CN219533491U - Projection lens - Google Patents

Abstract

The application discloses a projection lens, which comprises a four-piece imaging lens group and a plurality of spacers, wherein the four-piece imaging lens group comprises a first lens, a second lens, a third lens and a fourth lens which are sequentially arranged from an imaging side to an image source side along an optical axis; the plurality of spacers comprise a first spacer arranged on the image source side surface of the first lens, a second spacer arranged on the image source side surface of the second lens and a third spacer arranged on the image source side surface of the third lens; the radius of curvature R4 of the image source side surface of the second lens, the radius of curvature R5 of the image-side surface of the third lens, and the interval EP23 along the optical axis of the second spacer and the third spacer satisfy: 9.0< | (R4-R5)/EP 23| <28.0, the radius of curvature R6 of the image source side surface of the third lens, the radius of curvature R7 of the image side surface of the fourth lens, the inner diameter d3s of the image side surface of the third spacer, and the inner diameter d3m of the image source side surface of the third spacer satisfy: 2.0< R6/d3s+R7/d3m <6.0.

Description

Projection lens

Technical Field

The application relates to the field of optical devices, in particular to a four-piece projection lens.

Background

With the development of technology, the application of projection lenses is diversified, and the requirement of the application environment of the projection lenses is diversified, so that the projection lenses are forced to maintain stable performance and imaging quality in the diversified application environments.

In the conventional design process of the four-piece projection lens, in order to enable the four-piece projection lens to have good imaging quality and high-quality pictures at the same time, stray light needs to be avoided, and assembly stability of the lens needs to be improved, so how to arrange arrangement relation of each lens and the isolating piece, and inner and outer diameters of the isolating piece, so as to improve the stray light and improve the assembly stability of the lens, becomes a problem to be solved urgently in the field.

Disclosure of Invention

The present utility model provides a projection lens that at least partially solves or solves at least one problem, or other problems, found in the prior art.

An aspect of the present utility model provides a projection lens including a barrel, and a four-piece imaging lens group and a plurality of spacers disposed in the barrel, the four-piece imaging lens group including a first lens, a second lens, a third lens, and a fourth lens arranged in order from an imaging side to an image source side along an optical axis; the plurality of spacers comprise a first spacer, a second spacer and a third spacer, the first spacer is arranged on the image source side surface of the first lens and is contacted with the image source side surface of the first lens, the second spacer is arranged on the image source side surface of the second lens and is contacted with the image source side surface of the second lens, and the third spacer is arranged on the image source side surface of the third lens and is contacted with the image source side surface of the third lens; wherein a radius of curvature R4 of the image source side surface of the second lens, a radius of curvature R5 of the image forming side surface of the third lens, and a spacing EP23 of the second spacer and the third spacer along the optical axis satisfy: 9.0< | (R4-R5)/EP 23| <28.0, and the radius of curvature R6 of the image source side surface of the third lens, the radius of curvature R7 of the image side surface of the fourth lens, the inner diameter d3s of the image side surface of the third spacer, and the inner diameter d3m of the image source side surface of the third spacer satisfy: 2.0< R6/d3s+R7/d3m <6.0.

According to an exemplary embodiment of the present application, the first lens and the second lens have optical powers that differ in positive and negative.

According to an exemplary embodiment of the present application, an entrance pupil diameter EPD of the projection lens, an inner diameter d0s of an imaging side surface of the lens barrel, and an inner diameter d0m of an image source side surface of the lens barrel satisfy: 2.0< EPD/(d 0m-d0 s) <5.5.

According to an exemplary embodiment of the application, the first lens is a glass lens, the refractive index of the first lens being less than 1.53.

According to an exemplary embodiment of the present application, the inner diameter d1s of the imaging side surface of the first spacer, the inner diameter d2s of the imaging side surface of the second spacer, the refractive index N1 of the first lens, and the refractive index N2 of the second lens satisfy: 8.0mm < (d 2s-d1 s)/(N2-N1) <5.5mm.

According to an exemplary embodiment of the present application, the effective focal length f1 of the first lens, the effective focal length f2 of the second lens, the effective focal length f3 of the third lens, and the interval EP23 of the second spacer and the third spacer along the optical axis satisfy: -12.0< (f1+f2+f3)/EP 23< -3.5.

According to an exemplary embodiment of the present application, the maximum thickness CP1 of the first spacer, the air interval T12 of the first and second lenses on the optical axis, the maximum thickness CP2 of the second spacer, and the air interval T23 of the second and third lenses on the optical axis satisfy: 0< CP1/T12+CP2/T23<8.0.

According to an exemplary embodiment of the present application, the total effective focal length f of the projection lens, the outer diameter D1m of the image source side surface of the first spacer, and the outer diameter D3m of the image source side surface of the third spacer satisfy: 3.5< |f/(D3 m-D1 m) | <20.0.

According to an exemplary embodiment of the present application, the length L of the lens barrel in the direction of the optical axis and the total effective focal length f of the projection lens satisfy: l/f <1.0.

According to an exemplary embodiment of the present application, the radius of curvature R1 of the imaging side surface of the first lens, the radius of curvature R2 of the image source side surface of the first lens, the interval EP01 of the imaging side surface of the lens barrel and the first spacer along the optical axis, and the refractive index N1 of the first lens satisfy: 8.5< (R1-R2)/(EP 01 XN 1) <44.5.

According to an exemplary embodiment of the present application, the inner diameter d0s of the imaging side surface of the lens barrel, the interval EP01 of the imaging side surface of the lens barrel and the first spacer along the optical axis, and the center thickness CT1 of the first lens on the optical axis satisfy: 2.0mm < (d0sXCT 1)/EP 01<5.0mm.

According to an exemplary embodiment of the present application, the radius of curvature R5 of the imaging side surface of the third lens, the radius of curvature R7 of the imaging side surface of the fourth lens, and the inner diameter d3s of the imaging side surface of the third spacer satisfy: -16.0< (r5+r7)/d 3s <11.5.

According to an exemplary embodiment of the present application, the effective focal length f2 of the second lens, the effective focal length f3 of the third lens, the interval EP12 of the first spacer and the second spacer along the optical axis, and the interval EP23 of the second spacer and the third spacer along the optical axis satisfy: -20.0< |f3|/EP23+f2/EP12< -6.5.

According to an exemplary embodiment of the present application, the inner diameter d1s of the imaging side surface of the first spacer, the inner diameter d1m of the image source side surface of the first spacer, the radius of curvature R2 of the image source side surface of the first lens, and the radius of curvature R3 of the imaging side surface of the second lens satisfy: -39.5< (d1sxR2)/(d1mxR3) < -8.5.

