Optical imaging system and camera lens

Abstract

This invention discloses an optical imaging system and a camera lens. The optical imaging system includes a plurality of optical elements arranged along the optical path. All surfaces of the optical elements include at least two surface types: freeform surfaces, diffractive microstructure surfaces, and metasurfaces. When diffractive microstructure surfaces are included, they are arranged in pairs. Applying the optical imaging system of this invention to a camera lens can satisfy different full field of view angles, achieving high imaging quality and a compact structure while reducing the number of lenses.

Description

Technical Field

[0001] This invention relates to the field of optical imaging equipment technology, and in particular to an optical imaging system and a camera lens. Background Technology

[0002] With the popularization of mobile electronic devices, the technology of camera modules used in mobile electronic devices to help users acquire images (such as videos or pictures) has developed and progressed rapidly. In recent years, camera modules have been widely used in many fields such as medical care, security, and industrial production.

[0003] To meet increasingly diverse market demands, high pixel count, small size, and large aperture are irreversible development trends for existing camera modules. For example, Chinese patent document CN113703135A discloses a high-pixel, large-aperture, wide-angle forward-looking optical system and its application in a camera module; Chinese patent document CN109507784A discloses a high-pixel, large-aperture depth imaging optical system and its application in a camera module.

[0004] However, large aperture, high pixel count (larger image sensor area), and wide field of view lead to a longer overall optical length of the lens, a more complex optical system structure, and more difficult aberration correction.

[0005] In recent years, with the rapid development of optical component processing technology, the processing technology for high-precision complex optical surfaces has become increasingly mature. Utilizing high-precision single-point diamond lathes for precision mold processing and high-precision injection molding, mass production of high-precision complex surfaces can be achieved. Applying complex optical surfaces to small-sized optical devices (such as mobile phone camera modules and endoscopic imaging systems) will help reduce distortion over large field-of-view angles and, to some extent, reduce the overall optical length of camera modules. Summary of the Invention

[0006] This invention provides an optical imaging system and camera lens that achieves high imaging quality and a compact structure while reducing the number of lenses.

[0007] An optical imaging system includes a plurality of optical elements arranged along an optical path, wherein all surfaces of the plurality of optical elements include at least two types of surface types, namely freeform surfaces, diffractive microstructure surfaces, and metasurfaces; wherein, when diffractive microstructure surfaces are included, the diffractive microstructure surfaces are arranged in pairs.

[0008] In this invention, the freeform surface is a continuous smooth surface that is symmetrical about the X and Y directions, and the surface of the optical element is set as a diffractive microstructure surface or a metasurface to serve as a diffractive optical element.

[0009] Furthermore, the equation of the freeform surface is:

[0010]

[0011] Where: z(x, y) is the optical surface sagitta; k is the conic coefficient; c is the radius of curvature; r is the radius height along the optical axis. 2 =x 2 +y 2 A i These are the polynomial coefficients, E i (x, y) is a polynomial.

[0012] Furthermore, the freeform surface has a bisymmetric structure, and the polynomial E i In (x, y), the coefficients of the odd-degree terms of x and y are 0, as follows:

[0013]

[0014] Among them, A i These are polynomial coefficients.

[0015] When diffractive microstructures are included, in each pair of diffractive microstructures, the two layers of diffractive microstructures are arranged on the plane, spherical, aspherical or freeform surface substrate of the optical element with different refractive index materials, and the gap between the two layers of diffractive microstructures is air or other light-transmitting filling medium.

[0016] The spacing δ between the two diffraction microstructure planes is 1–20 μm, and the phase distributions of the diffraction microstructure planes are as follows: and

[0017]

[0018]

[0019] Z A (ρ), Z B (ρ) represents the microstructure morphology of the two diffraction microstructure planes, n A (λ) and n B (λ) represents the refractive index of the optical element made of the two materials; the heights of the two diffraction microstructures are H1 and H2, respectively, and the phase height distribution function of the diffraction microstructures satisfies the following condition:

[0020]

[0021] Where, λ 01 , λ 02 For the design wavelength, n A (λ 01 ), n A (λ 02 ) and nB (λ 01 ), n B (λ 02 ( ) is the design wavelength λ 01 , λ 02 The corresponding refractive indices of the two optical elements made of two different materials.

