WO2024066634A1

WO2024066634A1 - Projection lens, projection device and vehicle

Info

Publication number: WO2024066634A1
Application number: PCT/CN2023/105347
Authority: WO
Inventors: 贺保丁; 李睿; 张德伦; 罗宇哲
Original assignee: 华为技术有限公司
Priority date: 2022-09-27
Filing date: 2023-06-30
Publication date: 2024-04-04
Also published as: CN117784361A

Abstract

Provided in the embodiments of the present application are a projection lens, a projection device and a vehicle. The projection lens comprises a first lens, a second lens, a third lens and a fourth lens which are sequentially arranged from a projection side to a picture element side along an optical axis. The focal length f1 of the first lens and the focal length f2 of the second lens satisfy: 2≥|f1/f2|≥1.2; the focal length f12 of a first lens group consisting of the first lens and the second lens and the focal length EFL of the projection lens satisfy: f12/EFL≥5; and the focal length f3 of the third lens and the focal length f4 of the fourth lens satisfy: 1.5≥f3/EFL≥0.8, 1.5≥f4/EFL≥0.8, and f3>f4. The projection lens formed by a first lens, a second lens, a third lens and a fourth lens achieves a large-aperture design, can better match a micro light-emitting diode display chip, and facilitates the improvement in the utilization rate and output power of luminous energy, and improves the illumination brightness of a projection device.

Description

Projection lens, projection device and vehicle

This application claims priority to the Chinese patent application filed with the China Patent Office on September 27, 2022, with application number 202211186811.6 and application name “Projection Lens, Projection Device and Vehicle”, the entire contents of which are incorporated by reference in this application.

Technical Field

The present application relates to the field of projection display technology, and in particular to a projection lens, a projection device and a vehicle.

Background technique

With the continuous development of display technology, projection display has been widely used in daily life, such as common projectors, multimedia projection equipment, etc. In transportation equipment such as vehicles, the application of projection display technology has also received increasing attention, for example, head-up display projection devices installed inside vehicles, and smart lights installed on vehicles that have lighting, signal indication functions, as well as multi-pixel and smart projection functions.

Micro-LED (Light-Emitting Diode) projection display technology has the advantages of simple structure and low cost. Its projection display device includes a Micro-LED display chip and a projection lens. The Micro-LED display chip refers to a high-density, tiny-sized LED array integrated on a chip, which can independently switch and adjust the current for each independent microstructure area on the chip, realizing the combination of light source and projection chip functions, that is, the Micro-LED display chip is used as a light source and image generation module, which significantly simplifies the display system structure and reduces costs. The display image formed by the Micro-LED display chip is projected to the projection position through the projection lens to realize projection display.

In order to meet the demand for brightness of the projection device, the utilization rate and output power of the luminous energy can be improved. Therefore, there is an urgent need for a projection lens that can be applied to micro-light emitting diode display technology and has a large aperture design to increase the luminous flux, so that more light can be projected to the projection position through the projection lens, thereby improving the brightness performance of the projection device.

Summary of the invention

The present application provides a projection lens, a projection device and a vehicle. The projection lens can be well matched with a micro light emitting diode display chip and has a large aperture and high luminous flux, which is beneficial to improving the utilization rate and output power of the luminous energy and meeting the high brightness requirements of the projection device.

A first aspect of the present application provides a projection lens, comprising a first lens group, the first lens group comprising a first lens and a second lens, the projection lens further comprising a third lens and a second lens group, the second lens group comprising one or more fourth lenses, and along the direction of the optical axis from the projection side to the pixel side, the first lens, the second lens, the third lens, and the fourth lens of the second lens group are arranged in sequence;

The focal length f1 of the first lens and the focal length f2 of the second lens satisfy the condition: 2≥|f1/f2|≥1.2, and the focal length f12 of the first lens group and the focal length EFL of the projection lens satisfy the condition: f12/EFL≥5;

The focal length f3 of the third lens and the focal length EFL of the projection lens satisfy the conditional formula: 1.5≥f3/EFL≥0.8, the focal length f4 of the second lens group and the focal length EFL of the projection lens satisfy the conditional formula: 1.5≥f4/EFL≥0.8, and the focal length f3 of the third lens and the focal length f4 of the second lens group satisfy the conditional formula: f3>f4. The projection lens formed by making the first lens, the second lens, the third lens and the fourth lens satisfy the above conditional formula has a small aperture number F#, can realize a large aperture design, increase the luminous flux of the projection lens, is suitable for projection devices, can improve the utilization rate and output power of luminous energy, and improve the brightness of the projection device.

In addition, the projection lens realizes a large aperture design only through the first lens, the second lens, the third lens and the fourth lens. The projection lens can be a four-lens structure with fewer lenses, simple structure, small size and low cost. When the image display module of the projection device is a micro-light emitting diode display chip, the number of independent micro-structure switches inside the chip itself is relatively small, and the display pixels are relatively low. The projection lens with a simple structure has relatively low pixels, which can well match the micro-light emitting diode display chip with relatively low pixel requirements and meet the changing needs of the projected image, so that the projection lens has a large aperture, small size, low cost and is adapted to the design of a low-pixel image display module.

In a possible implementation, the focal length f1 of the first lens and the focal length f2 of the second lens satisfy the condition: 1.9≥|f1/f2|≥1.2, and the focal length f12 of the first lens group and the focal length EFL of the projection lens satisfy the condition: f12/EFL≥6;

The focal length f3 of the third lens and the focal length EFL of the projection lens satisfy the condition: 1.5 ≥ f3/EFL ≥ 0.9, and the focal length f4 of the second lens group The focal length EFL of the projection lens satisfies the condition: 1.4 ≥ f4/EFL ≥ 0.8. Optimizing the structure of the projection lens is further conducive to increasing the aperture and improving the utilization and output rate of the luminous energy.

In a possible implementation, the focal length f1 of the first lens and the focal length f2 of the second lens satisfy the condition: 1.8≥|f1/f2|≥1.2, and the focal length f12 of the first lens group and the focal length EFL of the projection lens satisfy the condition: f12/EFL≥6;

The focal length f3 of the third lens and the focal length EFL of the projection lens meet the condition: 1.5≥f3/EFL≥1.0, and the focal length f4 of the second lens group and the focal length EFL of the projection lens meet the condition: 1.3≥f4/EFL≥0.8. Optimizing the structure of the projection lens is further conducive to increasing the aperture and improving the utilization and output rate of the luminous energy.

In a possible implementation, the focal length f1 of the first lens and the focal length f2 of the second lens satisfy the condition: 1.7≥|f1/f2|≥1.2, and the focal length f12 of the first lens group and the focal length EFL of the projection lens satisfy the condition: f12/EFL≥7.5;

The focal length f3 of the third lens and the focal length EFL of the projection lens satisfy the condition: 1.5≥f3/EFL≥1.2, and the focal length f4 of the second lens group and the focal length EFL of the projection lens satisfy the condition: 1.2≥f4/EFL≥0.8. Optimizing the structure of the projection lens is further conducive to increasing the aperture, so that the projection lens has a higher light energy utilization rate and output rate.

In a possible implementation, the focal length f1 of the first lens and the focal length f2 of the second lens satisfy the condition: 1.6≥|f1/f2|≥1.2, and the focal length f12 of the first lens group and the focal length EFL of the projection lens satisfy the condition: f12/EFL≥8;

The focal length f3 of the third lens and the focal length EFL of the projection lens meet the conditional formula: 1.5≥f3/EFL≥1.1, and the focal length f4 of the second lens group and the focal length EFL of the projection lens meet the conditional formula: 1.0≥f4/EFL≥0.8. Optimizing the structure of the projection lens is further conducive to increasing the aperture, so that the projection lens has a higher light energy utilization rate and output rate.

In a possible implementation, the focal length f1 of the first lens and the focal length f2 of the second lens satisfy the condition: 1.4≥|f1/f2|≥1.2, and the focal length f12 of the first lens group and the focal length EFL of the projection lens satisfy the condition: f12/EFL≥8.9;

The focal length f3 of the third lens and the focal length EFL of the projection lens satisfy the condition: 1.5≥f3/EFL≥1.3, and the focal length f4 of the second lens group and the focal length EFL of the projection lens satisfy the condition: 1.5≥f4/EFL≥1.0. Optimizing the structure of the projection lens is further conducive to increasing the aperture, so that the projection lens has a higher light energy utilization rate and output rate.

In a possible implementation, the focal length f1 of the first lens and the focal length f2 of the second lens satisfy the condition: 1.5≥|f1/f2|≥1.2, and the focal length f12 of the first lens group and the focal length EFL of the projection lens satisfy the condition: f12/EFL≥10.6;

The focal length f3 of the third lens and the focal length EFL of the projection lens satisfy the conditional formula: 1.4≥f3/EFL≥0.8, and the focal length f4 of the second lens group and the focal length EFL of the projection lens satisfy the conditional formula: 1.5≥f4/EFL≥0.9. Optimizing the structure of the projection lens is further conducive to increasing the aperture, so that the projection lens has a higher light energy utilization rate and output rate.

In a possible implementation, the focal length f1 of the first lens and the focal length f2 of the second lens satisfy the condition: 1.9≥|f1/f2|≥1.3, and the focal length f12 of the first lens group and the focal length EFL of the projection lens satisfy the condition: f12/EFL≥9;

The focal length f3 of the third lens and the focal length EFL of the projection lens satisfy the condition: 1.2≥f3/EFL≥0.8, and the focal length f4 of the second lens group and the focal length EFL of the projection lens satisfy the condition: 1.5≥f4/EFL≥1.1. Optimizing the structure of the projection lens is further conducive to increasing the aperture, so that the projection lens has a higher light energy utilization rate and output rate.

