CN116990934A

CN116990934A - Projection lens, projection system and automobile

Info

Publication number: CN116990934A
Application number: CN202210450223.2A
Authority: CN
Inventors: 贺保丁; 李睿
Original assignee: Huawei Technologies Co Ltd
Current assignee: Huawei Technologies Co Ltd
Priority date: 2022-04-26
Filing date: 2022-04-26
Publication date: 2023-11-03

Abstract

The embodiment of the application provides a projection lens, a projection system and an automobile, relates to the technical field of optical imaging, and is used for solving the problems of small aperture, large volume, high cost, low resolution and the like of the conventional projection lens. The projection lens (100) comprises: along the optical axis direction, a first lens (110) with positive optical power, a second lens group (210) with optical power, a third lens (310) with negative optical power and a fourth lens (410) with positive optical power are sequentially arranged from the object side to the image side. Wherein the focal length f1 of the first lens (110), the focal length f2 of the second lens group (210), the focal length f3 of the third lens (310), the focal length f4 of the fourth lens (410), and the effective focal length EFL of the projection lens (100) satisfy: at least one of 1.ltoreq.f1/EFL.ltoreq.3, |f2/EFL.ltoreq.2, 1.ltoreq.f3/EFL.ltoreq.2, or 0.5.ltoreq.f4/EFL.ltoreq.1.

Description

Projection lens, projection system and automobile

Technical Field

The present application relates to the field of optical imaging technologies, and in particular, to a projection lens, a projection system, and an automobile.

Background

With the development of automobile technology, the requirements of people on the configuration of automobiles are also higher, and higher requirements on the functionality, the comfort and the entertainment of automobiles are also put forward. People can enjoy entertainment functions anytime and anywhere through the automobile projection technology.

However, since the projection distance of the conventional projection system is short, the aperture of the projection lens is small, and the power of the light source is low, the requirements of long projection distance and high power of the light source in the projection of the automobile cannot be met.

Disclosure of Invention

The embodiment of the application provides a projection lens, a projection system and an automobile, which are used for solving the problems of small aperture, large volume, high cost, low resolution and the like of the conventional projection lens.

In order to achieve the above purpose, the application adopts the following technical scheme:

in a first aspect of an embodiment of the present application, there is provided a projection lens, including: along the optical axis direction, a first lens with positive focal power, a second lens group with focal power, a third lens with negative focal power and a fourth lens with positive focal power are sequentially arranged from an object side to an image side. The focal length f1 of the first lens, the focal length f2 of the second lens group, the focal length f3 of the third lens, the focal length f4 of the fourth lens and the effective focal length EFL of the projection lens satisfy the following conditions: at least one of 1.ltoreq.f1/EFL.ltoreq.3, |f2/EFL.ltoreq.2, 1.ltoreq.f3/EFL.ltoreq.2, or 0.5.ltoreq.f4/EFL.ltoreq.1.

The projection lens provided by the embodiment of the application has the advantages that the first lens is the positive focal power lens, so that the convergence of the light rays with large aperture and large view field is facilitated, the light passing aperture of the lens is reduced, the design of the large aperture of the projection lens can be realized, when the light rays enter the first lens, the focusing is performed, the light passing aperture of the lens is further reduced, and the miniaturization of the projection lens is realized. The second lens group has focal power, can effectively correct the residual aberration of the projection lens, and improves the imaging quality of the projection lens. The third lens is a negative focal power lens, the fourth lens is a positive focal power lens, the negative focal power and the positive focal power are matched with each other, the deflection angle of light rays is controlled, aberration is balanced, and the imaging quality of the projection lens is improved.

The projection lens provided by the embodiment of the application sequentially arranges the lenses with specific focal power from the object side to the image side according to a specific sequence, and the projection lens meets the following conditions: the focal length f1 of the first lens, the focal length f2 of the second lens group, the focal length f3 of the third lens, the focal length f4 of the fourth lens, and the effective focal length EFL of the projection lens satisfy: at least one of 1.ltoreq.f1/EFL.ltoreq.3, |f2/EFL.ltoreq.2, 1.ltoreq.f3/EFL.ltoreq.2 or 0.5.ltoreq.f4/EFL.ltoreq.1, the imaging quality of the projection lens can be further improved, and the design of a large aperture is easier to realize. Therefore, the projection lens provided by the embodiment of the application can realize the projection lens with the characteristics of large aperture, low cost, small volume, high resolution and the like, and the projection picture of the projection lens has uniform brightness, so that the megapixel-level clear projection is realized.

In one possible implementation, the second lens group includes a second lens having positive optical power. The second lens group is a lens, and the projection lens is matched with each other by using four lenses, so that a large aperture is realized and the cost is low.

In one possible implementation, the diaphragm is arranged on the image side of the second lens. The diaphragm may be used to limit the projection lens aperture and thus the amount of light entering to vary the imaging brightness.

In one possible implementation, the second lens group includes a fifth lens having negative optical power and a sixth lens having positive optical power; the fifth lens is close to the first lens, and the sixth lens is close to the third lens. The second lens group is two lenses, and the projection lens utilizes five lenses to mutually match, so that a large aperture is realized and the cost is low.

In one possible implementation, the projection lens further includes a diaphragm; the diaphragm is positioned between the first lens and the fifth lens. The diaphragm may be used to limit the projection lens aperture and thus the amount of light entering to vary the imaging brightness.

In one possible implementation, the object-side surface of the first lens is convex. Therefore, the first lens can further have a converging effect on the light rays, and the converging effect of the first lens on the light rays is enhanced.

In one possible implementation, the object-side surface of the first lens element is convex, the image-side surface of the first lens element is concave, the object-side surface of the second lens element is concave, the object-side surface of the third lens element is convex, the image-side surface of the third lens element is concave, the object-side surface of the fourth lens element is convex, and the image-side surface of the fourth lens element is convex. Thus, the imaging effect is good, and the imaging quality is improved.

In one possible implementation manner, the object side surface of the first lens element is convex, the image side surface of the first lens element is convex, the object side surface of the fifth lens element is concave, the image side surface of the fifth lens element is a plane, the object side surface of the sixth lens element is concave, the image side surface of the sixth lens element is convex, the object side surface of the third lens element is convex, the image side surface of the third lens element is concave, the object side surface of the fourth lens element is convex, and the image side surface of the fourth lens element is convex. Thus, the imaging effect is good, and the imaging quality is improved.

In one possible implementation, the refractive index temperature coefficient DN/DT of the first lens satisfies: DN/DT <0. Thus, the heat difference of the projection lens is eliminated, and the reliability of the projection lens is improved.

In one possible implementation, the abbe number vd1 of the first lens satisfies: vd1 is more than or equal to 40. Thus, spherical aberration caused by the large aperture can be relieved, and the resolution of the projection lens can be improved.

In one possible implementation, the abbe number vd1 of the first lens, the abbe number vd3 of the third lens, and the abbe number vd4 of the fourth lens satisfy: (vd1+vd4)/vd3 is not less than 4. Thus, spherical aberration caused by the large aperture can be relieved, and the resolution of the projection lens can be improved.

In one possible implementation, the object side surface and the image side surface of the first lens element, the second lens element, the third lens element and the fourth lens element are spherical. In this way, the cost of the projection lens can be reduced.

In one possible implementation, the optical total length TTL of the projection lens and the effective focal length EFL of the projection lens satisfy: TTL/EFL is less than or equal to 1.5 and less than or equal to 2.5. In this way, a small volume of the projection lens can be achieved.

In one possible implementation, the back focal length BFL of the projection lens and the effective focal length EFL of the projection lens satisfy: BFL/EFL is more than or equal to 0.5 and less than or equal to 1.5. In this way, a long back focus of the projection lens can be achieved.

