CN112444930A

CN112444930A - Projection lens, focusing method and device of projection lens and projector

Info

Publication number: CN112444930A
Application number: CN201910834069.7A
Authority: CN
Inventors: 杜玉楠; 罗超; 王宇
Original assignee: Qingdao Hisense Laser Display Co Ltd
Current assignee: Qingdao Hisense Laser Display Co Ltd
Priority date: 2019-09-04
Filing date: 2019-09-04
Publication date: 2021-03-05

Abstract

The invention discloses a projection lens, a focusing method and device of the projection lens and a projector, and belongs to the field of projection. The projection lens includes: the lens comprises a first lens group, a second lens group, a third lens group, a first lens cone, a second lens cone and a third lens cone; the first lens cone, the second lens cone and the third lens cone are sequentially arranged along the light emergent direction of a light valve of a projector where the projection lens is located, the first lens group is located in the first lens cone, one part of lenses in the second lens group is located in the second lens cone, the other part of lenses is located in the third lens cone, and the third lens group is located in the third lens cone; the second lens group comprises n lenses, n is more than or equal to 1 and less than or equal to 3, and the n lenses are all configured to be connected with a driving assembly in the projector where the n lenses are located and move along the optical axis of the second lens group under the control of the driving assembly so as to change the image distance of the projection lens. The invention can simplify the focusing process of the projection lens. The invention is used for focusing of the projection lens.

Description

Projection lens, focusing method and device of projection lens and projector

Technical Field

The invention relates to the field of projection, in particular to a projection lens, a focusing method and a focusing device of the projection lens and a projector.

Background

The laser display projection technology is a novel display projection technology in the current market. The laser projector applying the technology can realize the automatic focusing function at present, and the laser projector capable of realizing the automatic focusing function is also called as an automatic focusing projector. Wherein, focusing refers to adjusting the image distance of the projector by adjusting the position of the focus of the projector.

The focusing projector comprises a driving assembly and a projection lens, and the projection lens comprises a focusing lens group for focusing. When the projection lens projects to the screen and the distance between the projection lens and the screen is changed, the driving assembly can control each focusing lens in the focusing lens group to move along the optical axis of the focusing lens group according to the corresponding relation between the preset distance and the image distance.

However, the number of lenses in a focusing lens group of the current focusing projector is large, the number of lenses is usually larger than six, and a non-focusing lens is usually arranged between two focusing lenses of the focusing lens group. Therefore, the number of lenses to be controlled by the driving assembly in the focusing process is large, and the focusing lenses arranged at intervals need to be controlled to move, so that the focusing process is complex.

Disclosure of Invention

The invention provides a projection lens, a focusing method and a focusing device of the projection lens and a projector, which can simplify the focusing process of the projection lens, and the technical scheme is as follows:

in a first aspect, a projection lens is provided, which includes: the lens comprises a first lens group, a second lens group, a third lens group, a first lens cone, a second lens cone and a third lens cone;

the first lens cone, the second lens cone and the third lens cone are sequentially arranged along the light emergent direction of a light valve of a projector where the projection lens is located, the first lens group is located in the first lens cone, one part of lenses in the second lens group is located in the second lens cone, the other part of lenses is located in the third lens cone, the third lens group is located in the third lens cone, and the first lens group, the second lens group and the third lens group share an optical axis;

the second lens group comprises n lenses, n is more than or equal to 1 and less than or equal to 3, and the n lenses are all configured to be connected with a driving assembly in the projector where the n lenses are located and move along the optical axis of the second lens group under the control of the driving assembly so as to change the image distance of the projection lens.

In a second aspect, a focusing method for a projection lens is provided, and is applied to a driving assembly in a projector, where the projection lens is the projection lens in any one of the first aspect, and the driving assembly is connected to n lenses in the second lens group, and the method includes:

and controlling the n lenses to move along the optical axis of the second lens group so as to change the image distance of the projection lens.

In a third aspect, a focusing apparatus for a projection lens is provided, where the focusing apparatus for a projection lens includes various modules for performing the focusing method for a projection lens according to any one of the second aspects.

In a fourth aspect, a focusing apparatus for a projection lens is provided, including: a processor; and a memory for storing executable instructions for the processor;

when the processor executes the executable instructions, the focusing method of the projection lens according to any one of the second aspect can be implemented.

In a fifth aspect, a computer-readable storage medium having instructions stored therein is provided;

when the instructions are run on a processing component, the processing component is caused to execute the focusing method of the projection lens according to any one of the second aspect.

In a sixth aspect, there is provided a projector including: a driving assembly, a light valve and the projection lens of any one of the first aspect;

the projection lens comprises a first lens group, a second lens group and a third lens group, and the light valve, the first lens group, the second lens group and the third lens group are sequentially arranged;

the driving component is connected with each lens in the second lens group and is configured to control each lens to move along the optical axis of the second lens group.

The technical scheme provided by the invention can have the following beneficial effects:

the invention provides a projection lens, a focusing method and a focusing device of the projection lens and a projector. The number of lenses required to be controlled by the driving assembly is small, and the driving assembly does not need to control the lenses arranged at intervals to move so as to change the image distance of the projection lens, so that the focusing process is simplified.

Drawings

In order to illustrate the embodiments of the present invention more clearly, the drawings that are needed in the description of the embodiments will be briefly described below, it being apparent that the drawings in the following description are only some embodiments of the invention, and that other drawings may be derived from those drawings by a person skilled in the art without inventive effort.

Fig. 1 is a schematic application environment diagram of a projector according to an embodiment of the present invention;

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

FIG. 3 is a schematic diagram of an imaging optical path of a projection lens with a 100-inch frame size according to an embodiment of the present invention;

FIG. 4 is a schematic diagram of an imaging optical path of a projection lens with a 90-inch frame size according to an embodiment of the present invention;

FIG. 5 is a schematic diagram of an imaging optical path of a projection lens with a 120-inch frame size according to an embodiment of the present invention;

fig. 6 is a schematic view of an imaging contrast simulation interface of a projection lens according to an embodiment of the present invention when the size of a screen is 100 inches;