The application relates to a four-piece projection lens, wherein light rays reach the imaging side of a first lens through the imaging side of a fourth lens and finally are imaged on a projection surface when the projection lens is imaged, the shapes of the three lenses are effectively limited by controlling the curvature radiuses of the imaging side or the imaging side of the second lens, the third lens and the fourth lens, and simultaneously controlling the interval between the second separator and the third separator along the optical axis and the inner diameters of the imaging side surface and the imaging side surface of the third separator, so that the problems of poor lens molding, surface type influence and other parameters caused by the limit process of the shape of the optical axis area of the second lens, the third lens and the fourth lens are avoided, the edge thickness of the lens (such as the third lens) close to the imaging side in the projection lens is restrained, and the inner diameters of the third separator are reasonably arranged, so that the lenses on two sides of the third separator can bear the lens well, the stability of the projection lens and the yield in the assembly process are facilitated to be improved, and the projection lens obtains good imaging quality.

Drawings

Other features, objects and advantages of the present application will become more apparent upon reading of the detailed description of non-limiting embodiments, made with reference to the accompanying drawings in which:

fig. 1 shows a schematic structure of a projection lens according to the present application;

fig. 2 shows a schematic configuration of a projection lens according to example 1 of the first embodiment of the present application;

fig. 3 is a schematic view showing the structure of a projection lens according to example 2 of the first embodiment of the present application;

fig. 4 is a schematic view showing the structure of a projection lens of example 3 according to the first embodiment of the present application;

fig. 5A to 5D show an on-axis chromatic aberration curve, an astigmatic curve, a distortion curve, and a magnification chromatic aberration curve, respectively, of the projection lens according to the first embodiment of the present application;

fig. 6 is a schematic view showing the structure of a projection lens of example 1 according to a second embodiment of the present application;

fig. 7 is a schematic view showing the structure of a projection lens according to example 2 of the second embodiment of the present application;

fig. 8 is a schematic view showing the structure of a projection lens of example 3 according to a second embodiment of the present application;

fig. 9A to 9D show an on-axis chromatic aberration curve, an astigmatic curve, a distortion curve, and a magnification chromatic aberration curve, respectively, of a projection lens according to a second embodiment of the present application;

Fig. 10 is a schematic view showing the structure of a projection lens of example 1 according to a third embodiment of the present application;

fig. 11 is a schematic view showing the structure of a projection lens according to example 2 of the third embodiment of the present application;

fig. 12 is a schematic view showing the structure of a projection lens of example 3 according to a third embodiment of the present application; and

fig. 13A to 13D show an on-axis chromatic aberration curve, an astigmatism curve, a distortion curve, and a magnification chromatic aberration curve, respectively, of a projection lens according to a third embodiment of the present application.

Detailed Description

For a better understanding of the application, various aspects of the application will be described in more detail with reference to the accompanying drawings. It should be understood that the detailed description is merely illustrative of exemplary embodiments of the application and is not intended to limit the scope of the application in any way. Like reference numerals refer to like elements throughout the specification.

It should be noted that in the present specification, the expressions of first, second, third, etc. are only used to distinguish one feature from another feature, and do not represent any limitation on the feature. Accordingly, a first lens discussed below may also be referred to as a second lens or a third lens without departing from the teachings of the present application.

In the drawings, the thickness, size, and shape of the lenses have been slightly exaggerated for convenience of explanation. Specifically, the spherical or aspherical shape shown in the drawings is shown by way of example. That is, the shape of the spherical or aspherical surface is not limited to the shape of the spherical or aspherical surface shown in the drawings. The figures are merely examples and are not drawn to scale.

Herein, the paraxial region refers to a region near the optical axis. If the lens surface is convex and the convex position is not defined, then the lens surface is convex at least in the paraxial region; if the lens surface is concave and the concave position is not defined, it means that the lens surface is concave at least in the paraxial region. When the projection lens is applied to, for example, AR, VR devices, the surface of each lens closest to the human eye side is referred to as the image side surface of the lens, and the surface of each lens closest to the image source side is referred to as the image source side surface of the lens.

It will be further understood that the terms "comprises," "comprising," "includes," "including," "having," "containing," and/or "including," when used in this specification, specify the presence of stated features, elements, and/or components, but do not preclude the presence or addition of one or more other features, elements, components, and/or groups thereof. Furthermore, when describing embodiments of the application, use of "may" means "one or more embodiments of the application. Also, the term "exemplary" is intended to refer to an example or illustration.

Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

It should be noted that, without conflict, the embodiments of the present application and features of the embodiments may be combined with each other. The application will be described in detail below with reference to the drawings in connection with embodiments.

Fig. 1 shows a schematic diagram of a structural layout of a projection lens and a part of parameters according to an exemplary embodiment of the present application. Those skilled in the art will appreciate that some of the parameters commonly used in the art, such as the maximum thickness CP2 of the second separator, are not shown in fig. 1. Fig. 1 illustrates only partial parameters of a lens barrel and a spacer of a projection lens of the present application for better understanding of the present application, as shown in fig. 1, D1s represents an inner diameter of an image-source side surface of a first spacer, D1m represents an inner diameter of an image-source side surface of the first spacer, D1m represents an outer diameter of an image-source side surface of the first spacer, D2s represents an inner diameter of an image-source side surface of a second spacer, D3s represents an inner diameter of an image-source side surface of a third spacer, D3m represents an outer diameter of an image-source side surface of the third spacer, D0s represents an inner diameter of an image-source side surface of the lens barrel, D0m represents an inner diameter of an image-source side surface of the lens barrel, EP01 represents a spacing between the image-source side surface of the lens barrel and the first spacer along an optical axis, CP1 represents a maximum thickness of the first spacer, EP12 represents a spacing between the first spacer and the second spacer along the optical axis, CP2 represents a maximum thickness of the second spacer, D3m represents an inner diameter of the image-source side surface of the third spacer, D0m represents an inner diameter of the image-source side surface of the third spacer, and EP 0s represents an inner diameter of the third spacer along the optical axis.

The features, principles, and other aspects of the present application are described in detail below.

As shown in fig. 2 to 4, 6 to 8, and 10 to 12, the projection lens according to the exemplary embodiment of the present application may include a barrel and a four-piece type imaging lens group disposed inside the barrel, and the four-piece type imaging lens group may include a first lens, a second lens, a third lens, and a fourth lens sequentially arranged from an imaging side to an image source side along an optical axis. In the first lens to the fourth lens, an air space may be provided between any adjacent two lenses.

