting the projection size of the projection lens is high at present.

Disclosure of Invention

The embodiment of the invention provides a projection lens and laser projection equipment. The problem that the complexity of adjusting the projection size of the projection lens in the related art is high can be solved, and the technical scheme is as follows:

according to a first aspect of the present invention, there is provided a projection lens, comprising a refractive lens group and a reflective lens sequentially arranged along a light-emitting direction of a light valve;

the refraction lens group comprises a first lens group, a second lens group, a third lens group and a fourth lens group which are sequentially arranged along the light emergent direction;

the third lens group comprises at least one sub lens group, and each sub lens group can move along the light emitting direction or the reverse direction of the light emitting direction;

the first lens group, the second lens group, the third lens group and the fourth lens group satisfy a focal length formula, and the focal length formula is as follows:

wherein, F is the equivalent focal length of the refractor set, FB is the equivalent focal length of the first lens set, FC is the equivalent focal length of the second lens set, FT is the equivalent focal length of the third lens set, FG is the equivalent focal length of the fourth lens set, and FM is the equivalent focal length of the reflector.

Optionally, the third lens group includes a first sub lens group, a second sub lens group and a third sub lens group sequentially arranged along the light emitting direction;

first sub mirror group includes the edge 1 lens, 2 nd lens and the 3 rd lens that the light-emitting direction set gradually, second sub mirror group includes the edge 4 th lens and the 5 th lens that the light-emitting direction set gradually, third sub mirror group includes the edge the 6 th lens, the 7 th lens and the 8 th lens that the light-emitting direction set gradually, 4 th lens are aspherical lens, except in the third mirror group the outer lens of 4 th lens are spherical lens.

Optionally, the 2 nd lens and the 3 rd lens are attached to form a double cemented lens, and the 6 th lens and the 7 th lens are attached to form a double cemented lens.

Optionally, in the first sub-lens group, diopter of the 1 st lens element is positive, and diopter of the double cemented lens formed by the 2 nd lens element and the 3 rd lens element is positive;

in the second sub-lens group, the diopters of the 4 th lens and the 5 th lens are negative;

in the third sub-lens group, diopter of a double cemented lens formed by the 6 th lens and the 7 th lens is positive, and diopter of the 8 th lens is positive.

Optionally, a distance of movement of each of the sub-lens groups along the light emitting direction or a direction opposite to the light emitting direction is less than or equal to 4 mm.

Optionally, the first lens group includes a9 th lens, a10 th lens, an 11 th lens, a12 th lens, a13 th lens, a14 th lens, a15 th lens, a16 th lens, and a17 th lens that are sequentially disposed along the light exit direction, the 10 th lens and the 14 th lens are both aspheric lenses, and lenses other than the 10 th lens and the 14 th lens in the first lens group are both spherical lenses;

the 11 th lens and the 13 th lens are respectively bonded on two surfaces of the 12 th lens to form a triple cemented lens, and the 16 th lens and the 17 th lens are bonded to form a double cemented lens.

Optionally, the projection lens further includes a diaphragm disposed between the 14 th lens and the 15 th lens.

Optionally, the second lens group includes an 18 th lens, a19 th lens and a20 th lens that are sequentially arranged along the light exit direction, and the 18 th lens, the 19 th lens and the 20 th lens are all spherical lenses;

the 19 th lens and the 20 th lens are jointed to form a double-cemented lens.

Optionally, the fourth lens group includes a21 st lens and a22 nd lens sequentially disposed along the light exit direction, where the 21 st lens is an aspheric lens and the 22 nd lens is a spherical lens.

According to a first aspect of the present invention, there is provided a laser projection apparatus comprising a light source, a light valve, a screen and the projection lens of any one of the first aspects,

the light source is used for providing a laser beam to the light valve;

the light valve is used for modulating the laser beam provided by the light source and then emitting the laser beam to the projection lens;

the projection lens is used for imaging the laser beam provided by the light valve and then emitting the laser beam to a screen.

