A projection lens for ar-hud

Abstract

This invention provides a projection lens for an AR-HUD, comprising: a first lens group, an aperture stop, a second lens group, a beam splitter, a protective glass, and an image source arranged sequentially; the first lens group is used to adjust the projection field of view and balance the system field curvature; the second lens group is used to balance system aberrations and chromatic aberrations; the aperture stop is used to control the amount of light entering the image source; the beam splitter is used to split the light emitted from the image source; the image source is used to emit light; and the protective glass is used to protect the image source; the first lens group includes: a first lens, a second lens, a third lens, and a fourth lens arranged sequentially; the front surface of the first lens is tilted at -12° to the projection surface; the second lens group includes: a fifth lens, a sixth lens, and a seventh lens arranged sequentially; the rear surface of the seventh lens is tilted at -0.76°. This invention solves the problem in the prior art where a bright spot can be seen at the lens exit pupil when looking through the diffuser, resulting in low image quality.

Description

Technical Field

[0001] This invention relates to the field of light projection technology, and in particular to a projection lens for AR-HUD. Background Technology

[0002] HUD, or Head-Up Display, is a technology that evolved from reflector sights. Before World War II, it was used on gun sights and fighter jet sights. After World War II, HUD technology began to be gradually applied to fighter jets, displaying speed, altitude, radar information, and sight information on the cockpit canopy or transparent panel. In the 21st century, HUD technology has begun to be widely used in automobiles, projecting vehicle speed, navigation information, and other data onto the windshield in real time, greatly improving driving safety and the human-machine interaction experience.

[0003] The PGU is the image source for the HUD and is the core component of the HUD. There are various solutions, such as TFT screen and DLP with diffusion film.

[0004] AR-HUD, or Augmented Reality Head-Up Display, has a wider field of view and a longer projection distance than a regular HUD. This allows AR-HUD to highly integrate projected information with the traffic environment, making it an important component of intelligent driving and smart cockpit solutions.

[0005] Most existing HUDs use TFT technology, but due to issues such as sunlight backflow, it is impossible to increase the field of view and projection distance of the HUD, making it difficult to meet the requirements of AR-HUD for a large field of view and a large projection distance.

[0006] The DLP solution with a diffuser film can effectively prevent sunlight backflow, allowing for a wider field of view and projection distance, which better meets the needs of AR-HUDs. However, the diffuser film cannot completely disperse the light randomly; looking through the diffuser film at the lens, a bright spot can be seen at the lens exit pupil, resulting in low image quality, which will greatly affect the final display effect of the HUD. Summary of the Invention

[0007] In order to overcome the shortcomings of the prior art, the purpose of this invention is to provide a projection lens for AR-HUD, which solves the problem in the prior art that the diffusion film in AR-HUD cannot completely and randomly disperse the light, and the bright spot of the lens exit pupil can be seen when looking at the lens through the diffusion film, resulting in low image quality.

[0008] To achieve the above objectives, the present invention provides the following solution:

[0009] A projection lens for AR-HUD, comprising:

[0010] The first lens group, aperture stop, second lens group, beam splitter, protective glass and image source are arranged in sequence;

[0011] The first lens group is used to adjust the size of the projection field of view and balance the field curvature of the system; the second lens group is used to balance the aberrations and chromatic aberrations of the system; the aperture is used to control the amount of light entering the light emitted by the image source; the beam splitter is used to split the light emitted by the image source; the image source is used to emit light; and the protective glass is used to protect the image source.

[0012] The first lens group includes: a first lens, a second lens, a third lens, and a fourth lens arranged in sequence; the front surface of the first lens is inclined at -12° to the projection plane;

[0013] The second lens group includes a fifth lens, a sixth lens, and a seventh lens arranged in sequence; the rear surface of the seventh lens is tilted at -0.76°.

[0014] Preferably, the first and second lenses are both negative power lenses, the third, fourth and seventh lenses are all positive power lenses, and the fifth and sixth lenses are negative power cemented doublet lenses.

[0015] Preferably, the ratio of the focal length of the first lens group to the focal length of the projection lens is 1.559, the ratio of the focal length of the first lens to the focal length of the first lens group is -1.605, the ratio of the focal length of the second lens to the focal length of the first lens group is -1.409, the ratio of the focal length of the third lens to the focal length of the first lens group is 1.646, and the ratio of the focal length of the fourth lens to the focal length of the first lens group is 1.458.

