Projection lens and head-up display system

Abstract

The invention discloses a projection lens and a head-up display system, and the projection lens comprises a plurality of lenses and a diaphragm, and the diaphragm is located at the light-emitting sides of the plurality of lenses, and is used for limiting the light-emitting range of the projection lens, so that the projection lens can be matched with an optical waveguide; by limiting the ratio of the effective focal length f to TTL * F.NO in the projection lens, the projection lens has the characteristic of large aperture, the size of the projection lens is effectively reduced, and the projection lens is ultrathin and miniaturized.

Description

Technical Field

[0001] The present invention relates to the field of projection display technology, and in particular to a projection lens and a head-up display 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] In a head-up display (HUD) system, the image projected by the projection lens is projected onto the windshield, and then reflected by the windshield to the human eye, so that the human eye can see the virtual image in front. Usually, in order to reduce the volume of the HUD system, an optical waveguide can be set on the light-emitting side of the projection lens, but the current projection lens has the problem of being large in size and difficult to match with the optical waveguide. Summary of the invention

[0004] The present invention provides a projection lens and a head-up display system, wherein the projection lens has the characteristics of miniaturization and can be matched with an optical waveguide and a variety of projection systems.

[0005] In one aspect, the present invention provides a projection lens, comprising: a plurality of lenses and an aperture; the aperture is located at the light exit side of the plurality of lenses;

[0006] The projection lens satisfies the following relationship:

[0007]

[0008] Wherein, f represents the effective 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 projection lens includes five lenses, and the five lenses include a first lens, a second lens, a third lens, a fourth lens and a fifth lens which are sequentially arranged in a direction gradually away from the aperture stop;

[0010] The refractive powers of the first lens, the second lens, the third lens, the fourth lens and the fifth lens are positive, positive, negative, negative and positive, respectively.

[0011] In some embodiments of the present invention, the first lens, the second lens, the third lens, the fourth lens and the fifth lens are all spherical lenses.

[0012] In some embodiments of the present invention, the third lens satisfies the following relationship:

[0013] 0.2≤ct3 / et3≤0.6;

[0014] f3 ≥ -11;

[0015] Wherein, ct3 represents the center thickness of the third lens along the optical axis, et3 represents the edge thickness of the third lens along the optical axis, and f3 represents the effective focal length of the third lens.

[0016] In some embodiments of the present invention, the fourth lens satisfies the following relationship:

[0017] 2≤|c18-c19|≤10;

[0018] Wherein, c18 represents the curvature radius of the object-side surface of the fourth lens, and c19 represents the curvature radius of the image-side surface of the fourth lens.

[0019] In some embodiments of the present invention, the aperture size of the aperture in a direction perpendicular to the optical axis is 14 mm to 16 mm.

[0020] In some embodiments of the present invention, the projection lens satisfies the following relationship:

[0021] 0.2≤(CT1+CT5) / ∑CT≤0.6;

[0022] Wherein, CT1 represents the center thickness of the first lens along the optical axis, CT5 represents the center thickness of the fifth lens along the optical axis, and ΣCT represents the sum of the center thicknesses of the five lenses along the optical axis.

[0023] In some embodiments of the present invention, the imaging distance of the projection lens is from 2 m to infinity.

[0024] In some embodiments of the present invention, the length from the image-side surface of the first lens to the object-side surface of the fifth lens on the optical axis is less than 32 mm, and the chromatic aberration of the projection lens is less than 0.3 pixels.

[0025] Another aspect of the present invention provides a head-up display system, comprising any one of the above-mentioned projection lenses, and the head-up display system further comprises:

[0026] A light source device, used for emitting projection light;

[0027] An illumination system is located at the light-emitting side of the light source device, and the illumination system includes a light-homogenizing component and a light-modulating component; the projection lens is located at the light-emitting side of the light-modulating component;

[0028] An optical waveguide is located at the light output side of the projection lens, the optical waveguide includes a coupling-in area and a coupling-out area, and the projection lens is arranged close to the coupling-in area; the optical waveguide is used to receive the light emitted by the projection lens and transmit it to the windshield, so that the windshield reflects the output light of the optical waveguide into the driver's eyes.

