CN111290100B

CN111290100B - Projection lens and projection imaging system

Info

Publication number: CN111290100B
Application number: CN201811505431.8A
Authority: CN
Inventors: 阴亮; 罗超; 马铭晨
Original assignee: Qingdao Hisense Laser Display Co Ltd
Current assignee: Qingdao Hisense Laser Display Co Ltd
Priority date: 2018-12-10
Filing date: 2018-12-10
Publication date: 2022-11-01
Anticipated expiration: 2038-12-10
Also published as: CN111290100A

Abstract

The invention relates to a projection lens and a projection imaging system, and belongs to the field of laser projection. The projection lens includes: the refraction system and the reflection system are sequentially arranged along the incident and transmission direction of the image beam and share the optical axis, and the refraction system is used for refracting the image beam entering the refraction system into the reflection system; the reflection system is used for reflecting the image light beam output by the refraction system to a projection screen; the refractive system includes a triplexer lens and a doublet lens. The invention realizes the reduction of the volume of the projection lens while having higher resolution. The invention is used for designing the projection lens.

Description

Projection lens and projection imaging system

Technical Field

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

Background

The laser display projection technology is a novel projection display technology in the current market, and for a laser projector applying the technology, a projection lens is one of core components of the laser projector, and the projection lens is very important from design to processing.

In order to meet the requirement of higher image quality (such as 4K image quality), the current projection lens needs to have higher resolution, especially for an ultra-short-focus lens, the projection ratio is small, the design complexity of the lens is higher, and thus the number of required lenses is very large, for example, the number range of the lenses of the ultra-short-focus lens in the current market is generally about 20. However, the lens with a larger number not only has a higher complexity of processing and assembling, but also makes the volume of the projection lens larger, which is not favorable for miniaturization of the projection apparatus. Therefore, a projection lens with a small size and a high resolution is needed.

Disclosure of Invention

The embodiment of the invention provides a projection lens and a projection imaging system, which can solve the problem of large volume of the projection lens, and the technical scheme is as follows:

in a first aspect, a projection lens is provided, which includes:

a refraction system and a reflection system arranged in sequence along the incident and transmission direction of the image beam and sharing the optical axis,

the refraction system is used for refracting the image beam entering the refraction system into the reflection system;

the reflection system is used for reflecting and imaging the image light beam output by the refraction system onto a projection screen;

the refractive system includes a triplexer lens and a doublet lens.

In a second aspect, there is provided a projection imaging system, comprising: a light valve, a Total Internal Reflection (TIR) prism and any one of the projection lenses of the first aspect;

the light valve and the TIR prism are sequentially arranged along the direction close to the first lens group;

the light valve is used for generating the image light beam when being illuminated;

the TIR prism is used for reflecting the image light beam to the projection lens.

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

the projection lens and the refraction system of the projection lens in the projection imaging system provided by the embodiment of the invention comprise the tri-cemented lens and the double-cemented lens, and the tri-cemented lens and the double-cemented lens have higher chromatic aberration correction capability and are matched with other lenses, so that the projection lens has higher chromatic aberration and aberration correction capability at the same time, the use number of conventional lenses and lens combinations 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.

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 diagram of an implementation environment related to an embodiment of the present invention.

Fig. 2 is a schematic diagram of another implementation environment related to the embodiment of the invention.

Fig. 3 is a schematic structural diagram of a projection lens according to an exemplary embodiment of the present invention.

Fig. 4 is a schematic structural diagram of a projection lens according to an exemplary embodiment of the present invention.

Fig. 5 is a schematic structural diagram of a projection lens according to an exemplary embodiment of the present invention.

Fig. 6 is a schematic structural diagram of a projection lens according to an exemplary embodiment of the present invention.

Fig. 7 is a schematic diagram of an imaging contrast simulation interface of a projection lens according to an exemplary embodiment of the present invention.

Fig. 8 is a schematic diagram of spot imaging of a projection lens according to an exemplary embodiment of the present invention.

Fig. 9 is a graph of optical characteristics of a projection lens according to an exemplary embodiment of the present invention.

Fig. 10 is a graph illustrating optical characteristics of a projection lens according to an exemplary embodiment of the present invention.

Fig. 11 is a graph illustrating optical characteristics of a projection lens according to an exemplary embodiment of the present invention.

Fig. 12 is a graph illustrating optical characteristics of a projection lens according to an exemplary embodiment of the present invention.

Fig. 13 is a graph illustrating optical characteristics of a projection lens according to an exemplary embodiment of the present invention.

Fig. 14 is a graph illustrating optical characteristics of a projection lens according to an exemplary embodiment of the present invention.

Fig. 15 is a graph illustrating optical characteristics of a projection lens according to an exemplary embodiment of the present invention.

Fig. 16 is a graph illustrating optical characteristics of a projection lens according to an exemplary embodiment of the present invention.

