Light collecting system

Abstract

The application discloses a light collecting system, which comprises a light emitting source, a first lens, a second lens and a third lens which are sequentially arranged on the light emitting path of the light emitting source and coaxially arranged; the focal lengths of the first lens, the second lens and the third lens are f1, f2 and f3 respectively, the combined focal length is f, f1, f2 and f3 are all greater than 0, the farthest distance from the light emitting surface of the light emitting source to the light emitting surface of the third lens is L, L and f satisfy 1.52 < L / f < 1.88; the effective light passing aperture of the first lens is D1, the gap spacing between the light emitting surface of the light emitting source and the first lens is L1, D1 and L1 satisfy 7 < D1 / L1 < 11; and the third lens is an aspheric lens. The light collecting system has the advantages of large numerical aperture, high light collecting rate and small imaging difference, the imaging optical system aberration correction degree of the light collecting system is high, and the optical effect is excellent.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of optical technology, more particularly, to a light collecting system BACKGROUND

[0002] The application of laser excited fluorescent powder, LED, EEL, VCSEL, fiber-coupled laser light source basically needs to use a light collecting module to better utilize the light source. In particular, for LED or fluorescent powder sheet excited by laser, the light is basically emitted in an angle of 180 degrees, and the brightness is low, so a light collecting module with a large numerical aperture (NA) needs to be added to collect light to meet the brightness requirement. The numerical aperture is the product of the refractive index (n) of the medium between the lens and the object being detected and the sine of the half aperture angle (2a), which is expressed by the formula as follows: NA=nd*sin a. The aperture angle, also known as the "mirror mouth angle", is the angle formed by the effective diameter of the front lens of the objective lens and the object point on the optical axis of the lens. The larger the aperture angle, the greater the light flux entering the lens, which is proportional to the effective diameter of the lens and inversely proportional to the distance from the focal point. The numerical aperture is an important parameter to judge the performance of the optical module. The larger the NA, the more light energy is collected. When NA=1, it means that the collected energy has no loss. Most of the collimation modules on the market have a numerical aperture NA of 0.7. It is rare for NA to exceed 0.8, and there has been no report of NA exceeding 0.9. The reason is that when the NA increases, the lens aberration will be greatly affected, which will affect the imaging effect, and the design of a large NA is difficult. SUMMARY

[0003] The present application aims to overcome at least one of the above-mentioned defects of the prior art, and provides a light collecting system with a large numerical aperture, which can balance a large numerical aperture, a high light collecting rate and a small imaging aberration. The imaging optical system of the light collecting system has a high aberration correction degree and excellent optical effect.

[0004] The technical solutions adopted by the present application are as follows:

[0005] A light collecting system, comprising a light emitting source, a first lens, a second lens and a third lens which are sequentially arranged on the light emitting path of the light emitting source and coaxially arranged; the focal lengths of the first lens, the second lens and the third lens are f1, f2 and f3 respectively, and the combined focal length is f, wherein f1, f2 and f3 are all greater than 0, the farthest distance from the light emitting surface of the light emitting source to the light emitting surface of the third lens is L, and L and f satisfy: 1.52

[0006] In one of the embodiments, the first lens is a plano-convex lens, the surface facing the light collecting surface of the phosphor is a plane, and the surface facing away from the light source is a convex surface with a radius of curvature R12;

[0007] The second lens is a biconvex lens or a meniscus lens, the surface facing away from the light source is a convex surface, the radius of curvature of the surface facing the light source is R21, and the radius of curvature of the surface facing away from the light source is R22, |R22|*8<|R21|<|R22|*15, |R12|<|R22|<|R12|*1.7.

[0008] The third lens is a plano-convex or meniscus aspheric lens, the surface facing the light source is a plane or a concave surface, and the surface facing away from the light source is a convex aspheric surface, the approximate spherical radius of curvature of the convex aspheric surface is R32, |R12|*0.8<|R32|<|R12|*1.6.

[0009] In one of the embodiments, the effective clear apertures of the second lens and the third lens are D2 and D3 respectively, and the first lens, the second lens and the third lens satisfy: 1≤|R12| / D1≤3.5; 1.3≤D2 / |R22|≤1.84; 0.34≤|R32| / D3≤0.75.