[0022] The aforementioned diffraction microstructure is a blazed binary optical microstructure, specifically: ridge-shaped or cylindrical diffraction microstructure optical surfaces with dimensions smaller than wavelength are fabricated on a substrate using photolithography and etching processes. The equivalent refractive index dispersion relationship of the diffraction microstructure satisfies the following relationship:

[0023]

[0024] Where, n(f, λ) ∞ ) is the equivalent refractive index under the static limit; Q(f, ε) is an expression related to the fill factor f and the dielectric constant ε of the material; Λ is the subwavelength structure period; and λ is the wavelength of the incident light wave.

[0025]

[0026] Where d is the diameter of the microstructure cylinder or the width of the ridge; and satisfies f.Λ>δt, (1-f)·Λ>δt; where δt is the finest fabricated linewidth; the equivalent refractive index is between n eff (f1, λ0) and n eff (f2, λ0), meaning the fill factor of the microstructure is between f1 and f2; the etching depth h satisfies:

[0027]

[0028] When the design wavelength λ0 is reached, the equivalent phase distribution of the microstructure at different fill factors is as follows:

[0029]

[0030] Phase transfer function and The relationship between them is:

[0031]

[0032] The metasurface is an artificial two-dimensional material with nanoscale elliptical cylinders, cuboids or irregular shapes as basic units, set on a planar or curved substrate, including transmissive or reflective metasurfaces.

[0033] Using the aforementioned optical imaging system, this invention also designs a variety of camera lenses with different full field of view (FOV).

[0034] In the first type of camera lens, the field of view (FOV) of the camera lens satisfies FOV > 90°. The optical imaging system described above is used, and the optical elements included in the optical imaging system are at least three lenses. The surfaces of all lenses include at least one freeform surface and at least one pair of diffractive microstructure surfaces or one metasurface.

[0035] As one embodiment of the first camera lens, the lenses in the optical imaging system along the optical axis from the object side to the image side sequentially include: a first lens, a second lens, a third lens, a fourth lens, a fifth lens, and a sixth lens;

[0036] The first lens has negative optical power, the second lens has negative optical power, the third lens has positive optical power, the fourth lens has negative optical power, the fifth lens has negative optical power, and the sixth lens has positive optical power; all surfaces of the first to the sixth lenses include at least one freeform surface and at least one pair of diffractive microstructure surfaces or one metasurface.

[0037] In the second type of camera lens, the field of view (FOV) of the camera lens satisfies FOV<30°. The optical imaging system described above is used. The optical elements included in the optical imaging system are at least one lens and at least one prism containing a refractive surface and a reflective surface. The surfaces of all lenses contain at least one freeform surface and at least one pair of diffractive microstructure surfaces or one metasurface.

[0038] As one embodiment of the second type of camera lens, the optical imaging system includes a first lens, a second prism and a third lens in sequence along the optical axis from the object side to the image side;

[0039] The first lens has positive optical power, the second prism has two transmission surfaces and three reflection surfaces, and the third lens has negative optical power.

[0040] The second surface of the first lens is adjacent to the first transmission surface of the second prism, with a spacing of 1 to 20 μm, and the surface shapes are the same; the second surface of the first lens and the first transmission surface of the second prism are diffraction microstructure surfaces; the three reflecting surfaces of the second prism are freeform surfaces.

[0041] The second reflecting surface of the second prism is located in the optical path of the first reflecting surface of the second prism, and the third reflecting surface of the second prism is located in the optical path of the second reflecting surface of the second prism; the central normals of the first reflecting surface, the second reflecting surface, and the third reflecting surface of the second prism all intersect.

