Projection lens and projection illumination system

Abstract

The invention discloses a projection lens and a projection illumination system. The projection lens comprises a first lens, a second lens, a third lens and a fourth lens which are coaxially arranged in sequence from an image side to an object side, the diopter of the first lens is negative, the diopter of the second lens is negative, the diopter of the third lens is positive, and the diopter of the fourth lens is positive. By limiting the ratio of the focal length of an optical system to TTL * F.NO, the projection lens can be ensured to have the characteristic of large aperture, the size of the lens is effectively reduced, the ultrathin characteristic and miniaturization of projection are realized, the total length of the projection lens along the optical axis direction is reduced to be less than 23mm, the size of the projection lens is reduced, and the size of the projection lens is reduced. Therefore, the lamp is more suitable for the welcome lamp of the vehicle.

Description

Technical Field

[0001] The present invention relates to the field of projection technology, and in particular to a projection lens and a projection lighting system. Background Art

[0002] Laser projection display technology, also known as laser projection technology or laser display technology, is a display technology that uses red, green and blue primary color lasers as light sources, which can reproduce the rich colors of the objective world in the most realistic way. With the development of laser projection technology, its application requirements are becoming more and more diversified. In different application scenarios, the performance requirements for projection lenses are also different.

[0003] With the rapid development of smart cars, the application scenarios of in-vehicle projection systems are becoming more and more diverse. Dynamic display welcome light carpets are popular among users as a very ceremonial configuration, but current projection lighting products can only display simple icon content and cannot achieve dynamic display of arbitrary content. Summary of the invention

[0004] An embodiment of the present invention provides a projection lens, comprising: a first lens, a second lens, a third lens and a fourth lens coaxially arranged in sequence from an image side to an object side;

[0005] Wherein, the refractive power of the first lens is negative, the refractive power of the second lens is negative, the refractive power of the third lens is positive, and the refractive power of the fourth lens is positive;

[0006] The projection lens satisfies the following relationship:

[0007]

[0008] f represents the focal length of the projection lens, TTL represents the length of the projection lens on the optical axis, and F.NO represents the aperture value of the projection lens.

[0009] In some embodiments of the present invention, the first lens and the third lens are aspherical lenses, and the second lens and the fourth lens are spherical lenses;

[0010] The first lens and the third lens are made of glass.

[0011] In some embodiments of the present invention, the first lens satisfies:

[0012] 0.2≤ct1 / et1≤0.6;

[0013] f1≤-10mm;

[0014] Wherein, ct1 represents the center thickness of the first lens along the optical axis, et1 represents the edge thickness of the first lens along the optical axis, and f1 represents the focal length of the first lens.

[0015] In some embodiments of the present invention, the second lens satisfies:

[0016] 0.4≤ct2 / et2≤0.8;

[0017] f2≥-100mm;

[0018] Wherein, ct2 represents the center thickness of the second lens along the optical axis, et2 represents the edge thickness of the second lens along the optical axis, and f2 represents the focal length of the second lens.

[0019] In some embodiments of the present invention, the third lens satisfies:

[0020] 2≤|c36-c37|≤10;

[0021] Wherein, c36 represents the curvature radius of the image-side surface of the third lens, and c37 represents the curvature radius of the object-side surface of the third lens.

[0022] In some embodiments of the present invention, the fourth lens satisfies:

[0023] 0.2≤ct4 / et4≤0.6;

[0024] Wherein, ct4 represents the center thickness of the fourth lens along the optical axis, and et2 represents the edge thickness of the fourth lens along the optical axis.

[0025] In some embodiments of the present invention, the projection lens satisfies the following relationship:

[0026] 0.4≤(CT1+CT3) / ∑CT≤0.9;

[0027] Wherein, CT1 represents the center thickness of the first lens along the optical axis, CT3 represents the center thickness of the third lens along the optical axis, and ΣCT represents the sum of the center thicknesses of the first lens, the second lens and the third lens along the optical axis.

[0028] In some embodiments of the present invention, the present invention further includes:

[0029] The aperture stop is located between the second lens and the third lens.

