Lens and vehicle lamp having the same

Abstract

The present invention relates to the technical field of lenses, and more particularly to a lens and a vehicle lamp including the lens. The lens is processed by a layered injection molding method, and includes a lens body having a first refracting and diffracting surface and a second refracting and diffracting surface facing each other along the optical axis direction, at least one of the refracting and diffracting surfaces has a diffractive structure that is rotationally symmetrical with respect to the optical axis, and the diopter of the diffractive structure accounts for 1% to 20% of the total diopter of the lens body. The present invention has good heat resistance properties, produces a clear and uncolored low beam cutoff line, and can save product costs, and is expected to be suitably applied.

Description

[Technical field]

[0001] The present invention relates to the technical field of lenses, and more particularly to a lens and a vehicle lamp including the lens. [Background technology]

[0002] Lens is the core element of high beam / low beam module, which has the function of bending light and projecting low beam shading image in front of the vehicle. The cost, weight and optical effect of lens are important points of focus in high beam / low beam module. Glass lens has low dispersion and good heat resistance, but it is difficult to process, high cost and heavy. Plastic lens has the advantages of light weight, low cost and easy processing, but commonly used plastic materials have their own shortcomings, for example, polymethylmethacrylate (PMMA) has low dispersion but cannot meet the heat resistance requirements of automobile headlights, polycarbonate (PC) has good heat resistance but large dispersion, which can make the low beam cutoff line bluish or yellowish light.

[0003] Chinese patent CN109716175A, entitled "Diffractive Lens and Vehicle Lamp Using the Same," discloses a vehicle lens that uses a diffractive structure to reduce the difference in thickness between the edge and center of the lens while ensuring the performance of the low beam cut-off line. This solution places many restrictions on the lens curvature, diopter and wall thickness based on cost and processability, reducing the lens design freedom and performance. Summary of the Invention [Problem to be solved by the invention]

[0004] In order to overcome the shortcomings of the conventional technology, the present invention has a technical problem to be solved to provide a lens that is lightweight, has good processability and heat resistance, ensures the clarity of the low beam cut-off line, and can reduce the phenomenon of the low beam cut-off line being colored, and a vehicle lamp equipped with the lens. [Means for solving the problem]

[0005] The technical means adopted by the present invention to solve this technical problem is a mixed refractive and diffractive lens, which is processed by a layered injection molding method and can collimate diffused light from a lens focal point to form parallel light. The mixed refractive and diffractive lens includes a lens body having a first refracting and diffractive surface and a second refracting and diffractive surface facing each other along an optical axis L, the second refracting and diffractive surface is located on one side closer to the lens focal point, and the first refracting and diffractive surface is located on one side away from the lens focal point, at least one of the first refracting and diffractive surface and the second refracting and diffractive surface has a diffractive structure that is rotationally symmetrical with respect to the optical axis L, and the diopter of the diffractive structure accounts for 1% to 20% of the total diopter of the lens body. The thickness of the lens body at the farthest point from the optical axis L in the light passing hole diameter is the edge thickness H1, and the distance between the intersection of the first refracting and diffracting surface and the optical axis L and the second refracting and diffracting surface is the lens center thickness H2, and H1:H2=1:30 to 1:2. It is a lens that can be used.

[0006] Furthermore, the first refracting / diffractive surface is a convex surface, and the second refracting / diffractive surface is a flat or convex surface.

[0007] Furthermore, the first refracting and diffractive surface is provided with a diffractive structure whose diopter occupies 1% to 20% of the total diopter of the lens body.

[0008] Furthermore, the second refracting and diffractive surface is provided with a diffractive structure whose diopter occupies 1% to 20% of the total diopter of the lens body.

[0009] Furthermore, each of the first refracting and diffractive surface and the second refracting and diffractive surface is provided with a diffractive structure whose sum of diopters accounts for 1% to 20% of the total diopter of the lens body.