In a second aspect of an embodiment of the present application, there is provided a projection system including: a light source, a light valve modulation part, and a projection lens according to any one of the first aspects; the light valve modulation component is positioned at the light emitting side of the light source and is used for modulating and reflecting incident light rays; the projection lens is positioned on the reflection light path of the light valve modulation component and used for imaging the emergent light of the light valve modulation component.

The projection system provided in the second aspect of the embodiment of the present application includes the projection lens of any one of the first aspect, and the beneficial effects of the projection lens are the same as those of the projection lens, and are not repeated here.

In a third aspect of an embodiment of the present application, there is provided an automobile including: a projection system and a processing unit of the second aspect; the processing unit is used for controlling the projection system.

The automobile provided in the third aspect of the embodiment of the present application includes the projection system of any one of the second aspect, and the beneficial effects thereof are the same as those of the projection system, and are not repeated here.

Drawings

Fig. 1 is a schematic structural diagram of an automobile according to an embodiment of the present application;

FIG. 2 is a schematic diagram of a projection system according to an embodiment of the present application;

fig. 3 is a schematic structural diagram of a projection lens according to an embodiment of the present application;

fig. 4 is a schematic structural diagram of another projection lens according to an embodiment of the present application;

FIG. 5A is a graph showing a modulation transfer function of the projection lens shown in FIG. 4 at room temperature;

FIG. 5B is a graph of the modulation transfer function of the projection lens of FIG. 4 at low temperature;

FIG. 5C is a graph of the modulation transfer function of the projection lens of FIG. 4 at high temperature;

FIG. 5D is a graph of field curvature of the projection lens of FIG. 4;

FIG. 5E is a graph of distortion of the projection lens of FIG. 4;

FIG. 5F is a graph of relative illuminance of the projection lens of FIG. 4;

FIG. 5G is a plot of the defocus modulation transfer function of the projection lens of FIG. 4;

FIG. 6A is a graph showing a modulation transfer function of the projection lens shown in FIG. 3 at room temperature;

FIG. 6B is a graph of the modulation transfer function of the projection lens of FIG. 3 at low temperature;

FIG. 6C is a graph of the modulation transfer function of the projection lens of FIG. 3 at high temperature;

FIG. 6D is a graph of field curvature of the projection lens of FIG. 3;

FIG. 6E is a graph of distortion of the projection lens of FIG. 3;

FIG. 6F is a graph of relative illuminance of the projection lens of FIG. 3;

FIG. 6G is a plot of the defocus modulation transfer function of the projection lens of FIG. 3;

FIG. 7A is a graph showing a modulation transfer function of the projection lens of FIG. 4 at room temperature;

FIG. 7B is a graph of the modulation transfer function of the projection lens of FIG. 4 at low temperature;

FIG. 7C is a graph showing a modulation transfer function of the projection lens of FIG. 4 at high temperature;

FIG. 7D is a graph of field curvature of the projection lens of FIG. 4;

FIG. 7E is a graph of distortion of the projection lens of FIG. 4;

FIG. 7F is a graph of relative illuminance of the projection lens of FIG. 4;

fig. 7G is a plot of the defocus modulation transfer function of the projection lens of fig. 4.

Drawings

1-an automobile; 2-an engine; 3-an electrical device; 4-chassis; 5-vehicle body; a 10-projection system; 100-projection lens; 200-light source; 300-a light valve modulating component; 110-a first lens; 210-a second lens group; 211-a second lens; 212-a fifth lens; 213-a sixth lens; 310-a third lens; 410-a fourth lens; 510-diaphragm.

Detailed Description

The following description of the technical solutions according to the embodiments of the present application will be given with reference to the accompanying drawings in the embodiments of the present application, and it is apparent that the described embodiments are only some embodiments of the present application, but not all embodiments.

Hereinafter, the terms "second," "first," and the like are used for descriptive convenience only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "second," "first," etc. may explicitly or implicitly include one or more such feature. In the description of the present application, unless otherwise indicated, the meaning of "a plurality" is two or more.

Furthermore, in embodiments of the present application, the terms "upper," "lower," "left," "right," and the like may be defined by, but are not limited to, orientations relative to the component illustrated in the figures, it being understood that the directional terms may be used for relative description and clarity, and may be modified accordingly in response to changes in the orientation of the component illustrated in the figures.

In embodiments of the present application, unless explicitly specified and limited otherwise, the term "connected" is to be construed broadly, and for example, "connected" may be either a fixed connection, a removable connection, or an integral unit; can be directly connected or indirectly connected through an intermediate medium.

In the embodiment of the present application, "and/or" describes the association relationship of the association object, which means that three relationships may exist, for example, a and/or B may be represented: a alone, a and B together, and B alone, wherein a, B may be singular or plural. The character "/" generally indicates that the context-dependent object is an "or" relationship.

In order to facilitate understanding of the technical scheme, technical terms related to the present application are explained below.

Image side, object side: is the range through which imaging light passes, wherein the imaging light includes a chief ray (chief ray) and an edge ray (marginal ray). The image side surface is a surface facing the image, and the object side surface is a surface facing the object.

Focal power (focal power): equal to the difference between the convergence of the image Fang Guangshu and the convergence of the object beam, the refractive power of the optical system to the incident parallel beam is characterized. Optical power is generally used Indicating (I)>The larger the number of parallel beams are, the more the parallel beams are folded.When the refraction is convergent; />When the refraction is divergent. />In the process, plane refraction is adopted, namely, the parallel light beams along the axis are refracted and still form the parallel light beams along the axis, and no refraction phenomenon occurs.

Thickness of lens (thickness): the thickness of the lens on the optical axis is the thickness of the lens.

Lens optical total length (total track length, TTL): the length from the object side surface of the first optical element facing the object side to the imaging surface in the lens on the optical axis is the total optical length. I.e. the total length from the barrel head to the imaging plane, is a major factor in forming the camera height. The total optical length is used to characterize the size of the lens.

Aperture stop): is a device for controlling the light quantity of light transmitted through the lens and entering the photosensitive surface in the machine body. F# is the relative value (the reciprocal of the relative aperture) of the focal length of the lens divided by the lens' through diameter. The smaller the f# value is, the more light is input in the same unit time, so that the lens can have a good use effect in a low-illumination environment. The larger the f# value, the smaller the depth of field, and the background of the photograph will be blurred.

Focal length (f), also known as focal length, is a measure of the concentration or divergence of light in an optical system, and refers to the perpendicular distance from the optical center of a lens or lens group to an imaging surface when a scene at infinity is rendered into a clear image on the imaging surface by the lens or lens group.

Effective focal length (effective focal length, EFL): the distance between the rear principal plane of the lens or lens group to the imaging plane. For a thin lens, the focal length is the distance from the center of the lens to the imaging surface; for thick lenses or lens groups, the focal length is equal to the effective focal length.

Back focal length (back focal length, BFL): the lens or lens group is the distance from the lens closest to the image side to the imaging surface of the optical lens.

Refractive index temperature coefficient (DN/DT): refers to the relationship of refractive index as a function of temperature.

Positive optical power: the lens or the lens group has positive focal length and has the effect of converging light.

Negative optical power: the lens or lens group has a negative focal length and has the effect of diverging light.

Abbe number: also called as dispersion coefficient, refers to the difference ratio of refractive indexes of optical materials at different wavelengths, and represents the degree of dispersion of the materials.

Chief ray: light passing through the center of the lens entrance pupil and exit pupil.

Chief ray angle of incidence (CRA): the incidence angle of the principal ray on the image plane, i.e. the incidence angle of the ray passing through the center of the lens entrance pupil and exit pupil on the image plane.

Temperature bleaching: the optimum image plane offset of the lens at a certain temperature and the optimum image plane offset at normal temperature, namely the shape, the size and the refractive index of the lens surface are changed along with the change of the temperature.

Modulation transfer function (modulation transfer function, MTF): the evaluation amount of the imaging quality of the lens is shown.