[0030] The embodiment of the present invention further provides a projection lighting system, which is installed at a rearview mirror, a turn signal lamp or a tail light of a vehicle and is used to project an image onto the ground near the vehicle;

[0031] The projection lighting system comprises:

[0032] A three-color laser light source device for emitting projection light;

[0033] An illumination system, located at the light-emitting side of the three-color laser light source device; the illumination system includes a light homogenization component and a light modulation component;

[0034] The projection lens is located at the light-emitting side of the light modulation component; the projection lens is any one of the above-mentioned projection lenses.

[0035] In some embodiments of the present invention, the light uniforming component adopts a fly-eye lens group; the lighting system further comprises a reflecting component, which is located at the light-emitting side of the fly-eye lens group and is used to receive the emitted light of the fly-eye lens group and reflect it to the light modulation component;

[0036] The fourth lens of the projection lens is a field lens, and the fourth lens is arranged adjacent to the light modulation component.

[0037] The projection lens and projection illumination system provided by the embodiments of the present invention include: a first lens, a second lens, a third lens and a fourth lens coaxially arranged in sequence from the image side to the object side; wherein the refractive power of the first lens is negative, the refractive power of the second lens is negative, the refractive power of the third lens is positive, and the refractive power of the fourth lens is positive; the projection lens satisfies: By limiting the ratio of the focal length of the optical system to TTL×F.NO, the projection lens can be guaranteed to have a large aperture while effectively reducing the size of the lens, achieving ultra-thin characteristics and miniaturization of the projection, and reducing the total length of the projection lens along the optical axis to less than 23mm, thereby reducing the size of the projection lens and making it more suitable for use in vehicle welcome lights. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for use in the embodiments of the present invention will be briefly introduced below. Obviously, the accompanying drawings introduced below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0039] Figure 1 A schematic diagram of the structure of a projection lens provided by an embodiment of the present invention;

[0040] Figure 2 A ray tracing diagram provided by an embodiment of the present invention;

[0041] Figure 3 A modulation transfer function curve diagram provided by an embodiment of the present invention;

[0042] Figure 4A defocus curve diagram provided by an embodiment of the present invention;

[0043] Figure 5 A spot diagram provided for an embodiment of the present invention;

[0044] Figure 6 A vertical axis chromatic aberration diagram provided by an embodiment of the present invention;

[0045] Figure 7 A schematic diagram of a field curvature curve provided by an embodiment of the present invention;

[0046] Figure 8 A schematic diagram of a distortion curve provided by an embodiment of the present invention;

[0047] Fig. 9 A schematic diagram of a telecentricity curve provided by an embodiment of the present invention;

[0048] Fig.10 A schematic diagram of the installation position of the projection illumination system provided by an embodiment of the present invention;

[0049] Fig.11 A schematic diagram of the structure of a projection illumination system provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0050] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and understandable, the present invention will be further described below with reference to the accompanying drawings and examples. However, the exemplary embodiments can be implemented in various forms and should not be understood as being limited to the embodiments described herein; on the contrary, these embodiments are provided to make the present invention more comprehensive and complete, and to fully convey the concepts of the exemplary embodiments to those skilled in the art. The same figure marks in the figures represent the same or similar structures, and thus their repeated descriptions will be omitted. The words expressing position and direction described in the present invention are all explained using the accompanying drawings as examples, but changes can be made as needed, and the changes made are all included in the scope of protection of the present invention. The drawings of the present invention are only used to illustrate the relative position relationship and do not represent the true proportions.

[0051] With the rapid development of smart cars, the application scenarios of vehicle projection systems are becoming more and more diverse. The dynamic display welcome light carpet is popular among users as a very ceremonial configuration. If the projection lighting products are used in combination with the vehicle's welcome lights, they can provide important safety value. For example, the projection lighting system can be installed on the vehicle's rearview mirror, turn signal or taillight to project images onto the ground near the vehicle, making the driver's intentions highly visualized and clearly presented to pedestrians, cyclists, and people using other means of transportation on the road, improving driving safety.

[0052] The embodiment of the present invention aims at this application scenario and proposes a projection lens and a projection lighting system. For the projection lens used for the welcome light, more attention is often paid to indicators such as its field of view angle, volume and cost. The embodiment of the present invention also uses these indicators as constraints to reasonably design the projection lens.

[0053] Figure 1 A schematic diagram of the structure of a projection lens provided by an embodiment of the present invention.