[0010] The vehicle lamp comprises a low beam light source, a low beam reflector, a low beam shading plate and a lens, the lens having the above-mentioned structure, the low beam reflector being arranged to cover the outside of the low beam light source, the lens being positioned on the light emission side of the low beam light source, and the low beam shading plate being positioned between the low beam light source and the lens.

[0011] The useful effects of the present invention are as follows: the structure is simple, the design is reasonable, it is easy to operate, the lens has good heat resistance and low dispersion, the lens has good collimation performance for the diffused light of different wavelengths from the focal point, the cutoff line of the low beam is clear, and the cutoff line can be avoided from being colored and blurred.

[0012] The invention will now be further described with reference to the drawings and examples. [Brief description of the drawings]

[0013] [Figure 1] FIG. 1 is a perspective view of a lens according to the present invention. [Diagram 2] FIG. 2 is a schematic diagram of the structure of FIG. [Diagram 3] This is the axial chromatic aberration curve of a PC material refractive lens. [Figure 4] FIG. 2 is a side view of a PC material refractive lens. [Diagram 5] This is the axial chromatic aberration curve of a diffractive lens. [Figure 6] This is a comparison table of the diffraction diopter ratio, edge and center thickness ratio, and axial chromatic aberration of PMMA lenses. [Figure 7] FIG. 2 is a side view of the lens in the performance test in Example 1. [Figure 8] FIG. 2 is a lens parameter table in the first embodiment. [Figure 9] FIG. 2 is a graph showing axial chromatic aberration curves of the lens in Example 1. [Figure 10] FIG. 11 is a lens parameter table in the second embodiment. [Figure 11] FIG. 11 is a diagram showing an on-axis chromatic aberration curve of the lens in Example 2. [Figure 12] 1 is a structural schematic diagram of a vehicle lamp according to the present invention; [Figure 13] A comparison diagram of low beam cut-off lines with and without lenses. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] The present invention will be described in more detail below with reference to the drawings and preferred embodiments. These drawings are all simplified schematic diagrams, and are merely used to explain the basic structure of the present invention, so that only the configurations related to the present invention are shown.

[0015] The lens shown in FIG. 1 and FIG. 2 is processed by a layered injection molding method, and has a lens body provided with a first refracting / diffractive surface 1 and a second refracting / diffractive surface 2 facing each other along the optical axis direction, the second refracting / diffractive surface 2 is located on one side closer to the lens focus, and the first refracting / diffractive surface 1 is located on one side farther from the lens focus, at least one of the first refracting / diffractive surface 1 and the second refracting / diffractive surface 2 has a diffractive structure that is rotationally symmetrical with respect to the optical axis, and the diopter of the diffractive structure accounts for 1% to 20% of the total diopter of the lens body. The total diopter of the lens body is the sum of the diopter of the refracting structure and / or the diffractive structure on the first refracting / diffractive surface 1 and the diopter of the refracting structure and / or the diffractive structure on the second refracting / diffractive surface 2. The thickness of the light passing hole in the lens body farthest from the optical axis L is the edge thickness H1, and the distance between the intersection of the first and second refracting and diffracting surfaces and the optical axis L is the lens center thickness H2, and H1:H2=1:30 to 1:2. do.

[0016] The lens material is an optical grade plastic, including, but not limited to, polycarbonate (PC), polymethylmethacrylate (PMMA), Osaka Gas Optical Resin (OKP series), Mitsubishi Gas Optical Resin (EP series), Japan Synthetic Rubber Optical Resin (ARTON F / D series), or Japan Zeon Optical Resin (Zeonex).

[0017] The first refracting / diffractive surface 1 is a convex surface, the second refracting / diffractive surface 2 is a flat or convex surface, and the radius of curvature of the second refracting / diffractive surface 2 is not smaller than 50 mm.

