CN114578634B

CN114578634B - Projection system and electronic equipment

Info

Publication number: CN114578634B
Application number: CN202011371461.1A
Authority: CN
Inventors: 郎海涛; 朱军强; 顾菲; 杨佳; 周燕; 张鹤腾
Original assignee: Ningbo Sunny Automotive Optech Co Ltd
Current assignee: Ningbo Sunny Automotive Optech Co Ltd
Priority date: 2020-11-30
Filing date: 2020-11-30
Publication date: 2024-07-16
Anticipated expiration: 2040-11-30
Also published as: CN114578634A

Abstract

The present application relates to a projection system and an electronic device comprising the projection system. The projection system sequentially comprises from a first side to a second side along an optical axis: a first lens with negative focal power, wherein a first side surface of the first lens is a convex surface, and a second side surface of the first lens is a concave surface; a second lens having positive optical power, the first side of which is convex, and the second side of which is convex; a third lens with negative focal power, wherein the first side surface of the third lens is a convex surface, and the second side surface of the third lens is a concave surface; a fourth lens with negative focal power, wherein the first side surface of the fourth lens is a concave surface, and the second side surface of the fourth lens is a convex surface; a fifth lens with positive focal power, wherein the first side surface of the fifth lens is concave, and the second side surface of the fifth lens is convex; a sixth lens with negative focal power, wherein the first side surface of the sixth lens is a convex surface, and the second side surface of the sixth lens is a concave surface; and a seventh lens with positive focal power, wherein the first side surface is a convex surface, and the second side surface is a convex surface.

Description

Projection system and electronic equipment

Technical Field

The present application relates to the field of optical elements, and more particularly, to a projection system and an electronic device.

Background

With the development of science and technology, projection systems play an irreplaceable role in more and more fields. Projection systems are required in the driving support field, such as automobiles, the monitoring field, the projection technical field, and the industrial field. Furthermore, the requirements of different fields on the performance of projection systems are also becoming more and more diverse. For example, the aspect ratio of a picture projected by the conventional projection technique is the same as that of a chip, and if a projected picture with a different aspect ratio is desired, it is necessary to cut the effective size of the chip.

Projection systems used in the field of vehicle technology have low chip size utilization due to the large difference between the aspect ratio of the image plane (the field of view ratio) and the aspect ratio of the object plane (i.e., the aspect ratio of the chip, e.g., 16:9). Therefore, how to improve the utilization rate of the chip and realize the projection images with different aspect ratios is one of the challenges to be solved by many lens designers at present.

Disclosure of Invention

In one aspect, the present application provides a projection system, which includes, in order from a first side to a second side along an optical axis: a first lens having optical power; a second lens having positive optical power, the first side of which is convex, and the second side of which is convex; a third lens with negative focal power, wherein the first side surface of the third lens is a convex surface, and the second side surface of the third lens is a concave surface; a fourth lens with negative focal power, wherein the first side surface of the fourth lens is a concave surface, and the second side surface of the fourth lens is a convex surface; a fifth lens with positive focal power, wherein the first side surface of the fifth lens is concave, and the second side surface of the fifth lens is convex; a sixth lens with negative focal power, wherein the first side surface of the sixth lens is a convex surface, and the second side surface of the sixth lens is a concave surface; a seventh lens having optical power.

In one embodiment, the maximum Fmax of the total effective focal length Fx of the projection system and the total effective focal length Fy of the projection system and the minimum Fmin of the total effective focal length Fx of the projection system and the total effective focal length Fy of the projection system and the total effective focal length Fmin of the projection system can satisfy: 1 < |Fmax/Fmin| is less than or equal to 3.

In one embodiment, at least one of the first lens to the seventh lens is a non-axisymmetric lens.

In one embodiment, the non-axisymmetric lens is a cylindrical lens or a free-form surface lens.

In one embodiment, at least one of the first lens and the seventh lens is a non-axisymmetric lens.

In one embodiment, the first lens is a non-axisymmetric lens having negative optical power in both meridional and sagittal sections, and having a convex first side in both meridional and sagittal sections, and a concave second side in both meridional and sagittal sections.

In one embodiment, the seventh lens is a non-axisymmetric lens having positive optical power in both meridional and sagittal sections, and having a first side that is convex in both meridional and sagittal sections, and a second side that is convex in both meridional and sagittal sections.

In one embodiment, the maximum Fmax of the total effective focal length Fx of the projection system and the total effective focal length Fy of the projection system and the minimum Fmin of the total effective focal length Fx of the projection system and the total effective focal length Fy of the projection system and the total effective focal length Fmin of the projection system can satisfy: i Fmax/fmin|=1.

In one embodiment, the first lens to the seventh lens are axisymmetric lenses.

In one embodiment, the axisymmetric lens is a spherical lens or an aspherical lens.

In one embodiment, the first lens has a negative optical power, the first side of which is convex and the second side of which is concave.

In one embodiment, the seventh lens has positive optical power, the first side of which is convex, and the second side of which is convex.

In one embodiment, the projection system further comprises a prism disposed between the seventh lens and the second side.

In one embodiment, the prism is a total internal reflection, TIR, prism.

In one embodiment, the projection system further comprises a stop disposed between the third lens and the fourth lens.

In one embodiment, the projection system further includes an image information generating unit disposed at a second side, wherein the image information generated by the image information generating unit is projected onto a projection surface of a first side, which is an imaging side of the projection system, after passing through the prism, the seventh lens, the sixth lens, the fifth lens, the fourth lens, the diaphragm, the third lens, the second lens, and the first lens in order, and the second side is an image source side of the projection system.

In one embodiment, the image information generating unit is a DMD chip or an LCD chip.

In one embodiment, the fourth lens and the fifth lens are cemented to form a cemented lens.

In one embodiment, a distance Sag1 on the optical axis between an intersection point of the first side surface of the first lens and the optical axis and a distance Sag2 on the optical axis between an intersection point of the second side surface of the first lens and the optical axis and a maximum light transmission caliber of the second side surface of the first lens may satisfy: sag1/Sag2 is less than or equal to 4.

In one embodiment, a distance Sag3 on the optical axis between an intersection point of the first side surface of the second lens and the optical axis and a distance Sag4 on the optical axis between an intersection point of the second side surface of the second lens and the optical axis and a maximum light transmission caliber of the second side surface of the second lens may satisfy: sag3/Sag4 is less than or equal to 4.

In one embodiment, the distance d2 between the second side of the first lens and the first side of the second lens on the optical axis and the distance TTL between the first side of the first lens and the image source surface of the projection system on the optical axis may satisfy: d2/TTL is more than or equal to 0.01.

In one embodiment, the effective focal length F3 of the third lens and the effective focal length F4 of the fourth lens may satisfy: the I F3/F4I is less than or equal to 3.

