CN112666676A

CN112666676A - Imaging lens and pixel projection imaging device

Info

Publication number: CN112666676A
Application number: CN201910979655.0A
Authority: CN
Inventors: 杨志; 金如河; 王学飞; 庞宏力; 李海涛; 魏朝巧
Original assignee: Mind Electronics Appliance Co Ltd
Current assignee: Mind Electronics Appliance Co Ltd
Priority date: 2019-10-15
Filing date: 2019-10-15
Publication date: 2021-04-16

Abstract

The invention provides an imaging lens and a pixel projection imaging device, comprising: the optical lens comprises a first lens, a second lens, a third lens and a fourth lens which are arranged in sequence from an image side to an object side along the same optical axis direction, wherein the first lens, the second lens, the third lens and the fourth lens all comprise two optical surfaces, one of the two optical surfaces faces the image side, and the other optical surface faces the object side; imaging light rays sequentially pass through two optical surfaces of the fourth lens, the third lens, the second lens and the first lens from the object side direction to form images on the image side; the imaging lens and the pixel projection imaging device provided by the invention have the advantages that the utilization rate of light source light is improved, and information on the object side can be clearly projected without loss.

Description

Imaging lens and pixel projection imaging device

Technical Field

The invention relates to the field of optical lenses, in particular to an imaging lens and a pixel projection imaging device.

Background

In recent years, with the development of unmanned/automatic driving technology, it is becoming more and more necessary that an automatic vehicle transfers vehicle information or interaction function to pedestrians, vehicles and the like in the external driving environment during the driving of the vehicle, especially during night driving, a general vehicle transfers and interacts information with the outside through vehicle lights, for example, the pedestrian and other vehicles are informed of the following traveling direction through a turn signal light, and the latest concept vehicle is a vehicle using the vehicle lights, the front/rear parts of the vehicle as information expression carriers, for example, integrating liquid crystal display panels, LED (light emitting diode) dot matrix display panels at the front grilles, the rear parts and the tail lights of the vehicle, or providing pixel projection technology on the headlights, and the automobile headlight projection lighting technology has relatively more development potential because it is a visual information interaction form based on light, and the projection area, distance and experience sense are better than the display panel with limited area.

At present, the car headlight projection technology is similar to the technical scheme of the traditional entertainment video display, and the selection of the projection technology is divided into several categories, namely projection type Liquid Crystal Display (LCD) projection based on the characteristics of a liquid crystal light valve, reflective Liquid Crystal On Silicon (LCOS) projection, DLP projection technology based on the texas instrument company Digital Micromirror (DMD) of a spatial light modulator, projection technology based on a laser scanning galvanometer (Scanner MEMS), and LED light source based on a pixel level, wherein the DLP technology can achieve the highest resolution, and currently, core devices such as a car-level DMD chip, an optical lens, and LED particles are developed late but rapidly, the Scanner MEMS technology projection system is complex, but the MEMS scanning speed can achieve an adjustable resolution, the system efficiency is high, but the market application of the matched MEMS chip, laser diode, and fluorescent panel is not mature, LCD projection is not suitable for working conditions of a vehicle due to the inherent temperature characteristic of liquid crystal, so that research is less, and the application scheme of the LED light source scheme at the pixel level is simpler than other schemes.

However, no matter which of the above-mentioned technologies is adopted for realization, the optical imaging projection lens is involved, and image information on an imaging photoelectric device or an imaging light source can be projected, but when the existing imaging lens projects an image displayed on a light source, problems that the projected image looks blurry due to insufficient reduction degree, and the utilization rate of light of the light source is low, so that the projection distance is too short, and the brightness is insufficient, and the image is difficult to distinguish are caused.

Disclosure of Invention

The invention provides an imaging lens and a pixel projection imaging device, which improve the utilization rate of light of a light source and perform lossless and clear projection imaging by mutually matching a plurality of lenses.

A first aspect of the present invention provides an imaging lens including:

the optical lens comprises a first lens, a second lens, a third lens and a fourth lens which are arranged in sequence from an image side to an object side along the same optical axis direction, wherein the first lens, the second lens, the third lens and the fourth lens all comprise two optical surfaces, one of the two optical surfaces faces the image side, and the other optical surface faces the object side; imaging light rays sequentially pass through two optical surfaces of the fourth lens, the third lens, the second lens and the first lens from the object side direction to form images on the image side;

wherein the first lens has a positive focal power, the second lens has a negative focal power, the third lens has a positive focal power, the fourth lens has a positive focal power, and the refractive index of the fourth lens is greater than 1.8.