[0042] In the third type of camera lens, the field of view (FOV) of the camera lens satisfies 30°≤FOV≤90°. The optical imaging system described above is used, and the optical elements included in the optical imaging system are at least four lenses. The surfaces of all lenses contain at least two freeform surfaces and at least a pair of diffractive microstructure surfaces or a metasurface.

[0043] As one embodiment of the third type of camera lens, the optical imaging system includes, in sequence from the object side to the image side along the optical axis, a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens, and an eighth lens;

[0044] Among them, the first lens has positive optical power, the second lens has negative optical power, the third lens has positive optical power, the fourth lens has optical power, the fifth lens has optical power, the sixth lens has positive optical power, the seventh lens has negative optical power, and the eighth lens has negative optical power.

[0045] All surfaces of the first to eighth lenses contain at least two freeform surfaces and at least a pair of diffractive microstructure surfaces or a metasurface.

[0046] Compared with the prior art, the present invention has the following beneficial effects:

[0047] 1. This invention utilizes freeform surface optical elements and diffractive optical elements to construct a conventional autofocus module, which can reduce the overall optical length and improve the imaging quality of the optical system. Freeform surfaces, diffractive microstructures, and metasurfaces can reduce or minimize aberrations in the optical system, achieving aberration correction and distortion reduction. They can also reduce the overall optical length and / or volume of the module.

[0048] 2. This invention uses complex optical surfaces (freeform surfaces, diffractive microstructure surfaces, and metasurfaces) in camera lens modules, which will help reduce distortion over a large field of view and reduce the overall optical length of the camera module to some extent. Attached Figure Description

[0049] Figure 1 This is a schematic diagram of the imaging structure of the freeform surface of the present invention;

[0050] Figure 2 A schematic diagram of paired diffraction microstructures;

[0051] Figure 3 for Figure 2 Enlarged schematic diagram;

[0052] Figure 4 The relationship between the morphology and phase distribution of the first type of diffraction microstructure;

[0053] Figure 5The relationship between the morphology and phase distribution of the second type of diffraction microstructure;

[0054] Figure 6 This is a schematic diagram of the metasurface structure;

[0055] Figure 7 This is a schematic diagram of an optical imaging system with a field of view of less than 30°, as shown in Example 1.

[0056] Figure 7 (a) is the optical path diagram of the optical imaging system of Example 1;

[0057] Figure 7 (b) is the modulation pass-through function curve of the optical imaging system in Example 1;

[0058] Figure 7 (c) shows the field curvature and distortion curves of the optical imaging system in Example 1;

[0059] Figure 7 (d) shows the diffraction efficiency curves of the diffraction structure formed by two diffraction microstructure surfaces in the optical imaging system of Example 1 at different wavelengths.

[0060] Figure 7 (e) is the equivalent phase distribution of the first diffraction microstructure surface in the optical imaging system of Example 1;

[0061] Figure 7 (f) shows the microstructure distribution of the first diffraction microstructure surface in the optical imaging system of Example 1;

[0062] Figure 7 (g) is the equivalent phase distribution of the second diffraction microstructure surface in the optical imaging system of Example 1;

[0063] Figure 7 (h) shows the microstructure distribution of the second diffraction microstructure surface in the optical imaging system of Example 1;

[0064] Figure 8 This is a schematic diagram of an optical imaging system with a field of view greater than 90°, as shown in Example 2.

[0065] Figure 8 (a) is the optical path diagram of the optical imaging system in Example 2;

[0066] Figure 8 (b) is the modulation pass-through function curve of the optical imaging system in Example 2;

[0067] Figure 8 (c) shows the field curvature and distortion curves of the optical imaging system in Example 2;

[0068] Figure 8(d) shows the diffraction efficiency curves of the diffraction structure composed of two diffraction microstructure surfaces in the optical imaging system of Example 2 at different wavelengths.