In one embodiment, the center thickness dn of the nth lens having the largest center thickness among the fourth to seventh lenses and the center thickness dm of the mth lens having the smallest center thickness among the fourth to seventh lenses may satisfy: and dn/dm is more than or equal to 0.2 and less than or equal to 5.5, wherein n and m are selected from 4, 5, 6 and 7.

In one embodiment, the maximum value Hmax of the image height Hx on the meridian section and the image height Hy on the sagittal section, of the projection distance d of the projection system corresponding to the maximum field angle of the projection system, may satisfy: d/Hmax is less than or equal to 2.

In one embodiment, the minimum value Fmin of the distance TTL between the first side of the first lens and the image source surface of the projection system on the optical axis and the total effective focal length Fx of the projection system on the meridian section and the total effective focal length Fy of the projection system on the sagittal section may be as follows: TTL/Fmin is less than or equal to 5.

In one embodiment, the distance BFL between the second side of the seventh lens and the image source surface of the projection system on the optical axis and the distance TL between the first side of the first lens and the second side of the seventh lens may satisfy: BFL/TL is greater than or equal to 0.05.

In another aspect, the present application provides a projection system, which sequentially includes, from a first side to a second side along an optical axis: a first lens having optical power; a second lens having positive optical power; a third lens having negative optical power; a fourth lens having negative optical power; a fifth lens having positive optical power; a sixth lens having negative optical power; a seventh lens having optical power; the maximum value Hmax of the image height Hx on the meridian section and the image height Hy on the sagittal section, of the projection distance d of the projection system corresponding to the maximum field angle of the projection system, may satisfy: d/Hmax is less than or equal to 2.

In one embodiment, the first side of the second lens is convex and the second side is convex.

In one embodiment, the first side of the third lens is convex and the second side is concave.

In one embodiment, the first side of the fourth lens is concave and the second side is convex.

In one embodiment, the first side of the fifth lens is concave and the second side is convex.

In one embodiment, the first side of the sixth lens is convex and the second side is concave.

In one embodiment, the first lens to the seventh lens are axisymmetric lenses.

In one embodiment, the prism is a total internal reflection, TIR, prism.

In one embodiment, the projection system further includes an image information generating unit disposed at a second side, wherein the image information generated by the image information generating unit is projected onto a projection surface of the second side after passing through the prism, the seventh lens, the sixth lens, the fifth lens, the fourth lens, the diaphragm, the third lens, the second lens, and the first lens in order, the first side being an imaging side of the projection system, and the second side being an image source side of the projection system.

In another aspect, the application provides an electronic device. The electronic device comprises a projection system provided according to the application.

The application adopts seven lenses, and realizes different magnification of the projection system on a meridian section and a sagittal section by optimally setting the characteristics of the shape, the focal power, the spherical surface, the aspheric surface and the like of each lens, thereby improving the utilization rate of the effective surface of a projection system chip and enabling the projection system to have at least one beneficial effect of miniaturization, high resolution, low cost, small front end caliber, good temperature performance and the like.

Drawings

Other features, objects and advantages of the present application will become more apparent from the following detailed description of non-limiting embodiments, taken in conjunction with the accompanying drawings. In the drawings:

fig. 1 is a schematic diagram showing the structure of a projection system according to embodiment 1 of the present application;

fig. 2 is a schematic diagram showing the structure of a projection system according to embodiment 2 of the present application;

fig. 3 is a schematic diagram showing the structure of a projection system according to embodiment 3 of the present application;

Fig. 4 is a schematic diagram showing the structure of a projection system according to embodiment 4 of the present application;

Fig. 5 is a schematic diagram showing the structure of a projection system according to embodiment 5 of the present application; and

Fig. 6 is a schematic diagram showing the structure of a projection system according to embodiment 6 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. The expression "and/or" includes any and all combinations of one or more of the associated listed items.

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. In particular, 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. The surface of each lens closest to the first side is referred to as the first side of the lens, and the surface of each lens closest to the second side is referred to as the second side of the lens, wherein the first side is the imaging side of the projection system and the second side is the image source side of the projection system.

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 a statement such as "at least one of the following" appears after a list of features that are listed, the entire listed feature is modified instead of modifying a separate element in the list. 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.

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

In an exemplary embodiment, the projection system includes, for example, seven lenses having optical power, namely, a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, and a seventh lens. The seven lenses are arranged in order along the optical axis from the imaging side to the image source side.

In an exemplary embodiment, the projection system may further include a prism disposed between the seventh lens and the image source side. The prism may be a total internal reflection, TIR, prism to turn the light path around.

In an exemplary embodiment, the projection system may further include an image information generating unit disposed between the prism and the image source side. The image information generated by the image information generating unit sequentially passes through the prism, the seventh lens, the sixth lens, the fifth lens, the fourth lens, the diaphragm, the third lens, the second lens and the first lens and then is projected onto the projection surface of the imaging side. The image information generating unit may be a DMD chip or an LCD chip.

In an exemplary embodiment, the first lens may have negative optical power, and the first side thereof may be convex and the second side thereof may be concave. The first lens may be a spherical lens. The first lens has negative focal power, is favorable to adjusting the light angle for light can be steady correctly and transition to the rear. The first side of the first lens is a convex surface, which is favorable for the projection system to be used in outdoor environment, is favorable for water drops to slide down, and the like.

In an exemplary embodiment, the second lens may have positive optical power, and both the first side and the second side thereof may be convex. The second lens may be a spherical lens. The focal power and the surface shape of the second lens can collect and adjust light rays, so that the light rays can be correctly and stably transited to the rear.

In an exemplary embodiment, the third lens may have negative power, and the first side thereof may be convex and the second side thereof may be concave. The third lens may be a spherical lens. The focal power and the surface shape of the third lens can further disperse and adjust light rays, and chromatic aberration is reduced.

In an exemplary embodiment, a diaphragm for restricting the light beam may be disposed between the third lens and the fourth lens to further improve the imaging quality of the projection system. The diaphragm is arranged between the third lens and the fourth lens, so that the effective beam converging of the light entering the projection system is facilitated, the aperture of the lens is reduced, and the total length of the projection system is shortened. In an embodiment of the present application, the diaphragm may be disposed in the vicinity of the second side of the third lens or in the vicinity of the first side of the fourth lens. It should be noted, however, that the locations of the diaphragms disclosed herein are merely examples and not limiting; in alternative embodiments, the diaphragm may be arranged in other positions as desired.

In an exemplary embodiment, the fourth lens may have negative optical power, the first side thereof may be concave, and the second side thereof may be convex. The fourth lens can be a spherical lens, the focal power and the surface shape of the fourth lens are arranged, smooth transition of light rays between the fourth lens and the fifth lens is facilitated, and meanwhile, the fourth lens with negative focal power is matched with the fifth lens with positive focal power, so that chromatic aberration is corrected.