[0016] Preferably, the ratio of the focal length of the second lens group to the focal length of the projection lens is 1.185, the ratio of the focal length of the fifth and sixth lenses to the focal length of the second lens group is -1.524, and the ratio of the focal length of the seventh lens to the focal length of the second lens group is 0.976.

[0017] Preferably, the first to seventh lenses are all glass lenses.

[0018] Preferably, the relative illumination of the projection lens is greater than 80% across the entire field of view, and the MTF of the projection lens across the entire field of view is greater than 70%.

[0019] Preferably, the distortion of the projection lens is less than 0.6%, and the TV distortion of the projection lens is less than 0.3%.

[0020] Preferably, the DMD chip of the projection lens is 0.3 inches and the model is DLP3030.

[0021] According to specific embodiments provided by the present invention, the present invention discloses the following technical effects:

[0022] This invention provides a projection lens for AR-HUD. By setting a lens with 100% off-axis projection and a 12° tilt, this invention improves the image quality of the projection lens and reduces the cost of the lens. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 A projection lens structure diagram for AR-HUD provided in an embodiment of the present invention;

[0025] Figure 2 A schematic diagram of the large off-axis and tilted projection of the projection lens provided in an embodiment of the present invention;

[0026] Figure 3 Spatial frequency MTF diagram provided for embodiments of the present invention;

[0027] Figure 4 A chromatic aberration diagram provided in an embodiment of the present invention;

[0028] Figure 5 The field curvature evaluation diagram provided in the embodiments of the present invention;

[0029] Figure 6 The distortion evaluation diagram is provided for an embodiment of the present invention.

[0030] Explanation of reference numerals in the attached figures:

[0031] 1-First lens group, 2-Second lens group, 3-Aperture stop, 4-Light and shadow device, 5-Protective glass, 6-Image source, G1-First lens, G2-Second lens, G3-Third lens, G4-Fourth lens, G5-Fifth lens, G6-Sixth lens, GM7-Seventh lens. Detailed Implementation

[0032] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0033] The purpose of this invention is to provide a projection lens for AR-HUD, which solves the problem in the prior art that in AR-HUD, the diffuser film cannot completely and randomly disperse the light, resulting in a bright spot visible at the lens exit pupil when looking through the diffuser film, leading to low image quality.

[0034] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0035] like Figure 1 As shown, the present invention provides a projection lens for AR-HUD, comprising:

[0036] The first lens group 1, the aperture 3, the second lens group 2, the beam splitter 4, the protective glass 5, and the image source 6 are arranged in sequence. The first lens group 1 is located in front of the aperture 3, and the second lens group 2 is located after the aperture 3.

[0037] The first lens group 1 is used to adjust the size of the projection field of view and balance the field curvature of the system; the second lens group 2 is used to balance the aberrations and chromatic aberrations of the system; the aperture 3 is used to control the amount of light entering the light emitted by the image source 6; the beam splitter 4 is used to split the light emitted by the image source 6; the image source 6 is used to emit light; and the protective glass 5 is used to protect the image source 6.

[0038] like Figure 2 As shown, the first lens group 1 includes a first lens G1, a second lens G2, a third lens G3, and a fourth lens G4 arranged sequentially; the front surface of the first lens G1 is inclined at -12° to the projection plane; the inclination direction is lateral coordinate inclination. The lens has a 100% offset, and the lens is inclined at 12° to the diffuser (projection plane).

[0039] The second lens group 2 includes a fifth lens G5, a sixth lens G6, and a seventh lens GM7 arranged in sequence; the rear surface of the seventh lens GM7 is tilted at -0.76°, and the S1 surface (front) and S2 surface (back) of the seventh lens GM7 are both aspherical. The optical elements of the lens behind GM7 are tilted at -0.76 degrees to the first and second lens groups in front.

[0040] Furthermore, the first lens G1 and the second lens G2 are both negative power lenses, the third lens G3, the fourth lens G4 and the seventh lens GM7 are all positive power lenses, and the fifth lens G5 and the sixth lens G6 are negative power cemented doublet lenses, which can effectively eliminate system chromatic aberration.

[0041] Furthermore, the ratio of the focal length of the first lens group 1 to the focal length of the projection lens is 1.559, the ratio of the focal length of the first lens G1 to the focal length of the first lens group 1 is -1.605, the ratio of the focal length of the second lens G2 to the focal length of the first lens group 1 is -1.409, the ratio of the focal length of the third lens G3 to the focal length of the first lens group 1 is 1.646, and the ratio of the focal length of the fourth lens G4 to the focal length of the first lens group 1 is 1.458.