Image Height (IH): the height of the image formed by the lens.

Field of view (FOV): in the optical instrument, a lens of the optical instrument is taken as a vertex, and an included angle formed by two edges of the maximum range of the lens, which can be passed through by an object image of a measured object, is called a field angle. The size of the angle of view determines the field of view of the optical instrument, and the larger the angle of view, the larger the field of view and the smaller the optical magnification.

The optical axis is a ray passing perpendicularly through the center of the ideal lens. When light parallel to the optical axis is incident into the convex lens, the ideal convex lens is a point where all the light is converged behind the lens, namely a focus

Distortion (distortion), also known as distortion, is the degree of distortion of an image of an object by an optical system relative to the object itself. The distortion is caused by the influence of the spherical aberration of the diaphragm, and the height of the intersection point of the chief rays with different fields of view and the Gaussian image plane after passing through the optical system is not equal to the ideal height, and the difference between the chief rays and the Gaussian image plane is the distortion. Therefore, the distortion only changes the imaging position of the off-axis object point on the ideal plane, so that the shape of the image is distorted, but the definition of the image is not affected.

The following describes the technical scheme in the embodiment of the present application in detail with reference to the accompanying drawings.

The embodiment of the application provides an automobile, which can be a car, an off-road car, a passenger car or a truck, and the like, and the embodiment of the application is not limited to the above.

An example of a structure of an automobile, as shown in fig. 1, an automobile 1 mainly includes an engine 2, electrical equipment 3, a chassis 4, and a vehicle body 5.

The engine 2 is a power unit of the automobile 1. The engine 2 includes a body, a crank mechanism, a valve train, a cooling system, a lubrication system, a fuel system, and an ignition system (a diesel engine does not have an ignition system).

The electrical device 3 includes a battery, a generator, a regulator, a starter, a meter, a lamp, an acoustic device, and a wiper.

The chassis 4 is used for supporting and installing the engine 2, the electrical equipment 3 and other parts to form the whole framework of the automobile 1, and receives the power of the engine 2 to enable the automobile 1 to move so as to ensure normal running. The chassis 4 comprises a drive train, a running gear, a steering gear and a braking gear.

The body 5 is mounted on the frame of the chassis 4 for the driver, passenger riding or loading of goods. The body of a car is generally of unitary construction. The car body mainly protects the driver and forms a good aerodynamic environment.

Nowadays, with the development of automobile technology in the fields of automatic driving, man-car interaction and the like, the configuration requirements of people on automobiles are higher and higher requirements on the functionality, comfort and entertainment of the automobiles are put forward. The intelligent car lamp is used as an important index of car intellectualization, plays an increasingly important role in car intellectualization development, and enables people to enjoy entertainment functions anytime and anywhere through car projection technology.

Conventional vehicle lamps employ halogen lamps as light sources. The halogen lamp has a simple structure, but its illumination brightness and illumination range cannot be precisely controlled.

The matrix light emitting diode (light emitting diode, LED) light source has a certain illumination brightness and a certain control capability for the illumination range.

However, the matrix type LED light source is used as an entrance-level intelligent lamp, the number of LEDs (the number of pixels) of the matrix type LED light source can only reach hundred levels, the illumination brightness and the illumination range cannot be controlled more precisely, the anti-dazzle effect is poor, and intelligent projection cannot be realized.

The pixel-level headlight adopted by the automobile projection technology controls the switch of each pixel unit to be closed through a digital micro-mirror (digital micromirror device, DMD) chip, so that accurate illumination brightness and illumination range are realized.

The embodiment of the application provides a projection system which can be applied to different projection application scenes such as indoor, outdoor, roads and the like; the method can also be applied to the field of projection imaging; it can also be applied to projectors, projection lamps, head Up Display (HUD) devices, etc. The embodiment of the present application is not limited thereto.

Currently, a conventional projection system is based on a digital light processing (digital light processing, DLP) architecture and a DMD chip as a core device, wherein light emitted from a projection light source is incident on the DMD chip to generate an image, and then the light emitted from the image generated by the DMD chip is incident on a projection lens, imaged by the projection lens, and finally received by a projection screen.

The projection system is mainly divided into an illumination light path and a projection lens. The illumination light path portion affects the energy utilization and energy output of the system, and the projection lens affects projection imaging quality, such as contrast, sharpness, etc. The DLP digital micromirror is connected with the illumination light path and the projection lens.

An exemplary projection system, as shown in fig. 2, the projection system 10 basically includes a projection lens 100, a light source 200 and a light valve modulation component 300.

The light source 200 is the projection light source. The light source 200 may be a laser light source, or may also be a lamp of the automobile 1. It will be appreciated that when the light source 200 is a lamp of the vehicle 1, the vehicle 1 further comprises a processing unit (not shown in fig. 1) for controlling the projection system 10.

The light valve modulating component 300 is located at the light emitting side of the light source 200, and is used for modulating and reflecting the incident light. The DMD chip is integrated into the light valve modulation member 300.

The projection lens 100 is located on the reflection light path of the light valve modulation component 300, and is used for imaging the emergent light of the light valve modulation component 300.

The conventional indoor projection system 10 has a short projection distance, and requires low power of the light source 200 and low aperture of the projection lens 100, for example, the aperture of the projection lens 100 is above F1.6. The existing projection system 10 is improved in terms of anti-glare, man-car information interaction, personalized illumination and the like, and is greatly improved in terms of safety and experience.

In the field of automotive projection, the projection distance is long and the coverage is large, and at the same time, in order to increase the road surface irradiation brightness, the luminous flux of the light source 200 and the transmission efficiency of the projection system 10 are to be improved as much as possible. The projection system 10 is designed to ensure energy utilization and energy output, and therefore needs to be implemented using a large aperture projection lens 100 or a high power light source 200.

However, the use of a high power light source 200 may also result in more energy loss, increase the operating temperature of the projection system 10, and reduce the useful life of the projection system 10. The conventional projection system 10 has a short projection distance, the aperture of the projection lens 100 is small, and the power of the light source 200 is low, which cannot meet the requirements of long projection distance and high power of the light source in the automobile projection.

As a core optical component of the projection system 10, the projection lens 100 needs to have a large aperture and a megapixel resolution to improve the energy transmission efficiency of the projection system 10.

Based on this, in order to improve the transmission efficiency and the resolution of the projection system 10, the embodiment of the present application provides a projection lens, which may be a four-lens projection lens having four lenses or a five-lens projection lens having five lenses.

As shown in fig. 3, the projection lens 100 includes: the first lens element 110, the second lens element group 210, the third lens element 310 and the fourth lens element 410 are arranged in order from the object side to the image side along the optical axis.

In the embodiment of the application, the lenses are coaxially arranged.

It is noted that in practical cases, the optical axes of the lenses may be slightly shifted due to assembly reasons or lens manufacturing process reasons, and in this case, the lenses may be considered to be coaxially disposed.

Each lens includes an object side surface facing the object side and an image side surface facing the image side.

It is understood that the lenses in the embodiments of the present application are lenses having positive or negative power, and the plane mirror is not considered as a lens of the projection lens of the present application when the plane mirror is interposed between a plurality of lenses. For example, when a plane mirror is provided between the third lens 310 and the fourth lens 410, the plane mirror cannot be considered as the fourth lens of the embodiment of the present application.

Wherein the first lens 110 has positive optical power. That is, the first lens 110 has a function of converging light.

It is understood that the object-side surface S1 of the first lens 110 may be any one of a convex surface, a concave surface, or a plane surface. The image side surface S2 of the first lens 110 may be any one of a convex surface, a concave surface, or a plane surface. The embodiment of the application is not limited to the above, and the application can be reasonably arranged according to actual conditions.