[0010] In one of the embodiments, the D1, D2 and D3 satisfy: D1<D2<D3, and 3*D1<D3<5*D1.

[0011] In one of the embodiments, the central thicknesses of the first lens and the third lens are T1 and T3 respectively, and the T1 and T3 satisfy: T1<T3, 2.2<D3 / T3<4.4.

[0012] In one of the embodiments, the gap distances of the first lens and the second lens, and the second lens and the third lens are L2 and L3 respectively, and the L1, L2 and L3 satisfy: 3*L1<L2, 3*L3≤L2.

[0013] In one of the embodiments, the first lens, the second lens and the third lens are glass lenses, and the refractive index nd of the materials used by the first lens, the second lens and the third lens satisfies: 1.45<nd<1.88.

[0014] In one of the embodiments, the depth z of the aspheric surface of the third lens satisfies:

[0015]

[0016] Wherein, α1=α6=α7=α8=0, k<0.

[0017] In one of the embodiments, the f satisfies 14mm < f < 16mm.

[0018] In one of the embodiments, the light emitting source is LED, EEL, VCSEL, fiber-coupled laser or semiconductor laser.

[0019] In one of the embodiments, the light emitting surface of the light emitting source is the light emitting surface of the laser-excited fluorescent powder layer. Further, the light emitting source emits blue laser with wavelength of 440-480nm, the blue laser is collimated or focused on the fluorescent powder, the plane where the fluorescent powder is located is the light emitting surface, at least part of the blue laser is converted into stimulated laser, the light after stimulation produces approximate Lambertian scattering, the divergence angle is large, the first lens, the second lens and the third lens can efficiently converge and collimate the Lambertian light, the light collection rate is high, the imaging difference is small, and the optical effect is excellent.

[0020] Compared with the prior art, the beneficial effects of the present application are that the lens group composed of three lenses is used to converge and collimate the light of the light emitting source, the numerical aperture of the light collection system is large and the light collection rate is high by controlling the focal length, combined focal length, length of the lens group, light transmission aperture of the first lens and the like, and at the same time, the imaging difference of the imaging optical system is small, the aberration correction degree is high, and the obtained light collection system has excellent light collection performance and optical effect. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 It is a schematic diagram of the optical structure of the light collection system of the present application.

[0022] Figure 2 It is a simulation analysis point diagram of the light collection system of embodiment 1 of the present application.

[0023] Figure 3 It is a simulation analysis aberration diagram of the light collection system of embodiment 1 of the present application.

[0024] Figure 4 It is a simulation analysis point diagram of the light collection system of embodiment 2 of the present application.

[0025] Figure 5 It is a simulation analysis aberration diagram of the light collection system of embodiment 2 of the present application. DETAILED DESCRIPTION

[0026] The drawings of the present application are only used for illustrative explanation and cannot be understood as the limitation of the present application. In order to better illustrate the following embodiments, some components in the drawings will be omitted, enlarged or reduced, and do not represent the actual product size; for those skilled in the art, it is understandable that some known structures and their descriptions in the drawings can be omitted.

[0027] The inventors found in the research process that the most difficult point to achieve high light collection efficiency and guarantee the optical effect is to simultaneously consider large numerical aperture and guarantee small imaging aberration, and currently there is no optical system with a numerical aperture of 0.9 or more on the market. In particular, for the optical system of a high-power laser light source, the level of light collection rate of the lens assembly will greatly affect the illumination and luminous flux of light, and therefore it is necessary to improve the light collection rate.

[0028] The present application is proposed based on the above problems.

[0029] In one embodiment of the present application, a light collection system is provided, comprising a light emitting source, a first lens, a second lens and a third lens which are sequentially arranged on the light emitting path of the light emitting source and coaxially arranged; the focal lengths of the first lens, the second lens and the third lens are f1, f2 and f3 respectively, and the combined focal length is f, wherein f1, f2 and f3 are all greater than 0, the farthest distance from the light emitting surface of the light emitting source to the light emitting surface of the third lens is L, and L and f satisfy: 1.52 < L / f < 1.88; the effective light passing aperture of the first lens is D1, the gap distance between the light emitting surface of the light emitting source and the first lens is L1, and D1 and L1 satisfy: 7 < D1 / L1 < 11; and the third lens is an aspheric lens.