[0042] Furthermore, the ratio of the focal length of the second lens group 2 to the focal length of the projection lens is 1.185, the ratio of the focal length of the fifth lens G5 and the sixth lens G6 to the focal length of the second lens group 2 is -1.524, and the ratio of the focal length of the seventh lens GM7 to the focal length of the second lens group 2 is 0.976.

[0043] Furthermore, all lenses from the first lens G1 to the seventh lens GM7 are glass lenses, exhibiting excellent temperature drift properties and maintaining very good image quality even at temperatures ranging from -40℃ to 85℃. Table 1 shows the specific parameters of the objective lens system, as detailed below:

[0044] Table 1. Specific parameters of the objective lens system

[0045]

[0046]

[0047] Table 2 shows the coefficients for P2 and GM7 aspherical lenses, as shown below:

[0048] Table 2. Coefficients of P2 and GM7 for Aspherical Lenses

[0049]

[0050] Where C is the curvature, K is the reciprocal of the radius of curvature, and P is the conic coefficient. 2 represents the plastic lens.

[0051] Furthermore, the relative illumination of the projection lens is greater than 80% across the entire field of view, and the MTF of the projection lens across the entire field of view is greater than 70%.

[0052] Specifically, such as Figure 3As shown, MTF (Modulation Transfer Function) is currently the most accurate and scientific evaluation standard for lenses. The vertical axis represents contrast ratio; the closer it is to 1, the better the lens image quality. The horizontal axis represents resolution, measured in line pairs per millimeter. The image source used in this embodiment has a pixel size of 7.6µm, corresponding to a design resolution of 66 line pairs per millimeter. Projection lenses generally require an MTF value of at least 0.3 for each field of view at the design resolution, while in this embodiment, the MTF values ​​for each field of view at each zoom position are all above 0.7.

[0053] Figure 4 This is a chromatic aberration diagram of the lens, with the vertical axis representing the image height field of view value and the horizontal axis representing the numerical value, in micrometers. The diagram plots the chromatic aberration values ​​for each field of view between blue, red, and green light (dominant wavelengths) based on the dominant wavelength. Projection lenses generally require the chromatic aberration value to be within 6 pixels of an image source. In this embodiment, the chromatic aberration is controlled to be within 3µm, which is less than 0.4 pixels (pixel size 7.6µm).

[0054] Furthermore, the distortion of the projection lens is less than 0.6%, and the TV distortion of the projection lens is less than 0.3%.

[0055] Specifically, Figure 5 This is a performance evaluation chart. Figure 6 This is a distortion evaluation diagram. The vertical axis represents the field of view of the lens. The horizontal axis of the field curvature diagram represents the magnitude of the field curvature value, and the horizontal axis of the distortion diagram represents the distortion amount. Distortion is a very important indicator for projection lenses, generally requiring control within 3%, while TV distortion is required to be controlled within 1%. The distortion shape of the embodiments in this application enables the system TV distortion to be very small, with system distortion within 0.6% and TV distortion within 0.3%.

[0056] Furthermore, the projection lens uses a 0.3-inch DMD chip, model DLP3030, and has an F-number of 2.4. The F-number of the lens can also be written as F#; the smaller the F-number, the larger the aperture.

[0057] This embodiment also specifically discloses:

[0058] Optical lenses satisfy the following condition:

[0059] 0.8 <ENPD / IH<0.9 (1)

[0060] Wherein, EPND represents the aperture of the optical lens, and IH represents the actual half-image height of the optical lens.

[0061] When condition (1) is met, a reasonable balance between the large light transmission capacity and the large imaging surface of the lens can be achieved.

[0062] In the implementation method, the optical lens satisfies the following condition:

[0063] 1.1mm -1 <T L / f / IH<1.3mm -1 (2)

[0064] Among them, T L The optical total length of the optical lens is represented by f, the effective focal length of the optical lens is represented by f, and the actual half-image height of the optical lens is represented by IH.

[0065] When condition (2) is satisfied, the relationship between the total length of the lens and its resolving power can be reasonably balanced. L When the / f / IH value exceeds the upper limit, the overall length of the lens is too large, or in other words, if the overall length is shortened, the image height will be insufficient; T L When the value of / f / IH exceeds the lower limit, the lens aberration correction becomes difficult due to the excessive optical focal length of each lens, and the resolving power decreases significantly.