It is noted herein that references to convex or concave in embodiments of the present application refer to either convex or concave at the paraxial region. The convex or concave surface at the paraxial region means whether the convex or concave surface is present at an infinite position close to the optical axis of the lens. I.e. paraxial, refers to a position infinitely close to the optical axis. It should be noted that, the shape of the lens, the degree of concavity and convexity of the object side surface and the image side surface are merely illustrative, and the embodiment of the present application is not limited in any way to concavity and convexity of a portion of the object side surface and the image side surface away from the optical axis.

In the projection lens 100 provided in the embodiment of the present application, the first lens 110 is made of a low-dispersion material. Thus, spherical aberration caused by the large aperture can be alleviated, and the resolution of the projection lens 100 can be improved. That is, the first lens 110 material has a low abbe number (also referred to as abbe number vd).

Illustratively, the abbe number vd1 of the first lens 110 satisfies: vd1 is more than or equal to 40.

The refractive index of the material of the first lens 110 varies with temperature, i.e., the refractive index temperature coefficient DN/DT of the first lens 110 satisfies: DN/DT <0, where DN is the amount of change in refractive index and DT is the amount of change in temperature.

In this way, the matching compensation of the refractive index temperature coefficient DN/DT of the lens is utilized to realize the mutually compensated athermal design, thereby improving the reliability of the projection lens 100 and meeting the high and low temperature reliability requirements of the projection system 10. After the projection lens 100 is focused at normal temperature, clear imaging can be realized without focusing again at the ambient temperature of-40-105 ℃.

The second lens group 210 has optical power. That is, the second lens group 210 may be provided as a lens group having positive optical power or a lens group having negative optical power according to actual needs, not as a planar lens group.

In some embodiments, as shown in fig. 3, projection lens 100 is a four-piece projection lens. The second lens group 210 includes a second lens 211. That is, the projection lens 100 includes the first lens 110, the second lens 211, the third lens 310, and the fourth lens 410 sequentially arranged from the object side to the image side along the optical axis direction.

Wherein the second lens 211 has positive optical power. That is, the second lens 211 has a function of converging light.

Illustratively, as shown in fig. 3, the object-side surface S31 of the second lens element 211 is concave, and the image-side surface S41 of the second lens element 211 is convex. At this time, the second lens 211 is a meniscus lens having positive optical power. Thus, the imaging effect of the projection lens 100 can be improved, and the imaging quality of the projection lens 100 can be improved.

It is understood that the object-side surface S31 of the second lens element 211 may be any one of a convex surface, a concave surface or a plane, and the image-side surface S41 of the second lens element 211 may be any one of a convex surface, a concave surface or a plane. The embodiment of the present application is not limited to this, and only needs to ensure that the second lens 211 has positive optical power.

In the embodiment of the present application, when the second lens group 210 includes the second lens 211, the first lens 110 further satisfies:

as shown in fig. 3, the object-side surface S1 of the first lens element 110 is convex, and the image-side surface S2 of the first lens element 110 is concave. At this time, the first lens 110 is a meniscus lens having positive optical power. Thus, the imaging effect of the projection lens 100 can be improved, and the imaging quality of the projection lens 100 can be improved.

Wherein, as shown in fig. 3, the projection lens 100 further comprises a diaphragm 510. In this case, the diaphragm 510 is disposed on the image side surface S4 of the second lens 211. The diaphragm 510 may be used to limit the projection lens aperture and thus the amount of light entering to change the imaging brightness.

In other embodiments, as shown in fig. 4, the projection lens 100 is a five-piece projection lens, and the second lens group 210 includes a fifth lens 212 and a sixth lens 213. The fifth lens 212 is adjacent to the first lens 110, and the sixth lens 213 is adjacent to the third lens 310.

That is, the projection lens 100 includes the first lens 110, the fifth lens 212, the sixth lens 213, the third lens 310, and the fourth lens 410, which are sequentially arranged from the object side to the image side along the optical axis direction.

Wherein the fifth lens 212 has negative optical power. That is, the fifth lens 212 has a function of dispersing light.

The sixth lens 213 has positive optical power. That is, the sixth lens 213 has a function of converging scattered light.

Illustratively, as shown in fig. 4, the object-side surface S32 of the fifth lens element 212 is concave, and the image-side surface S42 of the fifth lens element 212 is planar. At this time, the fifth lens 212 is a meniscus lens having negative optical power.

Illustratively, as shown in fig. 4, the object-side surface S33 of the sixth lens element 213 is concave, and the image-side surface S43 of the sixth lens element 213 is convex. At this time, the sixth lens 213 is a meniscus lens having positive optical power.

In the embodiment of the present application, when the second lens group 210 includes the fifth lens 212 and the sixth lens 213, the first lens 110 further satisfies:

as shown in fig. 4, the object-side surface S1 of the first lens element 110 is convex, and the image-side surface S2 of the first lens element 110 is convex. At this time, the first lens 110 is a biconvex lens having positive optical power.

Wherein the projection lens 100 further comprises a diaphragm 510. In this case, as shown in fig. 4, the diaphragm 510 is located between the first lens 110 and the fifth lens 212. The diaphragm 510 may be used to limit the projection lens aperture and thus the amount of light entering to change the imaging brightness.

In an embodiment of the present application, the third lens 310 has negative optical power. That is, the third lens 310 has a function of dispersing light.

As shown in fig. 4, an object-side surface S5 of the third lens element 310 is convex, and an image-side surface S6 of the third lens element 310 is concave. That is, the third lens 310 is a meniscus lens having negative optical power. Thus, the imaging effect of the projection lens 100 can be improved, and the imaging quality of the projection lens 100 can be improved.

It is understood that the object-side surface S5 of the third lens element 310 can be any one of a convex surface, a concave surface or a plane, and the image-side surface S6 of the third lens element 310 can be any one of a convex surface, a concave surface or a plane. The embodiment of the present application is not limited thereto.

In an embodiment of the present application, the fourth lens 410 has positive optical power. That is, the fourth lens 410 has a function of converging light.

As shown in fig. 4, the object-side surface S7 of the fourth lens element 410 is convex, and the image-side surface S8 of the fourth lens element 410 is convex. That is, the fourth lens 410 is a biconvex lens having positive optical power. Thus, the imaging effect of the projection lens 100 can be improved, and the imaging quality of the projection lens 100 can be improved.

It is understood that the object-side surface S7 of the fourth lens element 410 can be any one of a convex surface, a concave surface or a plane, and the image-side surface S8 of the fourth lens element 410 can be any one of a convex surface, a concave surface or a plane. The embodiment of the present application is not limited thereto.

In the projection lens 100 provided by the embodiment of the present application, the lenses having positive power (for example, the first lens 110 and the fourth lens 410) are made of a low-dispersion-coefficient material, and the lens having negative power (for example, the third lens 310) is made of a high-dispersion-coefficient material. That is, the lens with positive power is made of a high abbe number material, and the lens with negative power is made of a low abbe number material, so that the respective lenses of the projection lens 100 complement each other in terms of dispersion capability, and balance is achieved, so as to achieve the purpose of achromatism, and further improve the imaging quality.

The abbe numbers vd1, vd3 of the first lens 110, and vd4 of the third lens 310 and fourth lens 410 satisfy: (vd1+vd4)/vd3 is not less than 4.

The total focal length of the projection lens 100 is an effective focal length EFL of the projection lens 100 formed by the first lens 110, the second lens group 210, the third lens 310 and the fourth lens 410, and the effective focal length EFL of the projection lens 100 is related to the focal length of each lens.

In the embodiment of the present application, the focal length f1 of the first lens 110 and the effective focal length EFL of the projection lens 100 satisfy: the ratio of f1/EFL is less than or equal to 1 and less than or equal to 3. Thus, the imaging quality of the projection lens 100 is improved.