The technical scheme provided by the embodiment of the invention has the beneficial effects that at least:

the projection lens includes: a refractor set and a reflector. The refracting lens group comprises a first lens group, a second lens group, a third lens group and a fourth lens group. The third lens group comprises at least one sub lens group, each sub lens group can move along the light emitting direction or the reverse direction of the light emitting direction, the projection size of the projection lens can be adjusted, and the projection size of the projection lens is effectively simplified. Moreover, four lens groups in the refraction lens group meet a focal length formula, so that the projection lens can be continuously adjusted in a larger projection range through the third lens group.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the description of the embodiments will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.

FIG. 1 is a schematic illustration of an implementation environment in which embodiments of the present invention are concerned;

fig. 2 is a schematic structural diagram of a projection lens according to an embodiment of the present invention;

fig. 3 is a schematic structural diagram of another projection lens provided in an embodiment of the present invention;

FIG. 4 is an effective diagram illustrating the positions of the sub-lens groups when the projection size of the projection lens is 70 inches in the embodiment of the present invention;

FIG. 5 is an effect diagram of the positions of the sub-mirror groups when the projection size of the projection lens is 100 inches in the embodiment of the present invention;

FIG. 6 is a diagram illustrating the effect of the positions of the sub-lens groups when the projection size of the projection lens is 120 inches in the embodiment of the present invention;

FIG. 7 is a diagram illustrating the effect of the positions of the sub-lens groups when the projection size of the projection lens is 150 inches according to an embodiment of the present invention;

fig. 8 shows a laser projection apparatus according to an embodiment of the present invention.

With the above figures, certain embodiments of the invention have been illustrated and described in more detail below. The drawings and the description are not intended to limit the scope of the inventive concept in any way, but rather to illustrate it by those skilled in the art with reference to specific embodiments.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

Fig. 1 is a schematic diagram of an implementation environment according to an embodiment of the invention, which may include a screen 10 and a projection lens 20.

The projection lens 20 may transmit an image beam toward the screen 10, and the image beam may form an image on the screen 10. The current trend is to reduce the throw ratio of the projection lens 20 (throw ratio is the ratio of the projection distance s to the picture width h, and the projection distance s is the distance between the projection lens 20 and the screen 10), and the smaller the throw ratio, the larger the picture can be projected by the projection lens at the shorter projection distance. A projection lens with a relatively small transmission may be referred to as a short-focus or ultra-short-focus projection lens.

Fig. 2 is a schematic structural diagram of a projection lens according to an embodiment of the present invention, where the projection lens may be the projection lens 20 in the implementation environment shown in fig. 1, and the projection lens 20 includes a refractive lens group 21 and a reflective lens 22 sequentially arranged along a light emitting direction x of a light valve 30 (the light valve may not be included in the projection lens according to the embodiment of the present invention, and the projection lens according to the embodiment of the present invention may receive a light beam emitted from the light valve).

The light valve 30 is a Digital Micromirror Device (DMD), and the DMD may have a resolution of 2K or 4K. In addition, the light valve 30 includes a mirror array and a control circuit, and when the light valve 30 is illuminated, the control circuit controls the mirror array to reflect the light beam emitted from the light source system to generate an image light beam. How the light valve 30 specifically generates the image beam is related to the related art and will not be described herein.

The refractive lens group 21 may include a first lens group 211, a second lens group 212, a third lens group 213 and a fourth lens group 214 sequentially arranged along the light emitting direction x.

In the embodiment of the present invention, the first lens group 211 is used for correcting aberrations other than astigmatism and distortion. The second lens group 212 is used to compensate for aberrations generated during the adjustment of the projection size of the projection lens 20. The third lens group 213 is used to adjust the projection size of the projection lens 20. The fourth lens group 214 is used to adjust the aberration variation caused by different projection sizes in cooperation with the reflector 22, and the fourth lens group 214 is a fixed lens group (i.e. does not move along the light-emitting direction x or in the opposite direction of the light-emitting direction x), so as to keep the distance between the fourth lens group 214 and the reflector 22 unchanged when adjusting the projection sizes.

The third lens group 213 can include at least one sub-lens group. For example, the third lens group 213 may include a first sub lens group 213a, a second sub lens group 213b and a third sub lens group 213c sequentially arranged along the light emitting direction x. Each sub-lens group can move along the light emitting direction x or the reverse direction of the light emitting direction x. Since each of the sub-lens groups included in the third lens group 213 can move along the light-emitting direction x or in the opposite direction of the light-emitting direction x, the projection size of the projection lens can be adjusted by moving each of the sub-lens groups, thereby effectively simplifying the adjustment of the projection size of the projection lens.