In an exemplary embodiment, the fifth lens may have positive optical power, the first side thereof may be concave, and the second side thereof may be convex. The fifth lens may be a spherical lens. The focal power and the surface type of the fifth lens are matched with the fourth lens with negative focal power, so that chromatic aberration can be corrected.

In an exemplary embodiment, the sixth lens may have negative optical power, the first side thereof may be convex, and the second side thereof may be concave. The sixth lens may be a spherical lens. The arrangement of the focal power and the surface shape of the sixth lens is beneficial to smooth transition of light rays, and the sixth lens with negative focal power is matched with the lens with positive focal power in front, so that chromatic aberration is corrected.

In an exemplary embodiment, the seventh lens may have positive optical power, and both the first side and the second side thereof may be convex. The seventh lens may be a spherical lens. The focal power and the surface type of the seventh lens can reduce the magnification error of the system, namely, increase the telecentricity of the system and make the system become a telecentric system.

In an exemplary embodiment, the first lens may have negative optical power, and the first side thereof may be convex and the second side thereof may be concave. The first lens may be an even aspherical lens. The first lens is an even aspherical lens with negative focal power, which is beneficial to correcting picture distortion. The first side of the first lens is a convex surface, which is favorable for the projection system to be used in outdoor environment, is favorable for water drops to slide down, and the like.

In an exemplary embodiment, the seventh lens may have positive optical power, and both the first side and the second side thereof may be convex. The seventh lens may be an even aspherical lens. The seventh lens is an even aspherical lens with positive focal power, so that the multiplying power error of the system can be reduced, namely the telecentricity of the system is increased, and the system becomes a telecentric system.

In an exemplary embodiment, the first lens may have negative optical power, and the first side thereof may be convex and the second side thereof may be concave. The first lens may be a non-axisymmetric lens, for example, the first lens may be a cylindrical lens or a free-form surface lens. Preferably, the first side surface of the first lens may be an even aspherical surface, and the second side surface may be a free curved surface. The second side is a free curved surface, which is beneficial to adjusting the magnification of the meridian section and the sagittal section of the projection system, so that the meridian section and the sagittal section have different magnification. The first side is an even aspheric surface, so that the positioning processing of the second side of the first lens is facilitated. The first side of the first lens is a convex surface, which is favorable for the projection system to be used in outdoor environment, is favorable for water drops to slide down, and the like.

In an exemplary embodiment, the seventh lens may have positive optical power, and both the first side and the second side thereof may be convex. The seventh lens may be a non-axisymmetric lens, for example, the seventh lens may be a cylindrical lens or a free-form surface lens. Preferably, the first side of the seventh lens may be a free-form surface, and the second side may be an even-order aspherical surface. The first side is a free curved surface, which is beneficial to adjusting the magnification of the meridian section and the sagittal section of the projection system, so that the meridian section and the sagittal section have different magnifications. The second side is an even aspheric surface, which is beneficial to positioning and processing of the first side.

In an exemplary embodiment, the first lens to the seventh lens may each be a spherical lens. At this time, the total effective focal length Fx of the projection system on the meridional section may be the same as the total effective focal length Fy of the projection system on the sagittal section.

In an exemplary embodiment, the first lens and the seventh lens may be even aspherical lenses; the second lens, the third lens, the fourth lens, the fifth lens and the sixth lens may be spherical lenses. At this time, the total effective focal length Fx of the projection system on the meridional section may be the same as the total effective focal length Fy of the projection system on the sagittal section.

In an exemplary embodiment, the first lens and the seventh lens may be free-form surface lenses, and the second lens, the third lens, the fourth lens, the fifth lens, and the sixth lens may each be spherical lenses. By arranging the non-axisymmetric lens (such as a free-form surface lens), different magnification ratios are provided on a meridian section and a sagittal section of the projection system, and the utilization rate of the effective surface of the chip can be improved. Preferably, the first side surface of the first lens is an even aspheric surface, and the second side surface is a free-form surface; the first side surface of the seventh lens is a free curved surface, and the second side surface of the seventh lens is an even aspheric surface. At this time, the maximum value Fmax of the total effective focal length Fx of the projection system and the total effective focal length Fy of the projection system and the minimum value Fmin of the total effective focal length Fx of the projection system and the total effective focal length Fy of the projection system and the total effective focal length Fmin of the projection system and the total effective focal length Fy of the projection system can satisfy: 1 < |Fmax/Fmin| is less than or equal to 3.

As known to those skilled in the art, cemented lenses may be used to minimize chromatic aberration or eliminate chromatic aberration. The use of the cemented lens in the projection system can improve the image quality and reduce the reflection loss of light energy, thereby realizing high resolution and improving the imaging definition of the system. In addition, the use of a cemented lens may also simplify the assembly process during the manufacturing process of the system.

In an exemplary embodiment, the fourth lens and the fifth lens may be cemented to form a cemented lens. The fourth lens with the convex second side is glued with the fifth lens with the concave first side, so that the front light can be smoothly transited to the rear optical system, the size of the projection system can be reduced, and the optical performance of the projection system can be improved while the total length of the projection system is reduced. Of course, the fourth lens and the fifth lens may not be cemented, which is advantageous for improving the resolution.

The adoption of the gluing mode between the lenses has at least one of the following advantages: reducing self chromatic aberration, reducing tolerance sensitivity, and balancing the overall chromatic aberration of the system through residual partial chromatic aberration; the spacing distance between the two lenses is reduced, so that the total length of the system is reduced; the assembly parts between the lenses are reduced, so that the working procedures are reduced, and the cost is lowered; the tolerance sensitivity problems of the lens unit, such as inclination/core deflection and the like, generated in the assembly process are reduced, and the production yield is improved; the light quantity loss caused by reflection among lenses is reduced, and the illumination is improved; further reduces field curvature and effectively corrects off-axis aberrations of the projection system. The gluing design shares the whole chromatic aberration correction of the system, effectively corrects aberration, improves the resolution, and makes the whole projection system compact, thereby meeting the miniaturization requirement.

In an exemplary embodiment, in order to improve the resolution quality of the projection system, the first lens, the second lens, the third lens, the fourth lens, the fifth lens, the sixth lens, and the seventh lens may each be an aspherical lens. The aspherical lens is characterized in that: the curvature varies continuously from the center to the periphery of the lens. Unlike a spherical lens having a constant curvature from the center 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 aspheric lens, the aberration generated during imaging can be eliminated as much as possible, so that the imaging quality of the system is improved.