The projection lens may further include a plurality of spacers disposed in the barrel, the plurality of spacers including a first spacer disposed on and in contact with the image source side surface portion of the first lens, a second spacer disposed on and in contact with the image source side surface portion of the second lens, and a third spacer disposed on and in contact with the image source side surface portion of the third lens. The reasonable use of the spacer can effectively avoid the stray light risk, reduce the interference to the image quality, and then promote the imaging quality of the projection lens.

In an example, the radius of curvature R4 of the image source side surface of the second lens, the radius of curvature R5 of the image-side surface of the third lens, and the interval EP23 of the second spacer and the third spacer along the optical axis may satisfy: 9.0< | (R4-R5)/EP 23| <28.0; and the radius of curvature R6 of the image source side surface of the third lens, the radius of curvature R7 of the image-forming side surface of the fourth lens, the inner diameter d3s of the image-forming side surface of the third spacer, and the inner diameter d3m of the image source side surface of the third spacer may satisfy: 2.0< R6/d3s+R7/d3m <6.0. The projection lens is a four-piece projection lens, light rays reach the imaging side of the first lens through the imaging side of the fourth lens and finally are imaged on the projection surface when the projection lens is imaged, the problems of poor molding and surface type influencing parameters of the lens caused by limit process of the shape of the optical axis area of the second lens, the third lens and the fourth lens are avoided by controlling the curvature radius of the imaging side surface of the second lens, the curvature radius of the imaging side surface of the fourth lens, the interval between the second spacer and the third spacer along the optical axis and the inner diameter of the imaging side surface of the third lens and the inner diameter of the imaging side surface of the fourth lens, and the mutual relation between the thickness of the edge of the lens (such as the third lens) close to the imaging side surface of the third spacer and the inner diameter of the imaging side surface of the third lens in the constraint projection lens can be effectively limited, the interval between the second spacer and the third spacer along the optical axis and the imaging side surface of the third lens and the inner diameter of the imaging side surface of the third lens can be effectively limited, the good stability of the projection lens can be ensured, and the good quality of the projection lens can be improved by the third spacer and the good quality can be obtained.

In an exemplary embodiment, the first lens and the second lens may have positive and negative different optical powers. For example, the first lens may have positive optical power and the second lens may have negative optical power. The first lens and the second lens are controlled to have positive and negative different focal power, so that the combined focal power of the first lens and the second lens can be effectively restrained, and the spherical aberration and distortion of the projection lens can be reduced.

In an exemplary embodiment, an entrance pupil diameter EPD of the projection lens, an inner diameter d0s of an imaging side surface of the lens barrel, and an inner diameter d0m of an image source side surface of the lens barrel may satisfy: 2.0< EPD/(d 0m-d0 s) <5.5. Through controlling the interrelationship between the entrance pupil diameter of the projection lens, the inner diameter of the imaging side surface of the lens barrel and the inner diameter of the image source side surface of the lens barrel, the inner diameters of the imaging side surface and the image source side surface of the lens barrel can be controlled while the entrance pupil diameter of the projection lens is in a reasonable interval, in the projection process of the projection lens, the phenomenon passing through the entrance pupil diameter is reduced in equal proportion after passing through the image source side surface of the lens barrel, and finally the phenomenon of corresponding equal proportion reduction is generated on the projection surface after passing through the imaging side surface of the lens barrel through the internal optical structure of the projection lens, so that the integrity of the entrance pupil phenomenon is effectively ensured, and the loss of a projection picture is reduced.

In an exemplary embodiment, the first lens may be a glass lens, and the refractive index of the first lens may be less than 1.53. The first lens is controlled to be a glass lens, and the refractive index of the first lens is smaller than 1.53, so that the temperature drift of the projection lens can be corrected, and the dispersion of the projection lens can be reduced.

In an exemplary embodiment, the inner diameter d1s of the imaging side surface of the first spacer, the inner diameter d2s of the imaging side surface of the second spacer, the refractive index N1 of the first lens, and the refractive index N2 of the second lens may satisfy: 8.0mm < (d 2s-d1 s)/(N2-N1) <5.5mm. Through controlling the interrelationship between the internal diameter of the imaging side surface of the first isolation piece, the internal diameter of the imaging side surface of the second isolation piece, the refractive index of the first lens and the refractive index of the second lens, the refractive indexes of the first lens and the second lens can be controlled while the internal diameters of the imaging side surfaces of the first isolation piece and the second isolation piece are in a reasonable interval, the problems that the structure of the lens is too thin and the lens generates larger chromatic dispersion due to overlarge refractive index are avoided, the forming difficulty of the lens is reduced, and the assembly yield and the imaging quality of the projection lens are improved.

In an exemplary embodiment, the effective focal length f1 of the first lens, the effective focal length f2 of the second lens, and the effective focal length f3 of the third lens may satisfy the interval EP23 of the second spacer and the third spacer along the optical axis: -12.0< (f1+f2+f3)/EP 23< -3.5. Through controlling the interrelationship between the effective focal length of the first lens, the effective focal length of the second lens, the effective focal length of the third lens and the intervals of the second isolating piece and the third isolating piece along the optical axis, the intervals of the second isolating piece and the third isolating piece along the optical axis can be controlled while the effective focal lengths of the first lens, the second lens and the third lens are in a reasonable interval, the problem that the total effective focal length of the projection lens exceeds the whole focusing range and a clear picture cannot be projected on the projection surface due to overlarge effective focal length of the lens is avoided, and the second isolating piece and the third isolating piece can be utilized for blocking excessive light, so that the stray light phenomenon of the projection lens is improved.

In an exemplary embodiment, the maximum thickness CP1 of the first spacer, the air interval T12 of the first and second lenses on the optical axis, the maximum thickness CP2 of the second spacer, and the air interval T23 of the second and third lenses on the optical axis may satisfy: 0< CP1/T12+CP2/T23<8.0. Through controlling the maximum thickness of the first isolating piece, the air interval between the first lens and the second lens on the optical axis, and the correlation between the maximum thickness of the second isolating piece and the air interval between the second lens and the third lens on the optical axis, the maximum thickness of the first isolating piece and the maximum thickness of the second isolating piece are in a reasonable interval, the problem that the first lens and the second lens interfere when being assembled due to the fact that the thickness of the first isolating piece is too small is avoided, the imaging quality and performance of the projection lens are improved, the problem that the second isolating piece generates larger deformation in the assembling process due to the fact that the thickness of the second isolating piece is too small is also avoided, and the yield and the imaging quality of the projection lens are improved.