FIG. 7 is a schematic diagram of an imaging contrast simulation interface of a projection lens with a 90-inch frame size according to an embodiment of the present invention;

fig. 8 is a schematic view of an imaging contrast simulation interface of a projection lens according to an embodiment of the present invention when a picture size is 120 inches;

fig. 9 is a diagram of an image synthetic error on a sagittal sector of a projection lens according to an embodiment of the present invention when a picture size is 100 inches;

fig. 10 is a diagram illustrating an image synthetic error on a sagittal sector of a projection lens according to an embodiment of the present invention when a frame size is 100 inches;

fig. 11 is a diagram of an image synthetic error on a sagittal sector of a projection lens according to an embodiment of the present invention when a picture size is 100 inches;

fig. 12 is a diagram of an image synthetic error on a sagittal sector of a projection lens according to an embodiment of the present invention when a picture size is 100 inches;

fig. 13 is a diagram of an image synthetic error on a sagittal sector of a projection lens according to an embodiment of the present invention when a picture size is 100 inches;

fig. 14 is a diagram of an image synthetic error on a sagittal sector of a projection lens according to an embodiment of the present invention when a picture size is 100 inches;

fig. 15 is a diagram illustrating an image synthetic error on a sagittal sector of a projection lens according to an embodiment of the present invention when a frame size is 100 inches;

fig. 16 is a diagram of an image synthetic error on a sagittal plane of a projection lens according to an embodiment of the present invention when a picture size is 100 inches;

fig. 17 is a diagram of an image synthetic error on a sagittal sector of a projection lens according to an embodiment of the present invention when a picture size is 100 inches;

fig. 18 is a diagram of an image synthetic error on a sagittal sector of a projection lens according to an embodiment of the present invention when a picture size is 100 inches;

FIG. 19 is a diagram illustrating an image integration error of a projection lens according to an embodiment of the present invention in a meridian plane with a 100 inch frame size;

FIG. 20 is a diagram illustrating an image integration error of a projection lens according to an embodiment of the present invention in a meridian plane with a 100 inch frame size;

FIG. 21 is a diagram illustrating an image integration error of a projection lens according to an embodiment of the present invention in a meridian plane with a 100 inch frame size;

FIG. 22 is a diagram illustrating an image integration error of a projection lens according to an embodiment of the present invention in a meridian plane with a 100 inch frame size;

FIG. 23 is a diagram illustrating an image integration error of a projection lens according to an embodiment of the present invention in a meridian plane with a 100 inch frame size;

FIG. 24 is a diagram illustrating an image integration error of a projection lens according to an embodiment of the present invention in a meridian plane with a 100 inch frame size;

FIG. 25 is a diagram illustrating an image integration error of a projection lens according to an embodiment of the present invention in a meridian plane with a 100 inch frame size;

FIG. 26 is a diagram illustrating an image integration error of a projection lens according to an embodiment of the present invention in a meridian plane with a 100 inch frame size;

FIG. 27 is a diagram illustrating an image integration error of a projection lens according to an embodiment of the present invention in a meridian plane with a 100 inch frame size;

FIG. 28 is a diagram illustrating an image integration error of a projection lens according to an embodiment of the present invention in a meridian plane with a 100 inch frame size;

fig. 29 is a diagram illustrating an image synthetic error on a sagittal sector of a projection lens according to an embodiment of the present invention when a frame size is 90 inches;

fig. 30 is a diagram illustrating an image synthetic error on a sagittal plane of a projection lens according to an embodiment of the present invention when a frame size is 90 inches;

fig. 31 is a diagram illustrating an image synthetic error on a sagittal plane of a projection lens according to an embodiment of the present invention when a frame size is 90 inches;

fig. 32 is a diagram illustrating an image synthetic error on a sagittal plane of a projection lens according to an embodiment of the present invention when the size of the projection lens is 90 inches;

fig. 33 is a diagram illustrating an image integration error of a sagittal plane of a projection lens according to an embodiment of the present invention when the size of the projection lens is 90 inches;

fig. 34 is a diagram illustrating an image synthetic error on a sagittal plane of a projection lens according to an embodiment of the present invention when a frame size is 90 inches;

fig. 35 is a diagram illustrating an image synthetic error on a sagittal sector of a projection lens according to an embodiment of the present invention when a frame size is 90 inches;

fig. 36 is a diagram illustrating an image synthetic error on a sagittal plane of a projection lens according to an embodiment of the present invention when a frame size is 90 inches;

fig. 37 is a diagram illustrating an image synthetic error on a sagittal plane of a projection lens according to an embodiment of the present invention when the size of a frame is 90 inches;

fig. 38 is a diagram illustrating an image synthetic error on a sagittal plane of a projection lens according to an embodiment of the present invention when a frame size is 90 inches;

FIG. 39 is a diagram illustrating an image integration error of a projection lens according to an embodiment of the present invention in a meridian plane when a frame size is 90 inches;

FIG. 40 is a diagram illustrating an image integration error of a projection lens according to an embodiment of the present invention in a meridian plane with a 90-inch frame size;

FIG. 41 is a diagram illustrating an image integration error of a projection lens according to an embodiment of the present invention in a 90-inch frame size of a meridian plane;

FIG. 42 is a diagram illustrating an image integration error of a projection lens according to an embodiment of the present invention in a 90-inch frame size of a meridian plane;

FIG. 43 is a diagram illustrating an image integration error of a meridian plane of a projection lens according to an embodiment of the present invention when the size of the image plane is 90 inches;

FIG. 44 is a diagram illustrating an image integration error of a projection lens according to an embodiment of the present invention in a 90-inch frame in a meridian plane;

FIG. 45 is a diagram illustrating an image integration error of a projection lens according to an embodiment of the present invention in a meridian plane when a frame size is 90 inches;

FIG. 46 is a diagram illustrating an image integration error of a projection lens according to an embodiment of the present invention in a meridian plane when a frame size is 90 inches;

FIG. 47 is a diagram illustrating an image integration error of a projection lens according to an embodiment of the present invention in a 90-inch frame in a meridian plane;

FIG. 48 is a diagram illustrating an image integration error of a projection lens according to an embodiment of the present invention in a 90-inch frame size of a meridian plane;

fig. 49 is a graph of an image synthetic error on a sagittal plane of a projection lens according to an embodiment of the present invention when a picture size is 120 inches;

fig. 50 is a diagram illustrating an image synthetic error on a sagittal sector of a projection lens according to an embodiment of the present invention when a frame size is 120 inches;

fig. 51 is a diagram illustrating an image synthetic error on a sagittal sector of a projection lens according to an embodiment of the present invention when a frame size is 120 inches;

fig. 52 is a diagram illustrating an image synthetic error on a sagittal sector of a projection lens according to an embodiment of the present invention when a frame size is 120 inches;

fig. 53 is a diagram illustrating an image synthetic error on a sagittal sector of a projection lens according to an embodiment of the present invention when a frame size is 120 inches;

fig. 54 is a diagram illustrating an image synthetic error on a sagittal sector of a projection lens according to an embodiment of the present invention when a frame size is 120 inches;

fig. 55 is a diagram illustrating an image synthetic error on a sagittal sector of a projection lens according to an embodiment of the present invention when a frame size is 120 inches;

fig. 56 is a diagram illustrating an image synthetic error on a sagittal sector of a projection lens according to an embodiment of the present invention when a frame size is 120 inches;

fig. 57 is a diagram illustrating an image synthetic error on a sagittal sector of a projection lens according to an embodiment of the present invention when a frame size is 120 inches;

fig. 58 is a diagram illustrating an image synthetic error on a sagittal plane of a projection lens according to an embodiment of the present invention when a frame size is 120 inches;