In an exemplary embodiment, the projection system according to the present application may satisfy: nd1 is equal to or greater than 1.48, where Nd1 is the refractive index of the first lens. More specifically, nd1 may further satisfy: nd1 is more than or equal to 1.49. Satisfies Nd1 not less than 1.48, and can lead the incidence angle of light to be more gentle.

In an exemplary embodiment, the projection system according to the present application may satisfy: sag1/Sag2 is less than or equal to 4, wherein Sag1 is the distance between the intersection point of the first side surface of the first lens and the optical axis and the maximum light transmission caliber of the first side surface of the first lens on the optical axis, and Sag2 is the distance between the intersection point of the second side surface of the first lens and the optical axis and the maximum light transmission caliber of the second side surface of the first lens on the optical axis. More specifically, sag1 and Sag2 may further satisfy: sag1/Sag2 is less than or equal to 2. Meets the requirements of |Sag1/Sag2| less than or equal to 4, and is favorable for collecting light rays.

In an exemplary embodiment, the projection system according to the present application may satisfy: sag3/Sag4 is less than or equal to 4, wherein Sag3 is the distance between the intersection point of the first side surface of the second lens and the optical axis and the maximum light transmission caliber of the first side surface of the second lens on the optical axis, and Sag4 is the distance between the intersection point of the second side surface of the second lens and the optical axis and the maximum light transmission caliber of the second side surface of the second lens on the optical axis. More specifically, sag3 and Sag4 may further satisfy: sag3/Sag4 is less than or equal to 3.95. Meets the requirements of |Sag3/Sag4| less than or equal to 4, is beneficial to smooth transition of peripheral light rays and is beneficial to reduction of lens sensitivity.

In an exemplary embodiment, the projection system according to the present application may satisfy: d2/TTL is equal to or greater than 0.01, wherein d2 is the interval distance between the second side of the first lens and the first side of the second lens on the optical axis, and TTL is the distance between the first side of the first lens and the image source surface of the projection system on the optical axis. More specifically, d2 and TTL can further satisfy: d2/TTL is more than or equal to 0.015. Satisfies d2/TTL not less than 0.01, is favorable for smooth transition of light rays and is favorable for improving image quality.

In an exemplary embodiment, the projection system according to the present application may satisfy: and F3/F4 is less than or equal to 3, wherein F3 is the effective focal length of the third lens, and F4 is the effective focal length of the fourth lens. More specifically, F3 and F4 may further satisfy: the I F3/F4I is less than or equal to 2.5. Meets the requirement that the absolute value of F3/F4 is less than or equal to 3, is favorable for stably transiting light rays and is favorable for improving image quality.

In an exemplary embodiment, the projection system according to the present application may satisfy: and dn is more than or equal to 0.2 and less than or equal to 5.5, wherein dn is the center thickness of an nth lens with the largest center thickness from the fourth lens to the seventh lens, dm is the center thickness of an mth lens with the smallest center thickness from the fourth lens to the seventh lens, and n and m are selected from 4, 5, 6 and 7. More specifically, dn and dm may further satisfy: and dn/dm is more than or equal to 0.5 and less than or equal to 5.4. Satisfying the requirement of dn/dm of 0.2-5.5, being beneficial to less deflection change of light rays of the projection system at high and low temperatures and having good temperature performance.

In an exemplary embodiment, the projection system according to the present application may satisfy: d/Hmax is less than or equal to 2, wherein d is the projection distance of the projection system, and Hmax is the maximum value of the image height Hx on the meridian section and the image height Hy on the sagittal section corresponding to the maximum field angle of the projection system. In the present application, the throw ratio of the projection system can be represented by the ratio of d and Hmax, i.e., d/Hmax represents the ratio of the throw distance to the projection screen width (corresponding to the FOV angle). Satisfies d/Hmax less than or equal to 2, is favorable for making the projection system have larger projection picture and is favorable for shortening the projection distance.

In an exemplary embodiment, the projection system according to the present application may satisfy: TTL/Fmin is less than or equal to 5, wherein TTL is the distance between the first side surface of the first lens and the image source surface of the projection system on the optical axis, and Fmin is the minimum value of the total effective focal length Fx of the projection system on the meridian section and the total effective focal length Fy of the projection system on the sagittal section. More specifically, TTL and Fmin can further satisfy: TTL/Fmin is less than or equal to 4.5. The TTL/Fmin is less than or equal to 5, which is favorable for ensuring that the projection system has better performance and is favorable for realizing miniaturization.

In an exemplary embodiment, the projection system according to the present application may satisfy: BFL/TL is greater than or equal to 0.05, wherein BFL is the distance on the optical axis from the second side of the seventh lens to the image source surface of the projection system and TL is the distance from the first side of the first lens to the second side of the seventh lens. More specifically, BFL and TL may further satisfy: BFL/TL is greater than or equal to 0.1. The BFL/TL is more than or equal to 0.05, is favorable for making the back focus BFL of the projection system longer on the basis of realizing miniaturization, is favorable for assembling the system, shortens the total length TL of the lens group, makes the system structure compact, reduces the sensitivity of the lens to MTF, improves the production yield and reduces the production cost.

In an exemplary embodiment, the projection system provided by the present application may increase the resolution of the system by increasing the pixels on the meridional or sagittal section. It should be understood that the projection system provided by the present application may be used in, but not limited to, automotive head-up display systems, and may be used in other devices requiring projection.

The projection system according to the above embodiment of the present application achieves at least one of the advantages of low cost, small front end caliber, long back focal length, good temperature performance, good imaging quality, etc. by reasonably arranging the lens shapes, focal power, spherical surfaces and aspherical surfaces and matching with the prism and the image information generating unit, under the condition that only 7 lenses are used. Meanwhile, the utilization rate of the effective surface of the chip of the projection system is high. When the lenses in the projection system are spherical lenses, the lens group in the projection system is an axisymmetric lens with the absolute value of Fmax/Fmin being 1, and the lens group has good imaging quality, is easy to process and has low cost. When the projection system is provided with the even aspherical lens, the projection system has better imaging quality and smaller distortion, and the ratio of the absolute value to the absolute value of Fmax/Fmin in the projection system is equal to or less than 1. When the projection system is provided with the free-form surface lens, 1 < |Fmax/Fmin| in the projection system is less than or equal to 3, and the meridian section and the sagittal section of the projection system have different magnification, so that the requirements of projection surfaces with different proportions can be met.

In an exemplary embodiment, the first to seventh lenses in the projection system may each be made of glass. A projection system made of glass can inhibit the deflection of the back focus of the projection system along with the change of temperature so as to improve the stability of the system. Meanwhile, the glass material is adopted, so that the lens has better optical performance at high and low temperature, and the influence on the normal use of the system due to the imaging blurring of the system caused by the high and low temperature change in the use environment is avoided. In particular, when the importance is attached to annotating image quality and reliability, the first lens to the seventh lens may each be a glass aspherical lens. Of course, in applications where the temperature stability requirement is low, the first lens to the seventh lens in the optical system may be made of plastic. The optical lens is made of plastic, so that the manufacturing cost can be effectively reduced.