In an exemplary embodiment, the total effective focal length f of the projection lens, the outer diameter D1m of the image source side surface of the first spacer, and the outer diameter D3m of the image source side surface of the third spacer may satisfy: 3.5< |f/(D3 m-D1 m) | <20.0. Through controlling the correlation between the total effective focal length of the projection lens, the outer diameter of the image source side surface of the first separator and the outer diameter of the image source side surface of the third separator, the total effective focal length of the projection lens can be controlled while the outer diameters of the image source side surfaces of the first separator and the third separator are in a reasonable interval, the problem that imaging is enlarged due to overlarge total effective focal length of the projection lens, and then the object of imaging is reduced, and the problem of image definition is reduced is avoided, or the problem that imaging is reduced due to overlarge total effective focal length of the projection lens, serious vignetting is further generated, the illumination of aberration edges is reduced, and the imaging quality of the projection lens is influenced is avoided.

In the exemplary embodiment, the length L of the lens barrel in the direction of the optical axis and the total effective focal length f of the projection lens may satisfy: l/f <1.0. Through controlling the interrelationship between the length of lens cone in the direction of optical axis place and the total effective focal length of projection lens, can make the length of lens cone in the direction of optical axis place be in the reasonable interval to the total effective focal length of projection lens, reduce the volume of projection lens and the projection equipment that contains this projection lens, still can avoid the projection equipment that leads to because of the total effective focal length of projection lens is too big need keep away from the problem of projection plane.

In an exemplary embodiment, a radius of curvature R1 of the imaging side surface of the first lens, a radius of curvature R2 of the image source side surface of the first lens, a spacing EP01 of the imaging side surface of the barrel and the first spacer along the optical axis, and a refractive index N1 of the first lens may satisfy: 8.5< (R1-R2)/(EP 01 XN 1) <44.5. By controlling the mutual relation among the curvature radius of the imaging side surface of the first lens, the curvature radius of the image source side surface of the first lens, the interval between the imaging side surface of the lens barrel and the first spacer along the optical axis and the refractive index of the first lens, the interval between the imaging side surface of the lens barrel and the image source side surface along the optical axis and the refractive index of the first lens can be restrained while the curvature radius of the imaging side surface of the first lens and the curvature radius of the image source side surface of the first lens are in a reasonable interval, the integral structure of the first lens is effectively controlled on the basis that the first lens is a glass lens, and the edge thickness of the first lens is ensured, so that the processing difficulty of the first lens is reduced, and the production yield of the first lens is improved.

In an exemplary embodiment, an inner diameter d0s of the imaging side surface of the lens barrel, an interval EP01 of the imaging side surface of the lens barrel and the first spacer along the optical axis, and a center thickness CT1 of the first lens on the optical axis may satisfy: 2.0mm < (d0sXCT 1)/EP 01<5.0mm. Through the interrelationship between the spacing of the imaging side surface of the lens barrel, the imaging side surface of the lens barrel and the first spacer along the optical axis and the central thickness of the first lens on the optical axis, the inner diameter of the imaging side surface of the lens barrel can be restrained when the edge thickness and the central thickness of the first lens are in reasonable intervals, the thickness of the first lens bearing against the lens barrel is limited in a certain range, meanwhile, the projection surface can be ensured to have a larger light inlet area, and the problems that the projection picture is lost and the imaging quality of the projection lens is influenced due to the fact that the light inlet area is too small caused by too small inner diameter of the imaging side surface of the lens barrel are avoided.

In an exemplary embodiment, the radius of curvature R5 of the imaging side surface of the third lens, the radius of curvature R7 of the imaging side surface of the fourth lens, and the inner diameter d3s of the imaging side surface of the third spacer may satisfy: -16.0< (r5+r7)/d 3s <11.5. By controlling the correlations between the radius of curvature of the imaging side surface of the third lens, the radius of curvature of the imaging side surface of the fourth lens and the inner diameter of the imaging side surface of the third spacer, the inner diameter of the imaging side surface of the third spacer can be limited within a certain range while controlling the bending degree of the third lens and the fourth lens, the problems of overlarge center thickness, increased thickness ratio and difficult molding of the lens caused by over-convex lens are avoided, the problems of overlarge center thickness, difficult molding, large deformation in the assembling process and the like of the lens caused by over-concave lens are avoided, and the production yield of the projection lens is improved.

In an exemplary embodiment, the effective focal length f2 of the second lens, the effective focal length f3 of the third lens, the interval EP12 of the first spacer and the second spacer along the optical axis, and the interval EP23 of the second spacer and the third spacer along the optical axis may satisfy: -20.0< |f3|/EP23+f2/EP12< -6.5. By controlling the correlations between the effective focal length of the second lens, the effective focal length of the third lens, the intervals of the first spacer and the second spacer along the optical axis and the intervals of the second spacer and the third spacer along the optical axis, the edge thicknesses of the second lens and the third lens can be restrained while the effective focal lengths of the second lens and the third lens are in a reasonable interval, the deflection angles of the edge view fields in the second lens and the third lens are controlled, the sensitivity of the projection lens is reduced, and the assembly stability of the projection lens is improved.

In an exemplary embodiment, an inner diameter d1s of the imaging side surface of the first spacer, an inner diameter d1m of the image source side surface of the first spacer, a radius of curvature R2 of the image source side surface of the first lens, and a radius of curvature R3 of the imaging side surface of the second lens may satisfy: -39.5< (d1sxR2)/(d1mxR3) < -8.5. Through controlling the interrelationship between the internal diameter of the imaging side surface of the first isolation piece, the internal diameter of the image source side surface of the first isolation piece, the curvature radius of the image source side surface of the first lens and the curvature radius of the imaging side surface of the second lens, the bearing step difference between the first lens and the second lens can be ensured, and then the stability of the first lens and the second lens assembly is ensured, meanwhile, the surface profile of the first lens and the second lens can be controlled, the processability of the first lens and the second lens is improved, and the yield of the projection lens is improved.

In an exemplary embodiment, the projection lens further includes a diaphragm, which may be disposed between the imaging side and the first lens according to actual needs.

The projection lens according to the above embodiment of the present application may employ four lenses and a plurality of spacers. By reasonably distributing the parameters of each lens and each spacer, the forming difficulty of the lenses can be reduced, the chromatic dispersion of the projection lens can be reduced, the stray light phenomenon of the projection lens can be improved, and the assembly yield, the assembly stability, the imaging quality and the performance of the projection lens can be improved.

In an embodiment of the present application, at least one of the mirrors of each of the first to fourth lenses is an aspherical mirror. The aspherical lens is characterized in that: the curvature varies continuously from the center of the lens to the periphery of the lens. Unlike a spherical lens having a constant curvature from the center of the lens to the periphery of the lens, an aspherical lens has a better radius of curvature characteristic, and has advantages of improving distortion aberration and improving astigmatic aberration. By adopting the aspherical lens, aberration occurring during imaging can be eliminated as much as possible, thereby improving imaging quality. Optionally, the imaging side surface and the image source side surface of each of the first lens to the fourth lens are aspherical mirror surfaces.