FIG. 59 is a diagram illustrating an image integration error of a projection lens according to an embodiment of the present invention in a meridian plane with a 120 "frame size;

FIG. 60 is a diagram illustrating an image integration error of a projection lens according to an embodiment of the present invention in a meridian plane with a 120 inch frame size;

FIG. 61 is a diagram illustrating an image integration error of a projection lens according to an embodiment of the present invention in a meridian plane with a 120 inch frame size;

fig. 62 is a diagram illustrating an image integration error of a projection lens according to an embodiment of the present invention in a meridian plane when a picture size is 120 inches;

FIG. 63 is a diagram illustrating an image integration error of a projection lens according to an embodiment of the present invention in a meridian plane with a 120 inch frame size;

FIG. 64 is a diagram illustrating an image integration error of a projection lens according to an embodiment of the present invention in a meridian plane with a 120 inch frame size;

FIG. 65 is a diagram illustrating an image integration error of a projection lens according to an embodiment of the present invention in a meridian plane with a 120 inch frame size;

FIG. 66 is a diagram illustrating an image integration error of a projection lens according to an embodiment of the present invention in a meridian plane with a 120 inch frame size;

FIG. 67 is a diagram illustrating an image integration error of a projection lens according to an embodiment of the present invention in a meridian plane with a 120 inch frame size;

fig. 68 is a diagram illustrating an image integration error of a projection lens in a meridian plane when a picture size of the projection lens is 120 inches according to an embodiment of the present invention;

fig. 69 is a flowchart illustrating a focusing method for a projection lens according to an embodiment of the present invention;

fig. 70 is a block diagram of a focusing apparatus for a projection lens according to an embodiment of the present invention;

FIG. 71 is a block diagram of another focusing apparatus for a projection lens according to an embodiment of the present invention;

fig. 72 is a schematic view illustrating the direction of an image beam in a projector according to an embodiment of the present invention;

fig. 73 is a schematic diagram of an imaging optical path of a projector according to an embodiment of the present invention.

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

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention clearer, the present invention will be described in further detail with reference to the accompanying drawings, and it is apparent that the described embodiments are only a part of the embodiments of the present invention, not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Fig. 1 is a schematic diagram of an application environment of a projector according to an embodiment of the present invention, and referring to fig. 1, the application environment includes a projector 1 and a screen 2. The projector 1 may include: a light valve 10, a Total Internal Reflection (TIR) prism 20 and a projection lens 30, which are arranged in sequence, wherein the projection lens 30 comprises a refractive system S1 and a reflective system S2 arranged in sequence in a direction away from the TIR prism 20.

The light valve 10 is used to generate an image beam when being illuminated. Illustratively, the light valve 10 may be a digital micro-mirror device (DMD), which may have a resolution of 2K resolution (meaning that the pixel values per row of the device are at or near 2000), 3K resolution (meaning that the pixel values per row of the device are at or near 3000), or 4K resolution (meaning that the pixel values per row of the device are at or near 4096).

The TIR prism 20 is used to reflect the image beam to the refraction system S1 in the projection lens 30 to improve the brightness and contrast of the image beam entering the refraction system S1. For example, the TIR prism 20 may be 2 total reflection prisms, and may also be 2a total reflection prisms, where a is an integer greater than 1.

The refractive system S1 is used to refract the image beam entering the refractive system S1 to the reflective system S2, where the image beam is first imaged between the refractive system S1 and the reflective system S2 (i.e. the image beam forms a convergence point between the refractive system S1 and the reflective system S2).

After the first imaging, the reflection system S2 is used to project the image beam outputted from the refraction system S1 onto the screen 2, so as to display a large-sized projection picture on the screen 2. For example, the reflection system S2 can correct distortion aberration of the image beam refracted by the refraction system S1, and then project the image beam onto a screen to display a distortion-free projection picture on the screen.

Alternatively, as shown in fig. 1, the projector 1 may further include: and a mapping shift mirror group 40 disposed between the TIR prism 20 and the projection lens 30. The image shift mirror group 40 is configured to shift the image beam reflected by the TIR prism 20, and then transmit the shifted image beam to the projection lens, so as to improve the resolution of the picture finally reflected onto the projection screen. The mirror image shift assembly 40 may be a plate-shaped transparent device, such as a flat transparent glass plate. When the image shift mirror group 40 works, the image shift mirror group 40 can be driven by devices such as a motor and the like to vibrate at high frequency, so that the image light beams are shifted, the image light beams corresponding to two continuous projection pictures are staggered and superposed, and the clear projection pictures can be watched by human eyes by using the visual persistence effect of the human eyes, so that the projection display resolution is improved.

In the embodiment of the present invention, the projector 1 may be a projector capable of focusing (also referred to as a focusing projector), and accordingly, the projection lens 30 includes a focusing lens group for focusing. Illustratively, as shown in fig. 1, the projector 1 may further include: a drive assembly 50. When the projection lens 30 projects a projection image onto a screen and the distance between the projection lens 30 and the screen changes, the driving assembly 50 can control each focusing lens in the focusing lens group to move along the optical axis of the focusing lens group according to the corresponding relationship between the preset distance and the image distance.

However, in the related art, the number of lenses in the focusing lens group is large, and usually the number of lenses is larger than 6, and usually a non-focusing lens is disposed between two focusing lenses of the focusing lens group. Therefore, the number of lenses to be controlled by the driving assembly in the focusing process is large, and the focusing lenses arranged at intervals need to be controlled to move, so that the focusing process is complex.

Fig. 2 is a schematic structural diagram of a projection lens according to an embodiment of the present invention, where the projection lens can be applied to the projector 1 shown in fig. 1. Referring to fig. 2, the projection lens 30 includes: a first lens group 301, a second lens group 302, a third lens group 303, a first lens barrel, a second lens barrel and a third lens barrel. The first barrel, the second barrel, and the third barrel are not shown in fig. 2. The first lens barrel, the second lens barrel and the third lens barrel are sequentially arranged along the light emergent direction X of a light valve of a projector where the projection lens is located. The first lens group 301 is located in the first barrel, a part of lenses in the second lens group 302 is located in the second barrel, and another part of lenses is located in the third barrel. The third lens group 303 is disposed in the third lens barrel, and the first lens group 301, the second lens group 302 and the third lens group 303 share an optical axis L. The lenses in each lens group can only move in the lens cone where the lens group is located. The second lens group 302 includes n lenses, n is greater than or equal to 1 and less than or equal to 3, and fig. 2 illustrates that the second lens group 302 includes three lenses. The n lenses are configured to be connected to a driving component in the projector, and move along the optical axis L of the second lens group 302 under the control of the driving component, so as to change the image distance of the projection lens 30. The image distance of the projection lens refers to the distance from the main plane of the projection lens to the screen projected by the projection lens.