In a possible implementation, the focal length f1 of the first lens and the focal length f2 of the second lens satisfy the condition: 1.9≥|f1/f2|≥1.4, and the focal length f12 of the first lens group and the focal length EFL of the projection lens satisfy the condition: f12/EFL≥11.1;

The focal length f3 of the third lens and the focal length EFL of the projection lens meet the conditional formula: 1.3≥f3/EFL≥0.8, and the focal length f4 of the second lens group and the focal length EFL of the projection lens meet the conditional formula: 1.5≥f4/EFL≥1.0. Optimizing the structure of the projection lens is further conducive to increasing the aperture, so that the projection lens has a higher light energy utilization rate and output rate.

In a possible implementation, the focal length f1 of the first lens and the focal length f2 of the second lens satisfy the condition: 1.9≥|f1/f2|≥1.5, and the focal length f12 of the first lens group and the focal length EFL of the projection lens satisfy the condition: f12/EFL≥12;

The focal length f3 of the third lens and the focal length EFL of the projection lens satisfy the condition: 1.1≥f3/EFL≥0.8, and the focal length f4 of the second lens group and the focal length EFL of the projection lens satisfy the condition: 1.5≥f4/EFL≥1.2. Optimizing the structure of the projection lens is further conducive to increasing the aperture, so that the projection lens has a higher light energy utilization rate and output rate.

In a possible implementation, the focal length f1 of the first lens and the focal length f2 of the second lens satisfy the condition: 1.9≥|f1/f2|≥1.6, and the focal length f12 of the first lens group and the focal length EFL of the projection lens satisfy the condition: f12/EFL≥14;

The focal length f3 of the third lens and the focal length EFL of the projection lens meet the conditional formula: 1.0≥f3/EFL≥0.8, and the focal length f4 of the second lens group and the focal length EFL of the projection lens meet the conditional formula: 1.5≥f4/EFL≥1.3. Optimizing the structure of the projection lens is further conducive to increasing the aperture, so that the projection lens has a higher light energy utilization rate and output rate.

In a possible implementation, the focal length f1 of the first lens and the focal length f2 of the second lens satisfy the condition: 1.8≥|f1/f2|≥1.4, and the focal length f12 of the first lens group and the focal length EFL of the projection lens satisfy the condition: f12/EFL≥15;

The focal length f3 of the third lens and the focal length EFL of the projection lens satisfy the condition: 1.3≥f3/EFL≥0.9, and the focal length f4 of the second lens group and the focal length EFL of the projection lens satisfy the condition: 1.3≥f4/EFL≥0.8. Optimizing the structure of the projection lens is further conducive to increasing the aperture, so that the projection lens has a higher light energy utilization rate and output rate.

In a possible implementation, the focal length f1 of the first lens and the focal length f2 of the second lens satisfy the condition: 1.7≥|f1/f2|≥1.5, and the focal length f12 of the first lens group and the focal length EFL of the projection lens satisfy the condition: f12/EFL≥13.6;

The focal length f3 of the third lens and the focal length EFL of the projection lens satisfy the condition: 1.2≥f3/EFL≥1.0, and the focal length f4 of the second lens group and the focal length EFL of the projection lens satisfy the condition: 1.4≥f4/EFL≥1.1. Optimizing the structure of the projection lens is further conducive to increasing the aperture, so that the projection lens has a higher light energy utilization rate and output rate.

In a possible implementation, the aperture number #F of the projection lens satisfies the condition: 0.6≤F#≤1.0, and the aperture number F# is relatively small, which meets the design requirement of a large aperture of the projection lens.

In a possible implementation, the aperture number #F of the projection lens satisfies the condition: 0.6≤F#≤0.8. The aperture number is further optimized to better meet the large aperture design requirements.

In a possible implementation, the aperture number of the projection lens is 0.6≤F#≤0.7, realizing an ultra-large aperture design of the projection lens and significantly increasing the luminous flux of the projection lens.

In a possible implementation, the total optical length TTL of the projection lens and the focal length EFL of the projection lens satisfy the condition: 2.5≥TTL/EFL≥1.5, so that the projection lens has a smaller total optical length, thereby reducing the total length of the projection lens, which is conducive to realizing a small-volume design of the projection lens.

In a possible implementation, the total optical length TTL of the projection lens and the focal length EFL of the projection lens satisfy the condition: 2.3≥TTL/EFL≥1.5, thereby further reducing the length of the projection lens and satisfying the small volume design of the projection lens.

In a possible implementation, the total optical length TTL of the projection lens and the focal length EFL of the projection lens satisfy the condition: 2.0 ≥ TTL/EFL ≥ 1.5. Further reducing the length of the projection lens to meet the small volume design of the projection lens

In a possible implementation, the total optical length TTL of the projection lens and the focal length EFL of the projection lens satisfy the condition: 2.5 ≥ TTL/EFL ≥ 1.9. Further reducing the length of the projection lens to meet the small volume design of the projection lens

In a possible implementation, the total optical length TTL of the projection lens and the focal length EFL of the projection lens satisfy the condition: 2.5 ≥ TTL/EFL ≥ 2.1. Further reducing the length of the projection lens to meet the small volume design of the projection lens

In a possible implementation, the total optical length TTL of the projection lens and the focal length EFL of the projection lens satisfy the condition: 2.4 ≥ TTL/EFL ≥ 1.7. Further reducing the length of the projection lens to meet the small volume design of the projection lens

In a possible implementation, the back focal length BFL of the projection lens and the half image height of the projection lens satisfy the condition: 1.4≥BFL/IH≥0.6. In this way, while ensuring that the projection lens has a short total length, the projection lens can have a larger half image height, thereby realizing a large target surface design of the projection lens, which is beneficial to increase the light-emitting area, thereby increasing the light-emitting power of the projection device and further improving the brightness of the projection device.

In a possible implementation, the back focal length BFL of the projection lens and the half image height of the projection lens satisfy the condition: 1.4≥BFL/IH≥0.8. Further increasing the half image height can meet the large target surface design requirements of the projection lens and more effectively improve the luminous power of the projection device.

In a possible implementation, the back focal length BFL of the projection lens and the half image height of the projection lens satisfy the condition: 1.4 ≥ BFL/IH ≥ 1.1. Further increasing the half image height can meet the large target surface design requirements of the projection lens and more effectively improve the luminous power of the projection device.

In a possible implementation, the back focal length BFL of the projection lens and the half image height of the projection lens satisfy the condition: 1.2≥BFL/IH≥0.6. Further increasing the half image height can meet the large target surface design requirements of the projection lens and more effectively improve the luminous power of the projection device.

In a possible implementation, the back focal length BFL of the projection lens and the half image height of the projection lens satisfy the condition: 1.3≥BFL/IH≥0.6. Further increasing the half image height can meet the large target surface design requirements of the projection lens and more effectively improve the luminous power of the projection device.

In a possible implementation, the back focal length BFL of the projection lens and the half image height of the projection lens satisfy the condition: 1.2≥BFL/IH≥0.7. Further increasing the half image height can meet the large target surface design requirements of the projection lens and more effectively improve the luminous power of the projection device.

In a possible implementation, the Abbe number Vd1 of the first lens satisfies the condition: Vd1 ≥ 52, the Abbe number Vd2 of the second lens satisfies the condition: Vd2 ≤ 30, and the Abbe number Vd1 of the first lens and the Abbe number Vd2 of the second lens satisfy the condition: Vd1/Vd2 ≥ 1.8. In other words, the Abbe number of the first lens is greater than the Abbe number of the second lens, and the first lens is a lens with a high Abbe number, and the second lens is a lens with a low Abbe number. The first lens and the second lens can be complementary and balanced in terms of dispersion ability, which is conducive to reducing or eliminating imaging chromatic aberration. Further improve the imaging quality of the projection lens.

In a possible implementation, the Abbe number Vd1 of the first lens satisfies the condition: Vd1 ≥ 54, the Abbe number Vd2 of the second lens satisfies the condition: Vd2 ≤ 20, and the Abbe number Vd1 of the first lens and the Abbe number Vd2 of the second lens satisfy the condition: Vd1/Vd2 ≥ 2.7. The first lens and the second lens are optimized to further reduce or eliminate imaging chromatic aberration, so that the projection lens has better imaging quality.

In a possible implementation, the Abbe number Vd1 of the first lens satisfies the condition: Vd1 ≥ 56, the Abbe number Vd2 of the second lens satisfies the condition: Vd2 ≤ 24, and the Abbe number Vd1 of the first lens and the Abbe number Vd2 of the second lens satisfy the condition: Vd1/Vd2 ≥ 2.3. The first lens and the second lens are optimized to further reduce or eliminate imaging chromatic aberration, so that the projection lens has better imaging quality.

In a possible implementation, the first lens and the second lens are plastic lenses, and the third lens and the fourth lens are glass lenses. Under the condition of ensuring the optical performance of the projection lens, making some lenses plastic lenses is conducive to further reducing the cost of the projection lens. In addition, the projection lens using the glass lens and plastic lens structure can use the refractive index temperature coefficient of the glass lens and the refractive index temperature coefficient of the plastic lens to achieve mutual compensation, which is conducive to reducing the thermal difference of the projection lens and realizing the thermal difference elimination design of the projection lens, so that the projection lens can be applied to high and low temperature environments, and ensure the stability and reliability of the projection lens performance in different temperature environment scenes.

Moreover, the first lens and the second lens relatively far from the image display module are plastic lenses, which can reduce the influence of heat generated by the image display module during operation on the plastic lenses, and is conducive to further improving the reliability of the projection lens.

In a possible implementation, the first lens and the second lens are aspherical lenses, and the third lens and the fourth lens are spherical lenses, that is, the glass lens is a spherical lens, which has a lower cost. The plastic lens is an aspherical lens, which can ensure a large aperture design when matched with a spherical lens, and can also reduce or eliminate the spherical aberration introduced by the spherical lens, thereby ensuring the imaging performance of the projection lens and achieving a design that takes into account both high reliability and low cost.