The projection lens according to an exemplary embodiment of the present application is a low-volume optical system of high definition imaging quality, which is applicable to AR/VR, head-mounted devices.

However, those skilled in the art will appreciate that the number of lenses and spacers making up the projection lens can be varied to achieve the various results and advantages described in this specification without departing from the scope of the application as claimed.

Specific examples of projection lenses applicable to the above embodiments are further described below with reference to the accompanying drawings.

First embodiment

A projection lens according to a first embodiment of the present application is described below with reference to fig. 2 to 5D. Fig. 2 shows a schematic configuration of a projection lens 110 according to example 1 of the first embodiment of the present application; fig. 3 shows a schematic structural view of a projection lens 120 according to example 2 of the first embodiment of the present application; fig. 4 shows a schematic structural diagram of a projection lens 130 according to example 3 of the first embodiment of the present application.

As shown in fig. 2 to 4, each of the projection lenses 110, 120, 130 includes a lens barrel P0, and a four-piece imaging lens group and a plurality of spacers disposed in the lens barrel P0, the four-piece imaging lens group including, in order from an imaging side to an image source side: a first lens E1, a second lens E2, a third lens E3, and a fourth lens E4. The stop STO may be disposed between the imaging side and the first lens E1 according to actual needs. The plurality of spacers includes: the first separator P1, the second separator P2, and the third separator P3. The spacer can block excessive light rays in the imaging process from entering the next lens, and meanwhile, the lens and the lens barrel P0 are better supported, so that the structural stability of the projection lens is enhanced.

The first lens E1 has positive power, and its imaging side surface S1 is convex and its source side surface S2 is convex. The second lens E2 has negative power, the imaging side surface S3 thereof is convex, and the image source side surface S4 thereof is concave. The third lens E3 has negative power, and its imaging side surface S5 is concave and its source side surface S6 is concave. The fourth lens element E4 has positive refractive power, and has a convex image-side surface S7 and a concave image-source side surface S8. The filter has an imaging side surface S9 (not shown) and an image source side surface S10 (not shown). Light from the image source surface S11 (not shown) sequentially passes through the respective surfaces S10 to S1 and is finally projected onto a projection surface (not shown) provided on the imaging side. When the projection lens is applied to, for example, VR or AR devices, light from the image source surface sequentially passes through the surfaces S10 to S1 and can be finally projected to the human eye for imaging.

Table 1 shows basic parameter tables of the projection lens of the first embodiment, in which the units of radius of curvature, thickness/distance, and focal length are all millimeters (mm).

TABLE 1

In the present embodiment, the value of the total effective focal length of the projection lens is 5.80mm, the value of half of the maximum field angle of the projection lens is 15.36 °, and the value of the entrance pupil diameter EPD of the projection lens is 3.01mm.

In the first embodiment, the imaging side surface and the image source side surface of any one of the first lens E1 to the fourth lens E4 are aspherical, and the surface profile x of each aspherical lens can be defined by, but not limited to, the following aspherical formula:

wherein x is the distance vector height from the vertex of the aspheric surface when the aspheric surface is at the position with the height h along the optical axis direction; c is the paraxial curvature of the aspheric surface, c=1/R (i.e., paraxial curvature c is the inverse of radius of curvature R in table 1 above); k is a conic coefficient; ai is the correction coefficient of the aspherical i-th order. Table 2 shows the higher order coefficients A that can be used for each of the aspherical mirror surfaces S1-S8 in the first embodiment ₄ 、A ₆ 、A ₈ 、A ₁₀ 、A ₁₂ 、A ₁₄ And A ₁₆ 。

Face number

A4

A6

A8

A10

A12

A14

A16

S1

-2.68E-03

-2.99E-03

1.51E-03

-1.41E-03

4.76E-04

-6.72E-05

-1.83E-05

S2

2.29E-02

-1.23E-02

8.38E-03

-3.60E-03

-2.97E-04

6.57E-04

-1.27E-04

S3

-9.82E-02

4.86E-02

-4.49E-02

6.39E-02

-6.16E-02

2.94E-02

-5.19E-03

S4

-1.46E-01

7.23E-02

-8.71E-02

1.20E-01

-1.08E-01

4.14E-02

-2.31E-03

S5

-2.75E-01

2.55E-01

-6.39E-01

9.76E-01

-9.70E-01

5.32E-01

-1.25E-01

S6

-2.72E-01

4.49E-01

-7.81E-01

8.44E-01

-5.76E-01

2.14E-01

-3.23E-02

S7

-2.08E-01

1.47E-01

2.70E-02

-3.29E-01

3.94E-01

-2.15E-01

4.45E-02

S8

-1.59E-01

7.72E-02

-1.40E-02

-4.76E-02

4.80E-02

-2.00E-02

3.07E-03

TABLE 2

The projection lenses 110, 120, and 130 in examples 1, 2, and 3 of the first embodiment are different in the structural dimensions of the lens barrel and the spacer included. Tables 3-1 to 3-2 show some basic parameters of the lens barrels, spacers, of the projection lenses 110, 120 and 130 of the first embodiment, such as D1s, D1m, D2s, D3m, D0s, D0m, EP01, CP1, EP12, CP2, EP23 and L, etc., some of the basic parameters listed in tables 3-1 to 3-2 are measured according to the labeling method shown in fig. 1, and the basic parameters listed in tables 3-1 to 3-2 are all in millimeters (mm).

Examples/parameters	d1s	d1m	D1m	d2s	d3s	d3m	D3m	d0s
									1-1	3.173	2.927	4.068	2.116	2.423	2.423	4.588	4.174
1-2	3.211	2.986	4.108	2.116	2.348	2.348	3.450	4.174
									1-3	2.597	2.597	4.288	2.116	2.427	2.427	4.588	4.174

TABLE 3-1

Examples/parameters	d0m	EP01	CP1	EP12	CP2	EP23	L
								1-1	4.803	1.222	0.317	0.409	0.018	1.581	4.428
1-2	4.803	1.368	0.337	0.530	0.018	1.516	4.428
								1-3	4.803	1.222	0.018	0.545	0.018	1.531	4.428

TABLE 3-2

Fig. 5A shows on-axis chromatic aberration curves of the projection lenses 110, 120, and 130 of the first embodiment, which represent convergent focus deviations of light rays of different wavelengths after passing through the projection lenses 110, 120, and 130. Fig. 5B shows astigmatism curves of the projection lenses 110, 120, and 130 of the first embodiment, which represent meridional image surface curvature and sagittal image surface curvature corresponding to different angles of view. Fig. 5C shows distortion curves of the projection lenses 110, 120, and 130 of the first embodiment, which represent distortion magnitude values corresponding to different angles of view. Fig. 5D shows the magnification chromatic aberration curves of the projection lenses 110, 120, and 130 of the first embodiment, which represent the deviation of different image heights on the projection surface after light passes through the lenses. As can be seen from fig. 5A to 5D, the projection lenses 110, 120 and 130 according to the first embodiment can achieve good imaging quality.