However, those skilled in the art will appreciate that the various results and advantages described in this specification can be obtained by varying the number of lenses making up the system without departing from the technical solution claimed in the present application. For example, although seven lenses are described as an example in the embodiment, the projection system is not limited to including seven lenses. The projection system may also include other numbers of lenses, if desired.

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

Example 1

A projection system according to embodiment 1 of the present application is described below with reference to fig. 1. Fig. 1 shows a schematic configuration of a projection system according to embodiment 1 of the present application.

As shown in fig. 1, the projection system includes, in order from an imaging side to an image source side along an optical axis, a first lens L1, a second lens L2, a third lens L3, a fourth lens L4, a fifth lens L5, a sixth lens L6, and a seventh lens L7.

The first lens L1 to the seventh lens L7 are spherical lenses. The power and the surface shape of any one of the first lens L1 to the seventh lens L7 are the same in both the meridional section and the sagittal section.

The first lens L1 has negative power in both meridional and sagittal sections, and the first side S1 and the second side S2 thereof are both convex and concave. The second lens L2 has positive power in both meridional and sagittal sections, and both the first and second sides S3, S4 thereof are convex. The third lens L3 has negative power in both meridional and sagittal sections, and has a convex first side S5 and a concave second side S6. The fourth lens L4 has negative power in both meridional and sagittal sections, and has a concave first side S8 and a convex second side S9. The fifth lens L5 has positive power in both meridional and sagittal sections, and has a concave first side S9 and a convex second side S10. The sixth lens L6 has negative power in both meridional and sagittal sections, and has a convex first side S11 and a concave second side S12. The seventh lens L7 has positive power in both meridional and sagittal sections, and has convex first and second sides S13 and S14.

The projection system may further include a stop STO, which may be disposed between the third lens L3 and the fourth lens L4 to improve imaging quality. For example, the stop STO may be disposed near the first side S8 of the fourth lens.

Optionally, the projection system may further comprise a filter L8 and/or a cover glass L8' having a first side S15 and a second side S16. The filter L8 and/or the cover glass L8' may be used to correct color deviations and/or to protect the image information imaging unit IMA located at the image source surface S17. The image information imaging unit IMA is operable to generate image information of a desired image. Light from the image source surface of the projection system sequentially passes through the surfaces S16 to S1 and finally is projected on the projection surface. Table 1 shows the center radius of curvature R, the thickness T/distance d of each lens of the projection system of embodiment 1 (it is understood that the thickness T/distance d of the row where S1 is located is the center thickness T1 of the first lens L1, and the thickness T/distance d of the row where S2 is located is the distance d2 between the first lens L1 and the second lens L2, and so on), the refractive index Nd, and the abbe number Vd.

TABLE 1

Example 2

A projection system according to embodiment 2 of the present application is described below with reference to fig. 2. Fig. 2 shows a schematic configuration of a projection system according to embodiment 2 of the present application.

As shown in fig. 2, the projection system includes, in order from an imaging side to an image source side along an optical axis, a first lens L1, a second lens L2, a third lens L3, a fourth lens L4, a fifth lens L5, a sixth lens L6, and a seventh lens L7.

Optionally, the projection system may further comprise a filter L8 and/or a cover glass L8' having a first side S15 and a second side S16. The filter L8 and/or the cover glass L8' may be used to correct color deviations and/or to protect the image information imaging unit IMA located at the image source surface S17. The image information imaging unit IMA is operable to generate image information of a desired image. Light from the image source surface of the projection system sequentially passes through the surfaces S16 to S1 and finally is projected on the projection surface.

Table 2 shows the center radius of curvature R, thickness T/distance d, refractive index Nd, and abbe number Vd of each lens of the projection system of example 2.

TABLE 2

Example 3

A projection system according to embodiment 3 of the present application is described below with reference to fig. 3. Fig. 3 shows a schematic configuration of a projection system according to embodiment 3 of the present application.

As shown in fig. 3, the projection system includes, in order from an imaging side to an image source side along an optical axis, a first lens L1, a second lens L2, a third lens L3, a fourth lens L4, a fifth lens L5, a sixth lens L6, and a seventh lens L7.

The first lens L1 and the seventh lens L7 are both even aspherical lenses. The second lens L2, the third lens L3, the fourth lens L4, the fifth lens L5, and the sixth lens L6 are spherical lenses. The power and the surface shape of any one of the first lens L1 to the seventh lens L7 are the same in both the meridional section and the sagittal section.

Optionally, the projection system may further comprise a prism L8 having a first side S15 and a second side S16. The prism L8 may be a total reflection TIR prism and may be used to refract the light path. The projection system may further include an image information imaging unit L9 having a first side S17 and a second side S18. The image information imaging unit L9 is operable to generate image information of a desired image. Light from the image source surface of the projection system sequentially passes through the surfaces S18 to S1 and finally is projected on the projection surface.

Table 3 shows the center radius of curvature R, thickness T/distance d, refractive index Nd, and abbe number Vd of each lens of the projection system of example 3.

TABLE 3 Table 3

In embodiment 3, the first side S1 of the first lens L1 and the first side S13 and the second side S14 of the seventh lens L7 are both even-order aspherical surfaces, and the surface shape x of each even-order aspherical lens can be defined by, but not limited to, the following aspherical surface 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. The cone coefficients k and the higher order coefficients A4 and A6 that can be used for each of the aspherical mirror surfaces S1, S13 and S14 in example 3 are given in table 4.

Face number	k	A4	A6
				S1	0	-7.36E-07	3.80E-10
S13	0	-3.35E-05	-3.60E-08
				S14	0	-8.96E-06	-2.10E-08

TABLE 4 Table 4

Example 4

A projection system according to embodiment 4 of the present application is described below with reference to fig. 4. In this embodiment and the following embodiments, descriptions of portions similar to embodiment 3 will be omitted for brevity. Fig. 4 shows a schematic configuration of a projection system according to embodiment 4 of the present application.

As shown in fig. 4, the projection system includes, in order from an imaging side to an image source side along an optical axis, a first lens L1, a second lens L2, a third lens L3, a fourth lens L4, a fifth lens L5, a sixth lens L6, and a seventh lens L7.

Table 5 shows the center radius of curvature R, thickness T/distance d, refractive index Nd, and abbe number Vd of each lens of the projection system of example 4.