[0030] The light collection system provided by the present application comprises a light emitting source and three lenses, the light emitting source is used to emit light, and the three lenses are used to maximize the light collection of the emitted light, so as to avoid the loss of light as much as possible and guarantee the optical effect. The effective light passing aperture of the first lens is larger, and the numerical aperture of the light collection system is larger. However, the effective light passing aperture of the first lens is not limited to increase, and imaging aberration, size, spatial assembly, optical processing and the like also need to be considered comprehensively. The second lens is used to further converge and / or collimate the light collected by the first lens, and to reduce the size of the light collection system. The third lens uses an aspheric lens to better correct aberration and guarantee collimation, so that the light collection system can consider large numerical aperture, high light collection rate and small imaging aberration through the comprehensive action of the first lens, the second lens and the third lens. The imaging optical system aberration correction degree of the light collection system is high, and the optical effect is excellent.

[0031] Further, L and f preferably satisfy: 1.66 ≤ L / f ≤ 1.72.

[0032] Further, D1 and L1 preferably satisfy: 8 ≤ D1 / L1 ≤ 9.

[0033] In any embodiment, the first lens is a plano-convex lens, the light receiving surface of which facing the light source is a plane, and the light emitting surface of which facing away from the light source is a convex surface with a radius of curvature R12; the second lens is a biconvex lens or a meniscus lens, the light emitting surface of which facing away from the light source is a convex surface, the radius of curvature of the light receiving surface of the second lens facing the light source and the radius of curvature of the light emitting surface of the second lens facing away from the light source are R21 and R22 respectively, |R22|*8<|R21|<|R22|*15, |R12|<|R22|<|R12|*1.7; the third lens is a plano-convex or meniscus aspheric lens, the light receiving surface of which facing the light source is a plane or a concave surface, and the light emitting surface of which facing away from the light source is a convex aspheric surface, the approximate spherical radius of curvature of the convex aspheric surface is R32, |R12|*0.8<|R32|<|R12|*1.6. In particular, when |R22|*8≤|R21|≤|R22|*10, |R12|*1.17≤|R22|≤|R12|*1.7, the size of the light receiving system is smaller. The radius of curvature of the first lens, the second lens and the third lens can affect the focal length and imaging effect of the light receiving system.

[0034] In any embodiment, the effective clear apertures of the second lens and the third lens are D2 and D3 respectively, and the first lens, the second lens and the third lens satisfy: 1≤|R12| / D1≤3.5; 1.3≤D2 / |R22|≤1.84; 0.34≤|R32| / D3≤0.75. Further preferably, 1.22≤|R12| / D1≤1.89, 1.3≤D2 / |R22|≤1.35; 0.4≤|R32| / D3≤0.6.

[0035] More specifically, the D1, D2 and D3 satisfy: D1<D2<D3, and 3*D1<D3<5*D1. The clear aperture of each lens affects the light receiving angle.

[0036] In any embodiment, the central thicknesses of the first lens and the third lens are T1 and T3 respectively, and the T1 and T3 satisfy: T1<T3, 2.2<D3 / T3<4.4. Further preferably, 3≤D3 / T3≤4.

[0037] In any embodiment, the gap distances of the first lens and the second lens, and the second lens and the third lens are L2 and L3 respectively, and the L1, L2 and L3 satisfy: 3*L1<L2, 3*L3≤L2.

[0038] In any embodiment, the first lens, the second lens and the third lens are all glass lenses, and the refractive index nd of the material used for the first lens, the second lens and the third lens satisfies: 1.45<nd<1.88.

[0039] In any embodiment, the depth z of the aspheric surface of the third lens satisfies:

[0040]

[0041] wherein, a1=a6=a7=a8=0, k<0; c is 1 / R, R is the radius of curvature, k is the quadratic surface coefficient; r is the height, a1 to a8 are aspheric surface coefficients.

[0042] In any embodiment, the light emitting source is a LED, an EEL, a VCSEL, a fiber-coupled laser or a semiconductor laser.

