CN219978606U - Lens and projection optical machine - Google Patents

Abstract

The utility model discloses a lens and a projection optical machine, comprising: the lens system comprises a first lens, a second lens and a third lens, wherein the first lens is a positive focal power lens, the object side surface of the first lens is a convex surface, and the image side surface of the first lens is a concave surface; the second lens is a negative focal power lens, the object side surface of the second lens is a concave surface, and the image side surface of the second lens is a concave surface; the third lens is a positive focal power lens, the object side surface of the third lens is a concave surface, and the image side surface of the third lens is a concave surface; the fourth lens is a positive focal power lens, the object side surface of the fourth lens is a convex surface, and the image side surface of the fourth lens is a convex surface; the first lens, the second lens, the third lens and the fourth lens are distributed on the object side of the lens to the image source side of the lens along the optical axis, so that the reasonable distribution of the focal power of the lens is facilitated, the balance and the correction of various aberrations are facilitated, and the imaging quality and the definition are improved.

Description

Lens and projection optical machine

Technical Field

The present utility model relates to the field of projection technologies, and in particular, to a lens and a projection optical engine.

Background

At present, as the requirement of users on immersive experience is larger and larger, the development of augmented reality display technology is promoted, wherein how to improve imaging efficiency, promote the frivolity of display equipment and enhance near-to-eye display effect is a problem that needs to be solved in order to meet the actual application scene requirement.

Disclosure of Invention

The utility model provides a lens and a projection optical machine, so as to improve the defects.

In a first aspect, an embodiment of the present utility model provides a lens applied to a projection optical engine, where the lens includes a lens group, and the lens group includes: the lens system comprises a first lens, a second lens and a third lens, wherein the first lens is a positive focal power lens, the object side surface of the first lens is a convex surface, and the image side surface of the first lens is a concave surface; the second lens is a negative focal power lens, the object side surface of the second lens is a concave surface, and the image side surface of the second lens is a concave surface; the third lens is a positive focal power lens, the object side surface of the third lens is a concave surface, and the image side surface of the third lens is a concave surface; the fourth lens is a positive focal power lens, the object side surface of the fourth lens is a convex surface, and the image side surface of the fourth lens is a convex surface; the first lens, the second lens, the third lens and the fourth lens are distributed at intervals along an optical axis in a direction from an object side of the lens to an image source side of the lens.

In a second aspect, an embodiment of the present utility model further provides a projection optical engine, including a diaphragm, an image source surface and the lens described above, where the image source surface is disposed on an image source side of the lens and is adjacent to the fourth lens, the diaphragm is disposed on an object side of the lens and is adjacent to the first lens, and the image side of the fourth lens is configured to receive an effective optical signal emitted by the image source surface.

The utility model provides a lens and a projection optical machine, wherein the projection optical machine comprises a diaphragm, an image source surface and a lens, the lens is applied to the projection optical machine and comprises a lens group, and the lens group comprises: the lens system comprises a first lens, a second lens and a third lens, wherein the first lens is a positive focal power lens, the object side surface of the first lens is a convex surface, and the image side surface of the first lens is a concave surface; the second lens is a negative focal power lens, the object side surface of the second lens is a concave surface, and the image side surface of the second lens is a concave surface; the third lens is a positive focal power lens, the object side surface of the third lens is a concave surface, and the image side surface of the third lens is a concave surface; the fourth lens is a positive focal power lens, the object side surface of the fourth lens is a convex surface, and the image side surface of the fourth lens is a convex surface; in the direction from the object side of the lens to the image source side of the lens, the first lens, the second lens, the third lens and the fourth lens are distributed at intervals along the optical axis, and when the lens group meets the focal power and the surface type conditions, the reasonable distribution of the focal power of the lens is facilitated, so that various aberrations are balanced and corrected, and the imaging quality and definition of a virtual image are improved.

Additional features and advantages of embodiments of the utility model will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of embodiments of the utility model. The objectives and other advantages of embodiments of the utility model may be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present utility model, the drawings that are needed in the description of the embodiments will be briefly described below, it being obvious that the drawings in the following description are only some embodiments of the present utility model, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.