Fig. 17 is a graph illustrating optical characteristics of a projection lens according to an exemplary embodiment of the present invention.

Fig. 18 is a graph illustrating optical characteristics of a projection lens according to an exemplary embodiment of the present invention.

Fig. 19 is a schematic diagram of a system imaging optical path of a projection imaging system provided in accordance with an exemplary embodiment of the present invention.

Fig. 20 is a schematic diagram of an image beam profile in a projection imaging system according to an exemplary embodiment of the 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.

Referring to fig. 1, a schematic diagram of an implementation environment related to a projection lens provided in some embodiments of the present invention is shown. The implementation environment may include: the light source comprises a light valve 10, a Total Internal Reflection (TIR) prism 20 and a projection lens 40, wherein the diaphragm 10 and the TIR prism 20 are sequentially arranged in a direction close to the projection lens 40. The light valve is used for generating an image beam when being illuminated, and for example, the light valve may be a Digital Micromirror Device (DMD), the resolution of the DMD may be 2K, 3K or 4K, the 2K resolution means that each row of the DMD has a pixel value of 2000 or more, and usually means 2560 × 1440 resolution; the 3K resolution refers to up to or near 3000 pixel values per row of devices, typically referring to 3200 x 1800 resolution; the 4K resolution refers to device pixel values at or near 4096 per row, typically referred to as a 4096 × 2160 resolution; the TIR prism is used for reflecting the image light beam to the projection lens so as to improve the brightness and contrast of the image light beam entering the projection lens.

Optionally, please refer to fig. 2, which illustrates a schematic diagram of another implementation environment related to a projection lens provided in some embodiments of the present invention. The implementation environment related to the projection lens may further include: and the mapping deviation mirror group 30 is positioned on one side of the TIR prism 20 close to the projection lens 40, and the mapping deviation mirror group 30 is used for transmitting the image light beam after deviation processing to the projection lens after deviation processing of the image light beam reflected by the TIR prism. For example, the mirror image shifting mirror group may be a plate-shaped transparent device, such as a flat transparent glass. The function and location of the other devices in fig. 2 may be referenced to the function and location of the devices in fig. 1. The embodiment of the present invention will not be described in detail.

The embodiment of the invention provides a projection lens 40, which can be applied to the implementation environment shown in fig. 1 or fig. 2. As shown in fig. 3, the projection lens 40 includes:

a refractive system 41 and a reflective system 42. The refractive system 41 and the reflective system 42 are sequentially arranged along the incident and transmission direction (i.e. the X direction shown in fig. 3) of the image beam and are coaxial with the optical axis L. The refraction system 41 is configured to refract the image beam entering the refraction system into the reflection system, and the refraction system is specifically configured to perform aberration correction and chromatic aberration correction on the image beam entering the refraction system, and refract the image beam into the reflection system. The reflection system 42 is configured to reflect the image beam output by the refraction system to the projection screen, and the reflection system is specifically configured to perform distortion aberration correction on the image beam output by the refraction system and reflect the image beam to the projection screen.

Wherein the refractive system 41 comprises a tri-cemented lens 4111 and a bi-cemented lens 4112.

In summary, the refraction system of the projection lens provided in the embodiment of the present invention includes a tri-cemented lens and a bi-cemented lens, and both the tri-cemented lens and the bi-cemented lens have high chromatic aberration correction capability, and the tri-cemented lens and the bi-cemented lens are matched with other lenses, so that the projection lens has high chromatic aberration and aberration correction capability, and the number of conventional lenses and lens combinations can be greatly reduced, thereby enabling the projection lens to have high resolving power, and the number of the whole lenses of the projection lens to be correspondingly reduced, effectively shortening the length of the projection lens, and facilitating the realization of a projection lens with a small size.

Alternatively, as shown in fig. 4, the refraction system 41 includes a first lens group 411, a relay lens 412 and a second lens group 413 which are sequentially arranged along the incident and transmission direction of the image beam (i.e. the X direction shown in fig. 4), and the first lens group 411 includes a three cemented lens 4111 and a double cemented lens 4112.

It should be noted that: in the optical design of the lens, a unit composed of a plurality of lenses is generally regarded as a group, and the unit can be intuitively moved as a whole, for example, 10 lenses are provided in the lens, 5 lenses are divided into two groups, and the two groups are respectively regarded as a small whole and can be displaced relative to each other, where the displacement can be tolerance adjustment during assembly, or can be a distance change between the groups in coordination with lens zooming to change the focal length of the lens. While the relative position of the lenses within each group does not change, each group has its own focal parameters.