The first lens group 211, the second lens group 212, the third lens group 213 and the fourth lens group 214 in the projection lens 20 satisfy the focal length formula. The focal length formula may be:

wherein F is the equivalent focal length of the refractor set 21, FB is the equivalent focal length of the first lens set 211, FC is the equivalent focal length of the second lens set 212, FT is the equivalent focal length of the third lens set 213, FG is the equivalent focal length of the fourth lens set 214, and FM is the equivalent focal length of the reflector 22.

In the embodiment of the present invention, the four lens groups in the refractive lens group 21 satisfy the focal length formula, so that the projection size of the projection lens 20 is large (for example, greater than or equal to 70 inches), and each sub-lens group in the third lens group 213 can move, so that the projection size of the projection lens 20 can be adjusted when the projection size of the projection lens 20 is large. That is, the third mirror group 213 can continuously adjust the projection lens 20 in a wide projection range.

In summary, the projection lens according to the embodiment of the present invention includes: a refractor set and a reflector. The refracting lens group comprises a first lens group, a second lens group, a third lens group and a fourth lens group. The third lens group comprises at least one sub lens group, each sub lens group can move along the light emitting direction or the reverse direction of the light emitting direction, the projection size of the projection lens can be adjusted, and the projection size of the projection lens is effectively simplified. Moreover, four lens groups in the refraction lens group meet a focal length formula, so that the projection lens can be continuously adjusted in a larger projection range through the third lens group.

Referring to fig. 3, which shows a schematic structural view of another projection lens system according to an embodiment of the present invention, the first lens group 211, the second lens group 212, the third lens group 213, the fourth lens group 214, and the reflecting mirror 22 of the refractive lens group 21 are all located on the same optical axis L. The projection lens 20 may be a rotationally symmetric system.

Alternatively, the third lens group 213 may include a first sub-lens group 213a, a second sub-lens group 213b, and a third sub-lens group 213c sequentially arranged along the light emitting direction x. The third lens group 213 includes at least one of the three lens subgroups including a double cemented lens.

For example, the first sub-lens group 213a may include a1 st lens a1, a2 nd lens a2, and a3 rd lens a3, which are sequentially disposed in the light outgoing direction x. The second sub-lens group 213b may include a4 th lens a4 and a5 th lens a5 sequentially disposed along the light-emitting direction x. The third sub-lens group 213c may include a6 th lens a6, a7 th lens a7, and an 8 th lens a8, which are sequentially disposed in the light outgoing direction x.

The 2 nd lens a2 and the 3 rd lens a3 can be jointed to form a double-cemented lens; the 6 th lens a6 and the 7 th lens a7 can be bonded to form a double cemented lens. That is, the first sub-lens group 213a of the third lens group 213 includes a double cemented lens, and the third sub-lens group 213c includes a double cemented lens.

In the third lens group 213, the 4 th lens element a4 can be aspheric, and all the lenses of the third lens group 213 except the 4 th lens element a4 are spherical lenses. In the first sub-lens group 213a, diopter of the 1 st lens element a1 is positive, and diopter of the double cemented lens constituted by the 2 nd lens element a2 and the 3 rd lens element a3 is positive. In the second sub-lens group 213b, diopters of the 4 th lens a4 and the 5 th lens a5 are negative. In the third sub-lens group 213c, diopter of the double cemented lens constituted by the 6 th lens a6 and the 7 th lens a7 is positive, and diopter of the 8 th lens a8 is positive.

Optionally, a distance of movement of each sub-mirror group along the light exit direction x or a direction opposite to the light exit direction x is less than or equal to 4 millimeters (mm). That is, the distance d that each sub-mirror group can move satisfies: d is less than or equal to 4 mm.

Alternatively, the first lens group 211 may include a9 th lens a9, a10 th lens a10, an 11 th lens a11, a12 th lens a12, a13 th lens a13, a14 th lens a14, a15 th lens a15, a16 th lens a16, and a17 th lens a17, which are sequentially disposed in the light exit direction x.