[0054] like Figure 1 As shown, the projection lens provided by the embodiment of the present invention comprises: a first lens l1, a second lens l2, a third lens l3 and a fourth lens l4 which are coaxially arranged in sequence from the image side to the object side; wherein the refractive power of the first lens l1 is negative, the refractive power of the second lens l2 is negative, the refractive power of the third lens l3 is positive, and the refractive power of the fourth lens l4 is positive.

[0055] It is worth mentioning that when performing the optical design of the projection lens, the imaging position is taken as the object plane, and the light modulation component is taken as the image plane for optical design. Then, by utilizing the principle of reversible optical path, a projection display that meets the designed size and image quality can be achieved on the designed object plane.

[0056] In the embodiment of the present invention, the projection lens satisfies the following relationship:

[0057]

[0058] Among them, f represents the focal length of the projection lens, TTL represents the length of the projection lens on the optical axis, and F.NO represents the aperture value of the projection lens. By limiting the ratio of the focal length of the optical system to TTL×F.NO, the projection lens can be guaranteed to have a large aperture while effectively reducing the size of the lens, achieving the ultra-thin characteristics and miniaturization of the projection, and reducing the total length of the projection lens along the optical axis to less than 23mm, thereby reducing the size of the projection lens and making it more suitable for the vehicle welcome light.

[0059] like Figure 1 As shown, the projection lens further includes an aperture s, which is located between the second lens 12 and the third lens 13, and the first lens 11, the second lens 12, the aperture s, the third lens 13 and the fourth lens 14 are coaxially arranged. The aperture s can limit the field of view and eliminate stray light.

[0060] In the embodiment of the present invention, the first lens l1 and the third lens l3 are aspherical lenses made of glass; the second lens l2 and the fourth lens l4 are spherical lenses. The projection lens only includes four lenses, and only two aspherical lenses are needed to have better imaging quality. The optical system structure is simple and compact, and the total length of the lens can be reduced to less than 23 mm.

[0061] Among them, the first lens l1 satisfies:

[0062] 0.2≤ct1 / et1≤0.6;

[0063] f1≤-10mm;

[0064] ct1 represents the center thickness of the first lens l1 along the optical axis, et1 represents the edge thickness of the first lens l1 along the optical axis, and f1 represents the focal length of the first lens l1.

[0065] By controlling the parameters of the first lens l1 to meet the above ranges and controlling the incident and outgoing light angles on the surface of the first lens l1 to be ≤60°, the processability of the first lens can be ensured and excessive curvature can be avoided.

[0066] The second lens l2 satisfies:

[0067] 0.4≤ct2 / et2≤0.8;

[0068] f2≥-100mm;

[0069] Wherein, ct2 represents the center thickness of the second lens L2 along the optical axis, et2 represents the edge thickness of the second lens L2 along the optical axis, and f2 represents the focal length of the second lens L2.

[0070] By controlling the parameters of the second lens L2 to satisfy the above range, the light angle can be properly controlled.

[0071] The third lens l3 satisfies:

[0072] 2≤|c36-c37|≤10;

[0073] Wherein, c36 represents the curvature radius of the image-side surface of the third lens L3, and c37 represents the curvature radius of the object-side surface of the third lens L3.

[0074] By controlling the parameters of the third lens L3 to meet the above range, the size of the projection lens can be effectively reduced, the optical power of the projection lens can be reasonably distributed, and it is beneficial to control the aberrations of other lenses while maintaining the processing properties of the third lens L3.

[0075] The fourth lens l4 satisfies:

[0076] 0.2≤ct4 / et4≤0.6;

[0077] Wherein, ct4 represents the center thickness of the fourth lens L4 along the optical axis, and et2 represents the edge thickness of the fourth lens L4 along the optical axis.

[0078] By controlling the parameters of the fourth lens element L4 to meet the above range, the principal ray angle can be compressed to form a telecentric optical path on the image side (when designed), thereby compensating for the field curvature and distortion of the optical system.

[0079] The projection lens satisfies the following relationship:

[0080] 0.4≤(CT1+CT3) / ∑CT≤0.9;

[0081] Wherein, CT1 represents the center thickness of the first lens l1 along the optical axis, CT3 represents the center thickness of the third lens l3 along the optical axis, and ΣCT represents the sum of the center thicknesses of the first lens l1, the second lens l2 and the third lens l3 along the optical axis.