In the embodiment of the present invention, the first lens group 411, the relay lens 412 and the second lens group 413 may be referred to as a rear group, a middle group and a front group, and at this time, on the premise of having high aberration and chromatic aberration correction capability, the lens may have a large depth of field, and have a large tolerance range, that is, the lens may allow movement of the focal plane, and may also realize projection quality within a visual acceptance range, for example, at 100 inches, projection quality is the best, but at 90 inches or 120 inches, by moving the rear group, the middle group, and changing the position of the focal plane (by moving two groups, and simultaneously performing distortion correction), although the best resolution capability of 100 inches is not achieved, the visual viewing requirement may still be satisfied, that is, a certain projection size adjustment range, and at this time, it is necessary to have division of three groups, and the rear group, the middle group, that is, the first lens group 411 and the relay lens 412 are each used as an adjustment unit, and thus each group is regarded as a group. However, if the projection lens is determined to achieve a projection size of 100 inches, at this time, for reasons of small design tolerance adjustment, assembly, etc., the above-described lenses may be divided into two groups, i.e., the first lens group 411 is the rear group, and the relay lens 412 and the second lens group 413 are the front group, so that only the first lens group 411 is slightly displaced from the remaining group of lenses, and is mounted as a whole when assembled. At this time, the relative position of the relay lens 412 with respect to the second lens group 413 remains unchanged.

In the following description, for convenience of describing the processing procedure of the projection lens on the light beam in sequence, the projection lens is exemplarily divided into three groups, which can explain the transmission procedure of the light beam by different groups and the contribution of each group to the light beam imaging in the case of finer group division, but this does not limit the division of the projection lens in the embodiment. As described above, the relay lens may also be divided into the second lens group, so that the projection lens of the present embodiment has two groups.

Optionally, the projection lens 40 may be of an object-side telecentric design structure, that is, the light path of the projection lens is an object-side telecentric light path, and in the projection lens of the object-side telecentric design structure, the imaging light beam emitted from the same point on the light valve does not change with the change of the position of the light valve, so that the projection parallax caused by inaccurate focusing of the projection lens or the existence of depth of field is avoided, and the image quality of the projection lens is better compared with that of a projection lens of a non-object-side telecentric design structure.

Optionally, in the projection lens, a ratio of a second focal length to a first focal length is in a range of 2 to 12, the first focal length is an equivalent focal length of the projection lens, and the second focal length is an equivalent focal length of the first lens group; the ratio of the third focal length to the first focal length ranges from 20 to 30, and the third focal length is the equivalent focal length of the relay lens; the ratio of the fourth focal length to the first focal length is in the range of 25-35, and the fourth focal length is the equivalent focal length of the second lens group; the ratio of the fifth focal length to the first focal length is in the range of 5-10, and the fifth focal length is the equivalent focal length of the reflection system. The equivalent focal length is the focal length of the lens for converting the view angles of the images on the photosensitive elements with different sizes into the same imaging view angle on the 135-camera.

Alternatively, reflective system 42 can be a concave aspheric mirror.

Alternatively, referring to fig. 4, the first lens group 411 (referred to as the rear group) may include a three-cemented spherical lens 4111, a second aspheric lens 4118 with positive power, and a two-cemented spherical lens 4112 sequentially arranged along the incident and transmission direction of the image beam.

Alternatively, referring to fig. 5, the first lens group 411 may include a first aspheric lens 4114 with positive power, a third aspheric lens 4111 with positive power, a second aspheric lens 4118 with positive power, and a double-cemented spherical lens 4112 sequentially arranged along the incident and transmission direction of the image beam.

Alternatively, as shown in fig. 6, the first lens group 411 may further include other lenses, and for example, the first lens group 411 may include m lenses, where m is a positive integer and 6-straw m-straw 16. For example, the first lens group 411 includes 11 lenses, and the 11 lenses include 2 aspherical mirrors and 9 spherical mirrors. The first lens group includes a first spherical lens 4113 with positive focal power, a first aspheric lens 4114 with positive focal power, a third cemented spherical lens 4111, a second spherical lens 4115 with negative focal power, a third spherical lens 4116 with positive focal power, a fourth spherical lens 4117 with negative focal power, a second aspheric lens 4118 with positive focal power, and a double cemented spherical lens 4112, which are sequentially arranged along the direction of incidence and transmission of the image beam.

It should be noted that, in the projection lens, F/# is a parameter reflecting the light collecting or light collecting capability of the system, and F/# = F/d, where F is the focal length, d is the aperture of the diaphragm, and/represents a division number. The smaller the value of F/# is, the stronger the light collecting or light collecting ability of the system is.

As described above, in order to ensure good image quality, the projection lens adopts an object-side telecentric design structure, but the projection lens in the object-side telecentric design structure has larger aberration than the projection lens in the non-object-side telecentric design structure, so that the larger aberration needs to be eliminated. To eliminate this large aberration and meet the design requirements for smaller values of the lens lenses F/# a lens close to the light valve may be used to perform the primary aberration correction function of the projection lens.