Further, the two optical surfaces of the first lens are a first optical surface and a second optical surface which are convex surfaces, the two optical surfaces of the second lens are a third optical surface and a fourth optical surface which are concave surfaces, the two optical surfaces of the third lens are a fifth optical surface and a sixth optical surface which are convex surfaces, the two optical surfaces of the fourth lens are a seventh optical surface and an eighth optical surface which are concave surfaces, the first optical surface, the third optical surface, the fifth optical surface and the seventh optical surface face an image side, and the second optical surface, the fourth optical surface, the sixth optical surface and the eighth optical surface face an object side.

Further, the imaging lens satisfies the following conditions: 2 ° < HFOV <15 °;

wherein the HFOV is a half field angle of the entire imaging lens.

Further, the imaging lens satisfies the following conditions: 40< TTL < 80;

wherein, TTL is the whole optical total length of the imaging lens.

Further, the imaging lens satisfies the following conditions: 25< EFL < 40;

and EFL is the effective focal length of the whole imaging lens.

Further, the imaging lens satisfies the following conditions: MTF > (30% @4 lp/mm);

the MTF is a modulation transfer function and is used for reflecting the overall contrast and resolution of the imaging lens;

30% @4lp/mm indicates that the contrast of the imaging lens is 0.3 at a characteristic frequency of 4 lp/mm.

A second aspect of the present invention provides a pixel projection imaging apparatus comprising: the imaging lens comprises a diaphragm, an LED light source and the imaging lens provided by the first aspect, wherein the LED light source is located on the object side of the eighth optical surface of the imaging lens, and the diaphragm is located on the image side of the first optical surface of the imaging lens.

Furthermore, the number of the pixels of the LED light source is more than 100, and the LED chips of the pixels are in a micron order.

Further, the pixel projection imaging device satisfies the following conditions: tan β > 0.7;

wherein, beta is a half field angle of the maximum light-receiving angle of the LED light source.

Further, the seventh optical surface and the eighth optical surface are aspheric, and distortion of the pixel projection imaging device is less than 3%.

The invention provides an imaging lens, which comprises a first lens, a second lens, a third lens and a fourth lens which are arranged in sequence from an image side to an object side on the same optical axis, wherein the first lens, the second lens, the third lens and the fourth lens are all provided with two optical surfaces, the first lens has positive focal power, the second lens has negative focal power, the third lens has positive focal power, the fourth lens has positive focal power, the first lens is close to the image side, the fourth lens is close to the object side, the refractive index of the fourth lens is more than 1.8, the problem that the reduction degree of a projected mirror image to an original object is not complete when the lens is used for projection imaging is solved, compared with the prior art, the high refractive index of the fourth lens can enable more light of an object side light source to enter the imaging lens, the utilization rate of the imaging lens to the light source light is improved, and the half field angle of the maximum light collection angle of the light source light on the object side is ensured, the resolution of the mirror image projected by the imaging lens is improved.

Drawings

Fig. 1 is a schematic overall structure diagram of an imaging lens according to a first embodiment of the present invention;

fig. 2 is a schematic overall structure diagram of a pixel projection imaging apparatus according to a second embodiment of the present invention;

fig. 3 is a schematic structural diagram of a pixel projection imaging apparatus according to a second embodiment of the present invention.

Description of reference numerals:

1-an imaging lens;

10-a first lens;

20-a second lens;

30-a third lens;

40-a fourth lens;

11-a first optical surface;

12-a second optical surface;

21-a third optical surface;

22-a fourth optical surface;

31-a fifth optical surface;

32-a sixth optical surface;

41-a seventh optical surface;

42-eighth optical surface.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Example one

The present embodiment provides an imaging lens 1, as shown in fig. 1, including: the first lens 10, the second lens 20, the third lens 30 and the fourth lens 40 are arranged in order from the object side to the image side along the same optical axis direction, wherein the optical axis is a symmetry axis in an optical system, and it can be understood that the central lines of the first lens 10, the second lens 20, the third lens 30 and the fourth lens 40 are arranged, and the first lens 10, the second lens 20, the third lens 30 and the fourth lens 40 are arranged in order from the object side to the image side with the central line as the symmetry axis.