In summary, in the projection lens provided in the embodiments of the present invention, a portion of the lenses in the second lens group is located in the second lens barrel, another portion of the lenses is located in the third lens barrel, and the second lens group includes at most five lenses, and each lens in the second lens group can move along the optical axis of the second lens group under the control of the driving assembly to change the image distance of the projection lens. The number of lenses required to be controlled by the driving assembly is small, and the driving assembly does not need to control the lenses arranged at intervals to move so as to change the image distance of the projection lens, so that the focusing process is simplified.

It should be noted that: in the embodiment of the present invention, the projection lens includes a first lens group, a second lens group, and a third lens group, which are not limited in the embodiment of the present invention.

Alternatively, the second lens group 302 may include 3 lenses, one part of the lenses includes two lenses, and the other part of the lenses includes one lens. That is, two lenses are located in the second barrel, and one lens is located in the third barrel. For example, as shown in fig. 2, the second lens group 302 may include a first spherical lens 3021 with positive optical power, a second spherical lens 3022 with negative optical power, and a third spherical lens 3023 with positive optical power, which are sequentially arranged along the light-exiting direction of the light valve of the projector where the projection lens is located, where the first spherical lens 3021 is close to the first lens group 301, and the third spherical lens 3023 is close to the third lens group 303.

In general, when the size of a picture projected by a projection lens is adjustable, the vertical distance (also called projection distance) between the point where an image beam of the projection lens exits and a screen is also changed, and accordingly, the picture projected by the projection lens is unclear. In order to make the projection pictures of all sizes clear, the projection lens needs to be focused. In the embodiment of the present invention, when the projection lens is focused, the first lens group 301 and the third lens group 303 are kept still, and each lens in the second lens group 302 is moved along the optical axis L of the second lens group 302 under the control of the driving assembly to change the image distance of the projection lens 30.

Illustratively, when the projection distance becomes large such that the size of the screen becomes small relative to 100 inches, based on 100 inches of the size of the screen projected by the projection lens, the first spherical lens 3021, the second spherical lens 3022, and the third spherical lens 3023 move in the direction of approaching the first lens group 301 along the optical axis L of the second lens group 302 during focusing. When the projection distance is reduced to increase the size of the image frame relative to 100 inches, the first spherical lens 3021, the second spherical lens 3022, and the third spherical lens 3023 move in a direction away from the first lens group 301 along the optical axis L of the second lens group 302 during focusing.

For example, referring to fig. 3 to 5, fig. 3 is a schematic image light path diagram of a projection lens with a picture size of 100 inches according to an embodiment of the present invention, fig. 4 is a schematic image light path diagram of a projection lens with a picture size of 90 inches according to an embodiment of the present invention, and fig. 5 is a schematic image light path diagram of a projection lens with a picture size of 120 inches according to an embodiment of the present invention. As can be seen from fig. 3 to 5, in the projection lens with a picture size of 90 inches, relative to the projection lens with a picture size of 100 inches, the first spherical lens 3021, the second spherical lens 3022 and the third spherical lens 3023 all move along the optical axis L of the second lens group 302 in a direction approaching the first lens group 301. In the projection lens with a 120-inch frame size, the first spherical lens 3021, the second spherical lens 3022, and the third spherical lens 3023 all move along the optical axis L of the second lens group 302 in a direction away from the first lens group 301. The first spherical lens 3021, the second spherical lens 3022, and the third spherical lens 3023 may have different moving distances.

Optionally, the first lens group 301 may include m lenses, m is a positive integer, and 6 ≦ m < 16. By way of example, the first lens group 301 may comprise 6 lenses, or 7 lenses or 11 lenses.

When the first lens group 301 comprises 11 lenses, the first lens group 301 can comprise 2 aspheric lenses and 9 spherical lenses. For example, as shown in fig. 2, the first lens group 301 comprises: a fourth spherical lens 3011 with positive focal power, a fifth spherical lens 3012 with positive focal power, a third cemented spherical lens 3013 with positive focal power (composed of three spherical lenses cemented by glue), a sixth spherical lens 3014 with negative focal power, a seventh spherical lens 3015 with positive focal power, an eighth spherical lens 3016 with negative focal power, a ninth spherical lens 3017 with positive focal power, and a double cemented spherical lens 3018 with negative focal power (composed of two spherical lenses cemented by glue) arranged in sequence. The fourth spherical lens 3011 is far from the second lens group 302, and the double-cemented spherical lens 3018 is close to the second lens group 302.

Fig. 2 shows a case where first lens group 301 includes 11 lenses, and when first lens group 301 includes 6 lenses, first lens group 301 may include 1 aspherical lens and 5 spherical lenses. For example, the first lens group 301 may include: and the three cemented spherical lenses with positive focal power, the fourth aspheric lens with positive focal power and the double cemented spherical lenses with negative focal power are sequentially arranged, wherein the three cemented spherical lenses are far away from the second lens group 302, and the double cemented spherical lenses are close to the second lens group 302.

When the first lens group 301 comprises 7 lenses, the first lens group 301 can comprise 2 aspheric lenses and 5 spherical lenses. For example, the first lens group 301 may include: a fourth aspheric lens with positive focal power, a third cemented spherical lens with positive focal power, a fifth aspheric lens with positive focal power and a double cemented spherical lens with negative focal power, which are sequentially arranged, wherein the fourth aspheric lens is far away from the second lens group 302, and the double cemented spherical lens is close to the second lens group 302.

As shown in fig. 2, the triple cemented spherical lens 3013 may include: a tenth spherical lens a1 with positive focal power, an eleventh spherical lens a3 with negative focal power and a twelfth spherical lens a3 with positive focal power, which are arranged in sequence in the direction close to the second lens group 302. The double cemented spherical lens 3018 may include: a thirteenth spherical lens a4 with negative power and a fourteenth spherical lens a5 with positive power, which are arranged in sequence in the direction close to the second lens group 302.

The triple-cemented spherical lens 3013 and the double-cemented spherical lens 3018 are mainly used to correct chromatic aberration (including axial chromatic aberration and vertical-axis chromatic aberration) of the projection lens, and have a certain correction capability for monochromatic aberration (such as spherical aberration, coma aberration, astigmatism, field curvature, or distortion) of the projection lens. The image beam sequentially passes through the tri-cemented spherical lens 3013 and the bi-cemented spherical lens 3018, and after the tri-cemented spherical lens 3013 corrects the chromatic aberration of the projection lens, the bi-cemented spherical lens 3018 further corrects the residual chromatic aberration of the projection lens accurately. The focal power of the thirteenth spherical lens a4 included in the double-cemented spherical lens 3018 is negative, and the focal power of the fourteenth spherical lens a5 is positive, so that the positive chromatic aberration generated by the image light beam passing through the thirteenth spherical lens a4 and the negative chromatic aberration generated by the fourteenth spherical lens a5 cancel each other out, thereby correcting the chromatic aberration of the image light beam to 0. It should be noted that the positions of the triple-cemented spherical lens 3013 and the double-cemented spherical lens 3018 in the projection lens may be interchanged, which is not limited in the embodiment of the present invention.