Referring to fig. 6, as the first spherical lens 4113 is close to the light valve, the first spherical lens 4113 can perform a larger aberration correction function on the projection lens, and therefore a material with a larger refractive index needs to be selected, and the larger the refractive index is, the stronger the aberration correction capability is, for example, the value range of the refractive index of the material may be greater than 1.62.

Because the first spherical lens has a relatively large aberration correction effect, that is, the first spherical lens has a relatively strong aberration correction capability, an aspheric lens with a slightly low aberration correction capability may be selected as the first aspheric lens 4114 to perform aberration correction within the total aberration bearing capability of the projection lens system. Since the higher the refractive index of the material is, the larger the chromatic aberration generated by the material is, and under the condition that the refractive index of the material of the first spherical lens is higher, in order to control the chromatic aberration range of the projection lens, the material with the lower refractive index is selected as the first aspheric lens. For example, the first aspheric lens may be selected from the following types: L-BSL7, D-K59 or L-BAL 42. The refractive index of the material may be about 1.5. The first aspherical mirror mainly corrects astigmatism, coma aberration and field curvature of the projection lens.

It should be noted that the first spherical lens and the first aspheric lens may be replaced by a first lens, that is, the first lens group includes a first lens with positive focal power, a third cemented spherical lens, a second spherical lens with negative focal power, a third spherical lens with positive focal power, a fourth spherical lens with negative focal power, a second aspheric lens with positive focal power, and a double cemented spherical lens, which are sequentially arranged along the incident and transmission direction of the image beam, so as to further reduce the volume of the projection lens and reduce the cost. Illustratively, the first lens may be an aspheric lens or a spherical lens.

Optionally, the triple cemented spherical lens 4111 includes: and the fifth spherical lens c with positive focal power, the sixth spherical lens b with negative focal power and the seventh spherical lens a with positive focal power are sequentially arranged along the incident and transmission direction of the image light beam. The tri-cemented spherical lens 4111 is mainly used for correcting chromatic aberration of the projection lens, and has a certain correction capability on the aberration of the projection lens. In order to make the triple-cemented spherical lens capable of correcting chromatic aberration of the projection lens, three lenses of the triple-cemented spherical lens should be matched by selecting materials with abbe numbers (also called abbe numbers) different by more than a first specified threshold, and the first specified threshold may be determined by combining other configuration conditions of the projection lens, for example, the range of the first specified threshold may be 30-80. Therefore, after the abbe number of the sixth spherical lens b is selected to be as small as possible, the abbe numbers of the fifth spherical lens c and the seventh spherical lens a of the sixth spherical lens b are larger within the first specified threshold range, for example, the abbe number of the sixth spherical lens b may be smaller than 35, for example, 31.3, and the abbe numbers of the fifth spherical lens c and the seventh spherical lens a may be 65 to 95, for example, the abbe number of the fifth spherical lens c may be 70 or 90.

The abbe number is used to indicate the dispersive power of the transparent medium. In general, the larger the refractive index of the medium, the more chromatic dispersion, and the smaller the abbe number; conversely, the smaller the refractive index of the medium, the less noticeable the dispersion and the larger the Abbe number.

However, since the abbe number of the material is smaller, the refractive index of the material is larger, and the absorption rate of the larger refractive index to the blue light band is higher, in order to reduce the absorption rate of the sixth spherical lens to the blue light band, a negative power lens is selected for the sixth spherical lens, so that the image light beam passes through a thinner area of the sixth spherical lens, and the geometric optical transmission efficiency of the sixth spherical lens, that is, the transmission efficiency of the sixth spherical lens to the image light beam is further improved. For example, the refractive index of the sixth spherical lens may be greater than 1.8, and the refractive index of the fifth spherical lens may be in a range from 1.45 to 1.55.

The second spherical lens 4115 is a meniscus spherical lens, the third spherical lens 4116 is a biconvex spherical lens, the fourth spherical lens 4117 is a biconcave spherical lens, and the second aspherical lens 4118 is a positive-focus aspherical lens. The second aspherical mirror 4118 is mainly used for correcting spherical aberration and curvature of field of the projection lens.