In the first lens group 211, the 10 th lens a10 and the 14 th lens a14 are both aspheric lenses, and can be used for correcting astigmatism and coma of the system; the lenses of the first lens group 211 except the 10 th lens a10 and the 14 th lens a14 are all spherical lenses. The 11 th lens a11 and the 13 th lens a13 are respectively attached to both surfaces of the 12 th lens a12, that is, the 11 th lens a11, the 12 th lens a12 and the 13 th lens a13 can constitute a triple cemented lens; the 16 th lens a16 and the 17 th lens a17 are attached, that is, the 16 th lens a16 and the 17 th lens a17 can constitute a double cemented lens. Diopters of the 9 th lens a9, the 10 th lens a10, the 14 th lens a14 and the 15 th lens a15 are all positive; the diopter of the triple cemented lens constituted by the 11 th lens a11, the 12 th lens a12, and the 13 th lens a13 is negative, and the diopter of the double cemented lens constituted by the 16 th lens a16 and the 17 th lens a17 is negative.

The 10 th lens a10 can use a material with a lower refractive index and a low melting point, such as L-BSL7, D-K59, L-BAL42(L-BSL7, D-K59, L-BAL42 are models of three optical materials), and realizes the processing and manufacturing of the non-curved surface with lower cost.

The triple cemented lens of the 11 th lens a11, the 12 th lens a12, and the 13 th lens a13 can correct aberrations such as spherical aberration, curvature of field, chromatic aberration, etc. of the refractive lens group 21, and adjacent to the 10 th lens a10 of the aspherical lens, can largely control aberrations of the refractive lens group 21. The 12 th lens a12 has an abbe number less than 35 and a refractive index greater than 1.8. The 11 th lens a11 and the 13 th lens a13 have an Abbe number within a range of 1.45 to 1.60 and a refractive index within a range of 1.45 to 1.60. Wherein, the dispersion coefficient is also called Abbe number (English: Abbe) which is a physical quantity used for measuring the light dispersion degree of the medium. The larger the refractive index of the material is, the stronger the dispersion is, and the smaller the abbe number is.

The double cemented lens formed by the 16 th lens a16 and the 17 th lens a17 can be used to correct spherical aberration and chromatic aberration of the refractive lens group 21, and can be formed of a material having a small difference in abbe number to compensate for chromatic aberration generated by the 14 th lens a14 and the 15 th lens a 15.

In the embodiment of the present invention, the lenses of the first lens group 211 may be made of glass, so as to improve the ability of the first lens group 211 to resist thermal deformation, and avoid the problem of poor imaging quality caused by thermal deformation.

Alternatively, the second lens group 212 may include the 18 th lens a18, the 19 th lens a19, and the 20 th lens a20, which are sequentially disposed in the light exit direction x.

In the second lens group 212, the 18 th lens a18, the 19 th lens a19 and the 20 th lens a20 are all spherical lenses. The 19 th lens a19 is attached to the 20 th lens a20, i.e., the 19 th lens a19 and the 20 th lens a20 can constitute a double cemented lens. The diopter of the 18 th lens a18 is positive, and the diopter of the double cemented lens formed by the 19 th lens a19 and the 20 th lens a20 is positive.

Alternatively, the fourth lens group 214 may include the 21 st lens a21 and the 22 nd lens a22 arranged in order along the light exit direction x.

The fourth lens group 214 and the 21 st lens element a21 are aspheric lenses, which can be plastic aspheric lenses or glass aspheric lenses, and the focal power of the 21 st lens element 21 is negative. The 22 nd lens a22 is a spherical lens, and the power of the 22 nd lens a22 is positive.

Optionally, the projection lens further includes a stop 23, and the stop 23 is disposed between the 14 th lens a14 and the 15 th lens a 15. Therefore, the aberration can be conveniently corrected, and the system aperture can be controlled.

Optionally, the first lens group 211 can move along the light emitting direction or the direction opposite to the light emitting direction. Namely, the first lens group can move back and forth along the optical axis, so that the imaging quality of the system can be adjusted, and the tolerance of the system can be compensated to ensure the imaging quality of the system. The first lens group 211 can be moved by sliding or screw rotation.