Optionally, the third lens group 303 can include n lenses, n is a positive integer, and n is greater than or equal to 2 and less than 5. For example, the third lens group 303 may include two lenses, and in this case, the third lens group 303 may include 1 aspheric lens and 1 spherical lens. For example, as shown in fig. 2, the third lens group 303 may include: a fifteenth spherical lens 3031 of negative power and a sixteenth aspherical lens 3032 of negative power are arranged in this order. The fifteenth spherical lens 3031 is close to the second lens group 302, and the sixteenth spherical lens 3032 is far from the second lens group 302.

In general, the lenses of the projection lens can be made of glass material. However, the glass material is expensive, and the processing process is complicated when the aspherical lens is made of the glass material. Since the sixteenth aspheric lens 3032 is far away from the light valve, has a large caliber and is consumable, the material of the sixteenth aspheric lens 3032 may be plastic, such as 480R (a plastic type). The plastic material has low price, and the processing technology is simpler when the plastic material is used for manufacturing the aspheric lens. For example, the aspheric lens may be made of plastic material by a molding process.

The projection lens provided by the embodiment of the invention comprises 3 aspheric lenses in total, and the 3 aspheric lenses are respectively as follows: a fifth aspheric lens 3012, a ninth aspheric lens 3017, and a sixteenth aspheric lens 3032. The symmetrical aspheric lens is convenient to machine and manufacture due to the regular shape of the symmetrical aspheric lens, and is particularly easy to machine and manufacture due to the rotation symmetrical aspheric lens. Therefore, when the 3 aspheric lenses in the projection lens are all in a rotational symmetry structure, the processing process of the projection lens can be simplified, and the processing cost can be reduced.

The 3 aspherical lenses are mainly used for correcting aberration of the projection lens. Illustratively, the fifth aspheric lens 3012 can be used to correct coma, astigmatism, and curvature of field of the projection lens. The ninth aspheric lens 3017 may be used to correct spherical aberration and curvature of field of the projection lens. The sixteenth aspheric lens 3032 can be used to correct astigmatism, curvature of field, and distortion of the projection lens. Among them, distortion affects the shape of the image projected by the projection lens, and coma, astigmatism, curvature of field, spherical aberration, etc. all affect the definition of the image projected by the projection lens. The 3 aspheric lenses can correct coma aberration, astigmatism, curvature of field, spherical aberration and distortion, so that the display effect of the picture projected by the projection lens is improved.

Optionally, the projection lens may further include: an aperture stop (not shown in fig. 2) located between any two mirrors in first mirror group 301. Illustratively, the aperture stop is located between the sixth spherical lens 3014 and the seventh spherical lens 3015 in the first lens group. The aperture stop is used for limiting the aperture of an entrance transmission pupil so as to control the correction of the aberration of the projection lens by other structures in the projection lens.

Note that, since the aperture stop is mainly used to limit the aperture of the entrance transmission pupil, the temperature near the aperture stop is high as the energy density distribution around it is high. Therefore, in order to reduce the influence of the temperature near the aperture stop on the mirror, the mirror near the aperture stop (for example, the sixth spherical lens 3014 and the seventh spherical lens 3015) needs to be made of a material having a small expansion coefficient. For example, the lens can be made of glass materials with the models of L-TIM28, L-AM69HE and L-LALB, and the material with the smaller expansion coefficient can reduce the change of the lens surface shape (namely the R value, namely the curvature radius of the lens) caused by the temperature change of the material of the lens, thereby reducing the influence of the temperature drift on the projection lens.

It should be noted that the projection lens provided in the embodiment of the present invention includes a refractive system and a reflective system, which are sequentially arranged, where the refractive system includes the first lens group 301, the second lens group 302, and the third lens group 303. As shown in FIG. 2, the reflective system comprises an aspheric mirror 304 with positive optical power, the aspheric mirror 304 is adjacent to the third mirror group 303 and is used for reflecting the image beam refracted by the third mirror group 303 to the screen for displaying by the screen.

In the projection lens, the focal power of each lens can directly influence astigmatism, field curvature, distortion, axial chromatic aberration and vertical axis chromatic aberration, so that different positive and negative focal power combinations can play a certain role in aberration correction. In the projection lens provided in the embodiment of the present invention, when the first lens group 301 includes 11 lenses, the focal powers of the first lens group 301 are: positive, negative, positive; when the second lens group 303 includes 3 lenses, the focal powers of the second lens group 302 are: positive, negative, positive; when the third lens group 303 includes two lenses, the focal powers of the third lens group 303 are: negative and negative. Wherein, the total focal power of the refraction system is positive focal power, and the total focal power of the reflection system is also positive focal power. This ensures that the lenses of the projection lens correct aberrations to the best possible effect.

Optionally, the projection lens provided in the embodiment of the present invention can satisfy at least one of the following conditions: condition 1: the ratio of the effective focal length of the first lens group 301 to the effective focal length of the projection lens is a, where a is greater than or equal to 2 and less than or equal to 12. Condition 2: the ratio of the effective focal length of the second lens group to the effective focal length of the projection lens is b, and b is more than or equal to 16 and less than or equal to 36. Condition 3: the ratio of the effective focal length of the third lens group to the effective focal length of the projection lens is c, wherein c is more than or equal to 20 and less than or equal to 30. The effective focal length of the projection lens is the distance from the main image surface to the paraxial image surface behind the projection lens. The effective focal length of each lens group is: the distance from the rear main image surface to the paraxial image surface of the lens group. When the projection lens meets the at least one condition, the display effect of the picture projected on the screen by the projection lens is better.

Optionally, the effective focal length of the projection lens can be d, and d is greater than or equal to 2.359 mm and less than or equal to 2.370 mm. For example, the effective focal length of the projection lens may be 2.370mm, and the projection lens is an ultra-short focus projection lens.

Still alternatively, the size of the picture projected by the projection lens may be 90 inches to 120 inches, and correspondingly, the projection ratio of the projection lens may be e, and e is greater than or equal to 0.23 and less than or equal to 0.24. For example, the projection ratio of the projection lens may be 0.24. The projection ratio of the projection lens is the ratio of the projection distance to the width of the projection picture, i.e. the projection distance/the screen width. The throw ratio reflects the ultra-short focal property of the lens barrel. Compared with the traditional non-ultra-short-focus projector, the ultra-short-focus projection lens has smaller projection ratio (less than 1), so that the projection lens can be placed at a position very close to a projection screen, a large amount of space is saved, and shielding of image beams when the ultra-short-focus projection lens needs to be close to the projection screen is avoided.