Optionally, the double cemented spherical lens 4112 comprises: and the eighth spherical lens e with negative focal power and the ninth spherical lens d with positive focal power are sequentially arranged along the incident and transmission direction of the image light beam. The double cemented spherical lens 4112 is mainly used for correcting chromatic aberration of the projection lens, and also has a certain correction capability on the aberration of the projection lens. Because the residual chromatic aberration of the image beam by the projection lens is small after the image beam passes through the tri-cemented spherical lens 4111, and the correction capability of the double-cemented spherical lens 4112 on the chromatic aberration is smaller than that of the tri-cemented spherical lens 4111 on the chromatic aberration, the residual small chromatic aberration can be accurately corrected by the double-cemented spherical lens 4112, the eighth spherical lens e and the ninth spherical lens d in the double-cemented spherical lens 4112 select a material with an abbe number difference smaller than a second specified threshold value for matching, and the second specified threshold value can be determined by combining other configuration conditions of the projection lens. For example, the value of the ratio of the abbe numbers of the eighth spherical lens e and the ninth spherical lens d may range from 0.5 to 2, for example, 1.65; the abbe numbers of the eighth spherical lens e and the ninth spherical lens d may be 40.76 and 25.68, respectively, in which case the ratio of the abbe numbers of the eighth spherical lens e and the ninth spherical lens d is about 1.59. Meanwhile, the focal power of the eighth spherical lens e may be negative, and the focal power of the ninth spherical lens d may be positive, so that the positive chromatic aberration generated by the image beam passing through the eighth spherical lens e and the negative chromatic aberration generated by the ninth spherical lens d are mutually matched, and the chromatic aberration of the image beam can be corrected to be 0 by the eighth spherical lens e and the ninth spherical lens d.

It should be noted that the order of the positions of the above triple cemented lens and double cemented lens in the lens assembly can be changed.

Optionally, the relay lens 412 is a lens, which may be, for example, a spherical lens with positive optical power. The relay lens 412 has a positive lens characteristic, i.e., has a capability of converging light, for reducing a normalized height of the image beam output from the first lens group 411 on each lens in the second lens group 412. The normalized height is a ratio of an effective aperture of a lens (i.e. a maximum height corresponding to a light beam range of an image light beam) to an aperture of the lens (i.e. a maximum diameter of the lens, i.e. a lens height) (the maximum height is parallel to a direction of the lens height), i.e. a longitudinal height of the image light beam is reduced when the image light beam passes through the lens. By reducing the longitudinal height of the image beam, the sizes of the apertures of the second lens group 413 and the first lens group 411 can be reduced, which is favorable for reducing the volume of the projection lens and reducing the cost. Illustratively, the surface type of the relay lens may be a plano-convex type or a biconvex type.

Alternatively, the second lens group (which may be referred to as a front group) 413 includes n lenses, where n is a positive integer, and 2-n-5. Illustratively, the second lens group 413 includes 3 lenses, and the 3 lenses include 1 aspherical mirror and 2 spherical mirrors. The second lens group 413 includes: and a tenth spherical lens 4131 with positive power, an eleventh spherical lens 4132 with negative power, and a third aspherical lens 4133 with negative power, which are arranged in this order along the direction in which the image light beam is incident and transmitted. The second lens group 413 is used to correct distortion of the projection lens. The third aspheric lens 4133 is mainly used to correct astigmatism, curvature of field, and distortion. Illustratively, the surface type of the tenth spherical lens 4131 may be a biconvex surface type, the refractive index of which is about 1.7, for example, 1.72, and the abbe number of which may be 54.6. The surface type of the eleventh spherical lens 4132 may be a biconcave type with a middle thickness of 3-3.5mm, so that when the image beam passes through the eleventh spherical lens, the middle thickness is low to effectively reduce the light loss of the image beam, and the value range of the abbe number of the eleventh spherical lens may be greater than 50. The third aspherical surface 4133 has a refractive index of about 1.5.

Optionally, the symmetric aspheric lens has a regular shape, which is convenient for processing and manufacturing, and particularly, the rotationally symmetric aspheric lens is easier to process and manufacture, so that when the aspheric lenses in the projection lens, such as the first aspheric lens, the second aspheric lens and the third aspheric lens, all adopt rotationally symmetric structures, the processing mode of the aspheric lens can be simple, which is favorable for simplifying the processing of the projection lens and reducing the production cost.

It should be noted that, the lens of the projection lens is usually made of glass material, but the glass material is expensive, and the aspheric lens of the glass material is difficult to process for the aspheric lens, and the third aspheric lens is far away from the light valve, and has a larger aperture and is more consumable, so the third aspheric lens can be made of plastic, such as 480R, the price of the plastic material is low, and the aspheric lens of the plastic material is easier to process for the aspheric lens.

Optionally, the projection lens further includes: and an aperture stop located in the first lens group, illustratively located between the second spherical lens and the third spherical lens in the first lens group, the aperture stop for limiting an entrance transmission pupil aperture.

Note that since the aperture stop is used to limit the aperture of the entrance transmission pupil, the temperature in the vicinity of 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 needs to be made of a material having a small expansion coefficient. For example, the lens can be made of glass materials with the types of L-TIM28, L-AM69HE and L-LALB, and the material with the smaller expansion coefficient can reduce the change of the lens surface type (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 temperature drift on the projection lens.