Specifically, in the present embodiment, the imaging lens 1 is used for projecting an object through the lens, a side where the actual object is located is an object side, a side where the object on the object side is projected through the imaging lens 1 is an image side, and the first lens 10, the second lens 20, the third lens 30 and the fourth lens 40 are arranged in order from the image side to the object side, where the first lens 10 is close to the image side and the fourth lens 40 is close to the object side.

Alternatively, in this embodiment, the first lens 10, the second lens 20, the third lens 30 and the fourth lens 40 each have two optical surfaces, wherein the first lens 10 has a positive power, the second lens 20 has a negative power, the third lens 30 has a positive power, the fourth lens 40 has a positive power, the power represents the ability of the optical system to deflect light, or the refractive power of the imaging lens 1 to the incident parallel light beams, the positive power represents the ability to converge light, i.e., the light after passing through the lens is divergent compared to the light before entering the lens, the negative power represents the ability to diverge the light, i.e., the light after passing through the lens is divergent compared to the light before entering the lens, i.e., the first lens 10 has convergence, the second lens 20 has divergence to the light, and the third lens 30 has convergence to the light, the fourth lens 40 has a beam-converging property to light.

It should be noted that the divergence or convergence of light by a lens is represented by a lens structure, specifically, a convex lens has convergence, a concave lens has divergence, a convex lens refers to a lens with a thickness in the middle larger than the thickness of the edges of the two ends, a concave lens refers to a lens with a thickness in the middle smaller than the thickness of the edges of the two ends, however, the lens is composed of two lens surfaces, the convex lens is not a convex lens with both side lens surfaces, but the concave lens and the convex lens are the same in terms of the whole lens, therefore, even if the lens surface on one side of the lens is a convex lens and the lens surface on the other side of the lens is a concave lens, the lens is also a convex lens with positive focal power as long as the thickness of the middle of the whole lens is larger than the thickness of the edges of the end surfaces.

Optionally, in this embodiment, the refractive index of the fourth lens 40 is greater than 1.8, the fourth lens 40 is close to the object side, when the object side is projected through the imaging lens 1, light rays on the object side first enter the fourth lens 40, the refractive index of the fourth lens 40 is greater than 1.8, and when an object on the object side enters the fourth lens 40 through light, the larger the refractive index of the fourth lens 40 is, the larger the angle change representing the incident angle of the light rays entering the fourth lens 40 is, it can also be understood that the more light rays enter the fourth lens 40 from the object side are, therefore, by using the fourth lens 40 with a larger refractive index, as much light rays exiting from the object side are introduced into the fourth lens 40 as possible, and the utilization rate of light source light is improved.

It should be noted that, in the present embodiment, the high refractive index of the fourth lens 40 ensures the angle of the maximum light-receiving half-field angle, that is, the angle change amount of the object-side light source, the fourth lens 40 is a lens with positive refractive power, the fourth lens 40 has the capability of receiving light, and the light of the object-side light source enters the fourth lens 40 in a manner of diverging to the periphery, so that the incident angle of the light changes after passing through the fourth lens 40, and the included angle between the changed angular direction and the normal of the light emitted by the light source light is the half-field angle of the light-receiving angle.

The present embodiment provides an imaging lens 1, including a first lens 10, a second lens 20, a third lens 30, and a fourth lens 40 arranged in order from an image side to an object side on the same optical axis, where the first lens 10, the second lens 20, the third lens 30, and the fourth lens 40 all have two optical surfaces, where the first lens 10 has positive focal power, the second lens 20 has negative focal power, the third lens 30 has positive focal power, the fourth lens 40 has positive focal power, the first lens 10 is close to the image side, the fourth lens 40 is close to the object side, and a refractive index of the fourth lens 40 is greater than 1.8, so as to solve a problem that a reduction degree of a projected mirror image to an original object is not complete when the imaging lens projects an image, and compared with the prior art, a high refractive index of the fourth lens 40 enables more light from a light source to enter the imaging lens 1, thereby improving a utilization rate of light from the imaging lens 1 to the object side, the half field angle of the maximum light collection angle of the light source light is ensured, and the resolution of a mirror image projected by the imaging lens is improved.