[0082] By reasonably controlling the proportion of the center thickness of the first lens L1 and the third lens L3 to the center thickness of the first lens L1, the second lens L2 and the third lens L3, it is beneficial to reasonably distribute the optical power of the optical system, improve the spherical aberration and aberration of the optical system, and enhance the structural stability of the optical system.

[0083] The field of view (FOV) of the projection lens provided in the embodiment of the present invention reaches 70°. The projection ratio is the ratio of the width of the lens projection screen to the projection distance. The projection ratio of the projection lens provided in the embodiment of the present invention is 1.2, which is a more comfortable projection ratio value when used. The projection lens has a certain depth of field, does not need to adjust the back focus of the lens, and can be compatible with clear imaging at a distance of 800mm to 1200mm. The length of the projection lens is controlled below 23mm, which can greatly reduce the size of the projection lens, and then reduce the volume of the optical engine including the projection lens in the projection system, realize the miniaturization of the micro-projection system, and at the same time, the structure is simple to achieve the low-cost design goal. The F.NO of the lens characterizes the light collection ability of the lens. The larger the value, the smaller the light collection angle, and vice versa. The F.NO of the projection lens provided in the embodiment of the present invention is 2.4, which has a strong light collection ability and a large luminous flux, and the relative illumination is greater than 85%. The projection lens provided in the embodiment of the present invention can also be applied to the full-color laser spectrum. For the laser projection system, chromatic aberration is an important indicator affecting its projection quality. Chromatic aberration is caused by the different refractive indices of light of different wavelengths. The chromatic aberration of the projection lens provided in the embodiment of the present invention is less than 1 pixel, i.e., 0.007 mm, and has the advantage of small chromatic aberration.

[0084] In some embodiments, the projection lens provided by the embodiments of the present invention is used in conjunction with a digital light processing (DLP) system, wherein a digital micromirror device (DMD) is used as a light modulation component. Usually, the surface of the DMD also has a protective glass. When the display surface of the DMD is used as the image surface for optical design, the surface shape, curvature radius, thickness, material and other parameters of each optical component in the projection lens are shown in the following table, where the surface number is the order from the object surface to the image surface during optical design:

[0085] Face number Face type Radius of curvature thickness Material Semi-aperture OBJ Spherical unlimited unlimited S1 Aspheric 7.6 1.5 1.54；90.5 refraction 3.2 S2 Aspheric 1.8 3 refraction 2.2 S3 Spherical 9.5 3.8 1.79；24.2 refraction 1.6 S4 Spherical 6.8 0.8 refraction 1.6 S5 aperture Spherical unlimited 0.3 1.6 S6 Aspheric 6.6 3 1.58；84 refraction 2 S7 Aspheric -2.9 8 refraction 2 S8 Spherical 9 2 1.74；45.339 refraction 3 S9 Spherical unlimited 0.35 refraction 2.8 S10 Spherical unlimited 0.7 1.51；52.911 refraction 2.8 S11 Spherical unlimited 0.3 refraction 2.7 S12 Spherical unlimited 2.6

[0086] The coefficients for aspherical surfaces are as follows:

[0087] surface S2 S3 S6 S7 Conic surface constant -5.162 -0.837 3.995 10.44 1st order coefficient 0 0 0 0 2nd order coefficient 0.023 0.026 8.215E-03 0.026 3rd order coefficient 0 0 0 0 4th order coefficients -1.3E-03 1.3E-03 1.6E-04 -7E-04 5th order coefficient 0 0 0 0 6th order coefficient 1.4E-05 1.6E-04 6.2E-04 -1.7E-05 7th order coefficients 0 0 0 0 8th order coefficient -7.8E-03 6.7E-06 -2.7E-05 -9.2E-06 9th order coefficient 0 0 0 0 10th order coefficient 1.56E-06 -1.4E-06 -5.2E-06 4.2E-06 11th order coefficients 0 0 0 0 12th order coefficients -1.9E-17 2.1E-10 -1E-13 4.2E-13 13th order coefficients 0 0 0 0 14th order coefficients -3.5E-21 -2.9E-16 -2.1E-14 2.4E-12

[0088] The projection lens designed based on the above parameters is a miniature telephoto lens with a throw ratio of 1.2 and an effective focal length of 4 mm. The offset of the projection lens, i.e., the offset range between the projection lens and the center of the light modulation component, is 0. The resolution of the projection lens can reach 66 lp / mm, the projection distance is 1 m, the field of view of the projection lens can reach 70° (the field of view here refers to the diagonal field of view DFOV of the projection lens), and the chromatic aberration of the projection lens is less than 1 pixel.