In a possible implementation, the first lens has positive optical power, the second lens has negative optical power, the third lens has positive optical power, and the fourth lens has positive optical power. The optical power is reasonably distributed, which is beneficial to reducing aberrations and improving the imaging quality of the projection lens.

In a possible implementation, at least a portion of a surface of the first lens facing the projection side corresponding to the optical axis is a convex surface, and at least a portion of a surface of the first lens facing the pixel side corresponding to the optical axis is a convex surface.

At least a portion of a surface of the second lens facing the projection side corresponding to the optical axis is a convex surface, and at least a portion of a surface of the second lens facing the pixel side corresponding to the optical axis is a concave surface.

At least a portion of a surface of the third lens facing the projection side corresponding to the optical axis is a concave surface, and at least a portion of a surface of the third lens facing the pixel side corresponding to the optical axis is a convex surface.

At least the portion of the fourth lens element facing the projection side corresponding to the optical axis is a convex surface, and at least the portion of the fourth lens element facing the pixel side corresponding to the optical axis is a concave surface. In this way, the shape and focal length of each lens in the projection lens can be reasonably allocated, which is convenient for processing and assembly, and is also conducive to reducing aberrations and improving the imaging quality of the projection lens.

In a possible implementation, the projection lens further includes an aperture, which is located between the second lens and the third lens. The aperture can adjust the light intensity to further adjust the light flux.

A second aspect of the present application provides a projection lens, comprising a first lens group and a third lens group, wherein the first lens group comprises a first lens and a second lens, the third lens group comprises a plurality of third lenses, and the projection lens further comprises a fourth lens, wherein the first lens, the second lens, the third lens and the fourth lens are arranged in sequence from the projection side to the pixel side along the direction of the optical axis;

The focal length f3 of the third lens group and the focal length EFL of the projection lens meet the conditional formula: 1.5≥f3/EFL≥0.8, the focal length f4 of the fourth lens and the focal length EFL of the projection lens meet the conditional formula: 1.5≥f4/EFL≥0.8, and the focal length f3 of the third lens group and the focal length f4 of the fourth lens meet the conditional formula: f3>f4. It is also possible to achieve a design in which the projection lens has a large aperture, a small size, a low cost, and is adapted to a lower pixel image display module, thereby reducing costs while improving imaging quality.

A third aspect of the present application provides a projection lens, comprising a first lens group, a third lens group, and a second lens group, wherein the first lens group comprises a first lens and a second lens, the third lens group comprises a plurality of third lenses, and the second lens group comprises a plurality of fourth lenses, and the first lens, the second lens, the third lens, and the fourth lens are arranged in sequence from the projection side to the pixel side along the direction of the optical axis;

The focal length f3 of the third lens group and the focal length EFL of the projection lens satisfy the condition: 1.5≥f3/EFL≥0.8, the focal length f4 of the second lens group and the focal length EFL of the projection lens satisfy the condition: 1.5≥f4/EFL≥0.8, and the focal length f3 of the third lens group and the focal length f4 of the second lens group The conditional formula is satisfied: f3>f4. It is also possible to realize the design of a projection lens that has a large aperture, a small size, a low cost, and is adapted to a lower pixel image display module, thereby reducing costs while improving image quality.

A fourth aspect of the present application provides a projection device, comprising at least an image display module and the above-mentioned projection lens.

The projection surface of the image display module is opposite to the fourth lens of the projection lens closest to the pixel side. The image display module is configured to form a display image and transmit the display image to the projection lens through the projection surface. By including the projection lens, the projection lens has the characteristics of large aperture, adaptability to lower pixel image display modules and low cost, which is conducive to improving the utilization rate and output power of the luminous energy of the image display module by the projection device, thereby improving the brightness of the projection device. In addition, the projection lens and the image display module have good adaptability, which reduces the cost of the projection device while ensuring the performance of the projection device.

In a possible implementation, the image display module includes a chip and a plurality of micro light emitting diodes distributed in an array on the chip, which realizes the integration of the light source and the projection chip, simplifies the structure of the projection device, and can be well adapted to the projection lens.

A fifth aspect of the present application provides a vehicle, comprising at least a vehicle body and the above-mentioned projection device, wherein the projection device is arranged on the vehicle body.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a schematic diagram of the structure of a vehicle provided in an embodiment of the present application;

FIG2 is a schematic diagram of a projection device provided in an embodiment of the present application;

FIG3 is a schematic diagram of the structure of an image display module in a projection device provided in an embodiment of the present application;

FIG4 is a schematic diagram of the structure of a projection lens provided in an embodiment of the present application;

FIG5 is a schematic diagram of the structure of another projection device provided in an embodiment of the present application;

FIG6 is a modulation transfer function curve diagram of a projection lens at room temperature provided by an embodiment of the present application;

FIG. 7 is a modulation transfer function curve diagram of a projection lens at -40° C. provided in an embodiment of the present application;

FIG8 is a modulation transfer function curve diagram of a projection lens at 105° C. provided in an embodiment of the present application;

FIG9 is a field curvature diagram of a projection lens provided in an embodiment of the present application;

FIG10 is a distortion curve diagram of a projection lens provided in an embodiment of the present application;

FIG11 is a relative illumination curve of a projection lens provided in an embodiment of the present application;

FIG12 is a modulation transfer function curve diagram of another projection lens at room temperature provided by an embodiment of the present application;

FIG13 is a modulation transfer function curve diagram of another projection lens provided in an embodiment of the present application at -30°C;

FIG14 is a modulation transfer function curve diagram of another projection lens provided in an embodiment of the present application at 85° C.;

FIG15 is a field curvature diagram of another projection lens provided in an embodiment of the present application;

FIG16 is a distortion curve diagram of another projection lens provided in an embodiment of the present application;

FIG17 is a relative illumination curve of another projection lens provided in an embodiment of the present application;

FIG18 is a modulation transfer function curve diagram of another projection lens at room temperature provided in an embodiment of the present application;

FIG19 is a modulation transfer function curve diagram of another projection lens provided in an embodiment of the present application at -30°C;

FIG20 is a modulation transfer function curve diagram of a projection lens at 105° C. provided in an embodiment of the present application;

FIG21 is a field curvature diagram of another projection lens provided in an embodiment of the present application;

FIG22 is a distortion curve diagram of another projection lens provided in an embodiment of the present application;

FIG. 23 is a relative illumination curve of another projection lens provided in an embodiment of the present application.

Description of reference numerals:
100- projection device;
10-image display module; 11-chip; 12-micro light emitting diode;
20-projection lens; 201-first lens group; 21-first lens; 22-second lens; 23-third lens; 24-fourth lens;
200-projection position;
300- vehicle; 301- vehicle body; 302- lampshade.

Detailed ways

The terms used in the implementation section of this application are only used to explain the specific embodiments of this application and are not intended to limit this application.

The projection device is used to project the display image to the projection position through the projection lens to realize the projection display of the display image. The traditional projection device usually includes a light source, an image generation module and a projection lens. The light generated by the light source passes through the image generation module to form a display image. The display image passes through the projection lens, is magnified, focused, etc., and then projected to the projection position to realize the display of the image at the projection position. Among them, the image pixel formed by the image generation module is relatively high, and the pixel requirements of the projection lens matched therewith are also high. The projection lens has a high resolution, which makes the projection lens relatively large in size and high in cost.

With the continuous development of projection technology, in order to reduce the cost of projection devices, micro-light-emitting diode (Light-Emitting Diode, referred to as Micro LED) projection display technology has gradually attracted people's attention and research. Projection devices based on micro-light-emitting diode projection display technology include Micro LED display chips and projection lenses. Among them, Micro LED display chips refer to high-density, small-sized LED arrays integrated on a chip, which can independently switch and adjust the current for each independent micro-structure area on the chip, realizing the combination of light source and projection chip functions, that is, Micro LED display chips are used as light sources and image generation modules, which significantly simplifies the structure of projection devices and reduces costs. However, due to the small number of independent micro-structure switches inside the display chip itself and the relatively low display pixels, the use of traditional projection lenses will cause high costs and large volumes.

In addition, in order to meet the demand for the brightness of the projected image of the projection device, it is possible to start from improving the utilization rate of the luminous energy and the output power of the projection device. For example, the luminous flux of the projection lens can be increased so that the light emitted by the image display module can be fully irradiated to the projection position through the projection lens, thereby improving the utilization rate of the luminous energy and the output power. The luminous flux of the projection lens is directly related to the aperture of the lens. Therefore, realizing a large aperture design of the projection lens is conducive to improving the brightness of the projection device.

In addition, the luminous area can be increased to improve the luminous power of the image display module and thus the brightness, that is, to realize the large target surface design of the projection lens, which matches the image display module and is also conducive to improving the brightness of the projection device.

Based on this, the embodiments of the present application provide a projection lens and a projection device. The projection device can be a device based on micro light emitting diode projection technology. The projection lens can well match the micro light emitting diode display chip in the projection device, has a small size and low cost, and the projection lens has ultra-large aperture and large target surface characteristics, which can effectively improve the luminous flux and meet the high lighting brightness requirements of the projection device.

To facilitate understanding, the relevant technical terms involved in the embodiments of the present application are first explained and illustrated.

The pixel side is the side facing the display image with the lens as the boundary. In the embodiment of the present application, the side facing the image display module and facing away from the projection position with the projection lens as the boundary is the pixel side.

The projection side, with the lens as the boundary, the side facing away from the display image and facing the projection position is the projection side. In the embodiment of the present application, the side facing away from the image display module and facing the projection position is the projection side.

The optical axis refers to the straight line passing through the centers of the lenses of a lens (such as a projection lens).