[0069] Figure 8 (e) is the equivalent phase distribution of the first diffraction microstructure surface in the optical imaging system of Example 2;

[0070] Figure 8 (f) shows the microstructure distribution of the first diffraction microstructure surface in the optical imaging system of Example 2;

[0071] Figure 8 (g) is the equivalent phase distribution of the second diffraction microstructure surface in the optical imaging system of Example 2;

[0072] Figure 8 (h) shows the microstructure distribution of the second diffraction microstructure surface in the optical imaging system of Example 2;

[0073] Figure 9 This is a schematic diagram of an optical imaging system with a field of view between 30° and 90°, as described in Example 3.

[0074] Figure 9 (a) is the optical path diagram of the optical imaging system in Example 3;

[0075] Figure 9 (b) is the modulation pass-through function curve of the optical imaging system in Example 3;

[0076] Figure 9 (c) Field curvature and distortion curves of the optical imaging system in Example 3;

[0077] Figure 9 (d) shows the diffraction efficiency curves of the diffraction structure composed of two diffraction microstructure surfaces in the optical imaging system of Example 3 at different wavelengths.

[0078] Figure 9 (e) is the equivalent phase distribution of the first diffraction microstructure surface in the optical imaging system of Example 3;

[0079] Figure 9 (f) shows the microstructure distribution of the first diffraction microstructure surface in the optical imaging system of Example 3;

[0080] Figure 9 (g) is the equivalent phase distribution of the second diffraction microstructure surface in the optical imaging system of Example 3;

[0081] Figure 9 (h) shows the microstructure distribution of the second diffraction microstructure surface in the optical imaging system of Example 3. Detailed Implementation

[0082] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be noted that the embodiments described below are intended to facilitate the understanding of the present invention and do not constitute any limitation thereof.

[0083] In this invention, the optical imaging system includes freeform surface elements and diffractive optical elements. By using freeform surface elements and diffractive optical elements, the optical imaging system can achieve high imaging quality and a compact structure while reducing the number of lenses.

[0084] The freeform surface element is a continuous smooth surface that is symmetrical about the X and Y directions. The diffractive optical element is an optical element with at least one pair (double or multi-layer) diffractive microstructure surfaces or a metasurface diffractive optical element.

[0085] In this invention, the equation describing the freeform surface is:

[0086]

[0087] Where z(x, y) is the optical surface sagitta; k is the conic coefficient; c is the radius of curvature; r is the radius height along the optical axis; and r 2 =x 2 +y 2 A i These are polynomial coefficients.

[0088] The freeform surface has a double-symmetric structure, and the coefficients of the odd-degree terms of x and y in the polynomial are 0.

[0089]

[0090] like Figure 1 As shown, the imaging structure of the freeform surface is illustrated. The figure includes the first freeform surface 1, the second freeform surface 2, and the image sensor surface 3.

[0091] In each pair of diffraction microstructures, the two diffraction microstructures are arranged on a plane, spherical, aspherical or freeform surface substrate of an optical element made of different refractive index materials, and the gap between the two diffraction microstructures is air or other light-transmitting filling medium.

[0092] like Figure 2 and Figure 3 As shown, a pair of (double-layered) diffraction microstructures are illustrated. The figure includes lens 1 (4), lens 2 (5), the substrate surface of lens 1 (6), the substrate surface of lens 2 (7), the diffraction microstructure of lens 1 (8), the diffraction microstructure of lens 2 (9), and the filling medium (10). The filling medium (10) is either an air gap or a transparent dielectric layer. The refractive index of lens 1 (4) is n. A The refractive index of lens 25 is n. B The thickness of the filling medium 10 is δ.

[0093] The microstructure morphologies of the diffraction microstructure planes are Z A (ρ), Z B (ρ), the phase distributions of the diffraction microstructure planes are respectively and

[0094]

[0095]

[0096] Figure 4 The figure shows the relationship between the morphology and phase distribution of the first type of diffraction microstructure. In the figure, (a) is the shape distribution of the diffraction microstructure, (b) is the refractive index distribution of the diffraction microstructure material, and (c) is the phase distribution corresponding to the diffraction microstructure.