The focal length f2 of the second lens group 210 and the effective focal length EFL of the projection lens 100 satisfy: and the I f2/EFL I is more than or equal to 2. The focal length f3 of the third lens 310 and the effective focal length EFL of the projection lens 100 satisfy: the ratio of f3/EFL is 1-2. The focal length f4 of the fourth lens 410 and the effective focal length EFL of the projection lens 100 satisfy: and f4/EFL 1 is less than or equal to 0.5. Thus, the imaging quality of the projection lens 100 can be further improved.

In some embodiments, the object-side and image-side surfaces of the first lens element 110, the second lens element 210, the third lens element 310 and the fourth lens element 410 are spherical. Alternatively, the object-side surface and the image-side surface of each of the first lens element 110, the second lens element 210, the third lens element 310 and the fourth lens element 410 may be aspheric. Alternatively, the object side surfaces and the image side surfaces of the first lens element 110, the second lens element 210, the third lens element 310 and the fourth lens element 410 may have one spherical surface and the other aspherical surface.

Aspherical lenses refer to lenses in which the curvature varies continuously from the center of the lens to the periphery of the lens. The aspherical surface is high in manufacturing cost and is not easy to manufacture. The spherical lens is easy to manufacture and has low cost, and the cost of the projection lens 100 can be reduced.

In the embodiment of the application, the first lens element 110, the second lens element 210, the third lens element 310 and the fourth lens element 410 are all spherical glass lenses, so that the projection lens 100 is not easy to deform in a temperature range from low temperature to high temperature, and the reliability and the cost are high.

In the embodiment of the present application, the total optical length TTL of the projection lens 100 and the effective focal length EFL of the projection lens 100 satisfy: TTL/EFL is less than or equal to 1.5 and less than or equal to 2.5, thereby realizing small volume of the projection lens 100.

In the embodiment of the present application, the back focal length BFL of the projection lens 100 and the effective focal length EFL of the projection lens 100 satisfy: BFL/EFL is more than or equal to 0.5 and less than or equal to 1.5, thereby realizing the long back focus of the projection lens 100.

The projection lens 100 provided in the embodiment of the application includes: in the optical axis direction, a first lens 110 having positive optical power, a second lens group 210 having negative optical power, a third lens 310 having negative optical power, and a fourth lens 410 having positive optical power are arranged in order from the object side to the image side. The object side surface S1 of the first lens element 110 is convex. The first lens 110 of the projection lens 100 provided in the embodiment of the application is a positive focal power lens, which is favorable for converging light rays with a large aperture and a large field of view, so as to reduce the aperture of the lens, and can realize the design of the large aperture of the projection lens 100, and the object side surface S1 of the first lens 110 is a convex surface, and when the light rays enter the first lens 110, the light rays are focused first, so that the aperture of the lens is further reduced, and the miniaturization of the projection lens 100 is realized. The second lens group 210 has optical power, and can effectively correct the residual aberration of the projection lens 100, so as to improve the imaging quality of the projection lens 100. The third lens element 310 has a negative focal power, the fourth lens element 410 has a positive focal power, and the negative and positive focal powers cooperate with each other to control the deflection angle of the light beam, balance the aberration, and improve the imaging quality of the projection lens 100.

The projection lens 100 provided in the embodiment of the present application sequentially arranges lenses with specific optical powers from an object side to an image side according to a specific order from an optical axis direction, and the projection lens 100 satisfies: the focal length f1 of the first lens 110, the focal length f2 of the second lens group 210, the focal length f3 of the third lens 310, the focal length f4 of the fourth lens 410, and the effective focal length EFL of the projection lens 100 satisfy: when at least one of 1.ltoreq.f1/EFL.ltoreq.3, |f2/EFL.ltoreq.2, 1.ltoreq.f3/EFL.ltoreq.2, or 0.5.ltoreq.f4/EFL.ltoreq.1, the imaging quality of the projection lens 100 can be further improved, and the design of a large aperture can be more easily realized. Therefore, the projection lens 100 provided by the embodiment of the application can realize the projection lens with the characteristics of large aperture, low cost, small volume, high resolution and the like, and the projection lens 100 has uniform brightness of a projection picture, realizes megapixel-level clear projection, and improves the energy transmission efficiency of the projection system 10.

Meanwhile, the projection lens 100 provided by the embodiment of the application meets the design of relieving the heat difference in the temperature range of-40 ℃ to 105 ℃ and meets the reliability requirements at high temperature and low temperature.

In addition, the projection lens 100 provided by the embodiment of the application can effectively correct field curvature and distortion, realize low distortion and no distortion of pictures, and can be clearly focused without obvious change of field curvature when the projection lens is moved.

The projection lens 100 provided by the embodiment of the application is composed of only four or five lenses, and the ratio of the total optical length TTL of the projection lens 100 to the effective focal length EFL of the projection lens 100 is less than 2.5, so that the requirement of the projection lens 100 for small volume is met. The ratio of the back focal length BFL of the projection lens 100 to the effective focal length EFL of the projection lens 100 provided by the embodiment of the application is greater than 0.5, thereby meeting the use situation of the long back focal length of the projection lens 100.

The following is given as an example of a projection lens having the second lens group 210 of two lenses and an example of a projection lens having the second lens group 210 of one lens.

Example 1

As shown in fig. 4, in the projection lens 100 provided in the first embodiment of the present application, the second lens group 210 has two lenses, that is, the second lens group 210 includes a fifth lens 212 and a sixth lens 213.

The projection lens 100 includes a first lens 110, a fifth lens 212, a sixth lens 213, a third lens 310, and a fourth lens 410, which are sequentially arranged from an object side to an image side along an optical axis direction.

The object-side surface S1 of the first lens element 110 is convex, and the image-side surface S2 of the first lens element 110 is convex. The first lens 110 is a biconvex lens having positive optical power. The object-side surface S32 of the fifth lens element 212 is concave, and the image-side surface S42 of the fifth lens element 212 is planar. The fifth lens 212 is a meniscus lens having negative optical power. The object-side surface S33 of the sixth lens element 213 is concave, and the image-side surface S43 of the sixth lens element 213 is convex. The sixth lens 213 is a meniscus lens having positive optical power. The object-side surface S5 of the third lens element 310 is convex, and the image-side surface S6 of the third lens element 310 is concave. The third lens 310 is a meniscus lens having negative optical power. The object-side surface S7 of the fourth lens element 410 is convex, and the image-side surface S8 of the fourth lens element 410 is convex. The fourth lens 410 is a biconvex lens having positive optical power.

As shown in fig. 4, the projection lens 100 provided in the first embodiment further includes a diaphragm 510, where the diaphragm 510 is located between the first lens 110 and the fifth lens 212.

The focal length f1 of the first lens 110 and the effective focal length EFL of the projection lens 100 satisfy: the ratio of f1/EFL is less than or equal to 1 and less than or equal to 3.

The combined focal length of the fifth lens element 212 and the sixth lens element 213 is the focal length f2 of the second lens assembly 210, and the focal length f2 of the second lens assembly 210 and the effective focal length EFL of the projection lens 100 satisfy the following conditions: and the I f2/EFL I is more than or equal to 2.

The focal length f3 of the third lens 310 and the effective focal length EFL of the projection lens 100 satisfy: the ratio of f3/EFL is 1-2.

The focal length f4 of the fourth lens 410 and the effective focal length EFL of the projection lens 100 satisfy: and f4/EFL 1 is less than or equal to 0.5.

The refractive index temperature coefficient DN/DT of the first lens 110 satisfies: DN/DT <0.

The first lens L1 adopts a refractive index temperature coefficient DN/DT <0 material to realize athermalization.

The abbe number vd1 of the first lens 110 satisfies: vd1 is more than or equal to 40. The abbe numbers vd1, vd3, vd4 of the first lens 110, the third lens 310, and the fourth lens 410 satisfy the following conditions: (vd1+vd4)/vd3 is not less than 4.

The respective lenses of the projection lens 100 achieve achromatic effect by using a combination of positive lens low dispersion and negative lens high dispersion.