Fig. 1 is a schematic structural diagram of a projection optical engine according to an embodiment of the utility model.

Fig. 2 shows an astigmatism curve and a distortion curve of a lens group according to an embodiment of the present utility model.

Fig. 3 shows a chromatic aberration curve of magnification of a lens group according to an embodiment of the present utility model.

Fig. 4 shows an on-axis chromatic aberration curve of a lens group according to an embodiment of the present utility model.

Fig. 5 shows a graph of relative illuminance of a lens set according to an embodiment of the present utility model.

Fig. 6 shows an image plane chief ray incidence angle curve of a lens assembly according to an embodiment of the present utility model.

Fig. 7 shows an astigmatism curve and a distortion curve of a lens group according to another embodiment of the present utility model.

Fig. 8 shows a chromatic aberration of magnification curve of a lens group according to another embodiment of the present utility model.

Fig. 9 shows an on-axis chromatic aberration curve of a lens group according to another embodiment of the present utility model.

Fig. 10 shows a graph of relative illuminance of a lens set according to another embodiment of the present utility model.

Fig. 11 shows an image plane chief ray incident angle curve of a lens assembly according to an embodiment of the present utility model.

Fig. 12 shows an astigmatism curve and a distortion curve of a lens group according to still another embodiment of the present utility model.

Fig. 13 shows a chromatic aberration of magnification curve of a lens group according to still another embodiment of the present utility model.

Fig. 14 shows an on-axis chromatic aberration curve of a lens group according to still another embodiment of the present utility model.

Fig. 15 shows a relative illuminance curve of a lens set according to still another embodiment of the present utility model.

Fig. 16 shows an image plane chief ray incidence angle curve of a lens assembly according to still another embodiment of the present utility model.

Detailed Description

In order to make the present utility model better understood by those skilled in the art, the following description will clearly and completely describe the technical solutions in the embodiments of the present utility model with reference to the accompanying drawings, and it is apparent that the described embodiments are only some embodiments of the present utility model, not all embodiments. The components of the embodiments of the present utility model generally described and illustrated in the figures herein may be arranged and designed in a wide variety of different configurations. Thus, the following detailed description of the embodiments of the utility model, as presented in the figures, is not intended to limit the scope of the utility model, as claimed, but is merely representative of selected embodiments of the utility model. All other embodiments, which can be made by a person skilled in the art without making any inventive effort, are intended to be within the scope of the present utility model.

It should be noted that: like reference numerals and letters denote like items in the following figures, and thus once an item is defined in one figure, no further definition or explanation thereof is necessary in the following figures. Meanwhile, in the description of the present utility model, the terms "first", "second", and the like are used only to distinguish the description, and are not to be construed as indicating or implying relative importance.

Augmented reality (Augmented Reality, AR) technology is a technology that performs analog simulation processing on virtual information and superimposes the virtual information in the real world for application so that the virtual information can be perceived by human senses, and further, augmented reality display presents the virtual information based on human vision. Near-to-ear display (also known as wearable display), in which light field information is rendered by a display device placed within a non-apparent viewing distance of the human eye, so that a virtual scene is reconstructed in front of the eye, is a key of the augmented reality display technology. Near-eye display devices generally consist of an image high-low beam transmission system comprising an image source and a lens, the image source emitting image information, a small projection lens coupling the image information into an optical waveguide display lens for further incidence into the user's eye. If the front diaphragm of the lens is far away from the lens by a certain distance, the optical waveguide device and the miniature optical machine can be combined more flexibly, so that the variability of the design scheme of the AR display technology is improved.

The inventor finds that in application, in order to meet the requirements of actual application scenes, it is very critical to improve the use experience of wearing near-to-eye display equipment by a user and improve the imaging quality and the light and thin performance of the equipment, and further, miniaturization, small distortion and high image quality of a lens become main considerations which need to be improved.