[0018] At least one of the first refracting / diffractive surface 1 and the second refracting / diffractive surface 2 has a diffractive structure that is rotationally symmetric with respect to the optical axis, and specifically, The first refractive / diffractive surface 1 is provided with a diffractive structure whose diopter occupies 1% to 20% of the total diopter of the lens body. Or, the second refractive / diffractive surface 2 is provided with a diffractive structure whose diopter occupies 1% to 20% of the total diopter of the lens body; Alternatively, each of the first refracting / diffractive surface 1 and the second refracting / diffractive surface 2 is provided with a diffractive structure whose sum of diopters accounts for 1% to 20% of the total diopter of the lens body.

[0019] In order to ensure the clarity of the low beam cutoff line, the lens of the vehicle lamp generally has the following characteristics. The light parallel to the optical axis L passes through the lens, is bent (light refraction) by the lens, and is focused at the focal point of the lens. The light bending ability of the lens is called diopter. In a normal case, for a lens with known parameters, the focal length and diopter differ according to the wavelength of the light, so that the incident light parallel to the optical axis L with different wavelengths is focused at different positions behind the lens, forming longitudinal chromatic aberration. For the low beam of the vehicle headlight, the longitudinal chromatic aberration of the lens causes the low beam cutoff line to be diffused and colored, which affects the user experience. Below is a brief analysis of the axial dispersion of traditional lenses (refractive lenses) and diffractive lenses.

[0020] Refractive lenses complete the refraction of light by the difference in the refractive index of different materials. The refractive index of general materials is inversely correlated with the wavelength of light, that is, the longer the wavelength of light, the smaller the refractive index of the material, so positive dispersion occurs in the refraction of light in refractive lenses, that is, the longer the wavelength, the smaller the absolute diopter value of the lens. Take the commonly used visible light wavelengths of 480nm (blue light) and 644nm (red light) and the commonly used optical resin polycarbonate (PC) as an example. PC has a refractive index of n 480 is 1.5991, and n for 644 nm wavelength light 644 The refractive index is 1.5807. A ray of light enters the PC lens from the air. The parallel rays pass through the entrance and exit surfaces of the lens and are focused at the rear focal point of the lens. If the radii of curvature of the two optical surfaces are r1 and r2 respectively, the relationship between the focal lengths f1, f2 of the two surfaces and the radii of curvature is as follows:

number

[0021] If the lens center thickness is H2, the lens diopter is Φ r and the total focal length f is a function of f1, f2 and H2.

number

[0022] When the absolute values ​​of r1 and r2 are much larger than the lens center thickness d, (n-1) 2 The term may be ignored, i.e.

number

[0023] As mentioned above, PC material has different refractive indexes for different wavelengths of light, so the refractive lens has different focal lengths and diopters for different wavelengths of light. r644 and diopter Φ for 480 nm blue light r480 By comparing, the following formula was found:

number

[0024] This dispersion is introduced by refraction, so ΔΦ r As can be seen from the above formula, ΔΦ r is not related to the shape of the lens surface, but only related to the lens material and wavelength. Figure 3 is the axial chromatic aberration curve of the PC material refractive lens, the lens diopter is 23.36D, as can be seen from the curve, the axial chromatic aberration of the lens for red light and blue light is about 1.3mm, that is, the distance between the red light focus and the blue light focus on the optical axis L is 1.3mm, and the focus of 480nm light is closer to the lens, and the focus of 644nm light is farther away from the lens, and such chromatic aberration is called positive chromatic aberration.

[0025] Another common problem in refractive lenses is the large center-edge thickness difference, that is, after the lens material (PC) and refractive index (n=1.4938@546nm) are determined, the lens surface must have a sufficient inclination to refract the incident parallel light to the lens focus. Figure 4 is a side view of the above PC material refractive lens, with a lens diopter of 23.36D, a diameter of 28mm, an edge thickness of 1.5mm, and a center thickness of 17.16mm, with the difference between the edge thickness and the center thickness exceeding 1:10. In the injection molding process, the center of the lens will shrink due to the excessive center-edge thickness difference, which is unfavorable to the retention of the surface shape.