Alternatively, the mirror 22 may be a concave aspherical mirror or a free-form surface mirror. The power of the mirror 22 is positive.

Optionally, the projection lens further comprises a vibrating mirror disposed between the light valve 30 and the refractive mirror group 21. The vibration lens 24 vibrates to enable the image light beams corresponding to the two adjacent frames of projection images passing through the vibration lens to be not completely overlapped, and the image light beams corresponding to the two adjacent frames of projection images are sequentially emitted to the refraction mirror group, and the projection images are images displayed on the projection screen after the image light beams pass through the projection lens.

Optionally, the vibration mirror 24 is a flat glass. The vibration lens 24 can vibrate, the vibration lens 24 vibrates to make the image light beam corresponding to two adjacent frames of projection images passing through the vibration lens 24 not overlap completely, so that the image light beam emitted to the same pixel is increased, and further the resolution of imaging is improved, and because the vibration of the vibration lens 24 makes the image light beam corresponding to two adjacent frames of projection images staggered slightly, and further the transition between the pixels is smoother, so that the fine and smooth feeling of imaging is improved, and further the imaging quality is improved, and the image quality of high resolution is realized.

Optionally, a total reflection prism 25 may be further disposed between the light valve 30 and the vibration mirror 24, and the total reflection prism 25 includes two cemented total reflection prisms, a first total reflection prism (not shown in fig. 3) and a second total reflection prism (not shown in fig. 3), respectively. The light beam emitted from the illumination system is first emitted to the first total reflection prism, when the light beam is emitted to the first total reflection prism, the light beam is totally reflected, the light beam after total reflection is emitted to the light valve 30, and then reflected by the light valve 30 to form an image light beam, and then the generated image light beam is emitted to the total reflection prism 25 from the light valve 30, when the image light beam is emitted to the total reflection prism 25 from the light valve 30, the image light beam is not totally reflected, but directly penetrates through and emits the image light beam to the vibration lens 24. Because the first total reflection prism makes the light beam emitted to the first total reflection prism totally reflect, the light beam can be reflected to the light valve 30 by using one total reflection prism, so that multiple reflections are not required to be carried out by a plurality of common reflectors, the using number of the common reflectors is reduced, and the volume of the projection lens is greatly reduced; in addition, the total reflection prism 25 helps to meet the requirement of a telecentric light path, so that the image beam generated by the light valve 30 can be uniform, thereby improving the quality of the projected image.

The structure shown in fig. 3 is a secondary imaging structure, after the image beam of the light valve 30 passes through the refractor set 21, a primary imaging is performed between the reflector 22 and the refractor set 21, and after the primary imaging is reflected by the reflector 22, a secondary undistorted image is formed on the screen; the projection lens provided by the embodiment of the invention is compact as a whole, and the resolving power of the projection lens is improved through the diaphragm arrangement, the aspheric lens and the reflector to correct the large-field aberration, so that the high-resolution imaging quality is realized.

The F # of the projection lens 20 shown in fig. 3 is between 1.8 and 2.3, the length of the refractive lens group 212 is smaller than or equal to 275mm, the projection range is 70 to 150 inches, the projection ratio is smaller than or equal to 0.25, the telecentricity is smaller than or equal to 1 °, the offset (the offset is the offset of the light valve pixel surface with respect to the optical axis, english: offset) is 135% to 150%, and the back focal distance (the back focal distance is the physical distance from the light valve 30 to the 1 st lens a 1) is 28 to 45 mm.

Assuming that F # of the projection lens 20 is 2.3, transmittance is 0.25, back focal length is 42mm, the length of the refractive lens group 212 is 275mm, telecentricity is less than or equal to 0.7 °, 8.6 | FB/F |, 145.9 | FC/F |, 8.21 |. When each sub-lens group in the third lens group 213 is adjusted to move along the light-emitting direction x or in the opposite direction of the light-emitting direction x, the projection lens 20 can be adjusted within the projection range of 70 to 150 inches. For example, please refer to fig. 4 to 7. Fig. 4 is an effect diagram of the positions of the sub-lens groups when the projection size of the projection lens 20 is 70 inches, where | FT/F | ═ 8.8846; fig. 5 is an effect diagram of the positions of the sub-mirror groups when the projection size of the projection lens 20 is 100 inches, where | FT/F | -8.8752; fig. 6 is an effect diagram of the positions of the sub-lens groups when the projection size of the projection lens 20 is 120 inches, where | FT/F | -8.8672; fig. 7 is an effect diagram of the positions of the sub-lens groups when the projection size of the projection lens 20 is 150 inches, where | FT/F | -8.8623. The information of each lens and the meaning of the mark can refer to the embodiment shown in fig. 3, and are not described herein again