Referring to fig. 1, fig. 1 is a schematic structural diagram of a projection optical engine according to an embodiment of the present utility model. The projection optical machine 100 includes a diaphragm 110, an image source surface 120 and a lens 130, where the lens 130 may include a lens group, where the lens group includes a first lens 131, a second lens 132, a third lens 133 and a fourth lens 134, the first lens 131, the second lens 132, the third lens 133 and the fourth lens 134 are distributed at intervals along an optical axis from an object side of the lens 130 to an image source side of the lens 130, the image source surface 120 is disposed adjacent to the fourth lens 134, the diaphragm 110 is disposed adjacent to the first lens 131, further, the object side of the lens 130 may be a side of the lens 130 adjacent to the diaphragm 110, and the image source side of the lens 130 may be a side of the lens 130 adjacent to the image source surface 120. Specifically, the image source surface 120 may emit an effective optical signal to the lens 130, where the effective optical signal is transmitted through the fourth lens 134, the third lens 133, the second lens 132, and the first lens 131 to correct an image, and finally projected at infinity, i.e., on the object side, through the diaphragm 110.

In the embodiment of the present utility model, the first lens 131, the second lens 132, the third lens 133 and the fourth lens 134 are spherical lenses, specifically, the fourth lens 134 is a positive focal power lens, further, the fourth lens 134 has a first surface S41 and a second surface S42, and in the case that the fourth lens 134 is applied to the projection light engine 100, the second surface S42 of the fourth lens 134 faces the image source surface 120, therefore, the second surface S42 of the fourth lens 134 is taken as an image side surface of the fourth lens 134, the first surface S41 of the fourth lens 134 is taken as an object side surface of the fourth lens 134, as shown in fig. 1, the object side surface of the fourth lens is a convex surface, and the fourth lens 134 can receive and converge the effective optical signal emitted by the image source surface 120 and form a first transmission optical signal. The third lens 133 is a positive power lens, further, the third lens 133 has a third surface S31 and a fourth surface S32, and in the case where the third lens 133 is applied to the projection light engine 100, the fourth surface S32 of the third lens 133 faces the image source surface 120, so the fourth surface S32 of the third lens 133 is taken as an image side surface of the third lens 133, the third surface S31 of the third lens 134 is taken as an object side surface of the third lens 134, the object side surface of the third lens is a concave surface, the image side surface of the third lens is a convex surface, and the third lens 133 can receive and converge the first transmission light signal transmitted by the fourth lens 134 and form a second transmission light signal. The second lens 132 is a negative power lens, further, the second lens 132 has a fifth surface S21 and a sixth surface S22, and when the second lens 132 is applied to the projection light engine 100, the sixth surface S22 of the second lens 132 faces the image source surface 120, so the sixth surface S22 of the second lens 132 is used as an image side surface of the second lens 132, the fifth surface S21 of the second lens 132 is used as an object side surface of the second lens 132, the object side surface of the second lens is a concave surface, the image side surface of the second lens is also a concave surface, and the second lens 132 can receive and diverge the first transmitted light signal transmitted by the third lens 133 and form a third transmitted light signal. The first lens 131 is a positive power lens, further, the first lens 131 has a seventh surface S11 and an eighth surface S12, and in the case where the first lens 131 is applied to the projector 100, the eighth surface S12 of the first lens 131 faces the image source surface 120, and therefore, the eighth surface S12 of the first lens 131 is taken as an image side surface of the second lens 132, the seventh surface S11 of the first lens 131 is taken as an object side surface of the first lens 131, the object side surface of the first lens is a convex surface, the image side surface of the first lens is a plane, and the first lens 131 can receive and converge the second lens 132 to transmit the third transmitted light signal and form a fourth transmitted light signal.

In the embodiment of the present utility model, the lens 130 further satisfies: 24 ° < FOV <34 °, wherein FOV (Field of View) is the maximum angle of view of the lens group, specifically, in the optical system, the lens is taken as the vertex, the included angle formed by the two edges of the larger imaging range of the object to be measured passing through the lens is called the angle of view, it is understood that the maximum angle of view in the present embodiment refers to the included angle formed by the diaphragm taken as the vertex and the edge of the largest range of the imaging range of the image source surface passing through the lens, when the FOV condition is satisfied, the lens is favorable to satisfy the angle of view requirement, and the projection range of the lens is ensured to be sufficiently large.