[0029] The beneficial effects of the present invention are as follows:

[0030] The present invention provides a projection lens and a head-up display system, wherein the projection lens comprises: a plurality of lenses and an aperture, wherein the aperture is located on the light-emitting side of the plurality of lenses to limit the light-emitting range of the projection lens so that the projection lens can match the optical waveguide. The projection lens satisfies the following relationship:

[0031]

[0032] Among them, f represents the effective 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 effective focal length f in the projection lens to TTL×F.NO, the projection lens can have a large aperture characteristic while effectively reducing the size of the projection lens, which is conducive to achieving ultra-thin and miniaturized projection lenses. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] 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.

[0034] Figure 1 A schematic diagram of the structure of a projection lens provided by an embodiment of the present invention;

[0035] Figure 2 A ray tracing diagram provided by an embodiment of the present invention;

[0036] Figure 3 A modulation transfer function curve diagram provided by an embodiment of the present invention;

[0037] Figure 4 A defocus curve diagram provided by an embodiment of the present invention;

[0038] Figure 5 A spot diagram provided for an embodiment of the present invention;

[0039] Figure 6 A vertical axis chromatic aberration diagram provided by an embodiment of the present invention;

[0040] Figure 7A schematic diagram of a field curvature curve provided by an embodiment of the present invention;

[0041] Figure 8 A schematic diagram of a distortion curve provided by an embodiment of the present invention;

[0042] Fig. 9 A schematic diagram of a telecentricity curve provided by an embodiment of the present invention;

[0043] Fig.10 A schematic diagram of the structure of a head-up display system provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0044] 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.

[0045] The head-up display (HUD) system is essentially a projection system. The projection device projects the display image onto the windshield of the car, and the projection light is then reflected by the windshield into the human eye, so that the driver can see the projection image formed in front of the line of sight, and can obtain vehicle-related information while driving without lowering his head. Among them, the projection device usually includes three components: a light source device, a lighting system, and a projection lens. The light source device may include a projection light source for emitting projection light and a component for combining light. The lighting system may include a light homogenization component and a light modulation component. The projection light emitted by the light source device enters the lighting system, is homogenized and modulated by the lighting system, and then enters the projection lens, and is emitted after being imaged by the projection lens.

[0046] Since the HUD system needs to form a virtual image on the road surface at a certain distance in front of the vehicle, and in order to achieve the virtual image distance, a certain length of optical path needs to be established. In traditional HUD systems, free-form surface reflectors are usually used to shorten the optical path, but this will bring about the problem of large volume of the HUD system. Setting an optical waveguide on the light-emitting side of the projection device can help reduce the volume of the HUD system. However, due to the small coupling area of ​​the optical waveguide, the light-emitting area of ​​the current projection lens is easily larger than the area of ​​the optical waveguide coupling area, making it difficult to match the optical waveguide.

[0047] In view of this, an embodiment of the present invention provides a projection lens, which has the advantage of being small in size and can be matched with an optical waveguide.

[0048] Figure 1 A schematic diagram of the structure of a projection lens provided by an embodiment of the present invention.

[0049] like Figure 1 As shown, the projection lens includes multiple lenses and an aperture STO, and the aperture STO is located on the light-emitting side of the multiple lenses. The aperture STO of the projection lens is placed in front so that it coincides with the exit pupil of the projection lens, which can limit the size of the output light beam of the projection lens, thereby making the light-emitting range of the projection lens adapt to the size of the optical waveguide coupling area.

[0050] In the embodiment of the present invention, the coupling region of the optical waveguide can be a circular grating with a diameter of 14mm to 16mm, and the coupling region of the optical waveguide requires the incident light to be incident in parallel. In the above-mentioned projection lens, the aperture size of the aperture STO in the direction perpendicular to the optical axis is 14mm to 16mm, that is, the exit pupil diameter of the projection lens can be limited to 14mm to 16mm. In addition, by designing the surface shape and arrangement of each lens in the projection lens, the imaging distance range of the projection lens provided by the embodiment of the present invention is 2m to infinity, so that the outgoing light of the projection lens can be coupled into the above-mentioned optical waveguide, with a high light utilization rate, and the matching of the projection lens and the optical waveguide is achieved.