Further, the effective focal length of the projection lens provided by the embodiment of the present invention may range from 1.964 to 3.273mm (millimeter), for example, the effective focal length of the projection lens provided by the embodiment is 2.348mm, which is an ultra-short focus projection lens, and the effective focal length is the distance from the main image plane to the paraxial image plane behind the projection lens. In the embodiment of the invention, when the projection picture of the projection lens is 100 inches, the projection ratio of the projection lens is less than or equal to 0.24, the projection ratio refers to the linear relation between the linear distance between the reflector and the screen and the length of the projection picture, namely the projection distance/the length size of the screen, and the projection ratio reflects the ultra-short focal property of the lens. In another alternative embodiment, the projection lens may have a projection screen size of 90-120 inches and a projection ratio of 0.23-0.25. 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 the shielding of image beams when the projection lens needs to be close to the projection screen is avoided.

In an embodiment of the present invention, when the projection screen size of the projection lens is adjustable, preferably, the distance between the second lens group and the reflecting mirror is relatively fixed, and the distance between the relay lens and the second lens group is adjusted by moving the first lens group. In order to improve the adjustment efficiency, the distance between the second lens group and the reflector can be finely adjusted, and the adjustment distance range is within plus or minus 1mm.

When the size of the projection picture of the projection lens is fixed, the distance between the second lens group and the reflecting mirror is relatively fixed, such as 69.66971912mm or 71mm.

In the embodiment of the projection lens, a piece of tri-cemented lens, a piece of double-cemented lens and 3 pieces of aspheric lens are used and matched with other lenses, so that the projection lens has strong aberration and chromatic aberration correction capability.

In the projection lens provided by the embodiment of the present invention, the total length of the refractive system is L1 (i.e. the distance from the edge surface of the first spherical lens on the side close to the light valve to the edge surface of the third aspheric lens on the side close to the reflective system), and the distance between the refractive system and the reflective system is L2, wherein 1.4 and L1/L2<1.6, and since the thickness of the lenses in the reflective system can be ignored, L2 can be the value of subtracting L1 from the total length of the projection lens.

Because the number of lenses used is reduced, in the projection lens provided by the embodiment of the present invention, the number of lenses used is less than 16, so that the length range of the projection lens is 197-203mm, the length of the conventional projection lens is at least 210mm, the number of lenses is also about 20, the maximum value of the length of the projection lens is smaller than the minimum value of the length of the conventional projection lens, the length of the projection lens is smaller than the length of the conventional projection lens, the maximum aperture of the lenses in the projection lens is 52mm, the maximum aperture of the lenses in the conventional projection lens is 60mm, and the maximum aperture of the lenses in the conventional projection lens is also smaller than the maximum aperture of the conventional projection lens. Therefore, the overall volume of the projection lens is small.

In one embodiment of the present invention, when the projection lens includes: when the first spherical lens, the first aspheric lens, the fifth spherical lens, the sixth spherical lens, the seventh spherical lens, the second spherical lens, the third spherical lens, the fourth spherical lens, the second aspheric lens, the eighth spherical lens, the ninth spherical lens, the relay lens, the tenth spherical lens, the eleventh spherical lens, the third aspheric lens and the reflection system are sequentially arranged along the incident and transmission direction of the image beam, the thicknesses of the lenses (except for the reflection system) of the projection lens along the incident and transmission direction of the image beam are sequentially as follows: 7.79925152mm, 7.02mm, 5.03mm, 1.5mm, 4.32mm, 3.5mm, 4.27622172mm, 1.8mm, 4.47553268mm, 1.5mm, 4.58mm, 6.11544835mm, 14.7mm, 3.5mm and 3.45mm. The sequential distance between each lens of the projection lens along the incident and transmission direction of the image light beam is as follows: 0.249mm, 0mm, 0.93mm, 0.5mm, 0.3mm, 1.133mm, 0.6946996mm, 0mm, 7.42962132mm, 11.88678689mm, 2.63083486mm, 3.76248103mm, and 69.66971912mm.

Referring to fig. 7, fig. 7 is a schematic diagram of an imaging contrast simulation interface of a projection lens according to an embodiment of the present invention, which is also a distortion analysis diagram of a projection imaging system, as shown in fig. 7, where a cross line (+) in fig. 7 is a pre-imaging position, and a cross mark (x) is an imaging position of an actual projection lens, the higher the coincidence ratio of the cross line and the cross mark is, the lower the imaging distortion value is, and the lower the imaging distortion degree is. Suppose the projection lens is 100 inches (2214 x 1245 mm) in the projection picture²) The pre-imaging position is shown in FIG. 7, where the wavelength of the image beam is 0.5500 μm and the zoom ratio is 1The superposition rate of the projection lens and the actual projection lens is high, the maximum value of the distortion obtained by simulation in the simulation interface is 0.3841%, and therefore, the distortion degree of the imaging of the projection lens is low.