Table 1-1 below shows the optical parameters of the projection lens 100 according to the first embodiment of the present application.

Wherein F# is the aperture value of the projection lens 100; EFL is the effective focal length of projection lens 100; FOV is the field angle of projection lens 100; TTL is the total optical length of projection lens 100; TTL/EFL is the ratio of the total optical length TTL of the projection lens 100 to the effective focal length EFL of the projection lens 100; BFL/EFL is the ratio of the back focal length BFL of projection lens 100 to the effective focal length EFL of projection lens 100.

TABLE 1-1

F#	1.50
		EFL	44.44mm
FOV	8.9°
		TTL	83.09mm
TTL/EFL	1.87
		BFL/EFL	0.79

Tables 1-2 below show the optical parameters of each lens and STOP (STOP) in the projection lens 100 according to the first embodiment of the present application.

Wherein R is a radius of curvature; th is the center thickness of the lens; nd is the refractive index of the lens; vd is the abbe number of the lens.

Tables 1-2 below show the optical parameters of each lens in the projection lens 100 according to the first embodiment of the present application.

TABLE 1-2

In order to facilitate understanding of the projection lens 100 according to the first embodiment of the present application, simulation is performed, and a simulation effect thereof is described below.

Fig. 5A shows a Modulation Transfer Function (MTF) curve of the projection lens 100 at normal temperature (20 ℃) using the configuration of the projection lens 100 shown in fig. 4 and the data shown in the above tables 1-1 and 1-2.

FIG. 5B is a graph showing the modulation transfer function of the projection lens 100 at low temperature (-40 ℃ C.) using the configuration of the projection lens 100 shown in FIG. 4 and using the data shown in tables 1-1 and 1-2.

Fig. 5C is a graph showing a modulation transfer function of the projection lens 100 at a high temperature (105℃) using the configuration of the projection lens 100 shown in fig. 4 and the data shown in the above tables 1-1 and 1-2.

The abscissa of fig. 5A, 5B, and 5C is the spatial frequency in line pairs per millimeter (LP/mm), and the ordinate is the modulation contrast (OTF mode value, modulus of the OTF).

Each line in the figure shows the modulation contrast versus spatial frequency at different angles of view. Wherein T represents the meridian direction and S represents the arc losing direction.

As can be seen from the MTF curve of the projection lens 100 shown in fig. 5A at normal temperature, at a spatial frequency of 16.5LP/mm, the OTF coefficient corresponding to the central field of view (0.0000 (deg)) is above 0.7, and the OTF coefficient corresponding to the 1-time Image Height (IH) field of view (8.0000 (deg)) is above 0.6, so as to meet the requirement of the limiting angular resolution of human eyes.

As can be seen from the MTF curves of the projection lens 100 shown in fig. 5B and 5C at low temperature and high temperature, at a spatial frequency of 16.5LP/mm, the OTF coefficient corresponding to the central field of view is above 0.7, the OTF coefficient corresponding to the 1-fold image high field of view is above 0.5, and the resolution requirements of the eye limit angle are met in the temperature range from-40 ℃ to 105 ℃, so that the projection lens 100 of the first embodiment of the present application achieves the effect of eliminating the heat difference.

As can be seen from fig. 5A, 5B and 5C, the projection lens 100 according to the first embodiment of the application has small imaging deformation differences at low temperature and high temperature. At different temperatures, the modulation contrast of the projection lens 100 is basically the same, the temperature drift is well corrected, and the requirement of clear imaging can be met in a wider temperature range. That is, the projection lens 100 of the first embodiment of the present application can clearly image under a wide temperature condition, that is, the projection lens 100 has a smaller temperature drift in a larger temperature variation range, so that the projection lens 100 of the first embodiment of the present application can have a better imaging effect at different temperatures.

Fig. 5D shows a graph of field curves of the projection lens 100 when the structure of the projection lens 100 shown in fig. 4 is adopted and the data shown in the above tables 1-1 and 1-2 are adopted.

The abscissa of fig. 5D is the magnitude of the field curvature in mm and the ordinate is the normalized image height. Wherein T represents the meridian direction and S represents the arc losing direction.

As can be seen from fig. 5D, the projection lens 100 according to the first embodiment of the present application can focus on the same plane from the light with the wavelength of 460nm to the light with the wavelength of 617nm, and can be effectively controlled on the field curvature.

Fig. 5E shows a distortion graph of the projection lens 100 when the structure of the projection lens 100 shown in fig. 4 is adopted and the data shown in the above tables 1-1 and 1-2 are adopted.

The abscissa of fig. 5E is the magnitude of distortion in units of normalized image height, and the ordinate is no unit.

As can be seen from fig. 5E, the distortion is less than 1%. The distortion of the projection lens 100 provided in the first embodiment of the application is better corrected, the imaging distortion is smaller, and the requirement of low distortion is met.

Fig. 5F shows graphs of relative illuminance of the projection lens 100 when the structure of the projection lens 100 shown in fig. 4 is used and the data shown in tables 1-1 and 1-2 are used.

The relative illuminance (relative illumination, RI) refers to the ratio of the edge illuminance to the center illuminance of the imaging surface. The origin of coordinates (0, 0) of fig. 5F is the center of the imaging plane. The abscissa is the distance of the edge from the center, and the ordinate is the relative illuminance.

As can be seen from the relative illuminance curve of the projection lens 100 shown in fig. 5F, the origin of coordinates (0, 0) of fig. 5F is the center of the imaging surface, the brightness is 100%, and as moving toward the edge of the imaging surface, the brightness of the edge gradually becomes darker until at 8.9mm from the center, the brightness becomes about 90%. Therefore, the projection lens 100 according to the first embodiment of the application has uniform brightness.

Fig. 5G is a graph showing the defocus modulation transfer function of the projection lens 100 using the configuration of the projection lens 100 shown in fig. 4 and the data shown in tables 1-1 and 1-2.

The abscissa of fig. 5G is the focus offset in millimeters (mm), and the ordinate is the modulation contrast (OTF).

As can be seen from fig. 5G, in the projection lens 100 according to the first embodiment of the present application, the peak of the MTF curve from the center view field to the 1-time image height IH view field is in a relatively concentrated position, and the peak width is relatively wide. When the focus offset is between-0.1 and 0.1, the modulation contrast is still at a relatively high value.

The projection lens 100 provided in the first embodiment of the present application adopts five spherical glass lenses to cooperate with each other, the aperture can reach F1.50, the curvature of field and distortion can be effectively corrected, better optical performance can be obtained, and simultaneously, the requirements of large aperture, high reliability and low cost are satisfied.

Example two

As shown in fig. 3, in the projection lens 100 provided in the second embodiment of the present application, the second lens group 210 has one lens, that is, the second lens group 210 includes a second lens 211.

The projection lens 100 includes a first lens element 110, a second lens element 211, a third lens element 310 and a fourth lens element 410 arranged in order from an object side to an image side along an optical axis.

The object-side surface S1 of the first lens element 110 is convex, and the image-side surface S2 of the first lens element 110 is concave. The first lens 110 is a meniscus lens having positive optical power. The object side surface S31 of the second lens element 211 is concave, and the image side surface S41 of the second lens element 211 is convex. The second lens 211 is a meniscus lens having positive optical power. The object-side surface S5 of the third lens element 310 is convex, and the image-side surface S6 of the third lens element 310 is concave. The third lens 310 is a meniscus lens having negative optical power. The object-side surface S7 of the fourth lens element 410 is convex, and the image-side surface S8 of the fourth lens element 410 is convex. The fourth lens 410 is a biconvex lens having positive optical power.

As shown in fig. 3, the projection lens 100 provided in the second embodiment further includes a diaphragm 510. The image side S41 of the second lens 211 serves as a stop 510.