Focal length, also known as focal length, is usually expressed as effective focal length (EFL) to distinguish it from parameters such as front focal length and back focal length. Focal length or effective focal length is a measure of the concentration or dispersion of light in an optical system. It refers to the vertical distance from the optical center of a lens or lens group to the focal plane when an infinitely distant scene forms a clear image on the focal plane through a lens or lens group (such as a projection lens).

Back focal length (BFL) is the distance from the vertex of the last optical surface of the lens to the focal point behind the lens. In the embodiment of the present application, it refers to the distance from the vertex of a surface facing the pixel in the fourth lens adjacent to the pixel in the projection lens to the focal point behind the projection lens.

Aperture is used to control the amount of light that passes through the lens into the device. It is usually inside the lens, and the aperture size is expressed as the F# value.

The aperture number F# is a relative value obtained by dividing the focal length of the lens by the diameter of the lens (the inverse of the relative aperture). The smaller the aperture number F#, the more light enters in the same unit time. The larger the aperture number F#, the smaller the depth of field, and the background content of the photo will be blurred, producing an effect similar to that of a telephoto lens.

Total Track Length (TTL) refers to the distance from the vertex of the front surface of the first lens of the lens to the image plane to the projection surface of the image display module. In the embodiment of the present application, it refers to the distance from the vertex of the surface of the first lens adjacent to the projection side of the projection lens facing the projection side to the projection surface of the image display module.

Half image height (IH for short) refers to the radius of the imaging circle. In the embodiment of the present application, it refers to half of the diagonal of the projection surface of the image display module.

The target surface refers to the imaging part of the image sensor. In the embodiment of the present application, it refers to the light-emitting surface of the displayed image (such as the projection surface of the image display module). The larger the target surface, the larger the light-emitting area available for displaying the image, and the higher the brightness of the displayed image.

The field of view (FOV) is the angle formed by the two edges of the maximum range of the image that can pass through the lens, with the lens as the vertex. The size of the field of view determines the field of view of the lens. The larger the field of view, the larger the field of view.

Optical power represents the ability of a lens to refract an incident parallel light beam and is equal to the reciprocal of the focal length.

The Abbe number is used to measure the degree of light dispersion in a medium. The greater the degree of light dispersion, the smaller the Abbe number. Conversely, the smaller the degree of light dispersion, the larger the Abbe number.

Distortion refers to the difference in height between the off-axis point and the intersection of the principal ray on the image plane and the ideal (paraxial) image plane.

Relative illumination refers to the ratio of central illumination to peripheral illumination. If the relative illumination is too low, the center of the image will be brighter, while the surroundings will be darker, which is called vignetting, commonly known as shading. If the relative illumination is too low, it will also cause color distortion.

The temperature coefficient of refractive index refers to the coefficient of the relationship between the refractive index of an optical material and the change in temperature.

Luminous flux refers to the light energy emitted by a light source per unit time.

Athermalization refers to reducing or eliminating the effect of temperature on lens performance (such as imaging performance, etc.).

The projection device provided in the embodiment of the present application can be any device capable of realizing the projection function, such as a projector and a projection lamp. The projection device can be applicable to indoor projection, such as home projection, conference projection, cinema projection, indoor sign design projection, etc. Alternatively, the projection device can also be applicable to projection in outdoor and road scenes, such as advertising projection, outdoor projection, road sign projection, etc.

The projection device can also be a projection headlight, a vehicle head-up display (Head Up Display, HUD for short) device, or other device suitable for the projection needs of the vehicle.

FIG1 is a schematic diagram of the structure of a vehicle provided in an embodiment of the present application.

The embodiment of the present application further provides a vehicle 300, as shown in FIG1 , taking a car as an example, the vehicle 300 may include a vehicle body 301 and a projection device 100, taking the projection device 100 as a projection car lamp as an example, the projection device 100 is fixed on the vehicle body, specifically, the projection device may be located inside the vehicle body 301, and illustratively, a lampshade 302 may also be provided on the vehicle body 301, and the projection device 100 may be opposite to the lampshade 302. The display image projected by the projection device 100 can be irradiated to the outside of the vehicle body 301 through the lampshade 302, and the lighting and other display requirements of the vehicle 300 are realized through the projection device 100.

It should be understood that the vehicle 300 may also include other structures to complete its functions, for example, it may also include a braking system, a driving system, a camera, a sensor, a detector, etc.

FIG. 2 is a schematic diagram of a projection of a projection device provided in an embodiment of the present application.

Specifically, as shown in Figure 2, the projection device 100 may include an image display module 10 and a projection lens 20, wherein the image display module 10 can form a light display image to be projected, and the image display module 10 may include a projection surface 10a, and the projection surface 10a may be opposite to the light incident surface of the projection lens 20. The display image formed by the image display module 10 can be transmitted to the projection lens 20 through the projection surface 10a, and the projection lens 20 can magnify, focus, and focus the display image. After passing through the projection lens 20, the display image is irradiated to a preset projection position 200 to realize the projection display of the display image.

In the projection device 100, the side of the projection lens 20 facing the projection surface 10a of the image display module 10 is the pixel side, and the side of the projection lens 20 facing the projection position 200 and facing away from the image display module 10 is the projection side. The projection lens 20 forms an image at the projection position 200, and the imaging surface of the projection lens 20 can be the plane where the projection position 200 is located.

It should be understood that the projection position 200 is used to carry the display image projected by the projection device 100 to display the display image. The projection position 200 can be a projection screen, or the projection position 200 can also be a car window, glass, etc., or the projection position 200 can also be any structure such as a wall that can carry the display image.

FIG. 3 is a schematic diagram of the structure of an image display module in a projection device provided in an embodiment of the present application.

The image display module 10 may be a micro light emitting diode display chip (Micro LED display chip). Specifically, as shown in FIG. 3 , the image display module 10 may include a chip 11 and a plurality of micro light emitting diodes 12. The plurality of micro light emitting diodes 12 are arrayed on the chip 11, and the projection surface 10a may be a plane where the plurality of micro light emitting diodes 12 are arrayed. The light emitting diodes 12 serve as a light source, and the chip 11 can realize the functions of independent switching and current regulation of each independent microstructure on the chip 11, that is, the Micro LED display chip realizes the integration of the light source and the projection chip, simplifying the structure of the projection device 100.

Of course, in some other examples, the image display module 10 may also be other devices capable of forming a projection image. For example, the image display module 10 may be composed of an independent light source and an image forming module.

The projection lens in the projection device provided in the embodiment of the present application is described below with reference to the accompanying drawings.

FIG. 4 is a schematic diagram of the structure of a projection lens provided in an embodiment of the present application, and FIG. 5 is a schematic diagram of another projection lens provided in an embodiment of the present application Schematic diagram of the device structure.

The projection lens 20 may include multiple lenses with optical power. Specifically, refer to Figure 4, where L is the optical axis of the projection lens 20, the projection lens 20 may include at least a first lens 21, a second lens 22, a third lens 23 and a fourth lens 24 arranged in sequence from the projection side to the pixel side along the optical axis.

5 , when the projection lens 20 is applied to the projection device 100 , the fourth lens 24 closer to the pixel side is arranged facing the projection surface 10a of the image display module 10 . The fourth lens 24 can be the light incident surface of the projection lens 20 , and the first lens 21 is arranged facing the projection position 200 .

The first lens 21 , the second lens 22 , the third lens 23 and the fourth lens 24 may be single lens lenses, that is, the projection lens 20 includes four lenses, which is a four-lens structure.

It should be noted that the architecture of the projection lens 20 can be changed by adjusting the focal lengths of the first lens 21, the second lens 22, the third lens 23 and the fourth lens 24 included in the projection lens 20, thereby changing the performance of the projection lens 20 so that the projection lens 20 can achieve a large aperture design.

Specifically, the focal length of the projection lens 20 is EFL, the focal length of the first lens 21 is f1, and the focal length of the second lens 22 is f2. The focal length f1 of the first lens 21 and the focal length f2 of the second lens 22 can satisfy the condition: 2≥|f1/f2|≥1.2. The first lens 21 and the second lens 22 form a first lens group 201, and the focal length of the first lens group 201 is f12. The focal length f12 of the first lens group 201 and the focal length EFL of the projection lens 20 can satisfy the condition: f12/EFL≥5.

The focal length of the third lens 23 is f3, and the focal length f3 of the third lens 23 and the focal length EFL of the projection lens 20 can satisfy the conditional formula: 1.5≥f3/EFL≥0.8. The focal length of the fourth lens 24 is f4, and the focal length f4 of the fourth lens 24 and the focal length EFL of the projection lens 20 can satisfy the conditional formula: 1.5≥f4/EFL≥0.8, and the focal length f3 of the third lens 23 can be greater than the focal length f4 of the fourth lens 24. The projection lens 20 formed by the first lens 21, the second lens 22, the third lens 23 and the fourth lens 24 that satisfy the above conditional formula has a small aperture number F#, can realize a large aperture design, and increases the luminous flux of the projection lens 20. When applied to the projection device 100, it can improve the utilization rate and output power of the luminous energy of the image display module 10, and improve the illumination brightness of the projection device 100.

In addition, the projection lens 20 realizes a large aperture design only through the first lens 21, the second lens 22, the third lens 23 and the fourth lens 24. The projection lens 20 can be a four-lens structure with fewer lenses, simple structure, small size and low cost. The projection lens 20 with a simple structure has relatively low pixels, which can well match the micro-light emitting diode display chip with low pixel requirements and meet the changing requirements of the projected image, so that the projection lens 20 has a large aperture, small size, low cost and is adapted to the design of the low-pixel image display module 10.

It should be noted that the number of lenses included in the projection lens 20 may also be greater than 4. For example, in some other examples, along the optical axis direction from the projection side to the pixel side, the projection lens may include a first lens, a second lens, a third lens and a second lens group, and the second lens group may include multiple fourth lenses.