Referring to fig. 8, fig. 8 is a schematic view of a point array simulation interface of a projection lens according to an embodiment of the present invention, which is also called a point light spot imaging schematic view. Light rays with the wavelengths of 0.4550um, 0.5500um and 0.6200um are respectively plotted in fig. 8, point light spots on a projection screen are imaged after passing through the projection lens under 10 different viewing fields, and the 10 viewing fields are respectively marked by reference numerals 1-10. Wherein "+" indicates spot imaging of light having a wavelength of 0.4550um, "×" indicates spot imaging of light having a wavelength of 0.5500um, "\9633;" indicates spot imaging of light having a wavelength of 0.6200 um. The closer the size of the spot image (also called the diameter of the total diffuse spot, i.e. the geometric RADIUS, identified by GEO RADIUS in fig. 8) is to the diffraction limit of 1.392um, the higher the image quality contrast of the image formed by the projection lens. In fig. 8, the SCALE (indicated by SCALE BAR in fig. 8) is 40, that is, the ratio of the size of the image shown in fig. 8 to the size of the real image is 1.

Referring to fig. 9 to 18, fig. 9 to 18 are graphs of optical characteristics of a projection lens according to an embodiment of the present invention after normalization in 10 different fields of view, which are denoted by reference numerals 1 to 10 and shown in fig. 9, where the optical characteristics are also called ray fan diagrams (english: ray fan), and the graph of the optical characteristics in each of fig. 9 to 18 is used to show differences of 3 kinds of wavelength rays relative to a main wavelength ray (i.e., a ray passing through a light emitting point and a diaphragm center point) on an image plane under a field of view condition. The wavelengths of the 3 light rays are 0.4550um, 0.5500um, and 0.6200um, respectively, and each of the optical characteristic graphs in fig. 9 to 18 includes an image integrated error map M on a sagittal plane and an image integrated error map N on a meridian plane. In a coordinate system of an image comprehensive error map M on a sagittal fan, a horizontal axis PX is used for representing the normalized height of a light ray on the sagittal fan, which is a light beam section passing through a pupil X axis, entering a pupil, and EX is used for representing the difference between the height on an image surface and the height of a main light ray of a current field of view on the image surface when the light ray passing through a specified pupil in the sagittal fan is incident on the image surface; in the coordinate system of the integrated error map N of the image on the meridian fan, the horizontal axis PY represents the normalized height of the light incident on the pupil at the meridian fan, which is a beam profile passing through the Y axis of the pupil, and the vertical axis EY represents the difference between the height at the image plane of the light incident on the image plane 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. In each graph, the higher the coincidence ratio of a plurality of curves is, the smaller the chromatic aberration of the projection lens is, in the coordinate axis plane where EY and PY are located and the coordinate axis plane where EX and PX are located, and the smaller the chromatic aberration of the projection lens is as the curve approaches the PY axis or the PX axis. As can be seen from fig. 9 to 18, in the image integrated error map on the sagittal plane and the image integrated error map on the meridian plane for each field of view, the coincidence ratios of the plurality of curves are high and both are closer to the PY axis or the PX axis, and therefore, the chromatic aberration and the aberration of the projection lens are small.

Furthermore, for the aspheric lens, the plastic material is easy to process, and the price is low, so the material of the third aspheric lens can be plastic, thereby being beneficial to reducing the cost of the projection lens and reducing the processing difficulty of the projection lens.

As shown in fig. 1, an embodiment of the present invention provides a projection imaging system, including: a light valve 10, a total internal reflection TIR prism 20 and a projection lens 40. The projection lens 40 is any one of the projection lenses provided in the embodiments of the present invention. The light valve 10 and the TIR prism 20 are arranged in sequence in a direction close to the first lens group and are coaxial. The light valve is used for generating an image beam when being illuminated, and may be, for example, a Digital Micromirror Device (DMD), and the resolution of the DMD may be 2K, 3K or 4K. For example, the TIR prism may be 2 total reflection prisms, and may also be 2n total reflection prisms, where n is an integer greater than 1.

Optionally, as shown in fig. 2, the projection imaging system further includes a mirror shift group 30, and the mirror shift group 30 is located on a side of the TIR prism 20 close to the projection lens 40. The image deflection mirror group is used for deflecting the image light beam reflected by the TIR prism and transmitting the deflected image light beam to the projection lens. The image shift mirror group may be a plate-shaped transparent device, such as a flat transparent glass, and when the image shift mirror group is in operation, the image shift mirror group may be driven by a motor or the like to vibrate at a high frequency, so as to shift the image light beams.

In the projection imaging system provided by the embodiment of the present invention, the distance from the light valve to the first spherical lens of the first lens group is the Back working distance of the lens, and since the Back working distance is approximately equal to the Back Focal Length (BFL), the Back working distance is also generally referred to as BFL, and the distance L2 between the refractive system and the reflective system in the projection lens is generally equal to BFL, where 0.3 is less than BFL/L2<0.55.