[0097] Figure 5 The figure shows the relationship between the morphology and phase distribution of the second type of diffraction microstructure. In the figure, (a) is the shape distribution of the diffraction microstructure, (b) is the refractive index distribution of the diffraction microstructure material, and (c) is the phase distribution corresponding to the diffraction microstructure.

[0098] Metasurfaces are artificial two-dimensional materials with nanoscale elliptical cylinders, cuboids, or irregular shapes as basic units, set on planar or curved substrates. They include transmissive or reflective metasurfaces. Figure 6 As shown, (a) is a metasurface formed by the distribution of nanostructures on a planar substrate, and (b) is a metasurface formed by the distribution of nanostructures on a curved substrate. The figure includes a planar substrate 10, a nanostructure 11, and a curved substrate 12.

[0099] Using the aforementioned optical imaging system, this invention designs a variety of camera lenses with different full field of view (FOV).

[0100] Example 1

[0101] like Figure 7 The figure shows an optical imaging system with a field of view (FOV) of <35°. It includes lens 13, prism 14, lens 15, and image detector 16. S1 and S2 are the front and rear transmission surfaces of lens 13, with S2 being a diffraction microstructure surface. S3, S4, S5, S6, and S7 are the optical surfaces of prism 14, where S4, S5, and S6 are freeform reflecting surfaces, S3 is a diffraction microstructure surface, and S7 is a transmission surface. S8 and S9 are the front and rear transmission surfaces of lens 15. The adjacent spacing between the two diffraction microstructure surfaces S2 and S3 ranges from 2 to 20 micrometers, and both diffraction microstructure surfaces have the same base surface.

[0102] Figure 7 (a) is the optical path diagram of the optical imaging system; Figure 7(b) is the modulation pass-through function curve of the optical imaging system; Figure 7 (c) shows the field curvature and distortion curves of the optical imaging system; Figure 7 (d) shows the diffraction efficiency curves of the diffraction structure formed by two diffraction microstructure surfaces in the optical imaging system at different wavelengths. Figure 7 (e) represents the equivalent phase distribution of the first diffractive microstructure surface in the optical imaging system; Figure 7 (f) shows the microstructure distribution of the first diffraction microstructure surface in the optical imaging system; Figure 7 (g) represents the equivalent phase distribution of the second diffraction microstructure surface in the optical imaging system; Figure 7 (h) represents the microstructure distribution of the second diffraction microstructure surface in the optical imaging system.

[0103] In this embodiment, Figure 7 The optical imaging system shown is used in a mobile phone's built-in telephoto lens with a focal length of 19.2mm and a relative aperture of F#2.1. The detector is a 1 / 2.5″ CMOS sensor, employing three freeform reflective surfaces and two diffraction microstructures. All optical lenses are made of resin, and the material distribution is shown in Table 1 below.

[0104] Table 1

[0105]

[0106]

[0107] The second surface of lens one and the first surface of lens two are diffraction microstructure surfaces, spaced 20 micrometers apart. The microstructures on these surfaces are distributed on an aspherical substrate. The phase coefficients of the microstructure surfaces are shown in Table 2 below.

[0108] Table 2

[0109] Serial Number Phase coefficient L1S2 L2S1 1 <![CDATA[A1]]> -8.710E006 7.593E006 2 <![CDATA[A2]]> -5.721E009 7.883E009 3 <![CDATA[A3]]> -3.715E011 -7.400E011 4 <![CDATA[A4]]> 6.433E016 -6.514E016 5 <![CDATA[A5]]> 0 0 6 <![CDATA[A6]]> 0 0

[0110] Note: The normalized radius corresponding to the phase coefficient is 1.0 mm.