[0026] In the diffractive lens, one or two surfaces of the lens are provided with non-equidistant circular step structures, and the principle of diffraction optics is used to realize the diffraction of light. The pitch and height of the steps are determined by the angle of incidence, angle of emergence, optical path length modulation, lens refractive index, and harmonic diffraction coefficient of each point on the lens surface. Under the action of the diffractive structure, the deflection angle of light is directly proportional to the wavelength, that is, the longer the wavelength of light, the larger the lens diopter. Figure 5 shows the axial chromatic aberration curve of the diffractive lens, with a lens diopter of 23.81D, and the axial chromatic aberration of red and blue light is about 12mm, which is about 9 times that of the refractive lens, and the axial chromatic aberration direction is opposite to that of the refractive lens under the same conditions, so that the focus of 644nm light is closer to the lens, and the focus of 480nm light is farther from the lens, and such chromatic aberration is called negative chromatic aberration.

[0027] The refractive and diffractive mixed optical technology utilizes the dispersion properties of the above-mentioned refractive lenses and diffractive lenses, adds a diffractive structure to the traditional refractive optical surface, allocates a part of the diopter of the lens to the diffracted light beam, and the negative chromatic aberration of the diffracted light beam and the positive chromatic aberration of the refracted light beam cancel each other out, thereby reducing the overall dispersion of the lens.

[0028] The lens described in Chinese patent CN109716175A (patent title: Diffractive lens and vehicle lamp using the same) has the following characteristics. That is, the diffracted light is used to share 30% to 60% of the diopter of the lens, the thickness difference between the edge and center of the lens and the total thickness of the lens are low, and good primary injection molding characteristics are obtained, but this solution actually sacrifices design for the sake of processability. As mentioned above, the dispersion coefficient of the diffracted light is much larger than the dispersion of the refraction. For PC materials with high dispersion, the absolute value of the axial diffraction dispersion is 9 times the axial refraction dispersion, and for PMMA (polymethyl methacrylate) materials with low dispersion coefficient, the absolute value of the axial diffraction dispersion is 19 times the axial refraction dispersion. If a large amount of diffracted light is introduced, it will cause severe dispersion and affect the color of the light at the low beam cut-off line. Take the PMMA material used in Chinese patent CN109716175A as an example, the lens diameter is 56 mm, the total diopter of the lens body is 20 mm. -1 Assuming that the edge thickness is 1.5mm, the proportion of the lens diffraction diopter, the proportion of the edge and center thickness, and the axial chromatic aberration are as shown in the comparison table Figure 6. The axial chromatic aberration of the full refractive lens (the diffraction structure diopter accounts for 0% of the total diopter of the lens body) is positive, and the axial chromatic aberration of 640nm and 480nm light is 0.8mm. When the diffraction diopter accounts for 5% of the total diopter of the lens body, the diffraction chromatic aberration exceeds the refractive chromatic aberration, and the lens shows overall axial negative chromatic aberration. However, when the proportion of the diffractive diopter in the total diopter of the lens body exceeds 10%, the absolute value of the axial chromatic aberration of the lens is larger than that of the total refractive lens, that is, the axial chromatic aberration of the lens is increased by introducing the diffractive structure, when the diffractive diopter accounts for 30% of the total diopter of the lens, the ratio of the lens edge thickness to the center thickness is about 1:2, but the axial chromatic aberration reaches 8mm, and when the diffractive diopter accounts for 60% of the total diopter of the lens body, the axial chromatic aberration reaches 18mm. Therefore, the present invention limits the diopter of the lens diffractive structure to 20% or less of the total diopter of the lens, thereby avoiding the diffractive structure from introducing excessive chromatic aberration.

[0029] Layered injection molding is an effective means to solve the lens injection molding problems and improve the precision of the injection molded surface shape, and ensures the precision of the lens surface shape through the method of secondary injection molding, thus making it possible to more reasonably allocate the refractive / diffractive diopter of the lens and ensure the light color of the low beam cut-off line.