At this time, the focal length of the second lens 211 is the focal length f2 of the second lens group 210, and the focal length f2 of the second lens group 210 and the effective focal length EFL of the projection lens 100 satisfy the following conditions: and the I f2/EFL I is more than or equal to 2.

Table 2-1 below shows the optical parameters of the projection lens 100 according to the second embodiment of the present application.

Wherein, the physical meaning represented by each optical parameter is the same as that of the above table 1-1, and will not be described herein.

TABLE 2-1

F#	1.52
		EFL	44.90mm
FOV	8.8°
		TTL	71.67mm
TTL/EFL	1.60
		BFL/EFL	0.77

Table 2-2 below shows the optical parameters of each lens and STOP (STOP) in the projection lens 100 according to the second embodiment of the present application.

Wherein, the physical meaning represented by each optical parameter is the same as that of the above tables 1-2, and will not be described herein.

TABLE 2-2

In order to facilitate understanding of the projection lens 100 provided in the second embodiment of the present application, simulation is performed, and a simulation effect thereof is described below.

Fig. 6A is a graph showing a modulation transfer function of the projection lens 100 at normal temperature (20 ℃) when the structure of the projection lens 100 shown in fig. 3 is adopted and the data shown in the above-mentioned tables 2-1 and 2-2 are adopted.

FIG. 6B is a graph showing the modulation transfer function of the projection lens 100 at low temperatures (-40 ℃ C.) using the configuration of the projection lens 100 shown in FIG. 3 and using the data shown in tables 2-1 and 2-2 described above.

Fig. 6C is a graph showing a modulation transfer function of the projection lens 100 at a high temperature (105℃) using the structure of the projection lens 100 shown in fig. 3 and the data shown in the above-mentioned tables 2-1 and 2-2.

Fig. 6A, 6B, and 6C have the abscissa of spatial frequency in line pairs per millimeter (LP/mm) and the ordinate of modulation contrast (OTF).

As can be seen from the MTF curve of the projection lens 100 shown in fig. 6A at normal temperature, at a spatial frequency of 16.5LP/mm, the OTF coefficient corresponding to the central field of view (0.0000 (deg)) is above 0.7, and the OTF coefficient corresponding to the 1-fold image high field of view (8.0000 (deg)) is above 0.6, so as to meet the requirement of the human eye limit angular resolution.

As can be seen from the MTF curves of the projection lens 100 shown in fig. 6B and fig. 6C at low temperature and high temperature, the OTF coefficient corresponding to the central field of view is above 0.7, the OTF coefficient corresponding to the 1-fold image high field of view is above 0.6 at a spatial frequency of 16.5LP/mm, and the temperature range from-40 ℃ to 105 ℃ reaches the eye limit angle resolution requirement, and the projection lens 100 of the second embodiment of the present application achieves the effect of eliminating the heat difference.

As can be seen from fig. 6A, 6B and 6C, the projection lens 100 according to the second embodiment of the present application has small imaging deformation differences at low temperature and high temperature. At different temperatures, the modulation contrast of the projection lens 100 is basically the same, the temperature drift is well corrected, and the requirement of clear imaging can be met in a wider temperature range. That is, the projection lens 100 of the second embodiment of the present application can clearly image under a wide temperature condition, that is, the projection lens 100 has smaller temperature drift in a larger temperature variation range, so that the projection lens 100 of the second embodiment of the present application can have better imaging effect at different temperatures.

Fig. 6D shows a graph of field curves of the projection lens 100 when the structure of the projection lens 100 shown in fig. 3 is adopted and the data shown in the above-mentioned tables 2-1 and 2-2 are adopted.

The abscissa of fig. 6D is the magnitude of the field curvature in mm and the ordinate is the normalized image height. Wherein T represents the meridian direction and S represents the arc losing direction.

As can be seen from fig. 6D, the projection lens 100 provided in the second embodiment of the present application can focus on the same plane from the light with the wavelength of 460nm to the light with the wavelength of 617nm, and can be effectively controlled on the field curvature.

Fig. 6E shows a distortion graph of the projection lens 100 when the structure of the projection lens 100 shown in fig. 3 is adopted and the data shown in the above-mentioned tables 2-1 and 2-2 are adopted.

The abscissa of fig. 6E is the magnitude of distortion in units of normalized image height, and the ordinate is no unit.

As can be seen from fig. 6E, the distortion is less than 1%. The distortion of the projection lens 100 provided in the second embodiment of the present application is better corrected, the imaging distortion is smaller, and the requirement of low distortion is satisfied.

Fig. 6F shows graphs of relative illuminance of the projection lens 100 when the structure of the projection lens 100 shown in fig. 3 is used and the data shown in the above tables 2-1 and 2-2 are used.

The origin of coordinates (0, 0) of fig. 6F is the center of the imaging plane. The abscissa is the distance of the edge from the center, and the ordinate is the relative illuminance.

As can be seen from the relative illuminance curve of the projection lens 100 shown in fig. 6F, the origin of coordinates (0, 0) of fig. 6F is the center of the imaging surface, the brightness is 100%, and as moving toward the edge of the imaging surface, the brightness of the edge gradually becomes darker until the brightness becomes close to 100% at 8.8mm from the center. Therefore, the projection lens 100 according to the second embodiment of the present application has uniform brightness.

Fig. 6G is a graph showing the defocus modulation transfer function of the projection lens 100 using the configuration of the projection lens 100 shown in fig. 3 and the data shown in tables 2-1 and 2-2.

The abscissa of fig. 6G is the focus offset in millimeters (mm), and the ordinate is the modulation contrast (OTF).

As can be seen from fig. 6G, in the projection lens 100 provided in the second embodiment of the present application, the peak of the MTF curve from the center view field to the 1-time image height IH view field is in a relatively concentrated position, and the peak width is relatively wide. When the focus offset is between-0.1 and 0.1, the modulation contrast is still at a relatively high value.

The projection lens 100 provided in the second embodiment of the present application adopts four spherical glass lenses to cooperate with each other, the aperture can reach F1.52, the cost of the projection lens 100 is further reduced, the curvature of field and distortion can be effectively corrected, the better optical performance can be obtained, and meanwhile, the large aperture, high reliability and low cost can be satisfied.

Example III

As shown in fig. 4, in the projection lens 100 provided in the third embodiment of the present application, the second lens group 210 has two lenses, that is, the second lens group 210 includes a fifth lens 212 and a sixth lens 213.

As shown in fig. 4, the projection lens 100 provided in the third embodiment further includes a diaphragm 510, where the diaphragm 510 is located between the first lens 110 and the fifth lens 212.

The focal length of the fifth lens element 212 and the sixth lens element 213 is the focal length f2 of the second lens group 210, and the focal length f2 of the second lens group 210 and the effective focal length EFL of the projection lens 100 satisfy the following conditions: and the I f2/EFL I is more than or equal to 2.

Table 3-1 below shows the optical parameters of the projection lens 100 according to the third embodiment of the present application.

TABLE 3-1

F#	1.33
		EFL	44.78mm
FOV	8.8°
		TTL	84.73mm
TTL/EFL	1.89
		BFL/EFL	0.73

Table 3-2 below shows the optical parameters of each lens and STOP (STOP) in the projection lens 100 according to the third embodiment of the present application.

TABLE 3-2

In order to facilitate understanding of the projection lens 100 according to the third embodiment of the present application, a simulation effect thereof is described below.

Fig. 7A is a graph showing a modulation transfer function of the projection lens 100 at normal temperature (20 ℃) when the structure of the projection lens 100 shown in fig. 4 is adopted and the data shown in the above-mentioned tables 3-1 and 3-2 are adopted.

FIG. 7B is a graph showing the modulation transfer function of the projection lens 100 at low temperature (-40 ℃ C.) using the configuration of the projection lens 100 shown in FIG. 4 and using the data shown in tables 3-1 and 3-2.