Optionally, in the present embodiment, the first lens 10 includes a first optical surface 11 and a second optical surface 12 which are convex surfaces, the second lens 20 includes a third optical surface 21 and a fourth optical surface 22 which are concave surfaces, the third lens 30 includes a fifth optical surface 31 and a sixth optical surface 32 which are convex surfaces, the fourth lens 40 includes a seventh optical surface 41 which is convex surfaces and an eighth optical surface 42 which is concave surfaces, wherein the first optical surface 11, the third optical surface 21, the fifth optical surface 31 and the seventh optical surface 41 face the image side, the second optical surface 12, the fourth optical surface 22, the sixth optical surface 32 and the eighth optical surface 42 face the object side, and the lenses are composed of two optical surfaces, that is, the lens of one lens is composed of two mirror surfaces, that is, the optical surfaces, and the optical surface which is convex has the ability to collect light, the concave optical surface has the ability to spread light.

Optionally, in this embodiment of the present disclosure, the eighth optical surface 42 is a concave surface, the eighth optical surface 42 is a surface of the fourth lens 40 facing the object side, that is, an optical surface closest to the object side, and when light source light at the object side enters the imaging lens 1, the eighth optical surface 42 enters the eighth lens 42 most, in order to make light emitted by the object side light source enter the fourth lens 40 as much as possible, the eighth optical surface 42 is a concave mirror, and the seventh optical surface 41 is a convex mirror, but the ability of the eighth optical surface 42 to diverge the light beam is weaker than the ability of the seventh optical surface 41 to converge the light beam, so that the fourth lens 40 is also a convex lens with positive refractive power as a whole, thereby ensuring that the light source light at the object side is converged.

Optionally, the imaging lens 1 includes four lenses, wherein a concave lens with a divergent capability is required to balance aberration, all the lenses include a convex lens, which may have a too high requirement on the overall configuration of the imaging lens 1, in order to ensure that all the first lens 10, the second lens 20, the third lens 30, and the fourth lens 40 project an image of the object side onto the same point, so that the imaging is clear and complete, each lens needs to be designed precisely, and for convenience of adjustment, it is preferable that, in the imaging lens 1, a concave lens is provided to balance aberration, so that the results obtained by actual optical imaging and paraxial optics are the same, and aberration is avoided.

Optionally, in this embodiment, the half field angle HFOV of the imaging lens 1 satisfies: the focal length of the imaging lens 1 can be ensured by selecting a smaller angle of view, which is to say, the farther the distance from the image side of the imaging lens 1 to the lens is, and thus, the smaller the angle of view is, the larger the focal length is, that is, the smaller the angle of view is, so that the imaging lens 1 can perform long-distance projection.

Optionally, in this embodiment, the total optical length TTL of the imaging lens 1 satisfies: 40< TTL <80, where TTL is an overall optical length representing a distance from the surface on the object side to the first optical surface 11.

Optionally, in this embodiment, the effective focal length EFL of the imaging lens 1 satisfies: 25< EFL <40, EFL is an effective focal length of the imaging lens 1, and the focal length of the imaging lens 1 is generally expressed as an effective focal length, which is a value used to describe the ability of the optical system to collect light, that is, the effective focal length can be used to calculate the magnification of the imaging lens 1, i.e. the magnification relationship between the object on the object side and the image formed.

Optionally, in this embodiment, the imaging lens 1 satisfies: MTF > 30% @4lp/mm, MTF (modulation Transfer function) is an optical modulation Transfer function, M in MTF represents a ratio, namely, the maximum brightness of light minus the maximum darkness of light and the maximum brightness of light plus the maximum darkness of light, the ratio is the contrast of light, namely the meaning represented by M, generally speaking, the MTF is represented by a common MTF curve, namely a sinusoidal grating, specifically a grid with black and white intervals, and is used for reflecting the contrast of the imaging lens 1 and the resolution of the sinusoidal grating, wherein, MTF > 30% represents that the contrast of the lens is 0.3, 4lp/mm represents the resolution, namely 4 pairs of lines per millimeter can clearly distinguish 4 pairs of lines within one millimeter, wherein, the pairs of lines are worth being the sinusoidal grating, and the MTF function of the imaging lens 1 can ensure that the lens can clearly image, and imaging is not incomplete.