[0051] Optionally, the exit pupil diameter of the projection lens can be 1 mm smaller than the coupling area diameter of the optical waveguide, the distance between the exit pupil of the projection lens and the coupling area of ​​the optical waveguide can be set to about 1 mm, and the field of view of the projection lens is set to be consistent with the field of view of the optical waveguide, thereby improving the matching degree between the projection lens and the optical waveguide, which is conducive to achieving a better projection display effect. In the embodiment of the present invention, the field of view of the optical waveguide can be designed to be 18°×9°, and accordingly, the field of view of the projection lens is also 18°×9°, where 18° and 9° are the field of view angles in the horizontal direction and the vertical direction, respectively.

[0052] In the embodiment of the present invention, the projection lens as a whole satisfies the following relationship:

[0053]

[0054] Among them, f represents the effective 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 effective focal length f of the projection lens to TTL×F.NO, it is possible to ensure that the projection lens has a large aperture characteristic while effectively reducing the size of the projection lens, which is conducive to achieving ultra-thin and miniaturized projection lenses.

[0055] like Figure 1As shown, the projection lens includes five lenses, which include a first lens 1, a second lens 2, a third lens 3, a fourth lens 4 and a fifth lens 5 arranged in a direction gradually away from the aperture STO. The side where the aperture STO is located is the image side of the projection lens, and the side where the fifth lens 5 is located is the object side of the projection lens.

[0056] In the embodiment of the present invention, the first lens 1, the second lens 2, the third lens 3, the fourth lens 4 and the fifth lens 5 are all spherical lenses, and are made of glass for easy processing. The refractive powers of the first lens 1, the second lens 2, the third lens 3, the fourth lens 4 and the fifth lens 5 are positive, positive, negative, negative and positive respectively.

[0057] Specifically, the third lens 3 satisfies the following relationship:

[0058] 0.2≤ct3 / et3≤0.6;

[0059] f3 ≥ -11;

[0060] Among them, ct3 represents the center thickness of the third lens 3 along the optical axis, et3 represents the edge thickness of the third lens 3 along the optical axis, and f3 represents the effective focal length of the third lens 3. By controlling the parameters of the third lens 3 to satisfy the above formula, the light height in the projection lens can be appropriately increased, while ensuring the processability of the lens and avoiding excessive curvature. In addition, the third lens 3 has a large optical power and can be used to balance aberrations and field curvature.

[0061] The fourth lens 4 satisfies the following relationship:

[0062] 2≤|c18-c19|≤10;

[0063] Wherein, c18 represents the curvature radius of the object side surface of the fourth lens 4, and c19 represents the curvature radius of the image side surface of the fourth lens 4. By controlling the parameters of the fourth lens 4 to satisfy the above formula, it is helpful to reduce the size of the projection lens, reasonably distribute the optical power of the projection lens, and at the same time, it is beneficial to control the aberrations of other lenses and ensure the processability of the lens.

[0064] The fifth lens 5 can be used to balance the maximum light height in the projection lens to prevent the projection lens from generating a large field curvature.

[0065] The projection lens composed of the above five lenses also satisfies the following relationship:

[0066] 0.2≤(CT1+CT5) / ∑CT≤0.6;

[0067] Among them, CT1 represents the center thickness of the first lens 1 along the optical axis, CT5 represents the center thickness of the fifth lens 5 along the optical axis, and ∑CT represents the sum of the center thicknesses of the five lenses along the optical axis. By reasonably controlling the proportion of the center thickness of the first lens 1 and the fifth lens 5 along the optical axis to the sum of the center thicknesses of the five lenses in the projection lens along the optical axis, it is beneficial to reasonably allocate the optical power of each lens, improve the spherical aberration and aberration of the projection lens, and at the same time enhance the stability of the overall structure of the projection lens.