In the projection imaging system provided by the embodiment of the present invention, the total length of the refractive system is L1 (i.e. the distance from the edge surface of the first spherical lens close to the light valve to the edge surface of the third aspheric lens close to the reflective system), and the distance between the refractive system and the reflective system is L2, where BFL satisfies 0.05-restricted BFL/(L1 + L2) <0.25, so as to satisfy the ultra-short focus characteristics of the lens, that is, the characteristics of the ultra-short focus lens.

In the projection imaging system provided in the embodiment of the present invention, an offset of a light valve pixel plane with respect to an 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 the projection imaging system provided by the embodiment of the invention, in order to match with the miniaturization of the projection lens, the light valve DMD also adopts a small-size model correspondingly, so that the optical aperture of light emitted from the light valve is reduced, the optical aperture of a lens of the projection lens can also be smaller, and the miniaturization of the volume of the projection lens is facilitated.

Referring to fig. 19, fig. 19 is a schematic diagram of an imaging optical path of a system of a projection imaging system according to an embodiment of the present invention. As shown in fig. 19, when the light valve is illuminated, the light valve outputs an image beam, the image beam passes through the TIR prism and is reflected to the image deflecting mirror set, and then is transmitted to the refraction system 41, the image beam passes through the refraction system 41 and is converged to a certain extent, so as to perform a first imaging, after the imaged image beam enters the reflection system, the reflection system 42 reflects the image beam, and performs a second imaging on the projection screen, so as to display a large-size image obtained by the second imaging through the projection screen.

Referring to fig. 20, fig. 20 is a schematic view illustrating a direction of an image beam in a projection imaging system according to an embodiment of the invention. As shown in fig. 20, the image beam passes through the projection lens 40 and is reflected onto the projection screen 50, and a large-sized image is displayed on the projection screen 50.

In summary, the projection lens and the refraction system of the projection lens in the projection imaging system provided by the embodiments of the present invention include a tri-cemented lens and a bi-cemented lens, and because both the tri-cemented lens and the bi-cemented lens have high chromatic aberration correction capability, and the tri-cemented lens and the bi-cemented lens are mutually matched with other lenses, the projection lens can have high chromatic aberration and aberration correction capability, and the number of conventional lenses and lens combinations can be greatly reduced, so that the number of the whole lenses of the projection lens is correspondingly reduced while the projection lens has high resolving power, the length of the projection lens is effectively shortened, the projection lens with a miniaturized volume is favorably realized, and accordingly, the length of the projection imaging system is also effectively shortened, and the projection imaging system with a miniaturized volume is favorably realized.

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 refraction system is composed of a first lens group, a relay lens and a second lens group which are sequentially arranged along the incident and transmission direction of the image beam, and the first lens group comprises a triple cemented lens and a double cemented lens;

the first lens group consists of a first spherical lens with positive focal power, a first aspheric lens with positive focal power, a third cemented spherical lens, a second spherical lens with negative focal power, a third spherical lens with positive focal power, a fourth spherical lens with negative focal power, a second aspheric lens with positive focal power and a double cemented spherical lens which are sequentially arranged along the incidence and transmission directions of the image light beams; the tri-cemented spherical lens includes: the fifth spherical lens with positive focal power, the sixth spherical lens with negative focal power and the seventh spherical lens with positive focal power are sequentially arranged along the incidence and transmission direction of the image light beam; the double cemented spherical lens includes: the eighth spherical lens with negative focal power and the ninth spherical lens with positive focal power are sequentially arranged along the incident and transmission direction of the image light beam;

the second lens group consists of a tenth spherical lens with positive focal power, an eleventh spherical lens with negative focal power and a third aspheric lens with negative focal power which are sequentially arranged along the incident and transmission direction of the image light beam;

the relay lens is a positive focal power spherical lens;

the ratio of a second focal length to a first focal length is in a range of 2-12, the first focal length is an equivalent focal length of the projection lens, and the second focal length is an equivalent focal length of the first lens group;

the range of the ratio of the third focal length to the first focal length is 20-30, and the third focal length is the equivalent focal length of the relay lens;

the ratio of the fourth focal length to the first focal length is in the range of 25-35, and the fourth focal length is the equivalent focal length of the second lens group.

2. The projection lens of claim 1,

the relay lens is used for reducing the normalized height of the image light beam output by the first lens group on each lens in the second lens group.

3. The projection lens of claim 1 wherein the projection lens further comprises:

an aperture stop located in the first lens group, the aperture stop for limiting an entrance transmission pupil aperture.

4. The projection lens of any of claims 1 to 3,

the effective focal length of the projection lens is 1.964-3.273mm;

the projection ratio of the projection lens is 0.23-0.24.

5. A projection imaging system, comprising: a light valve, a total internal reflection TIR prism, and the projection lens of any of claims 1 to 4;