Second embodiment

A projection lens according to a second embodiment of the present application is described below with reference to fig. 6 to 9D. Fig. 6 shows a schematic structural diagram of a projection lens 210 of example 1 according to a second embodiment of the present application; fig. 7 shows a schematic structural diagram of a projection lens 220 according to example 2 of the second embodiment of the present application; fig. 8 shows a schematic structural diagram of a projection lens 230 according to example 3 of the second embodiment of the present application.

As shown in fig. 6 to 8, the projection lenses 210, 220, 230 each include a lens barrel P0, and a four-piece imaging lens group and a plurality of spacers disposed in the lens barrel P0, the four-piece imaging lens group including, in order from an imaging side to an image source side: a first lens E1, a second lens E2, a third lens E3, and a fourth lens E4. The stop STO may be disposed between the imaging side and the first lens E1 according to actual needs. The plurality of spacers includes: the first separator P1, the second separator P2, and the third separator P3. The spacer can block excessive light rays in the imaging process from entering the next lens, and meanwhile, the lens and the lens barrel P0 are better supported, so that the structural stability of the projection lens is enhanced.

The first lens E1 has positive power, and its imaging side surface S1 is convex and its source side surface S2 is convex. The second lens E2 has negative power, the imaging side surface S3 thereof is convex, and the image source side surface S4 thereof is concave. The third lens E3 has negative power, and its imaging side surface S5 is concave and its source side surface S6 is concave. The fourth lens element E4 has positive refractive power, and has a convex image-side surface S7 and a convex image-source side surface S8. The filter has an imaging side surface S9 (not shown) and an image source side surface S10 (not shown). Light from the image source surface S11 (not shown) sequentially passes through the respective surfaces S10 to S1 and is finally projected onto a projection surface (not shown) provided on the imaging side. When the projection lens is applied to, for example, VR or AR devices, light from the image source surface sequentially passes through the surfaces S10 to S1 and can be finally projected to the human eye for imaging.

Table 4 shows a basic parameter table of the projection lens of the second embodiment, in which the units of radius of curvature, thickness/distance, and focal length are all millimeters (mm).

TABLE 4 Table 4

In the present embodiment, the value of the total effective focal length of the projection lens is 5.50mm, the value of half of the maximum field angle of the projection lens is 16.10 °, and the value of the entrance pupil diameter EPD of the projection lens is 3.01mm.

In the second embodiment, the imaging side surface and the image source side surface of any one of the first lens E1 to the fourth lens E4 are aspherical. Table 5 shows the higher order coefficients A that can be used for each of the aspherical mirror surfaces S1-S8 in the second embodiment ₄ 、A ₆ 、A ₈ 、A ₁₀ 、A ₁₂ 、A ₁₄ And A ₁₆ 。

Face number

A4

A6

A8

A10

A12

A14

A16

S1

-2.23E-03

-1.42E-03

-1.58E-03

1.99E-03

-1.57E-03

5.89E-04

-1.03E-04

S2

1.67E-02

7.72E-03

-1.95E-02

1.86E-02

-1.03E-02

2.99E-03

-3.52E-04

S3

-1.20E-01

5.67E-02

-1.58E-02

-4.32E-03

7.03E-03

-3.69E-03

9.15E-04

S4

-1.73E-01

5.10E-02

3.32E-02

-1.27E-01

1.55E-01

-1.00E-01

2.67E-02

S5

-1.72E-01

-1.25E-01

2.28E-01

-2.68E-01

-1.55E-03

1.94E-01

-9.58E-02

S6

-7.33E-02

-3.25E-01

5.71E-01

-5.50E-01

3.28E-01

-1.16E-01

1.79E-02

S7

-5.79E-02

-2.38E-01

2.45E-01

8.42E-02

-2.58E-01

1.48E-01

-3.04E-02

S8

-9.98E-02

-7.16E-02

1.25E-01

-4.70E-02

1.29E-03

4.62E-04

3.80E-05

TABLE 5

The projection lenses 210, 220, and 230 in examples 1, 2, and 3 of the second embodiment are different in the structural dimensions of the lens barrel and the spacer included. Tables 6-1 to 6-2 show some basic parameters of the lens barrels, spacers, of the projection lenses 210, 220, and 230 of the second embodiment, such as D1s, D1m, D2s, D3m, D0s, D0m, EP01, CP1, EP12, CP2, EP23, and L, etc., some of the basic parameters listed in tables 6-1 to 6-2 are measured according to the labeling method shown in fig. 1, and the basic parameters listed in tables 6-1 to 6-2 are all in millimeters (mm).

Examples/parameters	d1s	d1m	D1m	d2s	d3s	d3m	D3m	d0s
									2-1	3.374	3.151	4.620	2.113	2.535	2.535	5.100	4.499
2-2	2.655	2.655	4.700	2.158	2.519	2.519	5.000	4.499
									2-3	3.303	3.259	4.640	2.113	2.575	2.575	3.741	4.499

TABLE 6-1

Examples/parameters	d0m	EP01	CP1	EP12	CP2	EP23	L
								2-1	5.269	1.222	0.310	0.594	0.018	1.683	4.425
2-2	5.169	1.368	0.018	0.741	0.018	1.683	4.425
								2-3	5.313	1.222	0.310	0.594	0.018	1.683	4.425

TABLE 6-2

Fig. 9A shows on-axis chromatic aberration curves of the projection lenses 210, 220, and 230 of the second embodiment, which represent convergent focus deviations of light rays of different wavelengths after passing through the projection lenses 210, 220, and 230. Fig. 9B shows astigmatism curves of the projection lenses 210, 220, and 230 of the second embodiment, which represent meridional image surface curvature and sagittal image surface curvature corresponding to different angles of view. Fig. 9C shows distortion curves of the projection lenses 210, 220, and 230 of the second embodiment, which represent distortion magnitude values corresponding to different angles of view. Fig. 9D shows magnification chromatic aberration curves of the projection lenses 210, 220, and 230 of the second embodiment, which represent deviations of different image heights on the projection surface after light passes through the lenses. As can be seen from fig. 9A to 9D, the projection lenses 210, 220, and 230 of the second embodiment can achieve good imaging quality.