[0066] In the implementation method, the optical lens satisfies the following condition:

[0067] 9.5mm <IH / tanθ<10mm (3)

[0068] Where f represents the effective focal length of the optical lens, and θ represents the half field of view of the optical lens.

[0069] When condition (3) is met, the distortion of the optical lens can be reasonably limited, reducing the difficulty of distortion correction. When the value of IH / tanθ exceeds the lower limit, the distortion of the lens will increase in the negative direction; when the value of IH / tanθ exceeds the upper limit, the distortion of the lens will increase in the positive direction.

[0070] In the implementation method, the optical lens satisfies the following condition:

[0071] CRA<1° (4)

[0072] Wherein, CRA represents the angle of incidence of the principal ray on the imaging plane of the optical lens.

[0073] When condition (4) is met, it can be well matched with the DMD chip and achieve good projection effect.

[0074] The beneficial effects of this invention are as follows:

[0075] The AR-HUD projection lens disclosed in this invention has a 100% offset and is tilted at 12° to the diffusion film (projection surface), which can effectively avoid the appearance of bright spots in the diffusion film.

[0076] The AR-HUD projection lens disclosed in this invention has an optical element behind the GM8 that is tilted by -0.76 degrees to the first and second lens groups in front, which can effectively balance the image quality loss caused by the tilt of the lens and diffuser. At the same time, because the prism (beam splitter) and DMD (protective glass and image source) are tilted together, the influence of tilt on the lighting system is avoided.

[0077] The AR-HUD projection lens disclosed in this invention has a small overall length, which easily meets the requirements for AR-HUD installation in vehicles.

[0078] The AR-HUD projection lens disclosed in this invention has a relative illumination of over 80% across the entire field of view and a MTF of over 0.7 across the entire field of view, resulting in excellent image quality. Distortion can be reduced to within 0.6%, and TV distortion is within 0.3%, demonstrating excellent distortion correction.

[0079] The AR-HUD projection lens disclosed in this invention uses an all-glass lens, which effectively reduces lens temperature drift and maintains excellent image quality performance at temperatures ranging from -40℃ to 85℃.

[0080] The AR-HUD projection lens disclosed in this invention has a simple structure, low tolerance sensitivity, and uses only 7 lenses, which effectively reduces lens cost and assembly difficulty.

[0081] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0082] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. Furthermore, those skilled in the art will recognize that, based on the ideas of the present invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A projection lens for an AR-HUD, characterized in that, include: The first lens group, aperture stop, second lens group, beam splitter, protective glass and image source are arranged in sequence; The first lens group consists of a first lens, a second lens, a third lens, and a fourth lens arranged in sequence; the front surface of the first lens is inclined at -12° to the projection plane; The second lens group consists of a fifth lens, a sixth lens, and a seventh lens arranged in sequence; the rear surface of the seventh lens is inclined at -0.76°. The first and second lenses are both negative power lenses, the third, fourth and seventh lenses are all positive power lenses, and the fifth and sixth lenses are negative power cemented doublet lenses; the ratio of the focal length of the first lens group to the focal length of the projection lens is 1.559; the ratio of the focal length of the second lens group to the focal length of the projection lens is 1.

185.

2. The projection lens for AR-HUD according to claim 1, wherein, The ratio of the focal length of the first lens to the focal length of the first lens group is -1.605, the ratio of the focal length of the second lens to the focal length of the first lens group is -1.409, the ratio of the focal length of the third lens to the focal length of the first lens group is 1.646, and the ratio of the focal length of the fourth lens to the focal length of the first lens group is 1.

458.

3. The projection lens for AR-HUD according to claim 1, wherein, The ratio of the focal length of the fifth and sixth lenses to the focal length of the second lens group is -1.524, and the ratio of the focal length of the seventh lens to the focal length of the second lens group is 0.

976.

4. The projection lens for AR-HUD according to claim 1, wherein, The first to the seventh lenses are all glass lenses.

5. A projection lens for AR-HUD according to claim 1, characterized in that, The relative illumination of the projection lens is greater than 80% across the entire field of view, and the MTF of the projection lens across the entire field of view is greater than 70%.

6. The projection lens for AR-HUD according to claim 1, wherein The distortion of the projection lens is less than 0.6%, and the TV distortion of the projection lens is less than 0.3%.

7. The projection lens for AR-HUD according to claim 1, wherein The projection lens has a 0.3-inch DMD chip, model DLP3030.

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