It should be noted that, in the related art, because the number of focusing lenses used for focusing is large, and a non-focusing lens may be disposed between two focusing lenses, a plurality of focusing lenses are usually located at different positions in the projection lens. Therefore, the aberration required to be corrected by the focusing lens is large, and the projection effect of the projection lens is easily influenced in the process of focusing the projection lens. In the embodiment of the present invention, the maximum number of the focusing lenses for focusing is 3, and all the focusing lenses are disposed at the middle position of the projection lens (i.e., a part of the lenses of the second lens group is located in the second lens barrel, and another part of the lenses is located in the third lens barrel). Since the image beam passes through the first lens group 301 and then passes through the second lens group 302, most of the aberration of the projection lens is corrected by the first lens group 301. Therefore, the aberration required to be corrected by the second lens group 302 is small, and the influence on the imaging effect of the projection lens in the process of focusing the projection lens is small. It can realize 4K high resolution imaging under 90 inches to 120 inches pictures only by moving 3 lenses.

The resolution of the projection lens provided by the embodiment of the invention can be 93 line pairs/millimeter (lp/mm) (that is, the resolution required by the resolution of 4K), and the projection lens can analyze the image with the resolution of 4K, so that the projection screen can present a higher-definition image, and the user experience is improved. The total length of the refractive system of the projection lens is L1 (i.e. the distance from the edge surface of the fourth spherical lens 3011 near the light valve to the edge surface of the sixteenth aspheric lens 3032 near the reflective system in fig. 2), and the distance between the refractive system and the reflective system is L2, wherein 1.38< L1/L2<1.78, since the thickness of the lens in the reflective system is negligible, L2 can be the total length of the projection lens minus L1.

Due to the reduction of the number of lenses used for focusing, the number of lenses used in the projection lens provided by the embodiment of the invention is 16, so that the length of the projection lens ranges from 183mm to 185mm, and for example, the length of the projection lens can be 183.27 mm. In the related art, the number of lenses of the projection lens capable of focusing is about 20, and the length of the lenses is at least 210 mm. Therefore, the maximum projection length of the projection lens capable of focusing provided by the embodiment of the invention is also smaller than the length of the projection lens capable of focusing in the related art. The maximum aperture of the lens in the projection lens is 50mm, the maximum aperture of the lens in the projection lens in the related art is 60mm, and the maximum aperture is smaller than that of the projection lens in the related art. Therefore, the projection lens capable of focusing provided by the embodiment of the invention has a smaller overall volume.

Referring to fig. 6 to 8, fig. 6 is a schematic diagram of an imaging contrast simulation interface of a projection lens according to an embodiment of the present invention when a picture size is 100 inches, which is also a distortion analysis diagram of a projector; FIG. 7 is a schematic diagram of an imaging contrast simulation interface of a projection lens with a 90-inch frame size according to an embodiment of the present invention; fig. 8 is a schematic view of an imaging contrast simulation interface of a projection lens with a 120-inch frame size according to an embodiment of the present invention. Referring to fig. 6 to 8, when the intersection of the horizontal line and the vertical line is the pre-imaging position and the cross mark (x) is the imaging position of the actual projection lens, the higher the overlapping ratio of the intersection and the cross mark is, the lower the distortion value of the image is, and the lower the distortion degree of the image is. Assuming that the wavelength of the image beam is 0.5500 μm and the zoom ratio is 1, as shown in FIG. 6, when the projection screen is 100 inches (2214X 1245 mm)²) The maximum distortion value obtained by simulation in this simulated interface was-0.1507%. As shown in FIG. 7, when the projection screen is 90 inches (1992X 1120 mm)²) The maximum distortion value obtained by simulation in this simulated interface was-0.2242%. As shown in FIG. 8, when the projection screen is 120 inches (2656X 1494 mm)²) The maximum distortion value obtained by simulation in this simulated interface was-0.1482%. Therefore, as can be seen from fig. 6 to 8, the degree of distortion of the image formed by the projection lens is low.

Referring to fig. 9 to 28, fig. 9 to 18 are graphs of integrated errors of images on sagittal sectors normalized under 10 different fields of view when the screen size of the projection lens is 100 inches according to an embodiment of the present invention, and fig. 19 to 28 are graphs of integrated errors of images on meridional sectors normalized under 10 different fields of view when the screen size of the projection lens is 100 inches according to an embodiment of the present invention. Fig. 9 to 28 are each used to show the difference between the 3 wavelength light rays and the dominant wavelength light ray (i.e. the light ray passing through the light emitting point and the central point of the diaphragm) at the image plane under a field condition when the projection screen is 100 inches. The wavelengths of the 3 lights were 0.45 μm, 0.55 μm, and 0.62 μm, respectively.

As shown in fig. 9 to 18, the sagittal fan plane is a beam profile passing through the pupil X-axis. In the coordinate system of the image integrated error map on the sagittal light sector, the horizontal axis PX is used to represent the normalized height of the light-intake pupil on the sagittal light sector, which is in the range-1 to 1. The vertical axis EX is used to indicate the difference between the height at the image plane of a ray passing through a prescribed pupil in the sagittal light fan and the height at the image plane of the principal ray of the current field of view, the difference in height being in μm. In each figure, in a coordinate axis plane where EX and PX are located, the higher the coincidence ratio of multiple curves is, the smaller the chromatic aberration of the projection lens is. When the curve is closer to the PX axis, the aberration of the projection lens is smaller.

As shown in fig. 19 to 28, the meridian plane is a beam profile passing through the pupil Y-axis. In the coordinate system of the image integrated error map on the meridian plane, the horizontal axis PY is used to represent the normalized height of the light-intake pupil on the meridian plane, which is in the range of-1 to 1. The vertical axis EY is used to indicate the difference between the height at the image plane of light passing through a given pupil in the meridian fan and the height at the image plane of the principal ray of the field of view, the difference in height being in μm. In each figure, the higher the coincidence ratio of the multiple curves is, the smaller the chromatic aberration of the projection lens is in the coordinate axis plane where EY and PY are located. When the curve is closer to the PY axis, the aberration of the projection lens is smaller.