[0068] In the embodiment of the present invention, by designing the surface shapes and combination of the five lenses in the projection lens, the length from the image side surface of the first lens 1 to the object side surface of the fifth lens 5 on the optical axis can be less than 32 mm. In the embodiment of the present invention, the total length of the projection lens can be controlled within 30 mm, that is, the total length of the projection lens is less than 30 mm, and the projection lens has the advantage of small size. The chromatic aberration of the projection lens can reach less than 0.3 pixels, that is, 0.0015 mm. The projection lens has the advantage of small chromatic aberration and is suitable for full-color laser projection systems. The projection ratio of the projection lens is 2.8, and the projection ratio is the ratio of the projected image projected by the projection lens to the projection distance. The above projection ratio can make the user watch the projected image more comfortably. The aperture value (F.NO value) of the projection lens is 2.4. The F.NO value characterizes the light receiving ability of the projection lens. The larger the F.NO value of the projection lens, the smaller its light receiving angle. The above F.NO value indicates that the projection lens provided in the embodiment of the present invention can have a strong light receiving ability and a large luminous flux. The relative illumination of the projection lens is greater than 85%, and the projected image can have a higher brightness.

[0069] The surface parameters of each optical component in the projection lens provided by the embodiment of the present invention and the spacing between the optical components are shown in the following table:

[0070] Face number Face type Radius of curvature thickness Material Semi-aperture OBJ Spherical unlimited unlimited Aperture Spherical unlimited 1.00 7.00 S2 Spherical 15.44 3.01 1.77；49.6 refraction 7.52 S3 Spherical 127.85 0.97 refraction 7.34 S4 Spherical 13.87 2.34 1.69；49.2 refraction 6.79 S5 Spherical 32.64 0.78 refraction 6.38 S6 Spherical 90.39 1.16 1.62；60.1 refraction 6.21 S7 Spherical 19.24 0.61 refraction 5.72 S8 Spherical 23.58 1.10 1.755；27.546 refraction 5.62 S9 Spherical 8.71 8.93 refraction 5.12 S10 Spherical -8.01 4.44 1.61；58.88 refraction 5.63 S11 Spherical -13.29 0.50 refraction 8 S12 Spherical unlimited 16 1.74；49.339 refraction 7.753 S13 Spherical unlimited 0.35 refraction 6.288 S14 Spherical unlimited 0.7 1.51；62.911 refraction 6.233 S15 Spherical unlimited 0.3 refraction 6.161 S16 Spherical unlimited 6.15

[0071] Based on the above parameters, the projection lens is a miniature telephoto lens, the projection ratio of the projection lens is 2.8, the effective focal length is 34.3mm, the offset of the projection lens, that is, the offset range between the projection lens and the center of the light modulation component is 0, the resolution capability of the projection lens can reach 66lp / mm, the projection distance can be in the range of 2m to infinity, the field of view of the projection lens can reach 20° (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 0.3pixel.

[0072] Based on the above parameters, the embodiment of the present invention simulates the light path in the projection lens using optical design software. Figure 2 A ray tracing diagram provided by an embodiment of the present invention.

[0073] like Figure 1 and Figure 2 As shown, the light modulation component 200 is located at the light incident side of the projection lens 100. For different projection technologies, the light modulation component 200 can specifically adopt a liquid crystal (LC) light valve, a liquid crystal on silicon (LCOS) light valve, a digital micro mirror device (DMD), etc. The embodiment of the present invention takes the use of a DMD chip as the light modulation component as an example for explanation. When the light modulation component 200 adopts a DMD chip, a total reflection prism 210 can also be arranged between the projection lens 100 and the light modulation component 200. The total reflection prism 210 is used to receive the projection light reflected to the light modulation component 200, and emit the light modulated by the light modulation component 200 to the projection lens 100.

[0074] like Figure 2 As shown, the chip modulated by the DMD chip is incident on the projection lens 100 after passing through the total reflection prism 210, and is refracted by each lens in the projection lens 100 in sequence and then emitted from the aperture STO.

[0075] The embodiment of the present invention also evaluates the image quality of the projection lens based on the above ray tracing results.

[0076] Figure 3 This is a modulation transfer function curve diagram provided by an embodiment of the present invention.

[0077] Figure 3 The 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 0.5 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.

[0078] Figure 4 This is a defocus curve diagram provided by an embodiment of the present invention.

[0079] Figure 4 The figure shows the defocus curves of light with a wavelength of 0.4650 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 0.6, and the image plane shift degree is within a reasonable range.

[0080] Figure 5 A point diagram provided for an embodiment of the present invention.