[0111] The substrate for the diffraction microstructure is an aspherical surface, and the corresponding aspherical coefficients are shown in Table 3 below:

[0112] Table 3

[0113] Serial Number Aspheric coefficient L4S2 L5S1 1 <![CDATA[ɑ1]]> 0.0 0.0 2 <![CDATA[ɑ2]]> 0.0019045101 0.0019045101 3 <![CDATA[ɑ3]]> 0.0075311795 0.0075311795 4 <![CDATA[ɑ4]]> -0.0028755655 -0.0028755655 5 <![CDATA[ɑ5]]> 0.00048739694 0.00048739694 6 <![CDATA[ɑ6]]> 0.00014100397 0.00014100397 7 <![CDATA[ɑ7]]> -8.3505669E-005 -8.3505669E-005 8 <![CDATA[ɑ8]]> 1.5847911E-005 1.5847911E-005

[0114] Both the front and rear surfaces of lens two are freeform surfaces, and the freeform surface coefficients are shown in Table 4 below:

[0115] Table 4

[0116]

[0117]

[0118] Note: The normalized radius is 2.052 mm.

[0119] The height of the microstructure on the surface of the first diffractive optical element is H1 = 8.223 μm, and the height of the microstructure on the surface of the second diffractive element is H2 = 10.751 μm; there are a total of 56 rings on the surface of the diffractive microstructure, and the narrowest ring width is 53.56 μm (e.g., Figure 7 (f)); The surface of the diffraction microstructure has a total of 60 rings, with the narrowest ring width being 39.21 μm (e.g., Figure 7 (h));

[0120] from Figure 7 (d) It can be seen that using a double-layer diffraction element can maintain high diffraction efficiency over a very wide wavelength range. In contrast, a single-layer diffraction element only achieves precise blazing at the designed wavelength (100% diffraction efficiency), while its diffraction efficiency drops very rapidly in the short-wave and long-wave ranges deviating from the designed wavelength. Furthermore, the calculations show that compared to a single-layer diffraction microstructure, using a double-layer microstructure significantly increases the depth of the microstructure (H1 = 23.2 μm, H2 = 16.8 μm; the depth of a single-layer diffraction structure is approximately 1 μm). The depth of the microstructure will be even greater in the mid-wave or long-wave infrared range. The values ​​of H1 and H2 depend on the dispersion characteristics of the two materials and the selected design wavelengths. Considering the limitations of actual processing technology, the aspect ratio of the microstructure that existing ICP equipment can process is 7–8; the greater the microstructure depth, the larger the finest linewidth.

[0121] Similar to single-layer diffractive optical elements, the fabrication of multilayer binary diffractive optical elements will generate etching depth errors, linewidth errors, and multiple overlay alignment errors. In addition, there are also lateral alignment errors between the diffractive microstructures and stacking tilt errors, which will reduce the diffraction efficiency of the element and affect the performance of the multilayer binary optical element.

[0122] Example 2

[0123] like Figure 8 As shown, this is an optical imaging system with a field of view (FOV) greater than 90°. The system includes lenses 17, 18, 19, 20, 21, and 22, and an image detector 23. The aperture stop is located between lenses 18 and 19. Surfaces P1 to P12 are all transmission surfaces. Among them, the second surface P8 of lens 20 and the first surface P9 of lens 21 are diffraction microstructure surfaces. The adjacent spacing between P8 and P9 is 2–20 micrometers, and both diffraction microstructure surfaces have the same base surface. The two front and rear surfaces P11 and P12 of lens 22 are freeform surfaces.

[0124] Figure 8 (a) is the optical path diagram of the optical imaging system; Figure 8 (b) is the modulation pass-through function curve of the optical imaging system; Figure 8 (c) shows the field curvature and distortion curves of the optical imaging system; Figure 8 (d) shows the diffraction efficiency curves of the diffraction structure formed by two diffraction microstructure surfaces in the optical imaging system at different wavelengths. Figure 8 (e) represents the equivalent phase distribution of the first diffractive microstructure surface in the optical imaging system; Figure 8 (f) shows the microstructure distribution of the first diffraction microstructure surface in the optical imaging system; Figure 8 (g) represents the equivalent phase distribution of the second diffraction microstructure surface in the optical imaging system; Figure 8 (h) represents the microstructure distribution of the second diffraction microstructure surface in the optical imaging system.