[0089] The embodiment of the present invention also uses optical design software to simulate the light path in the projection lens. Figure 2 A ray tracing diagram provided by an embodiment of the present invention.

[0090] like Figure 1 and Figure 2 As shown, the light modulation component 21 is located at the light incident side of the projection lens, and the fourth lens 14 in the projection lens is arranged adjacent to the light modulation component 21. The embodiment of the present invention is described by taking the light modulation component 21 as an example of using a DMD, and a protective glass is further arranged on the light exiting side of the light modulation component 21. The modulated light emitted from the display surface of the light modulation component 21 first passes through the protective glass, and then enters the projection lens from the side of the fourth lens 14 of the projection lens.

[0091] The embodiment of the present invention also evaluates the image quality of the projection lens based on the above ray tracing results.

[0092] Figure 3 This is a modulation transfer function curve diagram provided by an embodiment of the present invention.

[0093] Figure 3The Modulation Transfer Function (MTF) curves of light with wavelengths of 0.4650 μm to 0.6430 μm in different fields of view are shown, where the horizontal axis represents the spatial frequency in cycles / mm, and the vertical axis represents the MTF value, which can characterize the resolution of the projection lens. Figure 3 It can be seen that the MTF values ​​of the light are all above 0.35 and the curve is relatively flat, indicating that the imaging difference between the edge and the center of the projection lens is small and the imaging quality meets the design standard.

[0094] Figure 4 This is a defocus curve diagram provided by an embodiment of the present invention.

[0095] Figure 4 The figure shows the defocus curves of light with wavelengths of 0.4630 μm to 0.6430 μm in different fields of view when the spatial frequency is 50.0000 cycles / mm, where the horizontal axis represents the focal shift (defocus position) in mm and the vertical axis represents the MTF value. Figure 4 It can be seen that the MTF values ​​of the light at the optical axis are all above 0.5, and the image plane shift degree is within a reasonable range.

[0096] Figure 5 A point diagram provided for an embodiment of the present invention.

[0097] The spot diagram can reflect the clarity of the projection lens image. The more concentrated the points in the diagram, the less smear and the better the sharpness of the projection lens image. Figure 5 The image spot diagram (Spot Size diagram) of light with wavelengths of 0.643μm, 0.525μm and 0.463μm in six fields of view is shown. Figure 5 It can be seen that the images formed by the projection lens in different fields of view can be within a reasonable range. The root mean square (RNS) radius and geometric (GEO) radius data corresponding to the images formed in the six fields of view simulated by the embodiment of the present invention are shown in the following table:

[0098] Field of view 1 2 3 4 5 6 RNS radius (μm) 2.690 4.955 4.088 3.330 2.853 2.057 GEO radius (μm) 5.960 10.294 7.465 6.011 7.909 7.377

[0099] Figure 6 A vertical axis chromatic aberration diagram provided by an embodiment of the present invention.

[0100] Figure 6 The vertical chromatic aberration of light with wavelengths of 0.643 μm, 0.525 μm and 0.463 μm when imaged within a maximum field of view of 35° is shown, where the horizontal axis reflects the magnitude of the vertical chromatic aberration in μm, and the vertical axis is the field of view in degrees. The dotted line in the figure is the range of the Airy disk, which is Figure 6 It can be seen that within the Airy disk range, the vertical axis chromatic aberration of the image formed by the projection lens is within a reasonable range.

[0101] Figure 7 A schematic diagram of a field curvature curve provided by an embodiment of the present invention.

[0102] Figure 7 The figure shows the field curvature curves in the meridian and sagittal directions of the images formed by light rays with wavelengths of 0.643 μm, 0.525 μm and 0.463 μm under different fields of view, where the abscissa represents the field curvature in mm, and the ordinate represents the image height (field of view). Figure 7 The maximum field of view is 35.000 degrees. At this time, the sagittal field curvature is 0.0470mm and the meridian field curvature is 0.0248mm. The field curvature of the projection lens is within a reasonable range.

[0103] Figure 8 A schematic diagram of a distortion curve provided by an embodiment of the present invention.