TABLE 5

In embodiment 4, the first side surface S1 of the first lens L1 and the first side surface S13 and the second side surface S14 of the seventh lens L7 are both even-order aspherical surfaces, and the surface shape of each even-order aspherical lens can be defined by the formula (1) given in embodiment 3 above. The cone coefficients k and the higher order coefficients A4, A6, A8 and a10 that can be used for each of the aspherical mirror faces S1, S13 and S14 in example 4 are given in table 6.

Face number	k	A4	A6	A8	A10
						S1	2.70E-03	-7.53E-07	2.61E-09	-7.05E-12	8.31E-15
S13	-1.90E-02	-3.60E-05	-1.54E-08	-1.86E-10	-8.98E-13
						S14	4.08E-02	-9.28E-06	-2.60E-09	-3.58E-12	-1.69E-12

TABLE 6

Example 5

A projection system according to embodiment 5 of the present application is described below with reference to fig. 5. In this embodiment, a description of portions similar to embodiment 3 will be omitted for brevity. Fig. 5 shows a schematic configuration of a projection system according to embodiment 5 of the present application.

As shown in fig. 5, the projection system includes, in order from an imaging side to an image source side along an optical axis, a first lens L1, a second lens L2, a third lens L3, a fourth lens L4, a fifth lens L5, a sixth lens L6, and a seventh lens L7.

The first side surface S1 of the first lens L1 is an even aspheric surface, and the second side surface S2 is a free-form surface. The first side surface S13 of the seventh lens L7 is a free-form surface, and the second side surface S14 is an even-order aspheric surface. The second lens L2, the third lens L3, the fourth lens L4, the fifth lens L5, and the sixth lens L6 are spherical lenses. The power and the surface shape of any one of the first lens L1 to the seventh lens L7 are the same in both the meridional section and the sagittal section.

Table 7 shows the center radius of curvature R, thickness T/distance d, refractive index Nd, and abbe number Vd of each lens of the projection system of example 5.

TABLE 7

In embodiment 5, the first side surface S1 of the first lens L1 and the second side surface S14 of the seventh lens L7 are both aspherical surfaces of even order, and the surface shape of each aspherical surface lens of even order can be defined by the formula (1) given in embodiment 3 above. The cone coefficients k and the higher order coefficients A4, A6, A8, a10 and a12 that can be used for each of the aspherical mirrors S1 and S14 in example 5 are given in table 8.

Face number

k

A4

A6

A8

A10

A12

S1

-6.60E+00

-1.20E-05

-1.05E-07

1.48E-09

-1.11E-11

3.09E-14

S14

-1.57E-02

-2.18E-07

5.29E-09

3.81E-10

-4.14E-12

1.32E-14

TABLE 8

In embodiment 5, the second side surface S2 of the first lens L1 and the first side surface S13 of the seventh lens L7 are both free-form surfaces. Each defined by the surface form z of the curved lens can be defined using, but not limited to, the following free-form surface formula:

Wherein z is the distance sagittal height from the apex of the free-form surface when the free-form surface is at a position of x in the meridional cross-section direction and at a position of y in the sagittal cross-section direction; cx is the paraxial curvature of the free-form surface in the meridian cross-section direction, cx=1/Rx (i.e., the paraxial curvature cx is the inverse of the radius of curvature Rx in the meridian cross-section direction), cy is the paraxial curvature of the free-form surface in the sagittal cross-section direction, cy=1/Ry (i.e., the paraxial curvature cy is the inverse of the radius of curvature Ry in the sagittal cross-section direction); kx is a conic coefficient in the meridian cross-section direction, ky is a conic coefficient in the sagittal cross-section direction; ai is the correction coefficient of the i-th order of the free-form surface in the radial cross-section direction, and Bi is the correction coefficient of the i-th order of the free-form surface in the sagittal cross-section direction. Tables 9 and 10-1, 10-2 show the radii of curvature Rx, the conic coefficients kx and the higher order coefficients A4, A6, A8, a10 and a12 in the meridian cross-section direction and the radii of curvature Ry, the conic coefficients ky and the higher order coefficients B4, B6, B8, B10 and B12 in the sagittal cross-section direction that can be used for the free-form surfaces S2 and S13 in example 5.

Face number	Rx	kx	Ry	ky
					S2	19.77	-3.13	25.75	-6.42
S13	19.98	-2.00	29.68	-2.90

TABLE 9

Face number	A4	A6	A8	A10	A12
						S2	-2.84E-06	4.23E-08	-6.05E-10	5.96E-12	-2.51E-14
S13	1.15E-06	-6.24E-08	1.74E-09	-2.29E-11	1.14E-13

TABLE 10-1

Face number	B4	B6	B8	B10	B12
						S2	-1.18E-07	-5.02E-08	-1.15E-08	1.09E-09	-2.66E-11
S13	-1.29E-05	3.15E-06	-4.14E-07	2.58E-08	-6.02E-10

TABLE 10-2

Example 6

A projection system according to embodiment 6 of the present application is described below with reference to fig. 6. In this embodiment, descriptions of portions similar to those of embodiment 3 and embodiment 5 will be omitted for brevity. Fig. 6 shows a schematic configuration of a projection system according to embodiment 6 of the present application.

As shown in fig. 6, the projection system includes, in order from an imaging side to an image source side along an optical axis, a first lens L1, a second lens L2, a third lens L3, a fourth lens L4, a fifth lens L5, a sixth lens L6, and a seventh lens L7.

Table 11 shows the center radius of curvature R, thickness T/distance d, refractive index Nd, and abbe number Vd of each lens of the projection system of example 6.

TABLE 11

In embodiment 6, the first side surface S1 of the first lens L1 and the second side surface S14 of the seventh lens L7 are both aspherical, and the surface shape of each aspherical lens can be defined by the formula (1) given in embodiment 3 above. Table 12 shows the cone coefficients k and the higher order coefficients A4, A6, A8, A10 and A12 that can be used for each of the aspherical mirrors S1 and S14 in example 6.

Face number

k

A4

A6

A8

A10

A12

S1

-5.99E+00

-1.18E-05

-1.13E-07

1.55E-09

-1.12E-11

2.96E-14

S14

-8.69E-01

6.02E-06

1.52E-09

-1.62E-10

3.83E-12

-1.93E-14

Table 12

In embodiment 6, the second side surface S2 of the first lens L1 and the first side surface S13 of the seventh lens L7 are both free-form surfaces. The surface shape of each of the curved lenses can be defined by the formula (2) given in the above-described embodiment 5. Tables 13 and 14-1, 14-2 give the radii of curvature Rx, the conic coefficients kx and the higher order coefficients A4, A6, A8, a10 and a12 in the meridian cross-section direction and the radii of curvature Ry, the conic coefficients ky and the higher order coefficients B4, B6, B8, B10 and B12 in the sagittal cross-section direction, respectively, which can be used in the curved surfaces S2 and S13 in the embodiment 6.