[0030] 12 includes a low beam light source 707, a low beam reflector 706, a low beam shading plate 705, and a lens, and the lens has the above-mentioned structure, the low beam reflector 706 is provided so as to cover the outside of the low beam light source 707, the lens is located on the light emission side of the low beam light source 707, and the low beam shading plate 705 is located between the low beam light source 707 and the lens. In this figure, the second refracting / diffracting surface 2 is a usable entrance surface 703, and the first refracting / diffracting surface 1 is a usable exit surface 702. EXAMPLES

[0031] Fig. 7 is a side view of the performance test of the refractive-diffractive mixed lens, and Fig. 8 is a parameter table of the refractive-diffractive mixed lens in this embodiment. When the lens is used normally, the light source is located on the same side as the second refracting-diffractive surface 2, the second refracting-diffractive surface 2 is the incident surface, and the first refracting-diffractive surface 1 is the exit surface.

[0032] However, during performance testing, the collimating optical device generally adopts a reverse optical path design to detect and focus parallel light to evaluate the lens performance, so in Fig. 7, the right side is the lens focus 404, the first refracting / diffractive surface 1 is the test entrance surface 402, and the second refracting / diffractive surface 2 is the test exit surface 403. The test entrance surface 402 has an envelope surface 405 with a diffractive structure 406 provided thereon.

[0033] In this embodiment, the lens material is polycarbonate (PC), which has excellent heat resistance and a Vicat softening temperature of 140°C, which can meet the heat requirements of automobile headlights, but has a large dispersion coefficient. The design wavelengths of this embodiment are 480nm and 580nm, and the refractive indices of PC for these two wavelengths are n1=1.601 and n2=1.586, respectively. When the lens diopter is 23.06D, if a full refractive lens is used, the diopter difference between the two wavelengths is about -0.55D, accounting for -2.3% of the total diopter of the lens body. The diopter difference between the two wavelengths of the full diffractive lens is 4.07mm. -1 This is equivalent to 20.8% of the total lens diopter. To eliminate lens dispersion, the refractive diopter is about 9 times the diffractive diopter, and the diffractive diopter accounts for 10% of the total lens diopter.

[0034] FIG. 9 is a graph showing the axial chromatic aberration curve of the lens in this embodiment. It can be seen from this graph that after optimization using the refractive-diffractive mixing method, the axial chromatic aberration of the lens for light rays of 488nm to 644nm is less than 0.3mm, among which, the axial chromatic aberration of the light rays of 480nm and 580nm, which are mainly optimized, does not exceed 0.05mm. EXAMPLES

[0035] This embodiment differs from the first embodiment in that the lens parameter table is as shown in FIG.

[0036] The lens material in this embodiment is Mitsubishi Gas EP-6000, and the material refractive index N d = 1.64, and the dispersion coefficient, Abbe number V d=23.5, and the glass transition temperature reaches 145°C. The design wavelengths of this embodiment are 480nm and 644nm, and the refractive indices of EP-6000 for these two wavelengths are n1=1.657 and n2=1.631, respectively. When the total diopter of the lens body is 24.76D, if a fully refractive lens is used, the diopter difference between the two wavelengths is about -1.02D, which accounts for 4% of the total diopter of the lens body. To eliminate lens dispersion, the refractive diopter is about 8 times the diffractive diopter, and the diffractive diopter accounts for 11% of the total diopter of the lens body. FIG. 11 is a graph showing the axial chromatic aberration curve of the lens in Example 2. After optimization using the refractive-diffractive mixed method, the axial chromatic aberration of the lens for light of 480 nm to 644 nm is less than 0.3 mm, among which, the axial chromatic aberration of the optimized light of 480 nm and 644 nm does not exceed 0.05 mm.

[0037] To sum up, the present invention has a simple structure, a reasonable design, and is easy to operate. The lens has good heat resistance and low dispersion, and has good collimation performance for diffused light of different wavelengths from the focal point. As shown in FIG. 13, the present invention can make the low beam cutoff line clear and avoid the cutoff line from being colored and blurred.