Example two

The present embodiment provides a pixel projection imaging apparatus, as shown in fig. 2, including: diaphragm 50, LED light source 60 and imaging lens 1 in embodiment one, wherein, imaging lens 1 includes: the optical lens assembly comprises a first lens 10, a second lens 20, a third lens 30 and a fourth lens 40 which are arranged in sequence from the image side to the object side along the same optical axis, wherein the first lens 10 is close to a diaphragm 50, the fourth lens 40 is close to an LED light source 60, the first lens 10 has positive power and comprises a first optical surface 11 and a second optical surface 12 which are convex surfaces, the second lens 20 has negative power and comprises a third optical surface 21 and a fourth optical surface 22 which are concave surfaces, the third lens 30 has positive power and comprises a fifth optical surface 31 and a sixth optical surface 32 which are convex surfaces, and the fourth lens 40 has positive power and comprises a seventh optical surface 41 which is convex surfaces and an eighth optical surface 42 which is concave surfaces.

Alternatively, in the present embodiment, the LED light source 60 is located on the object side of the eighth optical surface 42, the LED light source 60 makes the light emitted by itself enter the eighth optical surface 42 and continuously pass forward until the light exits from the first optical surface 11, and projects the LED light source 60 to the front of the pixel projection imaging device, the diaphragm 50 is located on the image side of the first optical surface 11, that is, between the first optical surface 11 and the image side, the optical cable is located on the image side of the first optical surface 11, but the diaphragm 50 acts on the whole pixel projection imaging device, the diaphragm 50 can control the light output amount of the whole pixel projection imaging device, when the light in the LED light source 60 exits from the first optical surface 11, the light exits from the whole area of the mirror surface of the first optical surface 11, and the diaphragm 50 can control the area of the light exiting from the first optical surface 11, it can be understood that the diaphragm 50 is similar to a window, the area of light exiting the window is determined by the size of the window.

Optionally, in this embodiment, the LED light source 60 is composed of a plurality of pixel points, that is, the LED light source 60 is composed of a plurality of LED light emitting diodes, and each LED light emitting diode is an LED light emitting chip, that is, a pixel point, so the LED light source 60 is a pixel-level point light source, and the specification of each LED chip is micron-level, meanwhile, the number of the pixel points composing the LED light source 60 is greater than 100, the more the number of the pixel points of the LED light source 60 is, the higher the resolution of the projected image is, and simultaneously, the reduction degree of the pixilated projection of the projected LED light source 60 can be ensured, that each pixel point in the LED light source 60 can be clearly reduced, and the projected image can be clear, therefore, the definition of the projected image can be effectively improved by adding the pixel points.

It should be noted that, in this embodiment, the resolution of the imaging lens 1 in the pixel projection imaging device is higher than the physical resolution of the pixel chip of the LED light source 60, and the LED light source 60 can be understood as the object side of the pixel projection imaging device, that is, the pixel projection imaging device actually projects the LED light source 60 as a projected original object, and the projected image is the LED light source 60 itself, so that the resolution of the imaging lens 1 is higher than the resolution of the pixel point of the LED light source 60, and thus it can be ensured that the LED light source 60 clearly restores all the pixel points of the LED light source 60 through the image projected by the imaging lens 1, the completeness of information is ensured, and lossless projection display is performed.

Optionally, in this embodiment, as shown in fig. 3, the pixel projection imaging apparatus satisfies the condition: tan beta is greater than 0.7, wherein beta is a half field angle of the maximum light receiving angle of the LED light source 60, beta is an included angle between the light entering the eighth optical surface 42 and a normal line of the light emitted by the LED light source 60, and since the light emitted by the LED light source 60 is uniformly diffused all around and is not directed toward the imaging lens 1, in order to improve the utilization rate of the light source light, the fourth lens 40 close to the LED light source 60 is a convex lens with positive focal power, and meanwhile, the refractive index of the fourth lens 40 is greater than 1.8, so that the light of the LED light source 60 can be ensured to enter the imaging lens 1 as much as possible, and the utilization rate of the light source light can be improved.

Optionally, in this embodiment, the seventh optical surface 41 and the eighth optical surface 42 are aspheric surfaces, so as to ensure that the refractive index of the fourth lens 40 can be greater than 1.8, and meanwhile, the distortion of the pixel projection imaging device is less than 3%, the distortion of the lens is actually the distortion of the lens, once the distortion rate is too high, the distortion rate of the lens imaging is too high, and a large difference is generated between the image formed by the lens and the original object, so that it is difficult for the imaging lens 1 to perform lossless restoration of the LED light source 60 clearly.