Face number	Rx	kx	Ry	ky
					S2	19.51	-2.83	25.21	-5.85
S13	19.84	-2.00	29.02	-1.44

TABLE 13

Face number	A4	A6	A8	A10	A12
						S2	-5.40E-06	6.63E-08	-5.68E-10	8.17E-13	1.17E-14
S13	5.06E-06	-4.60E-08	1.56E-09	-2.18E-11	1.08E-13

TABLE 14-1

Face number	B4	B6	B8	B10	B12
						S2	2.31E-06	-3.74E-07	2.95E-08	-1.27E-09	2.12E-11
S13	1.70E-06	-9.96E-07	9.49E-08	-4.13E-09	7.26E-11

TABLE 14-2

In summary, examples 1 to 6 each satisfy the relationship shown in table 15 below. In Table 15, TTL, fy, fx, fmax, fmin, hx, hy, hmax, d, BFL, TL, F, F4, d2, dn, dm, sag1, sag2, sag3, sag4 are in millimeters (mm) and FOV are in degrees (°).

TABLE 15

The application also provides an electronic device which can comprise the projection system according to the embodiment of the application. The electronic device may be a stand alone electronic device such as a projector or may be an imaging module integrated on a device such as a projector. The electronic device may also be a stand-alone imaging device, such as a projection device, or may be an imaging module integrated on, such as a projection device.

The above description is only illustrative of the preferred embodiments of the present application and of the principles of the technology employed. It will be appreciated by persons skilled in the art that the scope of the application referred to in the present application 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 application (but not limited to) having similar functions are replaced with each other.

Claims

1. The projection system is characterized by comprising, in order from a first side to a second side along an optical axis:

A first lens having negative optical power;

a second lens having positive optical power, the first side of which is convex, and the second side of which is convex;

a third lens with negative focal power, wherein the first side surface of the third lens is a convex surface, and the second side surface of the third lens is a concave surface;

a fourth lens with negative focal power, wherein the first side surface of the fourth lens is a concave surface, and the second side surface of the fourth lens is a convex surface;

A fifth lens with positive focal power, wherein the first side surface of the fifth lens is concave, and the second side surface of the fifth lens is convex;

a sixth lens with negative focal power, wherein the first side surface of the sixth lens is a convex surface, and the second side surface of the sixth lens is a concave surface; and

A seventh lens having positive optical power;

The minimum value Fmin between the distance TTL from the first side surface of the first lens to the image source surface of the projection system on the optical axis and the total effective focal length Fx of the projection system on the meridian section and the total effective focal length Fy of the projection system on the meridian section satisfies: TTL/Fmin is less than or equal to 5; and

The number of lenses having optical power in the projection system is seven.

2. The projection system of claim 1, wherein a maximum Fmax of the total effective focal length Fx of the projection system and the total effective focal length Fy of the projection system and the minimum Fmin of the total effective focal length Fx of the projection system and the total effective focal length Fy of the projection system and the total effective focal length Fx of the projection system satisfy: 1 < |Fmax/Fmin| is less than or equal to 3.

3. The projection system of claim 2 wherein at least one of the first lens to the seventh lens is a non-axisymmetric lens.

4. A projection system according to claim 3, wherein the non-axisymmetric lens is a cylindrical lens or a free-form surface lens.

5. The projection system of claim 2 wherein at least one of the first lens and the seventh lens is a non-axisymmetric lens.

6. The projection system of claim 5 wherein the first lens is a non-axisymmetric lens and has a first side that is convex in both the meridional section and the sagittal section and a second side that is concave in both the meridional section and the sagittal section.

7. The projection system of claim 5 wherein the seventh lens is a non-axisymmetric lens and has a first side that is convex in both the meridional section and the sagittal section and a second side that is convex in both the meridional section and the sagittal section.

8. The projection system of claim 6 wherein the seventh lens is a non-axisymmetric lens and has a first side that is convex in both the meridional section and the sagittal section and a second side that is convex in both the meridional section and the sagittal section.

9. The projection system of claim 1, wherein a maximum Fmax of the total effective focal length Fx of the projection system and the total effective focal length Fy of the projection system and the minimum Fmin of the total effective focal length Fx of the projection system and the total effective focal length Fy of the projection system and the total effective focal length Fx of the projection system satisfy: i Fmax/fmin|=1.

10. The projection system of claim 9 wherein the first lens to the seventh lens are axisymmetric lenses.

11. The projection system of claim 10 wherein the axisymmetric lens is a spherical lens or an aspherical lens.

12. The projection system of claim 11 wherein the first lens has a convex first side and a concave second side.

13. The projection system of claim 11 wherein the seventh lens has a convex first side and a convex second side.

14. The projection system of claim 1 further comprising a prism disposed between the seventh lens and the second side.

15. The projection system of claim 14 wherein the prism is a total internal reflection, TIR, prism.

16. The projection system of claim 14, further comprising a stop disposed between the third lens and the fourth lens.

17. The projection system of claim 16, further comprising an image information generation unit disposed at the second side, wherein,

The image information generated by the image information generating unit sequentially passes through the prism, the seventh lens, the sixth lens, the fifth lens, the fourth lens, the diaphragm, the third lens, the second lens and the first lens and then is projected onto a projection surface on a first side, wherein the first side is an imaging side of the projection system, and the second side is an image source side of the projection system.

18. The projection system of claim 17, wherein the image information generating unit is a DMD chip or an LCD chip.

19. The projection system of claim 1 wherein the fourth lens and the fifth lens are cemented to form a cemented lens.

20. The projection system of any of claims 1-19, wherein a distance, sag1, on the optical axis of a maximum light passing aperture of a first side of the first lens from an intersection of the first side of the first lens and the optical axis to a distance, sag2, on the optical axis of a maximum light passing aperture of a second side of the first lens from an intersection of the second side of the first lens and the optical axis to the second side of the first lens satisfies: sag1/Sag2 is less than or equal to 4.

21. The projection system of any of claims 1-19, wherein a distance, sag3, on the optical axis, of a maximum light passing aperture of the first side of the second lens from an intersection of the first side of the second lens and the optical axis to the optical axis, and a distance, sag4, on the optical axis, of a maximum light passing aperture of the second side of the second lens from an intersection of the second side of the second lens and the optical axis satisfy: sag3/Sag4 is less than or equal to 4.

22. The projection system of any of claims 1-19 wherein a separation distance d2 on the optical axis of the second side of the first lens and the first side of the second lens and a distance TTL on the optical axis of the first side of the first lens to an image source plane of the projection system satisfy: d2/TTL is more than or equal to 0.01.