As shown in fig. 8, an embodiment of the present invention further provides a laser projection apparatus, which includes a light source 40, a light valve 30, a screen 10, and the projection lens 20 provided in the foregoing embodiment; the light source 40 is used to provide a laser beam to the light valve 30; the light valve 30 is used for modulating the laser beam provided by the light source 40 and then emitting the modulated laser beam to the projection lens 20; the projection lens 20 is used for imaging the laser beam provided by the light valve 30 and then emitting the imaged laser beam to the screen 10.

The optical path inside the projection lens 20 can be as shown in fig. 4 to 7.

In the present invention, the terms "first", "second", "third" and "fourth" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance. The term "plurality" means two or more unless expressly limited otherwise.

The above description is only exemplary of the present invention and should not be taken as limiting the invention, as any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A projection lens is characterized by comprising a refractor set and a reflector which are sequentially arranged along the light emergent direction of a light valve;

the refraction lens group consists of a first lens group, a second lens group, a third lens group and a fourth lens group which are sequentially arranged along the light emergent direction;

wherein, F is the equivalent focal length of the refractor set, FB is the equivalent focal length of the first mirror set, FC is the equivalent focal length of the second mirror set, FT is the equivalent focal length of the third mirror set, FG is the equivalent focal length of the fourth mirror set, and FM is the equivalent focal length of the reflector;

the first lens group is used for correcting aberration except astigmatism and distortion, the second lens group is used for compensating aberration generated in the process of adjusting the projection size of the projection lens, the third lens group is used for adjusting the projection size of the projection lens, and the fourth lens group is used for matching with the reflector to adjust aberration change caused by different projection sizes.

2. The projection lens of claim 1, wherein the third lens group comprises a first sub lens group, a second sub lens group and a third sub lens group sequentially arranged along the light exit direction;

3. The projection lens of claim 2 wherein the 2 nd lens and the 3 rd lens are bonded to form a double cemented lens, and the 6 th lens and the 7 th lens are bonded to form a double cemented lens.

4. The projection lens of claim 2, wherein in the first sub-lens group, the diopter of the 1 st lens is positive, and the diopter of the double cemented lens formed by the 2 nd lens and the 3 rd lens is positive;

5. The projection lens of claim 1, wherein the distance of each sub-lens group moving along the light-emitting direction or the direction opposite to the light-emitting direction is less than or equal to 4 mm.

6. The projection lens according to any one of claims 1 to 5, wherein the first lens group includes a9 th lens, a10 th lens, an 11 th lens, a12 th lens, a13 th lens, a14 th lens, a15 th lens, a16 th lens and a17 th lens that are sequentially arranged along the light exit direction, the 10 th lens and the 14 th lens are both aspheric lenses, and the lenses except the 10 th lens and the 14 th lens in the first lens group are both spherical lenses;

7. The projection lens of claim 6 further comprising a stop disposed between the 14 th lens and the 15 th lens.

8. The projection lens according to any one of claims 1 to 5, wherein the second lens group comprises an 18 th lens, a19 th lens and a20 th lens which are sequentially arranged along the light exit direction, and the 18 th lens, the 19 th lens and the 20 th lens are all spherical lenses;

the 19 th lens and the 20 th lens are jointed to form a double-cemented lens.

9. The projection lens according to any one of claims 1 to 5, wherein the fourth lens group comprises a21 st lens and a22 nd lens sequentially arranged along the light-emitting direction, the 21 st lens is an aspheric lens, and the 22 nd lens is a spherical lens.

10. A laser projection device, comprising a light source, a light valve, a screen, and a projection lens according to any one of claims 1 to 9,

the light source is used for providing a laser beam to the light valve;