Referring to fig. 29 to 68, fig. 29 to 38 are graphs of integrated errors of images on sagittal sectors normalized under 10 different fields of view when the size of a screen of a projection lens is 90 inches according to an embodiment of the present invention. Fig. 39 to 48 are graphs of integrated error of images on a meridian plane normalized under 10 different fields of view when a picture size of the projection lens is 90 inches according to an embodiment of the present invention. Fig. 49 to fig. 58 are graphs of integrated error of images on sagittal sectors normalized under 10 different fields of view when the size of a projection lens is 120 inches according to an embodiment of the present invention. Fig. 59 to 68 are graphs of integrated error of images on a normalized meridian plane of a projection lens under 10 different fields of view when a picture size is 120 inches according to an embodiment of the present invention. Fig. 29 to 38 may refer to fig. 9 to 18, fig. 39 to 48 may refer to fig. 19 to 28, fig. 49 to 58 may refer to fig. 9 to 18, and fig. 59 to 68 may refer to fig. 19 to 28, which are not repeated herein in the embodiments of the present invention. As can be seen from fig. 9 to 68, when the projection screen is 100 inches, 90 inches, or 120 inches, the total error map of the image on the sagittal plane and the total error map of the image on the meridional plane for each field of view have a high overlapping ratio of the plurality of curves and are closer to the PY axis or the PX axis, and therefore, the chromatic aberration and the aberration of the projection lens are small.

In summary, in the projection lens provided in the embodiments of the present invention, a portion of the lenses in the second lens group is located in the second lens barrel, another portion of the lenses is located in the third lens barrel, and the second lens group includes at most three lenses, and each lens in the second lens group can move along the optical axis of the second lens group under the control of the driving assembly to change the image distance of the projection lens. The number of lenses required to be controlled by the driving assembly is small, and the driving assembly does not need to control the lenses arranged at intervals to move so as to change the image distance of the projection lens, so that the focusing process is simplified.

Furthermore, the refraction system of the projection lens provided by the embodiment of the invention comprises a tri-cemented lens and a bi-cemented lens, and the tri-cemented lens and the bi-cemented lens are matched with other lenses, so that the projection lens has higher chromatic aberration and aberration correction capability, the number of conventional lenses and lens combination can be greatly reduced, the number of the whole lenses of the projection lens is correspondingly reduced while the projection lens has higher resolving power, the length of the projection lens is effectively shortened, and the projection lens with the miniaturized volume is favorably realized. And for the aspheric lens, the plastic material is easier to process, the price is lower, therefore, the twelfth aspheric lens can be made of plastic, thereby reducing the processing cost of the projection lens and reducing the processing difficulty of the projection lens.

The embodiment of the invention provides a focusing method of a projection lens, which can be applied to a driving assembly in a projector, wherein the projection lens can be any one of the projection lenses provided by the embodiment of the invention, and the driving assembly is connected with n lenses in a second lens group of the projection lens. Referring to fig. 69, the method includes:

step 201, controlling the n lenses to move along the optical axis of the second lens group to change the image distance of the projection lens.

Referring to fig. 2, the second lens group 302 may include a first spherical lens 3021, a second spherical lens 3022, and a third spherical lens 3023 sequentially arranged along the light-emitting direction of the light valve. Optionally, a distance sensor may be disposed at an end of the projector where the projection lens is located, the end being close to the screen, and the distance sensor is configured to detect a distance between the projection lens and the screen. Before the driving assembly controls the n lenses to move along the optical axis of the second lens group, the distance change between the projection lens and the screen can be determined through the distance sensor, and then the n lenses are controlled to move along the optical axis of the second lens group according to the distance change condition between the projection lens and the screen. Optionally, the distance sensor may also be disposed at other positions of the projection lens, which is not limited in this embodiment of the present invention.

For example, referring to fig. 2, when the driving assembly determines that the distance between the projection lens and the screen becomes larger through the distance sensor, the driving assembly may control the first spherical lens 3021, the second spherical lens 3022 and the third spherical lens 3023 to move along the optical axis L of the second lens group in a direction approaching the first lens group 301. When the driving assembly determines that the distance between the projection lens and the screen is smaller through the distance sensor, the driving assembly can control the first spherical lens 3021, the second spherical lens 3022 and the third spherical lens 3023 to move along the optical axis L of the second lens group in a direction away from the first lens group 301.

In summary, in the focusing method of a projection lens provided in the embodiments of the present invention, the driving assembly can control all lenses in the second lens group to move along the optical axis of the second lens group so as to change the image distance of the projection lens. Because a part of lenses in the second lens group is positioned in the second lens cone, the other part of lenses is positioned in the third lens cone, and the second lens group comprises at most three lenses, the number of the lenses which need to be controlled by the driving assembly is less, and the driving assembly does not need to control the lenses arranged at intervals to move so as to change the image distance of the projection lens, thereby simplifying the focusing process.

Having described the focus adjustment method of the projection lens according to the embodiment of the present invention, and having described the focus adjustment apparatus of the projection lens according to the embodiment of the present invention, the focus adjustment apparatus of the projection lens according to the embodiment of the present invention may be applied to a driving assembly, which may be the driving assembly 10 shown in fig. 1. It will be appreciated that the focus adjustment means applied to the projection lens of the drive assembly may be the drive assembly of the above method, having any of the functions of the drive assembly of the above method.

Fig. 70 is a block diagram of a focusing apparatus 300 for a projection lens according to an embodiment of the present invention, which can be applied to a driving assembly in the projector 1 shown in fig. 1. Referring to fig. 70, the apparatus 300 includes:

the control module 301 is configured to control the n lenses to move along the optical axis of the second lens group, so as to change the image distance of the projection lens.

Optionally, the control module 301 may include a control sub-module and a physical structure (e.g. a motor) connected to the n lenses, the physical structure being capable of moving under the control of the control sub-module to drive the n lenses to move along the optical axis of the second lens group.

Optionally, the second lens group includes a first spherical lens, a second spherical lens and a third spherical lens sequentially arranged along the light-emitting direction of the light valve, and the control module 301 is configured to:

when the projection lens projects to the screen and the distance between the projection lens and the screen is increased, the first spherical lens, the second spherical lens and the third spherical lens are controlled to move towards the direction close to the first lens group along the optical axis of the second lens group.

When the projection lens projects towards the screen and the distance between the projection lens and the screen is reduced, the first spherical lens, the second spherical lens and the third spherical lens are controlled to move towards the direction far away from the first lens group along the optical axis of the second lens group.

In summary, in the focusing apparatus of a projection lens provided in the embodiments of the present invention, the control module can control all lenses in the second lens group to move along the optical axis of the second lens group so as to change the image distance of the projection lens. Because a part of lenses in the second lens group is positioned in the second lens cone, the other part of lenses is positioned in the third lens cone, and the second lens group comprises at most three lenses, the number of the lenses which need to be controlled by the control module is less, and the control module does not need to control the lenses arranged at intervals to move so as to change the image distance of the projection lens, thereby simplifying the focusing process.

Fig. 71 is a block diagram of a focusing apparatus of a projection lens according to an embodiment of the present invention, and referring to fig. 71, the focusing apparatus 400 of a projection lens includes: a processor 401 and a memory 402 for storing executable instructions of the processor 401. When the processor runs the executable instruction, the focusing method of the projection lens provided by the embodiment of the invention can be realized.