Third embodiment

A projection lens according to a third embodiment of the present application is described below with reference to fig. 10 to 13D. Fig. 10 shows a schematic structural view of a projection lens 310 according to example 1 of the third embodiment of the present application; fig. 11 shows a schematic structural view of a projection lens 320 according to example 2 of the third embodiment of the present application; fig. 12 shows a schematic configuration of a projection lens 330 according to example 3 of the third embodiment of the present application.

As shown in fig. 10 to 12, the projection lenses 310, 320, 330 each include a lens barrel P0, and a four-piece imaging lens group and a plurality of spacers disposed in the lens barrel P0, the four-piece imaging lens group including, in order from an imaging side to an image source side: a first lens E1, a second lens E2, a third lens E3, and a fourth lens E4. The stop STO may be disposed between the imaging side and the first lens E1 according to actual needs. The plurality of spacers includes: the first separator P1, the second separator P2, and the third separator P3. The spacer can prevent excessive light rays in the imaging process from entering the next lens, so that the lens and the lens barrel P0 are better supported, and the structural stability of the projection lens is enhanced.

The first lens E1 has positive power, and its imaging side surface S1 is convex and its source side surface S2 is convex. The second lens E2 has negative power, the imaging side surface S3 thereof is convex, and the image source side surface S4 thereof is concave. The third lens E3 has negative power, the imaging side surface S5 thereof is convex, and the image source side surface S6 thereof is concave. The fourth lens E4 has negative power, the imaging side surface S7 thereof is convex, and the image source side surface S8 thereof is concave. The filter has an imaging side surface S9 (not shown) and an image source side surface S10 (not shown). Light from the image source surface S11 (not shown) sequentially passes through the respective surfaces S10 to S1 and is finally projected onto a projection surface (not shown) provided on the imaging side. When the projection lens is applied to, for example, VR or AR devices, light from the image source surface sequentially passes through the surfaces S10 to S1 and can be finally projected to the human eye for imaging.

Table 7 shows a basic parameter table of the projection lens of the third embodiment, in which the units of radius of curvature, thickness/distance, and focal length are all millimeters (mm).

TABLE 7

In this embodiment, the value of the total effective focal length of the projection lens is 5.85mm, the value of half of the maximum field angle of the projection lens is 15.72 °, and the value of the entrance pupil diameter EPD of the projection lens is 3.01mm.

In the third embodiment, the imaging side surface and the image source of any one of the first to fourth lenses E1 to E4The side surfaces are all aspheric. Table 8 shows the higher order coefficients A that can be used for each of the aspherical mirror surfaces S1-S8 in the third embodiment ₄ 、A ₆ 、A ₈ 、A ₁₀ 、A ₁₂ 、A ₁₄ And A ₁₆ 。

Face number

A4

A6

A8

A10

A12

A14

A16

S1

1.47E-03

-5.94E-03

7.38E-03

-6.52E-03

3.58E-03

-1.14E-03

1.55E-04

S2

-5.01E-02

1.11E-01

-1.07E-01

5.70E-02

-1.72E-02

2.63E-03

-1.29E-04

S3

-1.38E-01

6.94E-02

4.29E-02

-1.22E-01

9.50E-02

-3.33E-02

4.53E-03

S4

-1.25E-01

-1.83E-02

1.67E-01

-2.51E-01

1.84E-01

-6.82E-02

1.02E-02

S5

-6.87E-02

-2.09E-02

2.28E-02

-7.25E-02

8.82E-02

-5.35E-02

1.22E-02

S6

-8.34E-02

-1.31E-02

4.27E-02

-8.70E-02

5.90E-02

-1.25E-02

-1.01E-03

S7

-9.28E-02

-7.65E-03

7.63E-03

2.69E-02

-9.02E-02

7.41E-02

-1.99E-02

S8

-7.19E-02

-2.00E-02

4.72E-02

-4.83E-02

2.53E-02

-6.52E-03

6.46E-04

TABLE 8

The projection lenses 310, 320, and 330 in examples 1, 2, and 3 of the third embodiment are different in the structural dimensions of the lens barrel and the spacer included. Tables 9-1 to 9-2 show some basic parameters of the lens barrels, spacers, of the projection lenses 310, 320 and 330 of the third embodiment, such as D1s, D1m, D2s, D3m, D0s, D0m, EP01, CP1, EP12, CP2, EP23 and L, etc., some of the basic parameters listed in tables 9-1 to 9-2 were measured according to the labeling method shown in fig. 1, and the basic parameters listed in tables 9-1 to 9-2 were all in millimeters (mm).

Examples/parameters	d1s	d1m	D1m	d2s	d3s	d3m	D3m	d0s
									3-1	2.646	2.646	4.931	3.349	2.424	2.424	5.491	4.631
3-2	2.680	2.680	4.061	3.435	2.451	2.451	5.431	4.631
									3-3	2.646	2.646	4.931	3.384	2.458	2.458	3.936	4.631

TABLE 9-1

Examples/parameters	d0m	EP01	CP1	EP12	CP2	EP23	L
								3-1	5.681	1.448	0.018	0.596	0.747	1.521	5.379
3-2	5.621	1.448	0.018	0.596	0.747	1.521	5.379
								3-3	5.681	1.448	0.018	0.596	0.727	1.553	5.379

TABLE 9-2

Fig. 13A shows on-axis chromatic aberration curves of the projection lenses 310, 320, and 330 of the third embodiment, which represent convergent focus deviations of light rays of different wavelengths after passing through the projection lenses 310, 320, and 330. Fig. 13B shows astigmatism curves of projection lenses 310, 320, and 330 of the third embodiment, which represent meridional image surface curvature and sagittal image surface curvature corresponding to different angles of view. Fig. 13C shows distortion curves of projection lenses 310, 320, and 330 of the third embodiment, which represent distortion magnitude values corresponding to different angles of view. Fig. 13D shows a magnification chromatic aberration curve of the projection lenses 310, 320, and 330 of the third embodiment, which represents the deviation of different image heights on the projection surface after light passes through the lenses. As can be seen from fig. 13A to 13D, the projection lenses 310, 320 and 330 of the third embodiment can achieve good imaging quality.

In summary, the conditional expressions of the examples in the first to third embodiments satisfy the relationship shown in table 10.