In the embodiment of the present utility model, the lens 130 further satisfies: 1 ° < CRA <1 °, wherein CRA (Chief Ray Angle) is the chief ray incidence angle on the image source side of the lens 130, and when the above CRA condition is satisfied, the assembly of the optical lens is facilitated, and the cooperation of the optical lens and the illumination portion of the projection system is facilitated.

In the embodiment of the present utility model, the lens 130 further satisfies: 0.6< R1/f1<0.8, wherein R1 is the radius of curvature of the seventh surface S11 of the first lens, and f1 is the effective focal length of the first lens 131, specifically, the effective focal length can be calculated according to the object distance from the focal point of the lens to the object plane and the distance from the focal point of the lens to the imaging plane, when the first lens meets the above conditions, the shape of the first lens is limited, which is beneficial to ensuring the lens processing effect.

In the embodiment of the present utility model, the lens 130 further satisfies: 3.4< (R7-R8)/f 4<6.3, wherein R8 is the radius of curvature of the second surface S42 of the fourth lens, R7 is the radius of curvature of the first surface S41 of the fourth lens, and f4 is the effective focal length of the fourth lens 134, and when the fourth lens satisfies the above conditions, the shape of the fourth lens is limited, which is advantageous for balancing aberrations of the system.

In the embodiment of the present utility model, the lens 130 further satisfies: 2.2< CT4/ET4<2.6, wherein CET is the center thickness of the fourth lens 134 on the optical axis of the lens 130, ET4 is the edge thickness of the fourth lens 134, and when the above condition is satisfied, the shape of the fourth lens is limited, which is beneficial to ensuring the lens processing effect.

In the embodiment of the present utility model, the lens 130 further satisfies: 0< f4/f1<1.25, wherein f1 is the effective focal length of the first lens 131, and f4 is the effective focal length of the fourth lens 134, and when the effective focal lengths of the first lens and the fourth lens satisfy the above conditions, the positive power of the lens group can be reasonably distributed, which is beneficial to correcting off-axis aberration.

In the embodiment of the present utility model, the lens 130 further satisfies: 0.4< f2/f <0, where f2 is the effective focal length of the second lens 132 and f is the effective focal length of the lens 130, which is advantageous for correcting off-axis aberrations when the effective focal lengths of the second lens and the lens meet the above conditions.

In the embodiment of the present utility model, the projector 100 further satisfies: 2.3mm < BFL <3.2mm, wherein BFL (Back Focus Length) is the back focal length, specifically the distance from the second surface S42 of the fourth lens to the image source surface 120 along the optical axis of the lens 130, when the above conditions are met, the lens size is favorable for meeting the light and thin structural requirements, and the surface structure of the image source surface is easy to adapt.

In the embodiment of the present utility model, the projector 100 further satisfies: 0.9< EPD/IMH <1.3, where EPD is the entrance pupil diameter of the projection light engine 100, and IMH is one half of the diagonal length of the image source surface 120, specifically, the entrance pupil diameter refers to the size of an image formed by the optical system in front of the diaphragm, and when the above condition is satisfied, the energy matching between the lens and the illumination system is facilitated.

In the embodiment of the present utility model, the projector 100 further satisfies: and LS/TTL is more than or equal to 0 and less than or equal to 0.45, wherein LS is the distance from the diaphragm 110 to the seventh surface S11 of the first lens, TTL (Total Track Length) is the total length of the lens, and is the distance from the seventh surface S11 of the first lens to the second surface S42 of the fourth lens, and when the conditions are met, the energy matching of the lens and the near-eye display device is facilitated.