The embodiment of the invention also provides a computer-readable storage medium, wherein the computer-readable storage medium stores instructions, and when the instructions are run on the processing assembly, the processing assembly is enabled to execute the focusing method of the projection lens provided by the embodiment of the invention.

An embodiment of the present invention provides a projector, where the projector 1 may refer to the projector 1 shown in fig. 1, and as shown in fig. 1, the projector 1 includes: a light valve 10, a TIR prism 20, a projection lens 30, a mirror deflection assembly 40 and an actuator assembly 50. The projection lens 30 may be any one of the projection lenses provided in the embodiments of the present invention. The projection lens 30 includes a first lens group 301, a second lens group 302, and a third lens group 303. The light valve 10, the TIR prism 20, the first lens group 301, the second lens group 302 and the third lens group 303 are sequentially arranged. The driving assembly 50 is connected to each lens in the second lens group 302 and configured to control each lens to move along the optical axis of the second lens group 302. The specific structure and functions of each structure of the projector 1 may refer to the description of the projector 1 shown in fig. 1, and the details of the embodiment of the present invention are not repeated here.

In the projector 1 provided in the embodiment of the present invention, the total length of the refractive system is L1, the distance between the refractive system and the reflective system is L2, the distance between the light valve 10 and the first spherical lens of the first lens group 301 is the back working distance of the projection lens 30, and the back working distance is approximately equal to the Back Focal Length (BFL), so the back working distance is usually also referred to as BFL, where 0.3< BFL/L2<0.55, and 0.05< BFL/(L1+ L2) <0.25, which can satisfy the ultra-short focus characteristic of the projection lens. Optionally, in the projector, an offset of the light valve pixel plane with respect to the optical axis satisfies a relation: 132% < offset < 150%, the light valve pixel plane refers to the plane in which the light valve reflects the image beam.

In addition, in the projector provided by the embodiment of the invention, in order to match with the miniaturization of the projection lens, the light valve is correspondingly in a small-size model, so that the optical aperture of the light emitted from the light valve is reduced, and the optical aperture of the projection lens can also be reduced, thereby being beneficial to the miniaturization of the volume of the projection lens.

Fig. 72 is a schematic view of an image beam profile in a projector according to an embodiment of the present invention, referring to fig. 72, when the light valve 10 is illuminated, the light valve 10 outputs an image beam, and the image beam passes through the TIR prism 20 and is reflected to the image shift mirror assembly 40. And then transmitted to the refractive system S1 of the projection lens 30 through the image shift lens assembly 40. The image beam passes through the refraction system S1 and is converged to a certain degree, so as to perform the first imaging. After the image beam after the first imaging enters the reflection system S2 of the projection lens 30, the reflection system S2 reflects the image beam out to perform a second imaging on the screen, so as to display a large-size image on the screen.

Fig. 73 is a schematic diagram of an imaging optical path of a projector according to an embodiment of the present invention, and referring to fig. 73, the image beam is reflected to the screen 2 after being emitted from the projector 1, and a large-size image is displayed on the screen 2.

In summary, in the projector provided in the embodiments of the invention, a portion of the lenses in the second lens group is located in the second lens barrel, another portion of the lenses is located in the third lens barrel, and the second lens group includes at most three lenses, and the driving assembly can control each lens in the second lens group to move along the optical axis of the second lens group to change the image distance of the projection lens. The number of lenses required to be controlled by the driving assembly is small, and the driving assembly does not need to control the lenses arranged at intervals to move so as to change the image distance of the projection lens, so that the focusing process is simplified.

In this application, the terms "first," "second," "third," and "fourth," etc. are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.

Other embodiments of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. This application is intended to cover any variations, uses, or adaptations of the invention following, in general, the principles of the invention and including such departures from the present disclosure as come within known or customary practice within the art to which the invention pertains. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the invention being indicated by the following claims.

It will be understood that the invention is not limited to the precise arrangements described above and shown in the drawings and that various modifications and changes may be made without departing from the scope thereof. The scope of the invention is limited only by the appended claims.

Claims

1. A projection lens, comprising: the lens comprises a first lens group, a second lens group, a third lens group, a first lens cone, a second lens cone and a third lens cone;

2. The projection lens of claim 1 wherein n-3, the one lens segment comprises two lens segments and the other lens segment comprises one lens segment.

3. The projection lens of claim 2, wherein the second lens group comprises a first spherical lens with positive focal power, a second spherical lens with negative focal power and a third spherical lens with positive focal power, which are arranged in sequence along the light-exiting direction of the light valve, wherein the first spherical lens is close to the first lens group, and the third spherical lens is close to the third lens group.

4. The projection lens of any of claims 1 to 3, wherein the projection lens satisfies at least one of the following conditions:

the ratio of the effective focal length of the first lens group to the effective focal length of the projection lens is a, and a is more than or equal to 2 and less than or equal to 12;

the ratio of the effective focal length of the second lens group to the effective focal length of the projection lens is b, and b is more than or equal to 16 and less than or equal to 36;

the ratio of the effective focal length of the third lens group to the effective focal length of the projection lens is c, and c is more than or equal to 20 and less than or equal to 30;

the effective focal length of the projection lens is d, and d is more than or equal to 2.34 mm and less than or equal to 2.370 mm;

the projection ratio of the projection lens is e, and e is more than or equal to 0.23 and less than or equal to 0.24.

5. A focusing method for a projection lens, wherein the method is applied to a driving assembly in a projector, the projection lens is the projection lens according to any one of claims 1 to 4, the driving assembly is connected to n lenses in the second lens group, and the method comprises:

6. The method according to claim 5, wherein the second lens group comprises a first spherical lens, a second spherical lens and a third spherical lens sequentially arranged along the light-emitting direction of the light valve, and the controlling the n lenses to move along the optical axis of the second lens group comprises:

when the projection lens projects to the screen and the distance between the projection lens and the screen is increased, the first spherical lens, the second spherical lens and the third spherical lens are controlled to move towards the direction close to the first lens group along the optical axis of the second lens group;

and when the projection lens projects towards the screen and the distance between the projection lens and the screen is reduced, the first spherical lens, the second spherical lens and the third spherical lens are controlled to move towards the direction far away from the first lens group along the optical axis of the second lens group.

7. A focusing apparatus for a projection lens, comprising respective modules for performing the focusing method for a projection lens according to claim 5 or 6.

8. A focusing apparatus for a projection lens, comprising: a processor; and a memory for storing executable instructions for the processor;

wherein the processor, when executing the executable instructions, is capable of implementing the focusing method of the projection lens of claim 5 or 6.

9. A computer-readable storage medium having instructions stored therein;

when run on a processing component, cause the processing component to perform the method of focusing a projection lens of claim 5 or 6.

10. A projector, characterized in that the projector comprises: a driving assembly, a light valve and the projection lens of any one of claims 1 to 4;