Condition/example	1-1	1-2	1-3	2-1	2-2	2-3	3-1	3-2	3-3
										|(R4-R5)/EP23|	26.18	27.30	27.03	15.62	15.62	15.62	10.09	10.09	9.88
R6/d3s+R7/d3m	2.72	2.81	2.72	3.86	3.89	3.80	5.15	5.09	5.08
										EPD/(d0m-d0s)	4.78	4.78	4.78	3.91	4.49	3.70	2.86	3.04	2.86
(d2s-d1s)/(N2-N1)	-6.45	-6.68	-2.93	-7.69	-3.03	-7.25	4.29	4.60	4.50
										(f1+f2+f3)/EP23	-5.00	-5.22	-5.16	-4.57	-4.57	-4.57	-11.09	-11.09	-10.86
CP1/T12+CP2/T23	6.33	6.73	0.37	7.31	0.43	7.31	1.03	1.03	1.02
										|f/(D3m-D1m)|	11.15	8.81	19.33	11.46	18.33	6.12	10.45	4.27	5.88
L/f	0.76	0.76	0.76	0.80	0.80	0.80	0.92	0.92	0.92
										(R1-R2)/(EP01×N1)	15.88	14.20	15.88	10.84	9.69	10.84	43.78	43.78	43.78
(d0s×CT1)/EP01	4.01	3.58	4.01	4.40	3.94	4.40	3.11	3.11	3.11
										(R5+R7)/d3s	-14.78	-15.25	-14.76	-6.96	-7.01	-6.85	10.99	10.86	10.84
|f3|/EP23+f2/EP12	-15.25	-11.10	-10.74	-9.34	-7.02	-9.34	-18.96	-18.96	-19.05
										(d1s×R2)/(d1m×R3)	-15.49	-15.36	-14.29	-10.25	-9.57	-9.70	-38.84	-38.84	-38.84

Table 10

The above description is only illustrative of the preferred embodiments of the present utility model and of the principles of the technology employed. It will be appreciated by persons skilled in the art that the scope of the utility model referred to in the present utility model is not limited to the specific combinations of the technical features described above, but also covers other technical features formed by any combination of the technical features described above or their equivalents without departing from the inventive concept. Such as the above-mentioned features and the technical features disclosed in the present utility model (but not limited to) having similar functions are replaced with each other.

Claims (14)

1. Projection lens, its characterized in that includes:

a four-piece imaging lens group including a first lens, a second lens, a third lens, and a fourth lens arranged in order from an imaging side to an image source side along an optical axis;

a plurality of spacers including a first spacer provided on and in contact with an image source side surface of the first lens, a second spacer provided on and in contact with an image source side surface of the second lens, and a third spacer provided on and in contact with an image source side surface of the third lens; and

a lens barrel in which the four-piece imaging lens group and the plurality of spacers are disposed,

wherein a radius of curvature R4 of an image source side surface of the second lens, a radius of curvature R5 of an image forming side surface of the third lens, and a spacing EP23 of the second spacer and the third spacer along the optical axis satisfy: 9.0< | (R4-R5)/EP 23| <28.0, and

the radius of curvature R6 of the image source side surface of the third lens, the radius of curvature R7 of the image side surface of the fourth lens, the inner diameter d3s of the image side surface of the third spacer, and the inner diameter d3m of the image source side surface of the third spacer satisfy: 2.0< R6/d3s+R7/d3m <6.0.

2. The projection lens of claim 1 wherein the first and second lenses have optical powers that differ in positive and negative.

3. The projection lens according to claim 1, wherein an entrance pupil diameter EPD of the projection lens, an inner diameter d0s of an imaging side surface of the lens barrel, and an inner diameter d0m of an image source side surface of the lens barrel satisfy: 2.0< EPD/(d 0m-d0 s) <5.5.

4. The projection lens of claim 1 wherein the first lens is a glass lens and the refractive index of the first lens is less than 1.53.

5. The projection lens of claim 4, wherein an inner diameter d1s of an imaging side surface of the first spacer, an inner diameter d2s of an imaging side surface of the second spacer, a refractive index N1 of the first lens, and a refractive index N2 of the second lens satisfy: 8.0mm < (d 2s-d1 s)/(N2-N1) <5.5mm.

6. The projection lens of claim 1, wherein an effective focal length f1 of the first lens, an effective focal length f2 of the second lens, an effective focal length f3 of the third lens, and a spacing EP23 of the second spacer and the third spacer along the optical axis satisfy: -12.0< (f1+f2+f3)/EP 23< -3.5.

7. The projection lens according to claim 1, wherein a maximum thickness CP1 of the first spacer, an air interval T12 of the first lens and the second lens on the optical axis, a maximum thickness CP2 of the second spacer, and an air interval T23 of the second lens and the third lens on the optical axis satisfy: 0< CP1/T12+CP2/T23<8.0.

8. The projection lens according to claim 1, wherein a total effective focal length f of the projection lens, an outer diameter D1m of an image source side surface of the first spacer, and an outer diameter D3m of an image source side surface of the third spacer satisfy: 3.5< |f/(D3 m-D1 m) | <20.0.

9. The projection lens according to claim 1, wherein a length L of the lens barrel in a direction in which the optical axis is located and a total effective focal length f of the projection lens satisfy: l/f <1.0.

10. The projection lens according to claim 1, wherein a radius of curvature R1 of an imaging side surface of the first lens, a radius of curvature R2 of an image source side surface of the first lens, a spacing EP01 of an imaging side surface of the lens barrel and the first spacer along the optical axis, and a refractive index N1 of the first lens satisfy: 8.5< (R1-R2)/(EP 01 XN 1) <44.5.

11. The projection lens according to claim 1, wherein an inner diameter d0s of an imaging side surface of the barrel, an interval EP01 of the imaging side surface of the barrel and the first spacer along the optical axis, and a center thickness CT1 of the first lens on the optical axis satisfy: 2.0mm < (d0sXCT 1)/EP 01<5.0mm.

12. The projection lens according to claim 1, wherein a radius of curvature R5 of an imaging side surface of the third lens, a radius of curvature R7 of an imaging side surface of the fourth lens, and an inner diameter d3s of an imaging side surface of the third spacer satisfy: -16.0< (r5+r7)/d 3s <11.5.

13. The projection lens according to claim 1, wherein an effective focal length f2 of the second lens, an effective focal length f3 of the third lens, a spacing EP12 of the first spacer and the second spacer along the optical axis, and a spacing EP23 of the second spacer and the third spacer along the optical axis satisfy: -20.0< |f3|/EP23+f2/EP12< -6.5.

14. The projection lens according to claim 1, wherein an inner diameter d1s of an imaging side surface of the first spacer, an inner diameter d1m of an image source side surface of the first spacer, a radius of curvature R2 of an image source side surface of the first lens, and a radius of curvature R3 of an imaging side surface of the second lens satisfy: -39.5< (d1sxR2)/(d1mxR3) < -8.5.