[0081] 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 0.465μm 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:

[0082] Field of view 1 2 3 4 5 6 RNS radius (μm) 2.103 3.638 3.293 3.638 3.829 3.364 GEO radius (μm) 3.654 8.919 6.857 9.024 9.868 8.391

[0083] Figure 6 A vertical axis chromatic aberration diagram provided by an embodiment of the present invention.

[0084] Figure 6 The vertical chromatic aberration of light with wavelengths of 0.643 μm, 0.525 μm and 0.465 μm when imaged within a certain field of view is shown in the figure, 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.

[0085] Figure 7 A schematic diagram of a field curvature curve provided by an embodiment of the present invention.

[0086] 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 0.465 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 10.000 degrees. At this time, the sagittal field curvature is 0.0126mm and the meridian field curvature is 0.0104mm. The field curvature of the projection lens is within a reasonable range.

[0087] Figure 8 A schematic diagram of a distortion curve provided by an embodiment of the present invention.

[0088] Figure 8 The figure shows the distortion curves of the images formed by light rays with wavelengths of 0.643 μm, 0.525 μm and 0.465 μm within a certain field of view, where the abscissa represents the distortion percentage and the ordinate represents the image height (field of view). Figure 8The maximum field of view is 10,000 degrees, and the maximum distortion is 0.4018%. The distortion of the projection lens is within a reasonable range.

[0089] Fig. 9 A schematic diagram of a telecentricity curve provided in an embodiment of the present invention.

[0090] Fig. 9 A bar graph of the telecentricity of the outgoing light of the projection lens under different fields of view is shown, wherein the horizontal axis represents the size of the field of view, and the vertical axis represents the angle at which the main light corresponding to different fields of view deviates from the optical axis, i.e., the telecentricity. The specific data are shown in the following table. The telecentricity is less than 1 degree, and the projection lens has good performance.

[0091] Field of view 0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50 Telecentricity 0.00 0.06 0.13 0.19 0.25 0.31 0.36 0.41 0.45 0.49 0.51 Field of view 0.55 0.60 0.65 0.70 0.75 0.80 0.85 0.90 0.95 1.00 Telecentricity 0.53 0.54 0.54 0.53 0.50 0.45 0.38 0.34 0.68 1.00

[0092] 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.

[0093] Based on the same inventive concept, an embodiment of the present invention further provides a head-up display system.

[0094] Fig.10 A schematic diagram of the structure of a head-up display system provided in an embodiment of the present invention.

[0095] like Fig.10 As shown, the head-up display system includes a projection device T, an optical waveguide 300 and a windshield 400. Figure 1 , Figure 2 and Fig.10 The projection device T includes a light source device, an illumination system and a projection lens 100 .

[0096] Specifically, the light source device is used to emit projection light, and the light source device includes a projection light source. The projection light source can specifically be a 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 be 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 one beam for emission. The specific structure of the light-combining component can be designed to improve the uniformity and brightness of the light beam.

[0097] The lighting system is located on the light output side of the light source device, and the lighting system includes a light uniforming component and a light modulation component, wherein the light uniforming component can be a light guide or a compound eye lens group, and the light uniforming component can be used to shape and uniformize the output light of the light source device. The light modulation component 200 can adopt an LC light valve, an LCOS light valve or a DMD light valve according to different projection technologies, and the light modulation component is used to modulate the incident light and then output it to the projection lens, so as to improve the imaging quality of the projected image. The lighting system can also include a lens group, and the functions of the lens group can be focusing, diverging, shaping, etc. The number, type and arrangement of the lenses can be obtained by optical design according to specific usage requirements, and the embodiments of the present invention are not limited here.

[0098] The projection lens is located on the light-emitting side of the light modulation component. The projection lens can be used to image the projection light. The projection lens provided by the embodiment of the present invention has the advantages of small size and small chromatic aberration. When applied to the head-up display system, it can effectively reduce the size of the head-up display system while achieving high-quality full-color display.

[0099] In some embodiments, a display screen may be used to provide the required image, which is then imaged by a projection lens and incident on subsequent components.

[0100] The optical waveguide 300 may specifically be a geometric optical waveguide or a diffraction optical waveguide, etc. The light may be totally reflected multiple times in the optical waveguide 300, which is beneficial to reducing the volume of the system. The optical waveguide 300 includes an in-coupling region and an out-coupling region. By designing the specific structures of the in-coupling region and the out-coupling region of the optical waveguide 300, it is helpful to improve the imaging quality of the projection light. The optical waveguide 300 plays a decisive role in the field of view angle, imaging distance, eyebox and other parameters of the head-up display system.