In the embodiment of the present utility model, the projector 100 further satisfies: BFL/TTL >0.6, wherein, (Total Track Length) refers to the total lens length, which is the distance from the seventh surface S11 of the first lens to the second surface S42 of the fourth lens, BFL (Back Focus Length) refers to the back focal length, specifically the distance from the second surface S42 of the fourth lens to the image source surface 120 along the optical axis of the lens 130, and when the above conditions are satisfied, the structural requirement of the lens back focal length can be achieved, and the optical system is more adaptive to the illumination system of the projection optical machine.

In the embodiment of the present utility model, the projection light machine 100 further satisfies that the refractive index of the lens materials of the first lens 131, the second lens 132, the third lens 133 and the fourth lens 134 ranges from 1.69 to 1.85, and the abbe number of the lens materials of the first lens 131, the second lens 132, the third lens 133 and the fourth lens 134 ranges from 22.7 to 54.7, wherein the refractive index refers to the ratio of the propagation speed of light in air to the propagation speed in the lens, and the higher the refractive index is, the stronger the capability of deflecting incident light is; abbe number is also called as "dispersion coefficient" and is used to measure the light dispersion degree of transparent medium, and the smaller the Abbe number, the more serious the dispersion. In general, in order to pursue a high refractive index of a lens, the abbe number is necessarily low, and therefore, it is also very critical to reasonably select the refractive index of the lens and the parameter value of the abbe number to obtain the best projection effect.

Further, in the above embodiment, the four lenses may be made of glass material, and compared with the lenses made of plastic material, the lenses made of glass material are not easy to deform due to heating, so as to improve the thermal stability of the lens 130.

When the lens group included in the projector 100 meets the above-mentioned focal power and surface type conditions, the reasonable distribution of the focal power of the lens is facilitated, so that various aberrations are balanced and corrected, the imaging quality and definition of the virtual image are improved, the cost of the lens architecture and the tolerance sensitivity are low, the objective requirement of the AR technology on the manual small-batch assembly production of products is met, the imaging quality of the lens is good, the front distance range of the diaphragm is large, the rear intercept is long, and the accumulation of the initial architecture and basic performance parameter requirements is provided for researching and developing the AR lens in future.

As one embodiment, the lens parameters of the lens group included in the lens 130 may be as shown in table 1 below, wherein the units of radius of curvature, thickness, half-caliber, and focal length are all millimeters (mm).

TABLE 1

Face number	Surface type	Radius of curvature	Thickness of (L)	Material	Semi-caliber
						OBJ	Spherical surface	Infinity is provided	Infinity is provided
STO	Spherical surface	Infinity is provided	3.185		1.80
						S1	Spherical surface	5.471	1.900	1.72,50.4	2.65
S2	Spherical surface	Infinity is provided	2.437		2.51
						S3	Spherical surface	-6.469	0.736	1.85,23.8	2.10
S4	Spherical surface	5.955	1.761		2.19
						S5	Spherical surface	-17.286	1.500	1.73,54.7	2.81
S6	Spherical surface	-7.697	0.250		3.20
						S7	Spherical surface	10.118	1.615	1.83,42.7	3.73
S8	Spherical surface	-33.771	6.345		3.71
						S9	Spherical surface	Infinity is provided	0.000		2.81

Further, other parameter settings of the lens 130 and the projection light engine 100 in the present embodiment are shown in table 2.

TABLE 2

CRA(°)	0.5	BFL(mm)	6.34
				f4/f1	1.24	f2/f	-0.28
R1/f1	0.72	CT4/ET4	2.31
				(R7-R8)/f4	4.63	EPD/IMH	1.29
BFL/TTL	0.62	LS/TTL	0.31