[0104] Figure 8 The figure shows the distortion curves of the images formed by the light rays with wavelengths of 0.643 μm, 0.525 μm and 0.463 μm within the maximum field of view of 35°, where the abscissa represents the distortion percentage and the ordinate represents the image height (field of view). Figure 8 The maximum distortion is 1.9985%, and the distortion of the projection lens is within a reasonable range.

[0105] Fig. 9 A schematic diagram of a telecentricity curve provided in an embodiment of the present invention.

[0106] Fig. 9 The histogram shows the telecentricity of the output light of the projection lens under different fields of view, where the horizontal axis represents the field of view size, and the vertical axis represents the angle of the main light corresponding to different fields of view deviating from the optical axis, that is, the telecentricity. The specific data is shown in the following table. The telecentricity is less than 1 degree, and the projection lens has good performance:

[0107]

[0108]

[0109] comprehensive Figure 3 to Figure 9 It can be seen from the image quality evaluation results that the projection lens provided by the embodiment of the present invention has small aberrations during imaging and can have good imaging quality.

[0110] Based on the same inventive concept, the embodiment of the present invention also provides a projection lighting system, which can be used in conjunction with the vehicle's welcome light and can be installed on Fig.10 At the rearview mirror A, turn signal B or tail light C of the vehicle shown, the projection lighting system can project a long strip of screen onto the ground near the vehicle to prompt pedestrians near the vehicle to pay attention to relevant information.

[0111] Fig.11 A schematic diagram of the structure of a projection illumination system provided in an embodiment of the present invention.

[0112] like Fig.11 As shown, the projection illumination system includes: a three-color laser light source device 1, an illumination system 2 and any one of the above-mentioned projection lenses 3.

[0113] Specifically, the three-color laser light source device 1 is used to emit projection light, wherein the projection light source in the three-color laser light source device 1 is a three-color laser light source. Due to the high brightness and strong monochromaticity of the laser, the projected image can have better brightness and color performance. In order to achieve full-color projection display, the projection light source can use a laser that emits lasers of different colors, or a combination of multiple lasers that emit lasers of different colors. A light-combining component can be provided on the light-emitting side of the projection light source to combine lasers of different colors into white light for emission. The specific structure of the light-combining component can be designed to improve the uniformity and brightness of the light beam.

[0114] The illumination system 2 is located on the light-emitting side of the three-color laser light source device 1. The illumination system 2 includes a light-homogenizing component 22 and a light modulating component 21. In order to fold the light path and thus reduce the volume of the optical engine, a reflecting component 23 may also be included. Among them, the light beam emitted by the three-color laser light source device 1 needs to be homogenized by the light-homogenizing component 22, so as to form a light spot with a more uniform energy distribution to meet the illumination requirements of the light modulating component 21. The light-homogenizing component 22 may be a light pipe or a fly-eye lens group, etc. In the embodiment of the present invention, the light-homogenizing component 22 may be a fly-eye lens group, which is conducive to reducing the volume of the optical engine. The reflecting component 23 is located on the light-emitting side of the light-homogenizing component 22, and is used to receive the emitted light of the light-homogenizing component 22 (fly-eye lens group) and reflect it to the light modulating component 21. The light modulating component 21 may be an LC light valve, an LCOS light valve, or a DMD light valve according to different projection technologies. In the embodiment of the present invention, the light modulating component 21 may be a DMD. The light modulating component 21 is used to modulate the incident light and then emit it to the projection lens 3. In addition, the lighting system may also include a lens group, which may be used for focusing, diverging, shaping, etc. The number, type and arrangement of the lenses may be optically designed according to specific usage requirements.

[0115] The projection lens 3 is located on the light-emitting side of the light modulation component 21. It is worth noting that in the embodiment of the present invention, the fourth lens l4 in the projection lens is a field lens. The fourth lens l4 is used instead of the commonly used total reflection prism to compress the angle of the main light and compensate for the field curvature and distortion of the optical system. The projection lens images the projection light. The projection lens provided in the embodiment of the present invention has the advantages of small size and small chromatic aberration, and can achieve high-quality full-color display. When the projection lighting system is used in combination with the vehicle's welcome light, dynamic display of vehicle information can be achieved, which can improve driving safety.