Fig. 7C is a graph showing a modulation transfer function of the projection lens 100 at a high temperature (105℃) using the structure of the projection lens 100 shown in fig. 4 and the data shown in the above tables 3-1 and 3-2.

Fig. 7A, 7B, and 7C have the abscissa of spatial frequency in line pairs per millimeter (LP/mm) and the ordinate of modulation contrast (OTF).

As can be seen from the MTF curve of the projection lens 100 shown in fig. 7A at normal temperature, at a spatial frequency of 16.5LP/mm, the OTF coefficient corresponding to the central field of view (TS 0.0000 (deg)) is above 0.7, and the OTF coefficient corresponding to the 1-fold image high field of view (TS 8.0000 (deg)) is above 0.5, so as to meet the requirement of the human eye limit angle resolution.

As can be seen from the MTF curves of the projection lens 100 shown in fig. 7B and 7C at low temperature and high temperature, the OTF coefficient corresponding to the central field of view is above 0.6, the OTF coefficient corresponding to the 1-fold image high field of view is above 0.4 at a spatial frequency of 16.5LP/mm, and the temperature range from-40 ℃ to 105 ℃ reaches the eye limit angle resolution requirement, and the projection lens 100 of the third embodiment of the present application achieves the effect of eliminating the heat difference.

As can be seen from fig. 7A, 7B and 7C, the projection lens 100 according to the third embodiment of the present application has small imaging deformation differences at low temperature and high temperature. At different temperatures, the modulation contrast of the projection lens 100 is basically the same, the temperature drift is well corrected, and the requirement of clear imaging can be met in a wider temperature range. That is, the projection lens 100 of the third embodiment of the present application can clearly image under a wide temperature condition, that is, the projection lens 100 has smaller temperature drift in a larger temperature variation range, so that the projection lens 100 of the third embodiment of the present application can have better imaging effect at different temperatures.

Fig. 7D shows a graph of field curves of the projection lens 100 when the structure of the projection lens 100 shown in fig. 4 is adopted and the data shown in the above tables 3-1 and 3-2 are adopted.

The abscissa of fig. 7D is the magnitude of the field curvature in mm and the ordinate is the normalized image height. Wherein T represents the meridian direction and S represents the arc losing direction.

As can be seen from fig. 7D, the projection lens provided in the third embodiment of the present application can focus on the same plane from light with a wavelength of 460nm to light with a wavelength of 617nm, and is effectively controlled on field curvature.

Fig. 7E shows a distortion graph of the projection lens 100 when the structure of the projection lens 100 shown in fig. 4 is adopted and the data shown in the above tables 3-1 and 3-2 are adopted.

The abscissa of fig. 7E is the magnitude of distortion in units of normalized image height, and the ordinate is no unit.

As can be seen from fig. 7E, the distortion is less than 1%. The distortion of the projection lens 100 provided in the third embodiment of the present application is better corrected, the imaging distortion is smaller, and the requirement of low distortion is satisfied.

Fig. 7F shows a graph of the relative illuminance of the projection lens 100 using the configuration of the projection lens 100 shown in fig. 4 and using the data shown in tables 3-1 and 3-2.

The origin of coordinates (0, 0) of fig. 7F is the center of the imaging plane. The abscissa is the distance of the edge from the center, and the ordinate is the relative illuminance.

As can be seen from the relative illuminance curve of the projection lens 100 shown in fig. 7F, the origin of coordinates (0, 0) of fig. 7F is the center of the imaging surface, the brightness is 100%, and as moving toward the edge of the imaging surface, the brightness of the edge gradually becomes darker until at 8.8mm from the center, the brightness becomes about 80%. Therefore, the projection lens 100 according to the third embodiment of the present application has uniform brightness of the projection screen.

Fig. 7G is a graph showing the defocus modulation transfer function of the projection lens 100 using the configuration of the projection lens 100 shown in fig. 4 and the data shown in tables 3-1 and 3-2.

The abscissa of fig. 7G is the focus offset in millimeters (mm), and the ordinate is the modulation contrast (OTF).

As can be seen from fig. 7G, in the projection lens 100 provided in the third embodiment of the present application, the peak of the MTF curve from the center view field to the 1-time image height IH view field is in a relatively concentrated position, and the peak width is relatively wide. When the focus offset is between-0.1 and 0.1, the modulation contrast is still at a relatively high value.

The projection lens 100 provided in the third embodiment of the present application adopts five spherical glass lenses to mutually cooperate, so as to realize a larger aperture, the aperture can reach F1.33, field curvature and distortion can be effectively corrected, and further optical performance can be obtained, and meanwhile, the requirements of a large aperture, high reliability and low cost are satisfied.

The present application is not limited to the above embodiments, and any changes or substitutions within the technical scope of the present application should be covered by the scope of the present application. Therefore, the protection scope of the application is subject to the protection scope of the claims.

Claims

1. A projection lens, comprising:

the first lens, the second lens group, the third lens and the fourth lens are sequentially arranged from the object side to the image side along the optical axis direction;

the first lens has positive focal power;

the second lens group has optical power;

the third lens has negative focal power;

the fourth lens has positive focal power;

wherein the focal length f1 of the first lens, the focal length f2 of the second lens group, the focal length f3 of the third lens, the focal length f4 of the fourth lens and the effective focal length EFL of the projection lens satisfy: at least one of 1.ltoreq.f1/EFL.ltoreq.3, |f2/EFL.ltoreq.2, 1.ltoreq.f3/EFL.ltoreq.2, or 0.5.ltoreq.f4/EFL.ltoreq.1.

2. The projection lens of claim 1 wherein the second lens group comprises a second lens having positive optical power.

3. The projection lens of claim 1 wherein the second lens group comprises a fifth lens having negative optical power and a sixth lens having positive optical power; the fifth lens is adjacent to the first lens, and the sixth lens is adjacent to the third lens.

4. A projection lens according to claim 3, further comprising a diaphragm; the diaphragm is located between the first lens and the fifth lens.

5. The projection lens of any of claims 1-4 wherein the object side surface of the first lens is convex.

6. The projection lens of any of claims 1-5, wherein the object-side surface of the third lens is convex; the image side surface of the third lens is a concave surface.

7. The projection lens of any of claims 1-6, wherein an object side surface of the fourth lens is convex; the image side surface of the fourth lens is a convex surface.

8. The projection lens of any of claims 1-7 wherein the refractive index temperature coefficient DN/DT of the first lens satisfies: DN/DT <0.

9. The projection lens of any one of claims 1-8, wherein the abbe number vd1 of the first lens satisfies: vd1 is more than or equal to 40.

10. The projection lens according to any one of claims 1 to 9, wherein the abbe number vd1 of the first lens, the abbe number vd3 of the third lens, and the abbe number vd4 of the fourth lens satisfy: (vd1+vd4)/vd3 is not less than 4.

11. The projection lens of any of claims 1-10 wherein the object-side and image-side surfaces of the first lens element, the second lens element, the third lens element and the fourth lens element are spherical.

12. The projection lens of any of claims 1-11, wherein an optical total length TTL of the projection lens and an effective focal length EFL of the projection lens satisfy: TTL/EFL is less than or equal to 1.5 and less than or equal to 2.5.

13. The projection lens of any of claims 1-12, wherein a back focal length BFL of the projection lens and an effective focal length EFL of the projection lens satisfy: BFL/EFL is more than or equal to 0.5 and less than or equal to 1.5.

14. A projection system, comprising: a light source, a light valve modulation means and a projection lens according to any of claims 1-13;

the light valve modulation component is positioned at the light emitting side of the light source and is used for modulating and reflecting incident light rays;

the projection lens is positioned on the reflection light path of the light valve modulation component and is used for imaging the emergent light of the light valve modulation component.

15. An automobile, comprising: the projection system and processing unit of claim 14; the processing unit is used for controlling the projection system.