Optionally, in this embodiment, in terms of material selection of the first lens 10, the second lens 20, the third lens 30, and the fourth lens 40, generally, the fourth lens 40 closest to the LED light source 60 is made of glass, so as to avoid that heat emitted by the LED light source 60 affects performance of the fourth lens 40, meanwhile, if the first lens 10, the second lens 20, the third lens 30, and the fourth lens 40 are disposed in a relatively closed space together with the LED light source 60, in order to ensure performance of each lens, all the lenses need to be made of glass, and when the heat dissipation space is large, only the fourth lens 40 may be set to be glass, and other lenses are made of plastic.

Optionally, in this embodiment, the imaging lens 1 may include 3 to 7 lenses, that is, at least 3 lenses may be used, and at most 7 lenses are used to form the imaging lens 1, where at least one lens is required to have negative power for balancing aberration, and at least one surface of a lens closest to the LED light source 60 is aspheric, but the difficulty of implementing the 3 lenses is high, and in order to adjust the image distance, it is preferable that the imaging lens 1 is formed by 4 lenses in this embodiment.

The embodiment provides a pixel projection imaging device, which is used for projecting information displayed in an LED light source 60 through an imaging lens 1, and the utilization rate of light of a light source is improved through the arrangement of a fourth lens 40 at a high refractive index and a half field angle of a light receiving angle, so that a pixel point of the LED light source 60 is subjected to clear lossless projection.

In the present invention, unless otherwise expressly stated or limited, the terms "mounted," "connected," "secured," and the like are to be construed broadly and can, for example, be fixedly connected, detachably connected, or integrally formed; can be mechanically connected, electrically connected or can communicate with each other; either directly or indirectly through intervening media, either internally or in any other relationship. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.

In the description of the present invention, it is to be understood that the terms "comprises" and "comprising," and any variations thereof, as used herein, are intended to cover a non-exclusive inclusion, such that a process, method, system, article, or apparatus that comprises a list of steps or elements is not necessarily limited to those steps or elements expressly listed, but may include other steps or elements not expressly listed or inherent to such process, method, article, or apparatus.

Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. An imaging lens, characterized by comprising:

2. The imaging lens of claim 1, wherein the first lens comprises two optical surfaces that are a first optical surface and a second optical surface that are convex, respectively, the second lens comprises two optical surfaces that are a third optical surface and a fourth optical surface that are concave, respectively, the third lens comprises two optical surfaces that are a fifth optical surface and a sixth optical surface that are convex, respectively, and the fourth lens comprises two optical surfaces that are a seventh optical surface and an eighth optical surface that are convex and concave, respectively, wherein the first optical surface, the third optical surface, the fifth optical surface, and the seventh optical surface face the image side, and the second optical surface, the fourth optical surface, the sixth optical surface, and the eighth optical surface face the object side.

3. The imaging lens according to claim 2, characterized in that the imaging lens satisfies the following condition: 2 ° < HFOV <15 °;

wherein the HFOV is a half field angle of the entire imaging lens.

4. The imaging lens according to claim 3, characterized in that the imaging lens satisfies the following condition: 40< TTL < 80;

wherein, TTL is the whole optical total length of the imaging lens.

5. The imaging lens according to claim 4, characterized in that the imaging lens satisfies the following condition: 25< EFL < 40;

and EFL is the effective focal length of the whole imaging lens.

6. The imaging lens according to claim 5, characterized in that the imaging lens satisfies the following condition: MTF > (30% @4 lp/mm);

7. A pixel projection imaging apparatus, comprising: a diaphragm, an LED light source and the imaging lens of any one of the preceding claims 1 to 6, wherein the LED light source is located on the object side of the eighth optical surface of the imaging lens and the diaphragm is located on the image side of the first optical surface of the imaging lens.

8. The pixel projection imaging device according to claim 7, wherein the number of the pixels of the LED light source is greater than 100, and the LED chips of the pixels are in micron order.

9. The pixel projection imaging apparatus according to claim 8, wherein the pixel projection imaging apparatus satisfies the following condition: tan β > 0.7;

10. The pixel projection imaging device according to claim 9, wherein seventh optical surface and the eighth optical surface are aspheric and the distortion of the pixel projection imaging device is less than 3%.