That is, the lens near the pixel side can be a lens group, which is easy to implement and helps to improve the image quality. In addition, the lens group can be a lens group composed of glass lenses, which is conducive to reducing costs while improving the image quality.

The second lens group may include two fourth lenses. Of course, in some other examples, the number of the fourth lenses may be three or more. While realizing the large aperture design of the projection lens, it has a simpler structure and lower cost, and the formed projection lens architecture has relatively low pixels, which can better adapt to the micro light emitting diode display chip.

It should be noted that when the second lens group includes multiple fourth lenses, the multiple fourth lenses are arranged in sequence from the pixel side to the projection side along the optical axis direction, and the fourth lens closer to the pixel side among the multiple fourth lenses is opposite to the projection surface of the image display module.

When the projection lens includes a first lens group, a third lens group, and a second lens group, and the second lens group includes a plurality of fourth lenses, referring to the structure of the aforementioned four lenses, the focal length f1 of the first lens and the focal length f2 of the second lens satisfy the conditional formula: 2≥|f1/f2|≥1.2, and the focal length f12 of the first lens group and the focal length EFL of the projection lens satisfy the conditional formula: f12/EFL≥5;

The focal length f3 of the third lens and the focal length EFL of the projection lens satisfy the conditional formula: 1.5≥f3/EFL≥0.8, the focal length f4 of the second lens group and the focal length EFL of the projection lens satisfy the conditional formula: 1.5≥f4/EFL≥0.8, and the focal length f3 of the third lens and the focal length f4 of the second lens group satisfy the conditional formula: f3>f4. It should be noted that the focal length f4 of the second lens group refers to the focal length of the lens group composed of the plurality of fourth lenses.

Alternatively, in some other examples, along the optical axis direction from the projection side to the pixel side, the projection lens may include a first lens, a second lens, a third lens group and a second lens group, the third lens group includes a plurality of third lenses, and the second lens group includes a plurality of fourth lenses. Accordingly, the focal length f3 of the third lens group refers to the focal length of the lens group composed of the plurality of third lenses, which is easy to implement and is conducive to reducing costs while improving imaging quality.

The third lens group may include two third lenses, or the number of the third lenses may be other. The design of aperture, small size, low cost and adaptable to lower pixel image display modules.

Alternatively, in some other examples, along the optical axis direction from the projection side to the pixel side, the projection lens includes a first lens, a second lens, a third lens group and a fourth lens, and the third lens group includes a plurality of third lenses, which can also reduce costs while improving imaging quality. The resulting projection lens has a large aperture, a small size, a low cost and is adapted to the design of a lower pixel image display module.

In this embodiment, a projection lens including four lenses, namely, a first lens, a second lens, a third lens and a fourth lens, is taken as an example for description.

In order to further increase the aperture, improve the utilization rate and output rate of the projection lens for luminous energy, and enable the projection device to have a better luminous flux, the focal length f1 of the first lens and the focal length f2 of the second lens can satisfy the conditional formula: 1.9≥|f1/f2|≥1.2, the focal length f12 of the first lens group and the focal length EFL of the projection lens can satisfy the conditional formula: f12/EFL≥6. The focal length f3 of the third lens and the focal length EFL of the projection lens can satisfy the conditional formula: 1.5≥f3/EFL≥0.9, and the focal length f4 of the fourth lens and the focal length EFL of the projection lens can satisfy the conditional formula: 1.4≥f4/EFL≥0.8.

Alternatively, the focal length f1 of the first lens and the focal length f2 of the second lens may satisfy the conditional formula: 1.8≥|f1/f2|≥1.2, the focal length f12 of the first lens group and the focal length EFL of the projection lens may satisfy the conditional formula: f12/EFL≥6. The focal length f3 of the third lens and the focal length EFL of the projection lens may satisfy the conditional formula: 1.5≥f3/EFL≥1.0, and the focal length f4 of the fourth lens and the focal length EFL of the projection lens may satisfy the conditional formula: 1.3≥f4/EFL≥0.8.

Alternatively, the focal length f1 of the first lens and the focal length f2 of the second lens may satisfy the conditional formula: 1.7≥|f1/f2|≥1.2, the focal length f12 of the first lens group and the focal length EFL of the projection lens may satisfy the conditional formula: f12/EFL≥7.5. The focal length f3 of the third lens and the focal length EFL of the projection lens may satisfy the conditional formula: 1.5≥f3/EFL≥1.2, and the focal length f4 of the fourth lens and the focal length EFL of the projection lens may satisfy the conditional formula: 1.2≥f4/EFL≥0.8.

Alternatively, the focal length f1 of the first lens and the focal length f2 of the second lens may satisfy the conditional formula: 1.6≥|f1/f2|≥1.2, the focal length f12 of the first lens group and the focal length EFL of the projection lens may satisfy the conditional formula: f12/EFL≥8. The focal length f3 of the third lens and the focal length EFL of the projection lens may satisfy the conditional formula: 1.5≥f3/EFL≥1.1, and the focal length f4 of the fourth lens and the focal length EFL of the projection lens may satisfy the conditional formula: 1.0≥f4/EFL≥0.8.

Alternatively, the focal length f1 of the first lens and the focal length f2 of the second lens may satisfy the conditional formula: 1.4≥|f1/f2|≥1.2, the focal length f12 of the first lens group and the focal length EFL of the projection lens may satisfy the conditional formula: f12/EFL≥8.9. The focal length f3 of the third lens and the focal length EFL of the projection lens may satisfy the conditional formula: 1.5≥f3/EFL≥1.3, and the focal length f4 of the fourth lens and the focal length EFL of the projection lens may satisfy the conditional formula: 1.5≥f4/EFL≥1.0.

Alternatively, the focal length f1 of the first lens and the focal length f2 of the second lens may satisfy the conditional formula: 1.5≥|f1/f2|≥1.2, the focal length f12 of the first lens group and the focal length EFL of the projection lens may satisfy the conditional formula: f12/EFL≥10.6. The focal length f3 of the third lens and the focal length EFL of the projection lens may satisfy the conditional formula: 1.4≥f3/EFL≥0.8, and the focal length f4 of the fourth lens and the focal length EFL of the projection lens may satisfy the conditional formula: 1.5≥f4/EFL≥0.9.

Alternatively, the focal length f1 of the first lens and the focal length f2 of the second lens may satisfy the conditional formula: 1.9≥|f1/f2|≥1.3, the focal length f12 of the first lens group and the focal length EFL of the projection lens may satisfy the conditional formula: f12/EFL≥9. The focal length f3 of the third lens and the focal length EFL of the projection lens may satisfy the conditional formula: 1.2≥f3/EFL≥0.8, and the focal length f4 of the fourth lens and the focal length EFL of the projection lens may satisfy the conditional formula: 1.5≥f4/EFL≥1.1.

Alternatively, the focal length f1 of the first lens and the focal length f2 of the second lens may satisfy the condition: 1.9≥|f1/f2|≥1.4, and the focal length f12 of the first lens group and the focal length EFL of the projection lens may satisfy the condition: f12/EFL≥11.1.

The focal length f3 of the third lens and the focal length EFL of the projection lens may satisfy the condition: 1.3≥f3/EFL≥0.8, and the focal length f4 of the fourth lens and the focal length EFL of the projection lens may satisfy the condition: 1.5≥f4/EFL≥1.0.

Alternatively, the focal length f1 of the first lens and the focal length f2 of the second lens may satisfy the condition: 1.9≥|f1/f2|≥1.5, and the focal length f12 of the first lens group and the focal length EFL of the projection lens may satisfy the condition: f12/EFL≥12.

The focal length f3 of the third lens and the focal length EFL of the projection lens may satisfy the condition: 1.1≥f3/EFL≥0.8, and the focal length f4 of the fourth lens and the focal length EFL of the projection lens may satisfy the condition: 1.5≥f4/EFL≥1.2.

Alternatively, the focal length f1 of the first lens and the focal length f2 of the second lens may satisfy the condition: 1.9≥|f1/f2|≥1.6, and the focal length f12 of the first lens group and the focal length EFL of the projection lens may satisfy the condition: f12/EFL≥14.

The focal length f3 of the third lens and the focal length EFL of the projection lens may satisfy the condition: 1.0≥f3/EFL≥0.8, and the focal length f4 of the fourth lens and the focal length EFL of the projection lens may satisfy the condition: 1.5≥f4/EFL≥1.3.

Alternatively, the focal length f1 of the first lens and the focal length f2 of the second lens may satisfy the condition: 1.8 ≥ |f1/f2| ≥ 1.4, and the focal length f1 of the first lens group The focal length f12 and the focal length EFL of the projection lens may satisfy the condition: f12/EFL≥15.

The focal length f3 of the third lens and the focal length EFL of the projection lens may satisfy the condition: 1.3≥f3/EFL≥0.9, and the focal length f4 of the fourth lens and the focal length EFL of the projection lens may satisfy the condition: 1.3≥f4/EFL≥0.8.

Alternatively, the focal length f1 of the first lens and the focal length f2 of the second lens may satisfy the conditional formula: 1.7≥|f1/f2|≥1.5, the focal length f12 of the first lens group and the focal length EFL of the projection lens may satisfy the conditional formula: f12/EFL≥13.6. The focal length f3 of the third lens and the focal length EFL of the projection lens may satisfy the conditional formula: 1.2≥f3/EFL≥1.0, and the focal length f4 of the fourth lens and the focal length EFL of the projection lens may satisfy the conditional formula: 1.4≥f4/EFL≥1.1.

Specifically, the aperture number F# of the projection lens 20 may be in the range of 0.6≤F#≤1.0. The aperture number F# is relatively small, thus satisfying the design requirement of a large aperture of the projection lens 20 .

In order to further optimize the aperture number of the projection lens 20 and better meet the design requirements for a large aperture of the projection lens, the aperture number #F of the projection lens may be in the range of 0.6≤F#≤0.8.