23. The projection system of any of claims 1-19, wherein an effective focal length F3 of the third lens and an effective focal length F4 of the fourth lens satisfy: the I F3/F4I is less than or equal to 3.

24. The projection system of any of claims 1-19, wherein a center thickness dn of an nth lens having a largest center thickness among the fourth lens to the seventh lens and a center thickness dm of an mth lens having a smallest center thickness among the fourth lens to the seventh lens satisfy: and dn/dm is more than or equal to 0.2 and less than or equal to 5.5, wherein n and m are selected from 4,5, 6 and 7.

25. The projection system according to any one of claims 1-19, wherein the projection distance d of the projection system corresponds to the maximum field angle of the projection system, and the maximum value Hmax of the image height Hx on the meridional section and the image height Hy on the sagittal section satisfies: d/Hmax is less than or equal to 2.

26. The projection system of any of claims 1-19, wherein a distance BFL on the optical axis from the second side of the seventh lens to an image source surface of the projection system and a distance TL from the first side of the first lens to the second side of the seventh lens satisfy: BFL/TL is greater than or equal to 0.05.

27. The projection system is characterized by comprising, in order from a first side to a second side along an optical axis:

A first lens having negative optical power;

a second lens having positive optical power;

A third lens having negative optical power;

a fourth lens having negative optical power;

a fifth lens having positive optical power;

A sixth lens having negative optical power; and

A seventh lens having positive optical power;

Wherein, the projection distance d of the projection system and the maximum value Hmax of the image height Hx on the meridian section and the image height Hy on the sagittal section corresponding to the maximum field angle of the projection system satisfy: d/Hmax is less than or equal to 2;

the minimum value Fmin between the distance TTL from the first side surface of the first lens to the image source surface of the projection system on the optical axis and the total effective focal length Fx of the projection system on the meridian section and the total effective focal length Fy of the projection system on the sagittal section is as follows: TTL/Fmin is less than or equal to 5; and

The number of lenses having optical power in the projection system is seven.

28. The projection system of claim 27 wherein the second lens has a convex first side and a convex second side.

29. The projection system of claim 27 wherein the third lens has a convex first side and a concave second side.

30. The projection system of claim 27 wherein the fourth lens has a concave first side and a convex second side.

31. The projection system of claim 27 wherein the fifth lens has a concave first side and a convex second side.

32. The projection system of claim 27 wherein the sixth lens has a convex first side and a concave second side.

33. The projection system of claim 27 wherein a maximum Fmax of the total effective focal length Fx of the projection system and the total effective focal length Fy of the projection system and the minimum Fmin of the total effective focal length Fx of the projection system and the total effective focal length Fy of the projection system and the total effective focal length Fx of the projection system satisfy: 1 < |Fmax/Fmin| is less than or equal to 3.

34. The projection system of claim 33 wherein at least one of the first lens to the seventh lens is a non-axisymmetric lens.

35. The projection system of claim 34 wherein the non-axisymmetric lens is a cylindrical lens or a free-form surface lens.

36. The projection system of claim 35 wherein at least one of the first lens and the seventh lens is a non-axisymmetric lens.

37. The projection system of claim 36 wherein the first lens is a non-axisymmetric lens and has a first side that is convex in both the meridional section and the sagittal section and a second side that is concave in both the meridional section and the sagittal section.

38. The projection system of claim 36 wherein the seventh lens is a non-axisymmetric lens and has a first side that is convex in both the meridional section and the sagittal section and a second side that is convex in both the meridional section and the sagittal section.

39. The projection system of claim 37 wherein the seventh lens is a non-axisymmetric lens and has a first side that is convex in both the meridional section and the sagittal section and a second side that is convex in both the meridional section and the sagittal section.

40. The projection system of claim 27 wherein a maximum Fmax of the total effective focal length Fx of the projection system and the total effective focal length Fy of the projection system and the minimum Fmin of the total effective focal length Fx of the projection system and the total effective focal length Fy of the projection system and the total effective focal length Fx of the projection system satisfy: i Fmax/fmin|=1.

41. The projection system of claim 40 wherein the first lens to the seventh lens are axisymmetric lenses.

42. The projection system of claim 41 wherein the axisymmetric lens is a spherical lens or an aspherical lens.

43. The projection system of claim 42 wherein the first lens has a convex first side and a concave second side.

44. The projection system of claim 42 wherein the seventh lens has a convex first side and a convex second side.

45. The projection system of claim 27 further comprising a prism disposed between the seventh lens and the second side.

46. The projection system of claim 45 wherein the prism is a total internal reflection, TIR, prism.

47. The projection system of claim 45, further comprising a stop disposed between the third lens and the fourth lens.

48. The projection system of claim 47 further comprising an image information generation unit disposed at the second side, wherein,

49. The projection system of claim 48 wherein the image information generating unit is a DMD chip or an LCD chip.

50. The projection system of claim 27 wherein the fourth lens and the fifth lens are cemented to form a cemented lens.

51. The projection system of any of claims 27-50 wherein a distance, sag1, on the optical axis of a maximum clear aperture of the first side of the first lens from an intersection of the first side of the first lens and the optical axis to a distance, sag2, on the optical axis of a maximum clear aperture of the second side of the first lens from an intersection of the second side of the first lens and the optical axis satisfies: sag1/Sag2 is less than or equal to 4.

52. The projection system of any of claims 27-50 wherein a distance, sag3, on the optical axis of a maximum clear aperture of the first side of the second lens from an intersection of the second side of the second lens and the optical axis to a maximum clear aperture of the second side of the second lens to a distance, sag4, on the optical axis of the maximum clear aperture of the second side of the second lens satisfies: sag3/Sag4 is less than or equal to 4.

53. The projection system of any of claims 27-50 wherein a separation distance d2 on the optical axis of the second side of the first lens and the first side of the second lens from a distance TTL on the optical axis of the first side of the first lens to an image source surface of the projection system is: d2/TTL is more than or equal to 0.01.

54. The projection system of any of claims 27-50 wherein the effective focal length F3 of the third lens and the effective focal length F4 of the fourth lens satisfy: the I F3/F4I is less than or equal to 3.

55. The projection system of any of claims 27-50 wherein a center thickness dn of an nth lens having a largest center thickness among the fourth lens to the seventh lens and a center thickness dm of an mth lens having a smallest center thickness among the fourth lens to the seventh lens satisfy: and dn/dm is more than or equal to 0.2 and less than or equal to 5.5, wherein n and m are selected from 4, 5, 6 and 7.

56. The projection system of any of claims 27-50 wherein a distance BFL on the optical axis from the second side of the seventh lens to an image source surface of the projection system and a distance TL from the first side of the first lens to the second side of the seventh lens satisfy: BFL/TL is greater than or equal to 0.05.

57. An electronic device comprising a projection system according to any one of claims 1-56.