Wherein CRA is a chief ray incidence angle on an image source side of the lens 130, f1 is an effective focal length of the first lens 131, f4 is an effective focal length of the fourth lens 134, R1 is a radius of curvature of a seventh surface S11 of the first lens, f1 is an effective focal length of the first lens 131, R8 is a radius of curvature of a second surface S42 of the fourth lens, R7 is a radius of curvature of a first surface S41 of the fourth lens, f4 is an effective focal length of the fourth lens 134, BFL is a back focal length, specifically a distance from the second surface S42 of the fourth lens to the image source surface 120 along an optical axis of the lens 130, TTL is a total lens length, a distance from a seventh surface S11 of the first lens to the second surface S42 of the fourth lens, f2 is an effective focal length of the second lens 132, f is an effective focal length of the lens 130, CET is a center thickness of the fourth lens 134 on the optical axis of the lens 130, EPD is an edge thickness of the fourth lens 134, EPD is a diameter of the projection 100, LS is a distance from the first optical stop lens 110 to the second optical stop surface 120, and the lens 110 is a distance from the second optical stop surface 11 to the second optical stop surface 110 is set in addition to the diagonal: IMH is 2.8mm, FOV is 24.5 °, f is 12.9mm, where FOV is the maximum field angle of the lens group.

Referring to fig. 2 to 6, fig. 2 shows astigmatism curves of the lens group according to the above embodiment, which represent meridional image surface curvature and sagittal image surface curvature, and fig. 2 shows distortion curves of the lens group according to the above embodiment, which represent distortion magnitude values corresponding to different image heights; fig. 3 shows a chromatic aberration curve of magnification of the lens group according to the above embodiment, which represents chromatic aberration magnitude values of magnification corresponding to different image heights; FIG. 4 shows on-axis chromatic aberration curves of the lens group of the above embodiment, representing chromatic aberration magnitudes corresponding to different apertures of the central field of view; FIG. 5 shows the relative illuminance curves of the lens assembly of the above embodiment, showing the relative illuminance magnitude values corresponding to different image heights; fig. 6 shows the image plane chief ray incidence angle curves of the lens assembly according to the above embodiment, which represent the magnitude of the image plane chief ray incidence angle corresponding to different image heights, and it can be seen that when the optical mechanical parameters are set as described in the examples, the optical distortion of the lens assembly is controlled within 0.1%, and the lens assembly has good projection performance.

As another embodiment, the lens parameters of the lens group included in the lens 130 may be as shown in table 3 below, wherein the units of radius of curvature, thickness, half-caliber, and focal length are all millimeters (mm).

TABLE 3 Table 3

In this embodiment, the material of the third lens 133 has a higher refractive index, and can reach that the back focal length BFL of the lens increases by 0.3mm, and the ratio of the distance from the seventh surface S11 of the first lens to the second surface S42 of the fourth lens along the optical axis to the distance from the diaphragm 110 to the seventh surface S11 of the first lens increases to 0.41, and the radius absolute value of the front and back light passing surfaces of the second lens 132 is the same, which is beneficial for avoiding the assembly error of the spherical lens.

Further, in the present embodiment, as shown in table 4, other parameter settings of the lens 130 and the projection light engine 100, the parameter settings of the projection light engine 100 further include, in addition to table 4: i MH is 2.8mm, FOV is 24.1 DEG, f is 13.1mm.

TABLE 4 Table 4

CRA(°)	0.3	BFL(mm)	6.68
				f4/f1	1.24	f2/f	-0.30
R1/f1	0.72	CT4/ET4	2.19
				(R7-R8)/f4	6.30	EPD/IMH	1.29
BFL/TTL	0.64	LS/TTL	0.41

Referring to fig. 7 to 11, fig. 7 shows astigmatism curves of the lens group according to the above embodiment, which represent meridional image surface curvature and sagittal image surface curvature, and fig. 7 shows distortion curves of the lens group according to the above embodiment, which represent distortion magnitude values corresponding to different image heights; fig. 8 shows a chromatic aberration curve of magnification of the lens group of the above embodiment, which represents chromatic aberration magnitude values of magnification corresponding to different image heights; FIG. 9 shows on-axis chromatic aberration curves of the lens group of the above embodiment, representing chromatic aberration magnitude values corresponding to different apertures of the central field of view; FIG. 10 shows the relative illuminance curves of the lens assembly of the above embodiment, showing the relative illuminance magnitude values for different image heights; fig. 11 shows the image plane chief ray incidence angle curves of the lens assembly of the above embodiment, which represent the values of the image plane chief ray incidence angles corresponding to different image heights, it can be seen that when the optical mechanical parameters are set as described in the examples, the optical distortion of the lens assembly is controlled to be within 0.3%, so as to have good projection performance, and it can be obtained that, compared with the previous embodiment, the chromatic aberration of magnification of the lens assembly of the embodiment is obviously optimized, which is only half of the value of the chromatic aberration of magnification of the previous embodiment, which is about 1.2um.