Furthermore, the aperture number F# of the projection lens 20 may be less than 0.7, thereby realizing an ultra-large aperture design of the projection lens 20 and further increasing the luminous flux of the projection lens 20 .

Taking the total optical length of the projection lens 20 as TTL, the total optical length TTL of the projection lens 20 and the focal length EFL of the projection lens 20 can satisfy the condition: 2.5≥TTL/EFL≥1.5. In this way, the projection lens 20 has a smaller total optical length, which reduces the total length of the projection lens 20 and enables a small volume design of the projection lens 20.

In order to further reduce the total optical length of the projection lens and compress the length of the projection lens to better meet the small volume design requirements of the projection lens, the total optical length TTL of the projection lens and the focal length EFL of the projection lens can meet the condition: 2.3≥TTL/EFL≥1.5.

Alternatively, the total optical length TTL of the projection lens and the focal length EFL of the projection lens may satisfy the conditional formula: 2.0≥TTL/EFL≥1.5.

Alternatively, the total optical length TTL of the projection lens and the focal length EFL of the projection lens may satisfy the conditional formula: 2.5≥TTL/EFL≥1.9.

Alternatively, the total optical length TTL of the projection lens and the focal length EFL of the projection lens can satisfy the condition: 2.5 ≥ TTL/EFL ≥ 2.1. Further reducing the length of the projection lens to meet the small volume design of the projection lens

Alternatively, the total optical length TTL of the projection lens and the focal length EFL of the projection lens may satisfy the conditional formula: 2.4≥TTL/EFL≥1.7.

In addition, with the back focal length of the projection lens 20 as BFL and the half image height of the projection lens 20 as IH, the back focal length BFL of the projection lens 20 and the half image height of the projection lens 20 can satisfy the conditional formula: 1.4≥BFL/IH≥0.6. In this way, while ensuring that the projection lens 20 has a small total length, the projection lens 20 can have a larger half image height, thereby realizing a large target surface design of the projection lens 20, which is beneficial to the increase of the light-emitting area, thereby improving the light-emitting power of the projection device 100 and further improving the brightness of the projection device 100.

Under the condition of ensuring a short total length of the projection lens, in order to further increase the half-image height and better meet the large target surface design requirements of the projection lens, thereby more effectively improving the luminous power of the projection device, the back focal length BFL of the projection lens and the half-image height of the projection lens can meet the conditional formula: 1.4≥BFL/IH≥0.8.

Alternatively, the back focal length BFL of the projection lens and the half image height of the projection lens may satisfy the conditional expression: 1.4≥BFL/IH≥1.1.

Alternatively, the back focal length BFL of the projection lens and the half image height of the projection lens may satisfy the conditional expression: 1.2≥BFL/IH≥0.6.

Alternatively, the back focal length BFL of the projection lens and the half image height of the projection lens may satisfy the conditional expression: 1.3≥BFL/IH≥0.6.

Alternatively, the back focal length BFL of the projection lens and the half image height of the projection lens may satisfy the conditional expression: 1.2≥BFL/IH≥0.7.

That is, the projection lens in the embodiment of the present application can achieve the characteristics of large aperture, large target surface, small size and low cost through a simple lens structure, such as a four-piece lens structure. While improving the luminous flux of the projection lens 20, the size and cost of the projection lens 20 are greatly reduced, and it has good practicality.

Specifically, among the multiple lenses of the projection lens 20, some lenses can be plastic lenses, and some lenses can be glass lenses. Plastic lenses themselves have a lower cost. Under the condition of ensuring the optical performance of the projection lens 20, making some lenses plastic lenses is beneficial to further reduce the cost of the projection lens 20.

In addition, the projection lens 20 using a glass lens and a plastic lens structure can utilize the refractive index temperature coefficient of the glass lens and the refractive index temperature coefficient of the plastic lens. For example, the refractive index temperature coefficient of the glass lens is mostly negative, and the refractive index temperature coefficient of the plastic is mostly positive, which can achieve mutual compensation, which is beneficial to reducing the thermal difference of the projection lens 20, that is, reducing the impact of temperature on the imaging performance of the projection lens 20, etc., which is beneficial to the projection lens 20 to achieve a heat difference elimination design, so that the projection lens 20 can be suitable for high and low temperature environments, ensuring the stability and reliability of the performance of the projection lens 20 in different temperature environment scenes.

Specifically, the third lens 23 and the fourth lens 24 are located adjacent to the pixel side, and the first lens 21 and the second lens 22 are located adjacent to the projection side, that is, the third lens 23 and the fourth lens 24 are disposed adjacent to the image display module 10, etc., and the first lens 21 and the second lens 22 are disposed adjacent to the projection side. The lens 22 is located relatively far away from the image display module 10. The first lens 21 and the second lens 22 can be plastic lenses, and the third lens 23 and the fourth lens 24 can be glass lenses, which can reduce the influence of heat generated by the image display module 10 during operation on the plastic lenses, which is conducive to improving the reliability of the projection lens 20.

In addition, the first lens 21 and the second lens 22 can be aspherical lenses, and the third lens 23 and the fourth lens 24 can be spherical lenses, that is, the glass lens is a spherical lens, which has a lower cost. The plastic lens is an aspherical lens, which can ensure a large aperture design when matched with a spherical lens, and can also reduce or eliminate the spherical aberration introduced by the spherical lens, thereby ensuring the imaging performance of the projection lens 20, and taking into account both high reliability and low-cost design.

Among them, the fourth lens 24 and the third lens 23 on the adjacent pixel side can both have positive optical focal length, the second lens 22 can have negative optical focal length, and the first lens 21 can have positive optical focal length. The optical focal length is reasonably distributed, which is beneficial to reducing aberrations and improving the imaging quality of the projection lens 20.

The Abbe number of the first lens 21 is Vd1, and the Abbe number Vd1 of the first lens 21 can satisfy the conditional formula: Vd1 ≥ 52. The Abbe number of the second lens 22 is Vd2, and the Abbe number Vd2 of the second lens 22 can satisfy the conditional formula: Vd2 ≤ 30. And the Abbe number Vd1 of the first lens 21 and the Abbe number Vd2 of the second lens 22 can satisfy the conditional formula: Vd1/Vd2 ≥ 1.8.

That is to say, the Abbe number of the first lens 21 is greater than the Abbe number of the second lens 22, and the first lens 21 is a lens with a high Abbe number, and the second lens 22 is a lens with a low Abbe number. The first lens 21 and the second lens 22 can be complementary and balanced in terms of dispersion ability, which is beneficial to reduce or eliminate imaging chromatic aberration and further improve the imaging quality of the projection lens 20.

In order to further reduce or eliminate chromatic aberration and make the projection lens have better imaging quality, the Abbe number of the first lens and the second lens can be optimized. For example, the Abbe number Vd1 of the first lens can satisfy the condition: Vd1≥54, the Abbe number Vd2 of the second lens can satisfy the condition: Vd2≤20, and the Abbe number Vd1 of the first lens and the Abbe number Vd2 of the second lens can satisfy the condition: Vd1/Vd2≥2.7.

Alternatively, the Abbe number Vd1 of the first lens may satisfy the condition: Vd1≥56, the Abbe number Vd2 of the second lens may satisfy the condition: Vd2≤24, and the Abbe number Vd1 of the first lens and the Abbe number Vd2 of the second lens may satisfy the condition: Vd1/Vd2≥2.3.

As shown in Figure 4, at least the portion of the first lens 21 facing the projection side corresponding to the optical axis can be a convex surface, and at least the portion of the first lens 21 facing the pixel side corresponding to the optical axis can also be a convex surface, such as the first lens 21 can be a double convex lens.

At least the portion of the second lens 22 facing the projection side corresponding to the optical axis may be convex, and at least the portion of the second lens 22 facing the pixel side corresponding to the optical axis may be concave, for example, the second lens 22 may be a meniscus lens.

At least the portion of the third lens 23 facing the projection side corresponding to the optical axis can be a concave surface, and at least the portion of the third lens 23 facing the pixel side corresponding to the optical axis can be a convex surface. For example, the third lens 23 can also be a meniscus lens.

At least the portion of the fourth lens 24 facing the projection side corresponding to the optical axis may be a convex surface, and at least the portion of the fourth lens 24 facing the pixel side corresponding to the optical axis may be a concave surface, such as a meniscus-shaped lens. In this way, the shape and optical power of each lens in the projection lens 20 can be reasonably allocated, which is convenient for processing and assembly, and is also conducive to reducing aberrations and improving the imaging quality of the projection lens 20.

In addition, the projection lens 20 may further include an aperture, which may be located between the second lens 22 and the third lens 23. The aperture may play a role in adjusting the light intensity to achieve further adjustment of the light flux.

The architecture and performance of the projection lens provided in this application are described below with reference to specific examples.

Embodiment 1

In this example, the projection lens 20 includes four lenses, namely a first lens 21, a second lens 22, a third lens 23 and a fourth lens 24, which are arranged in sequence along the optical axis from the projection side to the pixel side (see FIG. 4 ). The first lens 21 and the second lens 22 are aspherical plastic lenses, and the third lens 23 and the fourth lens 24 are spherical glass lenses.

Among them, the focal length f1 of the first lens 21 is 37 mm, the focal length f2 of the second lens 22 is -18 mm, the focal length f1 of the first lens 21 and the focal length f2 of the second lens 22 satisfy: |f1/f2|=2.0, the focal length f12 of the first lens group 201 composed of the first lens 21 and the second lens 22 is 266.2 mm, the focal length EFL of the projection lens 20 is 29.82 mm, and the focal length f12 of the first lens group 201 and the focal length EFL of the projection lens 20 satisfy: f12/EFL=8.9.