[0116] According to the first inventive concept, the projection lens includes: a first lens, a second lens, a third lens and a fourth lens coaxially arranged in sequence from the image side to the object side; wherein the refractive power of the first lens is negative, the refractive power of the second lens is negative, the refractive power of the third lens is positive, and the refractive power of the fourth lens is positive. The projection lens includes only four lenses, which is conducive to reducing the size of the lens.

[0117] According to the second invention concept, the projection lens satisfies the following relationship:

[0118]

[0119] Among them, f represents the focal length of the projection lens, TTL represents the length of the projection lens on the optical axis, and F.NO represents the aperture value of the projection lens. By limiting the ratio of the focal length of the optical system to TTL×F.NO, the projection lens can be guaranteed to have a large aperture while effectively reducing the size of the lens, achieving ultra-thin characteristics and miniaturization of the projection, and reducing the total length of the projection lens along the optical axis to less than 23mm, making it more suitable for vehicle welcome lights.

[0120] According to the third invention concept, the aperture is located between the second lens and the third lens and is coaxially arranged with each lens. The aperture can limit the field of view and eliminate stray light.

[0121] According to the fourth invention, the first lens and the third lens are aspherical lenses made of glass; the second lens and the fourth lens are spherical lenses. The projection lens only includes four lenses, and only two aspherical lenses are needed to have better imaging quality. The optical system structure is simple and compact, and the processing difficulty is lower.

[0122] According to the fifth inventive concept, the first lens satisfies:

[0123] 0.2≤ct1 / et1≤0.6;

[0124] f1≤-10mm;

[0125] ct1 represents the center thickness of the first lens along the optical axis, et1 represents the edge thickness of the first lens along the optical axis, and f1 represents the focal length of the first lens. By controlling the parameters of the first lens to meet the above range and controlling the incident and outgoing light angles on the surface of the first lens to be ≤60°, the processability of the first lens can be guaranteed and excessive curvature can be avoided.

[0126] According to the sixth inventive concept, the second lens satisfies:

[0127] 0.4≤ct2 / et2≤0.8;

[0128] f2≥-100mm;

[0129] Wherein, ct2 represents the center thickness of the second lens along the optical axis, et2 represents the edge thickness of the second lens along the optical axis, and f2 represents the focal length of the second lens. By controlling the parameters of the second lens to meet the above range, the light angle can be properly controlled.

[0130] According to the seventh invention concept, the third lens satisfies:

[0131] 2≤|c36-c37|≤10;

[0132] Wherein, c36 represents the curvature radius of the image-side surface of the third lens, and c37 represents the curvature radius of the object-side surface of the third lens.

[0133] By controlling the parameters of the third lens to meet the above range, the size of the projection lens can be effectively reduced, the optical focal length of the projection lens can be reasonably distributed, and it is beneficial to the aberration control of other lenses while maintaining the processing technology of the third lens.

[0134] According to the eighth inventive concept, the fourth lens satisfies:

[0135] 0.2≤ct4 / et4≤0.6;

[0136] Among them, ct4 represents the center thickness of the fourth lens along the optical axis, and et2 represents the edge thickness of the fourth lens along the optical axis. By controlling the parameters of the fourth lens to meet the above range, the main light angle can be compressed to form a telecentric optical path on the image side (when designed), compensating for the field curvature and distortion of the optical system.

[0137] According to the ninth invention, the projection lens satisfies the following relationship:

[0138] 0.4≤(CT1+CT3) / ∑CT≤0.9;

[0139] Among them, CT1 represents the center thickness of the first lens along the optical axis, CT3 represents the center thickness of the third lens along the optical axis, and ∑CT represents the sum of the center thicknesses of the first lens, the second lens, and the third lens along the optical axis. By reasonably controlling the proportion of the center thickness of the first lens and the third lens to the center thickness of the first lens, the second lens, and the third lens, it is beneficial to reasonably distribute the optical power of the optical system, improve the spherical aberration and aberration of the optical system, and enhance the structural stability of the optical system.