As yet another embodiment, the lens parameters of the lens group included in the lens 130 may be as shown in table 5 below, wherein the units of radius of curvature, thickness, half-caliber, and focal length are all millimeters (mm).

TABLE 5

Face number	Surface type	Radius of curvature	Thickness of (L)	Material	Semi-caliber
						OBJ	Spherical surface	Infinity is provided	Infinity is provided
STO	Spherical surface	Infinity is provided	0.000		1.25
						S1	Spherical surface	5.475	0.800	1.69,54.6	1.29
S2	Spherical surface	122.074	2.890		1.33
						S3	Spherical surface	-4.973	0.600	1.81,22.7	1.66
S4	Spherical surface	7.832	0.524		1.91
						S5	Spherical surface	-12.313	2.250	1.82,46.6	2.02
S6	Spherical surface	-5.646	0.250		2.84
						S7	Spherical surface	9.911	1.664	1.82,46.6	3.55
S8	Spherical surface	-17.166	5.500		3.56
						S9	Spherical surface	Infinity is provided	0.000		2.80

In this embodiment, the diaphragm 110 is located immediately adjacent to the seventh surface S11 of the first lens, and the eighth surface S12 of the first lens is a concave surface having a certain curvature, increasing the degree of freedom in lens optimization.

Further, in the present embodiment, as shown in table 6, other parameter settings of the lens 130 and the projection light engine 100, the parameter settings of the projection light engine 100 include, in addition to table 6: IMH is 2.8mm, fov is 34.2 °, f is 9mm.

TABLE 6

CRA(°)	0.7	BFL(mm)	5.5
				f4/f1	0.96	f2/f	-0.40
R1/f1	0.67	CT4/ET4	2.63
				(R7-R8)/f4	3.44	EPD/IMH	0.89
BFL/TTL	0.61	LS/TTL	0

Referring to fig. 12 to 16, fig. 12 shows astigmatism curves of the lens group according to the above embodiment, which represent meridional image plane curvature and sagittal image plane curvature, and fig. 12 shows distortion curves of the lens group according to the above embodiment, which represent distortion magnitude values corresponding to different image heights; fig. 13 shows a chromatic aberration curve of magnification of the lens group of the above embodiment, which represents chromatic aberration magnitude values of magnification corresponding to different image heights; FIG. 14 shows on-axis chromatic aberration curves of the lens groups of the above embodiments, representing chromatic aberration magnitude values corresponding to different apertures of the central field of view; fig. 15 shows the relative illuminance curves of the lens groups according to the above embodiments, showing the relative illuminance magnitude values corresponding to different image heights; fig. 16 shows the image plane chief ray incidence angle curves of the lens assembly of the above embodiment, showing the magnitude of the image plane chief ray incidence angle corresponding to different image heights, and it can be seen that when the optical mechanical parameters are set as described in the examples, the optical distortion of the lens assembly is controlled to be within 0.5%, which has good projection performance, and it can be obtained that, compared with the first two embodiments, the lens field angle FOV of the embodiment is significantly improved by about 34 ° and improved by 10 °, and the distance TTL from the object side of the first lens to the image side of the fourth lens along the optical axis of the lens assembly is only 9mm and reduced by at least 1mm without largely changing the image height, distortion and CRA.

Finally, it should be noted that: the above embodiments are only for illustrating the technical solution of the present utility model, and are not limiting; although the utility model has been described in detail with reference to the foregoing embodiments, it will be appreciated by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some technical features thereof can be replaced by equivalents; such modifications and substitutions do not drive the essence of the corresponding technical solutions to depart from the spirit and scope of the technical solutions of the embodiments of the present utility model.