The focal length f3 of the third lens 23 is 45 mm, and the focal length f4 of the fourth lens 24 is 33 mm, and the focal length f3 of the third lens 23 is greater than the focal length f4 of the fourth lens 24. The focal length f3 of the third lens 23 and the focal length EFL of the projection lens 20 satisfy: f3/EFL=1.5, and the focal length f4 of the fourth lens 24 and the focal length EFL of the projection lens 20 satisfy: f4/EFL=1.1.

The Abbe number Vd1 of the first lens 21 is 55.98, the Abbe number Vd2 of the second lens 22 is 23.53, and the Abbe number Vd1 of the first lens 21 is The Abbe number Vd2 of the second lens 22 satisfies: Vd1/Vd2=2.4.

The first lens 21 has positive power and is a biconvex lens. The second lens 22 has negative power and is a meniscus lens, and the side of the second lens 22 facing the projection side is a convex surface. The third lens 23 has positive power and is also a meniscus lens, and the side of the third lens 23 facing the pixel side is a convex surface. The fourth lens 24 is a meniscus lens, and the side of the fourth lens 24 facing the projection side is a convex surface.

The aperture number F# of the projection lens 20 is 0.7.

The total optical length TTL of the projection lens 20 is 54.50 mm, the maximum diameter of the projection lens 20 is 42 mm, and the total optical length TTL of the projection lens 20 and the focal length EFL of the projection lens 20 satisfy: TTL/EFL=1.8.

The back focal length BFL of the projection lens 20 is 9.01 mm, and the half image height IH of the projection lens 20 is 6.61 mm. The back focal length BFL of the projection lens 20 and the half image height IH of the projection lens 20 satisfy: BFL/IH=1.4.

Table 1 below shows the optical parameters of each lens in a projection lens provided in an embodiment of the present application.

Among them, L1, L2, L3 and L4 represent the first lens 21, the second lens 22, the third lens 23 and the fourth lens 24 respectively, S1 and S2 represent the side of the first lens 21 facing the projection side and the side facing the pixel side respectively, S3 and S4 represent the side of the second lens 22 facing the projection side and the side facing the pixel side respectively, S5 and S6 represent the side of the third lens 23 facing the projection side and the side facing the pixel side respectively, S7 and S8 represent the side of the fourth lens 24 facing the projection side and the side facing the pixel side respectively.

R represents the radius of curvature of the lens. Th represents the center thickness of the lens or the thickness of the air gap between two adjacent lenses along the optical axis at the corresponding position of the optical axis. For example, Th corresponding to row S1 represents the center thickness of the first lens 21, and Th corresponding to row S2 represents the distance between the side of the first lens 21 facing the pixel side and the side of the second lens 22 facing the projection side in the optical axis direction and at the corresponding position of the optical axis, and so on.

Nd represents the refractive index of the lens. Vd represents the Abbe number of the lens, and f represents the focal length of the lens.

Table 2 below shows the aspheric coefficients of each lens in a projection lens provided in an embodiment of the present application.

The projection lens 20 includes four lenses, wherein the first lens 21 and the second lens 22 are aspherical lenses, and the aspherical lenses can meet the following requirements:

Among them, Z is the vector height of the aspherical surface, r is the radial coordinate of the aspherical surface, c is the vertex spherical curvature of the aspherical surface, k is the quadratic surface constant, and A2, A4, A6, and A8 are aspherical coefficients.

The optical parameters of the projection lens 20 composed of the above lenses can be seen in Table 3 below.

Table 3 shows the optical parameters of a projection lens provided in an embodiment of the present application.

It can be seen from Table 3 that the projection lens 20 provided in the embodiment of the present application has the characteristics of large aperture, large target surface, and low total optical length, which improves the luminous flux and imaging performance of the projection lens 20 and has a smaller volume.

FIG. 6 is a modulation transfer function curve diagram of a projection lens at room temperature provided in an embodiment of the present application.

In the embodiment of the present application, the room temperature is 20°C. As shown in FIG6, at a spatial frequency of 12.5LP/mm, the optical transfer function coefficient (OTF) corresponding to the central field of view of the projection lens 20 is above 0.8 (see the TS of 0.0000nm curve in FIG6), and the OTF coefficient corresponding to the 0.7 times IH field of view is above 0.5 (see the TS of 6.6000nm curve in FIG6). The projection lens 20 has good resolution and contrast, ensuring high imaging quality.

FIG. 7 is a modulation transfer function curve diagram of a projection lens provided in an embodiment of the present application at -40°C, and FIG. 8 is a modulation transfer function curve diagram of a projection lens provided in an embodiment of the present application at 105°C.

As shown in FIG. 7 and FIG. 8 , in the low temperature -40°C and high temperature 105°C scenes, at a spatial frequency of 12.5LP/mm, the OTF coefficient corresponding to the central field of view of the projection lens 20 is above 0.35, and the OTF coefficient corresponding to the 0.7 times IH field of view is above 0.2. The high or low temperature environment has little effect on the imaging performance of the projection lens 20, and the athermal design of the projection lens 20 is realized. After focusing at room temperature, switching to an environment of -40°C to 105°C can achieve clear imaging without refocusing, and has good imaging stability and reliability.

FIG. 9 is a field curvature diagram of a projection lens provided in an embodiment of the present application, and FIG. 10 is a distortion curve diagram of a projection lens provided in an embodiment of the present application.

9 and 10 respectively show the field curvature and distortion curves of light with wavelengths of 617 nm, 525 nm and 460 nm after passing through the projection lens 20, where S is the field curvature in the sagittal direction and T is the field curvature in the meridional direction. As can be seen from FIG. 9 , the projection lens 20 has a relatively small field curvature.

As can be seen from FIG. 10 , the distortion of the projection lens 20 is less than 3%, which means it has relatively small distortion and high imaging quality, and the displayed image projected by the projection lens 20 is not distorted.

FIG. 11 is a relative illumination curve of a projection lens provided in an embodiment of the present application.

FIG11 shows a relative illumination curve of light with a wavelength of 460 nm passing through the projection lens 20. As can be seen from FIG11, the relative illumination of the projection lens 20 is greater than 90%, the projection lens 20 has a large luminous flux, and the brightness of the displayed image projected by the projection lens 20 is very uniform.

Embodiment 2

In this example, the focal length f1 of the first lens is 24.9 mm, the focal length f2 of the second lens is -16.4 mm, the focal length f1 of the first lens and the focal length f2 of the second lens satisfy: |f1/f2|=1.5, the focal length f12 of the first lens group composed of the first lens and the second lens is 312.5 mm, the focal length EFL of the projection lens is 29.58 mm, and the focal length of the first lens group and the focal length EFL of the projection lens satisfy: f12/EFL=10.6.

The focal length f3 of the third lens is 44.1 mm, the focal length f4 of the fourth lens is 36.3, and the focal length f3 of the third lens is greater than the focal length f4 of the fourth lens. The focal length f3 of the third lens and the focal length EFL of the projection lens satisfy: f3/EFL=1.5, and the focal length f4 of the fourth lens and the focal length EFL of the projection lens satisfy: f4/EFL=1.2.

The Abbe number of the first lens Vd1=55.31, the Abbe number of the second lens Vd2=23.53, and the Abbe number Vd1 of the first lens and the Abbe number Vd2 of the second lens satisfy: Vd1/Vd2=2.4.

The first lens has positive power and is a biconvex lens. The second lens has negative power and is a meniscus lens, and the side of the second lens facing the projection side is convex. The third lens has positive power and is also a meniscus lens, and the side of the third lens facing the pixel side is convex. The fourth lens is a meniscus lens, and the side of the fourth lens facing the projection side is convex.

The aperture number F# of the projection lens is 0.7804.

The total optical length TTL of the projection lens is 55.00 mm, the maximum diameter of the projection lens is 42 mm, and the total optical length TTL of the projection lens and the focal length EFL of the projection lens satisfy: TTL/EFL=1.9.

The back focal length BFL of the projection lens is 9.46 mm, the half image height IH of the projection lens is 6.61 mm, and the back focal length BFL of the projection lens and the half image height IH of the projection lens satisfy: BFL/IH=1.4.

Table 4 below shows the optical parameters of each lens in another projection lens provided in an embodiment of the present application.

The description of each parameter in Table 4 refers to the first embodiment and will not be repeated in this embodiment.

Table 5 below shows the aspheric coefficients of each lens in another projection lens provided in an embodiment of the present application.

The projection lens includes four lenses, wherein the first lens and the second lens are aspherical lenses, and the aspherical lenses can meet the following requirements:

The optical parameters of the projection lens composed of the above lenses can be seen in Table 5 below.

Table 6 shows the optical parameters of another projection lens provided in an embodiment of the present application.

It can be seen from Table 6 that the projection lens provided in the embodiment of the present application has the characteristics of large aperture, large target surface, and low total optical length, which improves the luminous flux and imaging performance of the projection lens and has a smaller volume.

FIG. 12 is a modulation transfer function curve diagram of another projection lens at room temperature provided in an embodiment of the present application.

As shown in Figure 12, at the spatial frequency of 12.5LP/mm, the optical transfer function coefficient (OTF) corresponding to the central field of view of the projection lens is above 0.8 (see the TS of 0.0000nm curve in Figure 12), and the OTF coefficient corresponding to the 0.7 times IH field of view is above 0.5 (see the TS of 6.6000nm curve in Figure 12). The projection lens has good resolution and contrast, ensuring high imaging quality.

FIG. 13 is a modulation transfer function curve diagram of another projection lens provided in an embodiment of the present application at -30°C, and FIG. 14 is a modulation transfer function curve diagram of another projection lens provided in an embodiment of the present application at 85°C.