[0043] In any embodiment, the light emitting surface of the light emitting source is the light emitting surface of a laser-excited fluorescent powder layer. Further, the light emitting source emits blue laser with a wavelength of 440-480 nm, the blue laser is collimated or focused on the fluorescent powder, and the plane where the fluorescent powder is located is the light emitting surface. At least part of the blue laser is converted into stimulated laser, and the stimulated light produces approximate Lambertian scattering with a large divergence angle. The first lens, the second lens and the third lens can efficiently converge and collimate the Lambertian light, have high light collection efficiency, small imaging difference and excellent optical effect. Further, the light emitting surface of the fluorescent powder layer can be the light emitting surface of a fluorescent color wheel, i.e., the fluorescent powder layer is coated on a rotatable color wheel. Through the rotation design, the excitation point of the fluorescent powder is changed while the laser light source is fixed, and the laser is irradiated on the fluorescent powder in a certain trajectory, which is similar to a circular trajectory, thereby avoiding the laser being concentrated on a single point and burning the powder.

[0044] The following further illustrates with specific parameters.

[0045] Embodiment 1

[0046] As shown in Figure 1 the embodiment discloses a light collection system, which comprises a light emitting source, a first lens 1, a second lens 2 and a third lens 3 arranged in sequence on the light emitting path of the light emitting source and coaxially arranged; the focal lengths of the first lens 1, the second lens 2 and the third lens 3 are f1, f2 and f3 respectively, the combined focal length is f, f1, f2 and f3 are all greater than 0, the farthest distance from the light emitting surface A of the light emitting source 100 to the light emitting surface of the third lens 3 is L, L and f satisfy: 1.52<L / f<1.88, the effective light passing aperture of the first lens is D1, the gap distance between the light emitting surface of the light emitting source and the first lens is L1; the third lens is an aspheric lens. More specifically, in the embodiment, f=15 mm, L=24.9 mm, D1=9 mm and L1=1 mm.

[0047] More specifically, in this embodiment, the first lens 1 is a plano-convex lens, whose light-collecting surface facing the light source is a plane, and whose light-emitting surface facing away from the light source is a convex surface with a curvature radius of R12. The second lens is a biconvex lens, that is, its light-collecting surface facing the light source and its light-emitting surface facing away from the light source are both convex surfaces, and the curvature radii of the light-collecting surface of the second lens facing the light source and the curvature radii of the light-emitting surface facing away from the light source are R21 and R22, respectively. The third lens is a plano-convex aspheric lens, whose light-collecting surface facing the light source is a plane, and its light-emitting surface facing away from the light source is a convex and aspheric surface. In this embodiment, R12 = -17mm, R21 = 200mm, R22 = -20mm, and R32 = -15mm.

[0048] Furthermore, the effective clear apertures of the second lens and the third lens are D2 and D3 respectively. In this embodiment, D2 = 27 mm and D3 = 31 mm.

[0049] The gap between the first lens and the second lens, and the gap between the second lens and the third lens are L2 and L3 respectively. Figure 1 In the arrangement shown from left to right, the gap distance L1 described in the present invention refers to the shortest distance between the light-emitting surface of the light source and the light-receiving surface of the first lens facing the light source. The gap distance L2 refers to the shortest distance between the light-emitting surface of the first lens facing away from the light source and the light-receiving surface of the second lens facing the light source. The gap distance L3 refers to the shortest distance between the light-emitting surface of the second lens facing away from the light source and the light-receiving surface of the third lens facing the light source. More specifically, in this embodiment, L2 = 5.1 mm and L3 = 0.3 mm.

[0050] The center thicknesses of the first lens, the second lens, and the third lens are T1, T2, and T3, respectively. In this embodiment, T1 = 2 mm, T2 = 7.5 mm, and T3 = 9 mm.

[0051] In this embodiment, the depth z of the aspheric surface of the third lens satisfies:

[0052]

[0053] Among them, α1=α6=α7=α8=0; k<0;

[0054] α2=1.5×10 -5 , α3=2.1×10 -8 , α4=3.7×10 -10 , α5=-5×10 -13 ;

[0055] c is 1 / R, R is the radius of curvature, k is the quadratic surface coefficient, r is the height, and α1 to α8 are aspheric surface coefficients.