[0038] The above description of the specification is merely a specific embodiment of the present invention, and the various explanations given by way of examples do not limit the substance of the present invention. After reading the specification, a person skilled in the art can make modifications and variations to the above specific embodiments without departing from the substance and scope of the invention. [Explanation of symbols]

[0039] 1 First refracting and diffractive surface 2. Second refracting and diffractive surface 402 Test entrance surface 403 Test exit surface 404 Lens Focus 405 Envelope 406 Diffractive Structure 702 Used exit surface 703 Incidence plane used 705 Low beam shade 706 Low beam reflector 707 Low beam light source

Claims

1. A lens capable of collimating diffused light from a lens focal point to form parallel light, which is a refractive-diffractive mixed lens, comprising a lens body provided with a first refracting-diffractive surface (1) and a second refracting-diffractive surface (2) opposing each other along an optical axis L, the second refracting-diffractive surface (2) being located on one side closer to the lens focal point and the first refracting-diffractive surface (1) being located on one side away from the lens focal point, at least one of the first refracting-diffractive surface (1) and the second refracting-diffractive surface (2) having a diffractive structure which is rotationally symmetrical with respect to the optical axis L, the diopter of the diffractive structure accounting for 1% to 20% of the total diopter of the lens body, a thickness in the light passing hole diameter in the lens body farthest from the optical axis L is an edge thickness H1, and a distance between the intersection of the first refracting-diffractive surface (1) and the second refracting-diffractive surface (2) and the optical axis L is a lens center thickness H2, wherein H1:H2=1:X (10<X≦12).

2. 2. The lens according to claim 1, wherein the first refractive / diffractive surface (1) is a convex surface and the second refractive / diffractive surface (2) is a plane or convex surface.

3. 3. The lens according to claim 1, wherein the first refractive diffractive surface (1) is provided with a diffractive structure whose diopter occupies 1% to 20% of the total diopter of the lens body.

4. 3. The lens according to claim 1, wherein the second refractive / diffractive surface (2) is provided with a diffractive structure whose diopter occupies 1% to 20% of the total diopter of the lens body.

5. The lens according to claim 1 or 2, characterized in that each of the first refracting and diffractive surface (1) and the second refracting and diffractive surface (2) is provided with a diffractive structure whose sum of diopters accounts for 1% to 20% of the total diopter of the lens body.

6. A vehicle lamp comprising a low beam light source (707), a low beam reflector (706), a low beam shading plate (705) and a lens, the lens adopting the structure described in claim 1 or 2, the low beam reflector (706) being arranged to cover the outside of the low beam light source (707), the lens being positioned on the light emission side of the low beam light source (707), and the low beam shading plate (705) being positioned between the low beam light source (707) and the lens.

7. A vehicle lamp comprising a low beam light source (707), a low beam reflector (706), a low beam shading plate (705) and a lens, the lens adopting the structure described in claim 3, the low beam reflector (706) being arranged to cover the outside of the low beam light source (707), the lens being positioned on the light emission side of the low beam light source (707), and the low beam shading plate (705) being positioned between the low beam light source (707) and the lens.

8. A vehicle lamp comprising a low beam light source (707), a low beam reflector (706), a low beam shading plate (705) and a lens, the lens adopting the structure described in claim 4, the low beam reflector (706) being arranged to cover the outside of the low beam light source (707), the lens being positioned on the light emission side of the low beam light source (707), and the low beam shading plate (705) being positioned between the low beam light source (707) and the lens.

9. A vehicle lamp comprising a low beam light source (707), a low beam reflector (706), a low beam shading plate (705) and a lens, the lens adopting the structure described in claim 5, the low beam reflector (706) being arranged to cover the outside of the low beam light source (707), the lens being positioned on the light emission side of the low beam light source (707), and the low beam shading plate (705) being positioned between the low beam light source (707) and the lens.

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