As shown in Figures 13 and 14, in the low temperature -30℃ and high temperature 85℃ scenes, at a spatial frequency of 12.5LP/mm, the OTF coefficient corresponding to the central field of view of the projection lens is above 0.35, and the OTF coefficient corresponding to the 0.7 times IH field of view is above 0.2. The high or low temperature environment has little effect on the imaging performance of the projection lens, realizing the athermal design of the projection lens. After focusing at room temperature, switching to an environment of -30℃ to 85℃, there is no need to focus again, and clear imaging can be achieved, with good imaging stability and reliability.

FIG. 15 is a field curvature diagram of another projection lens provided in an embodiment of the present application, and FIG. 16 is a distortion curve diagram of another projection lens provided in an embodiment of the present application.

FIG15 and FIG16 respectively show the field curvature and distortion curves of light with wavelengths of 617 nm, 525 nm and 460 nm after passing through the projection lens, where S is the field curvature in the sagittal direction and T is the field curvature in the meridional direction. It can be seen from FIG15 that the projection lens has a smaller field curvature.

As can be seen from FIG. 16 , the distortion of the projection lens is less than 3%, has relatively small distortion, and has high imaging quality, and the displayed image projected by the projection lens is not distorted.

FIG. 17 is a relative illumination curve of another projection lens provided in an embodiment of the present application.

FIG17 shows a relative illumination curve of light with a wavelength of 460 nm passing through a projection lens. As can be seen from FIG17 , the relative illumination of the projection lens is greater than 90%, the projection lens has a large luminous flux, and the brightness of the displayed image projected by the projection lens is very uniform.

Embodiment 3

In this example, the focal length f1 of the first lens is 28.2 mm, the focal length f2 of the second lens is -18.1 mm, the focal length f1 of the first lens and the focal length f2 of the second lens satisfy: |f1/f2|=1.6, the focal length f12 of the first lens group composed of the first lens and the second lens is 329.1 mm, the focal length EFL of the projection lens is 29.53 mm, and the focal length f12 of the first lens group and the focal length EFL of the projection lens satisfy: f12/EFL=11.1.

The focal length f3 of the third lens is 43.3 mm, the focal length f4 of the fourth lens is 34.3, and the focal length f3 of the third lens is greater than the focal length f4 of the fourth lens. The focal length f3 of the third lens and the focal length EFL of the projection lens satisfy: f3/EFL=1.5, and the focal length f4 of the fourth lens and the focal length EFL of the projection lens satisfy: f4/EFL=1.2.

The Abbe number of the first lens Vd1=55.31, the Abbe number of the second lens Vd2=29.91, and the Abbe number Vd1 of the first lens and the Abbe number Vd2 of the second lens satisfy: Vd1/Vd2=1.8.

The aperture number F# of the projection lens is 0.807.

The total optical length TTL of the projection lens is 55.84 mm, the maximum diameter of the projection lens is 42 mm, and the total optical length TTL of the projection lens and the focal length EFL of the projection lens satisfy: TTL/EFL=1.9.

The back focal length BFL of the projection lens is 9.00 mm, the half image height IH of the projection lens is 6.61 mm, and the back focal length BFL of the projection lens and the half image height IH of the projection lens satisfy: BFL/IH=1.4.

Table 7 below shows the optical parameters of each lens in another projection lens provided in an embodiment of the present application.

The description of each parameter in Table 7 refers to the first embodiment and will not be repeated in this embodiment.

Table 8 below shows the aspheric coefficients of each lens in another projection lens provided in an embodiment of the present application.

The optical parameters of the projection lens composed of the above lenses can be seen in Table 9 below.

Table 9 shows the optical parameters of another projection lens provided in an embodiment of the present application.

It can be seen from Table 9 that a projection lens provided in an embodiment of the present application has the characteristics of a large aperture, a large target surface, and a low total optical length, which improves the luminous flux and imaging performance of the projection lens and has a smaller volume.

FIG. 18 is a modulation transfer function curve diagram of another projection lens at room temperature provided in an embodiment of the present application.

As shown in Figure 18, at the spatial frequency of 12.5LP/mm, the optical transfer function coefficient (OTF) corresponding to the central field of view of the projection lens is above 0.8 (see the TS of 0.0000nm curve in Figure 18), and the OTF coefficient corresponding to the 0.7 times IH field of view is above 0.5 (see the TS of 6.6000nm curve in Figure 18). The projection lens has good resolution and contrast, ensuring high imaging quality.

FIG. 19 is a modulation transfer function curve diagram of another projection lens provided in an embodiment of the present application at -30°C, and FIG. 20 is a modulation transfer function curve diagram of a projection lens provided in an embodiment of the present application at 105°C.

As shown in Figures 19 and 20, in the low temperature -30℃ and high temperature 105℃ scenes, at a spatial frequency of 12.5LP/mm, the OTF coefficient corresponding to the central field of view of the projection lens is above 0.35, and the OTF coefficient corresponding to the 0.7 times IH field of view is above 0.2. The high or low temperature environment has little effect on the imaging performance of the projection lens, realizing the athermal design of the projection lens. After focusing at room temperature, switching to an environment of -30℃ to 105℃, there is no need to focus again, and clear imaging can be achieved, with good imaging stability and reliability.

FIG. 21 is a field curvature diagram of another projection lens provided in an embodiment of the present application, and FIG. 22 is a distortion curve diagram of another projection lens provided in an embodiment of the present application.

Figures 21 and 22 respectively show the field curvature and distortion curves of light with wavelengths of 617nm, 525nm and 460nm after passing through the projection lens, where S is the field curvature in the sagittal direction and T is the field curvature in the meridional direction. It can be seen from Figure 21 that the projection lens has a smaller field curvature.

As can be seen from FIG. 22 , the distortion of the projection lens is less than 3%, has relatively small distortion, and has high imaging quality, and the displayed image projected by the projection lens is not distorted.

FIG23 shows a relative illumination curve of light with a wavelength of 460 nm passing through a projection lens. As can be seen from FIG23 , the relative illumination of the projection lens is greater than 90%, the projection lens has a large luminous flux, and the brightness of the displayed image projected by the projection lens is very uniform.

Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the embodiments of the present application, rather than to limit them. Although the embodiments of the present application have been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

A projection lens, characterized in that it comprises a first lens group, wherein the first lens group comprises a first lens and a second lens, the projection lens further comprises a third lens and a second lens group, the second lens group comprises one or more fourth lenses, and along the direction of the optical axis from the projection side to the pixel side, the first lens, the second lens, the third lens and the fourth lens of the second lens group are arranged in sequence;

The focal length f1 of the first lens and the focal length f2 of the second lens satisfy the condition: 2≥|f1/f2|≥1.2, and the focal length f12 of the first lens group and the focal length EFL of the projection lens satisfy the condition: f12/EFL≥5;

The focal length f3 of the third lens and the focal length EFL of the projection lens satisfy the condition: 1.5≥f3/EFL≥0.8, the focal length f4 of the second lens group and the focal length EFL of the projection lens satisfy the condition: 1.5≥f4/EFL≥0.8, and the focal length f3 of the third lens and the focal length f4 of the second lens group satisfy the condition: f3>f4.
The projection lens according to claim 1, characterized in that the aperture number F# of the projection lens satisfies the condition: 0.6≤F#≤1.0.
The projection lens according to claim 1 or 2, characterized in that the total optical length TTL of the projection lens and the focal length EFL of the projection lens satisfy the condition: 2.5≥TTL/EFL≥1.5.
The projection lens according to any one of claims 1 to 3, characterized in that a back focal length BFL of the projection lens and a half image height of the projection lens satisfy the condition: 1.4 ≥ BFL/IH ≥ 0.6.
The projection lens according to any one of claims 1 to 4, characterized in that the Abbe number Vd1 of the first lens satisfies the condition: Vd1 ≥ 52, the Abbe number Vd2 of the second lens satisfies the condition: Vd2 ≤ 30, and the Abbe number Vd1 of the first lens and the Abbe number Vd2 of the second lens satisfy the condition: Vd1/Vd2 ≥ 1.8.
The projection lens according to any one of claims 1 to 5, characterized in that the first lens and the second lens are plastic lenses, and the third lens and the fourth lens are glass lenses.
The projection lens according to claim 6, characterized in that the first lens and the second lens are aspherical lenses, and the third lens and the fourth lens are spherical lenses.
The projection lens according to any one of claims 1 to 7, characterized in that the first lens has positive focal power, the second lens has negative focal power, the third lens has positive focal power, and the fourth lens has positive focal power.
The projection lens according to any one of claims 1 to 8, characterized in that at least a portion of a surface of the first lens facing the projection side corresponding to the optical axis is a convex surface, and at least a portion of a surface of the first lens facing the pixel side corresponding to the optical axis is a convex surface;

At least a portion of a side of the second lens facing the projection side corresponding to the optical axis is a convex surface, and at least a portion of a side of the second lens facing the pixel side corresponding to the optical axis is a concave surface;

At least a portion of a side of the third lens facing the projection side corresponding to the optical axis is a concave surface, and at least a portion of a side of the third lens facing the pixel side corresponding to the optical axis is a convex surface;

At least a portion of a surface of the fourth lens facing the projection side corresponding to the optical axis is a convex surface, and at least a portion of a surface of the fourth lens facing the pixel side corresponding to the optical axis is a concave surface.
The projection lens according to any one of claims 1 to 9, further comprising an aperture stop, wherein the aperture stop is located between the second lens and the third lens.
A projection device, characterized in that it comprises at least an image display module and the projection lens according to any one of claims 1 to 9;

The projection surface of the image display module is opposite to the fourth lens of the projection lens closest to the pixel side. The image display module is configured to form a display image and transmit the display image to the projection lens through the projection surface.
The projection device according to claim 11, characterized in that the image display module comprises a chip and a plurality of micro light emitting diodes distributed in an array on the chip.
A vehicle, characterized in that it comprises at least a vehicle body and the projection device according to claim 11 or 12, wherein the projection device is arranged on the vehicle body.