[0056] Further, the first lens, the second lens and the third lens in the embodiment are glass lenses, and the refractive index nd of the material used by the first lens, the second lens and the third lens satisfies 1.45 < nd < 1.88.

[0057] The light emitting source is an LED, an EEL, a VCSEL, a fiber-coupled laser or a semiconductor laser.

[0058] The light emitting surface of the light emitting source is the light emitting surface of the laser-excited fluorescent powder sheet. More specifically, the light emitting source in the embodiment emits blue laser with a wavelength of 440-480 nm, the blue laser is collimated or focused on the fluorescent powder, and the plane where the fluorescent powder is located is the light emitting surface. At least part of the blue laser is converted into stimulated light, and the stimulated light is approximately Lambertian scattering with a large divergence angle. The first lens, the second lens and the third lens can efficiently converge and collimate the Lambertian light, and the light collection rate is high, the imaging difference is small, and the optical effect is excellent.

[0059] The simulation analysis point diagram of the embodiment 1 is shown in Figure 2 The RMS radius of the light collection system is 2.164, indicating that the optical system has high spot aggregation degree and excellent optical effect. The simulation analysis aberration diagram of the light collection system is shown in Figure 3 The maximum scale is ±5mr, and the actual value is about ±4mr, indicating that the optical system has small aberration.

[0060] Based on the above parameters of the embodiment, the numerical aperture of the light collection system is 0.94 and the light collection rate is 94% through simulation calculation by the zemax software. Therefore, the light collection system can balance the large numerical aperture, the high light collection rate and the small imaging difference, the imaging optical system of the light collection system has high aberration correction degree, and the optical effect is excellent.

[0061] Embodiment 2

[0062] As shown in Figure 1 The embodiment 2 discloses a light collection system, which comprises a light emitting source, a first lens 1, a second lens 2 and a third lens 3 arranged in sequence on the light emitting path of the light emitting source and coaxially arranged; the focal lengths of the first lens 1, the second lens 2 and the third lens 3 are f1, f2 and f3 respectively, and the combined focal length is f, the f1, f2 and f3 are all greater than 0, the farthest distance from the light emitting surface A of the light emitting source 100 to the light emitting surface of the third lens 3 is L, the L and the f satisfy 1.52 < L / f < 1.88, the effective light passing aperture of the first lens is D1, and the gap distance between the light emitting surface of the light emitting source and the first lens is L1; the third lens is an aspheric lens. In the embodiment, f = 14.5 mm, L = 25 mm, D1 = 8 mm and L1 = 1 mm.

[0063] The first lens 1 is a plano-convex lens, the light receiving surface facing the light source is a plane, and the light emitting surface away from the light source is a convex surface with a radius of curvature R12. The third lens is a plano-convex aspheric lens, the light receiving surface facing the light source is a plane, and the light emitting surface away from the light source is a convex aspheric surface, the approximate spherical curvature radius of the convex aspheric surface is R32. Different from example 1, the second lens is a concave-convex lens, that is, the light receiving surface facing the light source is a concave surface, and the light emitting surface away from the light source is a convex surface. The curvature radii of the light receiving surface and the light emitting surface of the second lens are R21 and R22, respectively. In this embodiment, R12=-9.8mm, R21=-142mm, R22=-16mm, and R32=-15.6mm.

[0064] The effective clear apertures of the second lens and the third lens are D2 and D3, respectively. In this embodiment, D2=21mm and D3=26mm.

[0065] Further, the gap distances of the first lens and the second lens, and the second lens and the third lens are L2 and L3, respectively. Specifically, in this embodiment, L2=6.7mm and L3=2mm.

[0066] The center thicknesses of the first lens, the second lens, and the third lens are T1, T2, and T3, respectively. In this embodiment, T1=2.7mm, T2=5.1mm, and T3=7.5mm.

[0067] The depth z of the aspheric surface of the third lens in this embodiment satisfies:

[0068]

[0069] wherein α1=α6=α7=α8=0; k<0;

[0070] α2=-2.1×10 -6 , α3=-2.57×10 -7 , α4=1.52×10 -8 , α5=-5.3×10 -11 ;

[0071] c is 1 / R, R is the curvature radius, k is the quadratic surface coefficient, and r is the height. α1 to α8 are aspheric surface coefficients.