[0140] According to the tenth invention concept, the field of view angle of the projection lens reaches 70°, and the projection ratio is 1.2. The projection lens has a certain depth of field, does not need to adjust the back focus of the lens, and is compatible with clear imaging at a distance of 800mm to 1200mm. The length of the projection lens is controlled below 23mm, which can greatly reduce the size of the projection lens, and then reduce the volume of the optical engine including the projection lens in the projection system, realize the miniaturization of the micro-projection system, and at the same time, the structure is simple to achieve the low-cost design goal. The F.NO of the projection lens is 2.4, which has a strong light collecting ability and a large luminous flux, and the relative illumination is greater than 85%. The projection lens can also be applied to the full-color laser spectrum. The chromatic aberration of the projection lens is less than 1pixel, that is, 0.007mm, and has the advantage of small chromatic aberration.

[0141] According to the eleventh invention concept, the projection lighting system includes a three-color laser light source device, a lighting system and a projection lens. Among them, the fourth lens in the projection lens is a field lens, and the fourth lens is used instead of the commonly used total reflection prism. It is arranged adjacent to the light modulation component in the lighting system, which can compress the angle of the main light and compensate for the field curvature and distortion of the optical system. The projection lighting system can achieve a high-quality full-color display. When the projection lighting system is used in combination with the vehicle's welcome light, it can realize the dynamic display of vehicle information and improve driving safety.

[0142] Although the preferred embodiments of the present invention have been described, those skilled in the art may make other changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0143] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A projection lens, characterized in that: include: A first lens, a second lens, a third lens and a fourth lens are coaxially arranged in sequence from the image side to the object side; Wherein, the refractive power of the first lens is negative, the refractive power of the second lens is negative, the refractive power of the third lens is positive, and the refractive power of the fourth lens is positive; The projection lens satisfies the following relationship: f represents the focal length of the projection lens, TTL represents the length of the projection lens on the optical axis, and F.NO represents the aperture value of the projection lens.

2. The projection lens according to claim 1, wherein: The first lens and the third lens are aspherical lenses, and the second lens and the fourth lens are spherical lenses; The first lens and the third lens are made of glass.

3. The projection lens according to claim 2, wherein: The first lens satisfies: 0.2≤ct1 / et1≤0.6; f1≤-10mm; Wherein, ct1 represents the center thickness of the first lens along the optical axis, et1 represents the edge thickness of the first lens along the optical axis, and f1 represents the focal length of the first lens.

4. The projection lens according to claim 2, wherein: The second lens satisfies: 0.4≤ct2 / et2≤0.8; f2≥-100mm; Wherein, ct2 represents the center thickness of the second lens along the optical axis, et2 represents the edge thickness of the second lens along the optical axis, and f2 represents the focal length of the second lens.

5. The projection lens according to claim 2, wherein: The third lens satisfies: 2≤|c36-c37|≤10; Wherein, c36 represents the curvature radius of the image-side surface of the third lens, and c37 represents the curvature radius of the object-side surface of the third lens.

6. The projection lens according to claim 2, wherein: The fourth lens satisfies: 0.2≤ct4 / et4≤0.6; Wherein, ct4 represents the center thickness of the fourth lens along the optical axis, and et2 represents the edge thickness of the fourth lens along the optical axis.

7. The projection lens according to any one of claims 2 to 6, characterized in that: The projection lens satisfies the following relationship: 0.4≤(CT1+CT3) / ∑CT≤0.9; Wherein, CT1 represents the center thickness of the first lens along the optical axis, CT3 represents the center thickness of the third lens along the optical axis, and ΣCT represents the sum of the center thicknesses of the first lens, the second lens and the third lens along the optical axis.

8. The projection lens according to any one of claims 1 to 6, wherein: Also includes: The aperture stop is located between the second lens and the third lens.

9. A projection lighting system, characterized in that: The projection lighting system is installed on the rearview mirror, turn signal or tail light of the vehicle and is used to project images onto the ground near the vehicle; The projection lighting system comprises: A three-color laser light source device for emitting projection light; An illumination system, located at the light-emitting side of the three-color laser light source device; the illumination system includes a light homogenization component and a light modulation component; A projection lens is located at the light-emitting side of the light modulation component; the projection lens is the projection lens according to any one of claims 1 to 8.

10. The projection illumination system according to claim 9, characterized in that: The light homogenizing component adopts a fly-eye lens group; the lighting system also includes a reflecting component, which is located at the light-emitting side of the fly-eye lens group and is used to receive the output light of the fly-eye lens group and reflect it to the light modulation component; The fourth lens of the projection lens is a field lens, and the fourth lens is arranged adjacent to the light modulation component.

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