[0101] The projection lens provided in the embodiment of the present invention has a suitable exit pupil range and emits parallel light, which can meet the coupling requirements of the optical waveguide, so that the projection lens can match the optical waveguide 300. The projection lens 100 is arranged close to the coupling area of ​​the optical waveguide 300 so that the output light beam of the projection lens is coupled into the optical waveguide 300. The light is coupled out after multiple total reflections in the optical waveguide 300, and then incident on the windshield 400. The windshield 400 can reflect the output light of the optical waveguide 300 into the driver's eyes, so that the driver can see the virtual image formed at a certain distance. The above-mentioned head-up display system has the advantage of small size.

[0102] It can be understood that, in some embodiments, the above-mentioned projection lens can also be applied to other projection systems. Since the projection lens has the advantages of small size and small chromatic aberration, applying it to the projection system can reduce the volume of the projection system and achieve better color projection display effects to meet more diversified product needs.

[0103] According to the first inventive concept, the projection lens includes multiple lenses and an aperture, and the aperture is located on the light-exiting side of the multiple lenses. The aperture of the projection lens is placed forward so that it coincides with the exit pupil of the projection lens, which can limit the size of the light beam emitted by the projection lens, thereby making the light-exiting range of the projection lens adapt to the size of the optical waveguide coupling area.

[0104] According to the second invention concept, the exit pupil diameter of the projection lens is limited to 14 mm to 16 mm, and the imaging distance range of the projection lens is from 2 m to infinity, so that the outgoing light of the projection lens can be coupled into the optical waveguide, with a high light utilization rate, thereby achieving matching between the projection lens and the optical waveguide.

[0105] According to the third inventive concept, the exit pupil diameter of the projection lens can be 1 mm smaller than the diameter of the coupling area of ​​the optical waveguide, the distance between the exit pupil of the projection lens and the coupling area of ​​the optical waveguide can be set to be about 1 mm, and the field of view angle of the projection lens is set to be consistent with the field of view angle of the optical waveguide, thereby improving the matching degree between the projection lens and the optical waveguide, which is conducive to achieving better projection display effects.

[0106] According to the fourth invention, by limiting the ratio of the effective focal length f of the projection lens to TTL×F.NO, it satisfies the formula It can ensure that the projection lens has a large aperture characteristic while effectively reducing the size of the projection lens, which is conducive to achieving ultra-thinness and miniaturization of the projection lens.

[0107] According to the fifth invention concept, the projection lens includes a first lens, a second lens, a third lens, a fourth lens and a fifth lens arranged in a direction gradually away from the aperture, and the five lenses are all spherical lenses and are made of glass for easy processing.

[0108] According to the sixth invention concept, by controlling the parameters of the third lens to satisfy the formulas 0.2≤ct3 / et3≤0.6 and f3≥-11, the light height in the projection lens can be appropriately increased while ensuring the processability of the lens and avoiding excessive curvature. In addition, the third lens has a larger optical focal length and can be used to balance aberrations and field curvature.

[0109] According to the seventh invention concept, by controlling the parameters of the fourth lens to satisfy the formula 2≤|c18-c19|≤10, it can help to reduce the size of the projection lens, so that the optical focal length of the projection lens can be reasonably distributed, and it is also beneficial to control the aberrations of other lenses and ensure the processability of the lens.

[0110] According to the eighth inventive concept, the fifth lens can be used to balance the maximum light height in the projection lens, so as to prevent the projection lens from generating a large field curvature.

[0111] According to the ninth invention concept, by reasonably controlling the proportion of the center thickness of the first lens and the fifth lens along the optical axis direction to the sum of the center thickness of the five lenses in the projection lens along the optical axis direction, so as to satisfy the formula 0.2≤(CT1+CT5) / ∑CT≤0.6, it is beneficial to reasonably distribute the optical power of each lens, improve the spherical aberration and aberration of the projection lens, and at the same time enhance the stability of the overall structure of the projection lens.