[0072] The light emitting source in this embodiment is a blue laser with a wavelength of 440-480 nm, which is collimated or focused on the phosphor, and the plane where the phosphor is located is the light emitting surface. At least part of the blue laser is converted into stimulated light, and the stimulated light produces approximate Lambertian scattering with a large divergence angle. The first lens, the second lens and the third lens can efficiently collect and collimate the Lambertian light with high light collection efficiency and small imaging difference, and the optical effect is excellent.

[0073] The simulation analysis point diagram of this embodiment 2 is shown in Figure 4 The RMS radius of the light collection system is 6.543, indicating that the optical system has high spot aggregation degree and excellent optical effect. The simulation analysis aberration diagram of the light collection system is shown in Figure 5 The maximum scale is ±10mr, and the actual value is about ±6mr, indicating that the optical system has small aberration (although not as good as embodiment 1, but the effect is still good).

[0074] Based on the above parameters of this embodiment, the numerical aperture of the light collection system is 0.92 and the light collection efficiency is 92% through the simulation calculation by the zemax software. It can be seen that the light collection system can balance the large numerical aperture, high light collection efficiency and small imaging difference, and the imaging optical system of the light collection system has high aberration correction degree and excellent optical effect.

[0075] In summary, the light collection system has high light collection efficiency, the numerical aperture is not less than 0.9, and the light collection efficiency is not less than 90%.

[0076] Obviously, the above embodiments of the present application are only examples for clearly illustrating the technical solutions of the present application, and are not intended to limit the specific embodiments of the present application. Any modification, equivalent replacement and improvement made within the spirit and principle of the claims of the present application shall be included in the protection scope of the claims of the present application.

Claims

1. A light collecting system, characterized by, The light emitting source comprises a lens total number of 3, a first lens, a second lens and a third lens which are sequentially arranged on the light emitting path of the light emitting source and coaxially arranged; the focal lengths of the first lens, the second lens and the third lens are f1, f2 and f3 respectively, the combined focal length is f, f1, f2 and f3 are all greater than 0, the farthest distance from the light emitting surface of the light emitting source to the light emitting surface of the third lens is L, L and f satisfy 1.52 The first lens is a plano-convex lens, the light receiving surface facing the light emitting source is a plane, and the light emitting surface away from the light emitting source is a convex surface with a curvature radius R12; The second lens is a double-convex lens or a meniscus lens, the light emitting surface away from the light emitting source is a convex surface, the curvature radius of the light receiving surface facing the light emitting source and the curvature radius of the light emitting surface away from the light emitting source are R21 and R22 respectively, |R22|*8 The third lens is a plano-convex or meniscus aspheric lens, the light receiving surface facing the light emitting source is a plane or a concave surface, and the light emitting surface away from the light emitting source is a convex aspheric surface, the approximate spherical curvature radius of the convex aspheric surface is R32, |R12|*0.8 The first lens, the second lens and the third lens are all glass lenses, and the refractive index nd of the materials used by the first lens, the second lens and the third lens satisfies 1.45 2. The light collection system of claim 1, wherein The effective light passing apertures of the second lens and the third lens are D2 and D3 respectively, and the first lens, the second lens and the third lens satisfy 1 3. The light collection system of claim 2, wherein, The D1, D2 and D3 satisfy D1 4. The light collection system of claim 2, wherein The center thicknesses of the first lens and the third lens are T1 and T3 respectively, and T1 and T3 satisfy T1 5. The light collection system of claim 1, wherein, The gap distances of the first lens and the second lens, and the second lens and the third lens are L2 and L3 respectively, and L1, L2 and L3 satisfy 3*L1 6. The light collection system of claim 1, wherein, The depth z of the aspheric surface of the third lens satisfies wherein , k < 0; c is 1 / R, R is the radius of curvature, k is the conic constant; r is the height, to is the aspherical coefficient.

7. The light collection system of any of claims 1 to 6, wherein, The light emitting source is an LED, an EEL, a VCSEL, a fiber-coupled laser or a semiconductor laser.

8. The light collection system of any of claims 1 to 6, wherein, The light emitting surface of the light emitting source is the light emitting surface of a laser-excited fluorescent powder layer.

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