Claims (14)

1. A lens for use in a projection engine, the lens comprising a lens assembly, the lens assembly comprising:

the lens system comprises a first lens, a second lens and a third lens, wherein the first lens is a positive focal power lens, the object side surface of the first lens is a convex surface, and the image side surface of the first lens is a concave surface;

the second lens is a negative focal power lens, the object side surface of the second lens is a concave surface, and the image side surface of the second lens is a concave surface;

the third lens is a positive focal power lens, the object side surface of the third lens is a concave surface, and the image side surface of the third lens is a concave surface;

the fourth lens is a positive focal power lens, the object side surface of the fourth lens is a convex surface, and the image side surface of the fourth lens is a convex surface;

the first lens, the second lens, the third lens and the fourth lens are distributed at intervals along an optical axis in a direction from an object side of the lens to an image source side of the lens.

2. A lens according to claim 1, characterized in that it satisfies: 24 ° < FOV <34 °, wherein FOV is the maximum field angle of the lens group.

3. A lens according to claim 1, characterized in that it satisfies: -1 ° < CRA <1 °, wherein CRA is the chief ray incidence angle at the image source side of the lens.

4. A lens according to claim 1, characterized in that it satisfies: 0< f4/f1<1.25, wherein f1 is an effective focal length of the first lens and f4 is an effective focal length of the fourth lens.

5. A lens according to claim 1, characterized in that it satisfies: 0.6< R1/f1<0.8, wherein R1 is the radius of curvature of the object side surface of the first lens and f1 is the effective focal length of the first lens.

6. A lens according to claim 1, characterized in that it satisfies: 3.4< (R7-R8)/f 4<6.3, wherein R8 is a radius of curvature of an image side of the fourth lens, R7 is a radius of curvature of an object side of the fourth lens, and f4 is an effective focal length of the fourth lens.

7. A lens according to claim 1, characterized in that it satisfies: -0.4< f2/f <0, where f2 is the effective focal length of the second lens and f is the effective focal length of the lens.

8. A lens according to claim 1, characterized in that it satisfies: 2.2< ct4/ET4<2.6, wherein CET is a center thickness of the fourth lens on the optical axis, ET4 is an edge thickness of the fourth lens.

9. A lens according to claim 1, characterized in that it satisfies: refractive indexes of lens materials of the first lens, the second lens, the third lens and the fourth lens range from 1.69 to 1.85, and abbe numbers of lens materials of the first lens, the second lens, the third lens and the fourth lens range from 22.7 to 54.7.

10. A projection light engine, characterized by comprising a diaphragm, an image source surface and a lens according to any one of claims 1-9, wherein the image source surface is arranged on the image source side of the lens and is adjacent to the fourth lens, the diaphragm is arranged on the object side of the lens and is adjacent to the first lens, and the image side of the fourth lens is used for receiving an effective light signal emitted by the image source surface.

11. The projection light engine of claim 10, wherein the projection light engine satisfies: 2.3mm < BFL <3.2mm, wherein BFL is the distance along the optical axis from the image side of the fourth lens to the image source surface.

12. The projection light engine of claim 10, wherein the projection light engine satisfies: 0.9< EPD/IMH <1.3, wherein EPD is the entrance pupil diameter of the projection light engine and IMH is one half of the diagonal length of the image source surface.

13. The projection light engine of claim 10, wherein the projection light engine satisfies: and LS/TTL is more than or equal to 0 and less than or equal to 0.45, wherein LS is the distance from the diaphragm to the object side surface of the first lens, and TTL is the distance from the object side surface of the first lens to the image side surface of the fourth lens.

14. The projection light engine of claim 10, wherein the projection light engine satisfies: BFL/TTL >0.6, wherein TTL is the distance along the optical axis from the object side of the first lens to the image side of the fourth lens, and BFL is the distance along the optical axis from the image side of the fourth lens to the image source side.