[0112] According to the tenth invention, by designing the surface shapes and combination of the five lenses in the projection lens, the total length of the projection lens can be made less than 30 mm, and the projection lens has the advantage of a small size.

[0113] According to the eleventh invention concept, the chromatic aberration of the projection lens can be less than 0.3 pixels, i.e., 0.0015 mm. The projection lens has the advantage of small chromatic aberration and is suitable for a full-color laser projection system.

[0114] According to the twelfth inventive concept, the projection ratio of the projection lens is 2.8, which can enable the user to watch the projected image more comfortably.

[0115] According to the thirteenth invention, the aperture value (F.NO value) of the projection lens is 2.4, the projection lens can have a strong light collecting ability and a large luminous flux. The relative illumination of the projection lens is greater than 85%, and the projected image can have a high brightness.

[0116] According to the fourteenth inventive concept, the projection lens provided by the embodiment of the present invention has a suitable exit pupil range and emits parallel light, which can meet the coupling requirements of the optical waveguide, so that the projection lens can match the optical waveguide and be applied to the head-up display system, which can effectively reduce the volume of the head-up display system and achieve a higher quality full-color display.

[0117] According to the fifteenth inventive concept, the projection lens provided in the embodiment of the present invention can also be applied to other projection systems. Since the projection lens has the advantages of small size and small chromatic aberration, applying it to the projection system can reduce the volume of the projection system and achieve better color projection display effects to meet more diversified product needs.

[0118] 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.

[0119] 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: It comprises a plurality of lenses and an aperture; the aperture is located at the light exit side of the plurality of lenses; The projection lens satisfies the following relationship: Wherein, f represents the effective 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 projection lens comprises five lenses, wherein the five lenses comprise a first lens, a second lens, a third lens, a fourth lens and a fifth lens which are sequentially arranged in a direction gradually away from the aperture stop; The refractive powers of the first lens, the second lens, the third lens, the fourth lens and the fifth lens are positive, positive, negative, negative and positive, respectively.

3. The projection lens according to claim 2, wherein: The first lens, the second lens, the third lens, the fourth lens and the fifth lens are all spherical lenses.

4. The projection lens according to claim 2, wherein: The third lens satisfies the following relationship: 0.2≤ct3 / et3≤0.6; f3≥-11； Wherein, ct3 represents the center thickness of the third lens along the optical axis, et3 represents the edge thickness of the third lens along the optical axis, and f3 represents the effective focal length of the third lens.

5. The projection lens according to claim 2, wherein: The fourth lens satisfies the following relationship: 2≤|c18-cl9|≤10; Wherein, c18 represents the curvature radius of the object-side surface of the fourth lens, and c19 represents the curvature radius of the image-side surface of the fourth lens.

6. The projection lens according to any one of claims 1 to 5, characterized in that: The aperture size of the aperture in the direction perpendicular to the optical axis is 14 mm to 16 mm.

7. The projection lens according to any one of claims 2 to 5, characterized in that: The projection lens satisfies the following relationship: 0.2≤(CT1+CT5) / ∑CT≤0.6; Wherein, CT1 represents the center thickness of the first lens along the optical axis, CT5 represents the center thickness of the fifth lens along the optical axis, and ΣCT represents the sum of the center thicknesses of the five lenses along the optical axis.

8. The projection lens according to any one of claims 2 to 5, characterized in that: The imaging distance of the projection lens is from 2m to infinity.

9. The projection lens according to any one of claims 2 to 5, characterized in that: The length from the image side surface of the first lens to the object side surface of the fifth lens on the optical axis is less than 32 mm, and the chromatic aberration of the projection lens is less than 0.3 pixels.

10. A head-up display system, characterized in that: The head-up display system comprises the projection lens according to any one of claims 1 to 9, and further comprises: A light source device, used for emitting projection light; An illumination system is located at the light-emitting side of the light source device, and the illumination system includes a light-homogenizing component and a light-modulating component; the projection lens is located at the light-emitting side of the light-modulating component; An optical waveguide is located at the light output side of the projection lens, the optical waveguide includes a coupling-in area and a coupling-out area, and the projection lens is arranged close to the coupling-in area; the optical waveguide is used to receive the light emitted by the projection lens and transmit it to the windshield, so that the windshield reflects the output light of the optical waveguide into the driver's eyes.

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