[0125] In this embodiment, Figure 8 The optical imaging system shown is used in the ultra-wide-angle lens of a mobile phone. It has a focal length of 4.0mm, a relative aperture of F# of 2.2, a total optical system length of 7.1mm, a 1 / 2.3” CMOS detector, and employs a freeform lens (both the front and back surfaces of the lens are polynomial freeform surfaces) and two microstructured diffraction surfaces. All optical lens materials are resin materials, and the material distribution is shown in Table 5 below.

[0126] Table 5

[0127]

[0128] The second surface of lens four and the first surface of lens five are diffractive microstructure surfaces, spaced 20 micrometers apart. The microstructures on these surfaces are distributed on an aspherical substrate. The height of the microstructure on the APL5014 substrate is H1 = 7.9839 μm; the height of the microstructure on the EP9000 substrate is H2 = 5.5917 μm. Both the front and rear surfaces of lens six are freeform surfaces.

[0129] The surface phase coefficients of the microstructures are shown in Table 6 below:

[0130] Table 6

[0131]

[0132] Note: The normalized radius corresponding to the phase coefficient is 100 mm.

[0133] The substrate for the diffraction microstructure is an aspherical surface, and the corresponding aspherical coefficients are shown in Table 7 below:

[0134] Table 7

[0135]

[0136] Both the front and rear surfaces of lens six are freeform surfaces, and the freeform surface coefficients are shown in Table 8 below:

[0137] Table 8

[0138]

[0139]

[0140] Note: The normalized radius is 2.052 mm.

[0141] Example 3

[0142] like Figure 9 The figure shows an optical imaging system with a field of view (FOV) between 30° and 90°. It includes lenses 24, 25, 26, 27, 28, 29, 30, and 31, and an image detector 21. The aperture stop is located between lenses 26 and 27. Q1 to Q16 are all transmission surfaces. The second surface S2 of lens 24 and the first surface Q3 of lens 25 are microstructured diffraction surfaces. The adjacent spacing between the two microstructured surfaces Q2 and Q3 ranges from 2 to 20 micrometers, and both microstructured diffraction surfaces have the same base surface curvature. The front and rear surfaces Q15 and Q16 of lens 31 are freeform surfaces.

[0143] Figure 9 (a) is the optical path diagram of the optical imaging system; Figure 9 (b) is the modulation pass-through function curve of the optical imaging system; Figure 9 (c) shows the field curvature and distortion curves of the optical imaging system; Figure 9 (d) shows the diffraction efficiency curves of the diffraction structure formed by two diffraction microstructure surfaces in the optical imaging system at different wavelengths. Figure 9 (e) represents the equivalent phase distribution of the first diffractive microstructure surface in the optical imaging system; Figure 9 (f) shows the microstructure distribution of the first diffraction microstructure surface in the optical imaging system; Figure 9 (g) represents the equivalent phase distribution of the second diffraction microstructure surface in the optical imaging system; Figure 9 (h) represents the microstructure distribution of the second diffraction microstructure surface in the optical imaging system.

[0144] In this embodiment, Figure 8 The optical imaging system shown is used in the main camera lens of a mobile phone. It has a focal length of 8.65mm, a relative aperture of F# 1.72, an image plane diameter (diagonal) of 16.2mm, and a total length of 10.15mm. It employs a freeform lens (with both front and rear surfaces being polynomial freeform surfaces) and two microstructured diffraction surfaces (such as…). Figure 9(As shown in Table 9). All optical lens materials are resin materials, and the material distribution is shown in Table 9 below:

[0145] Table 9

[0146]

[0147]

[0148] The second surface of lens one and the first surface of lens two are diffractive microstructure surfaces, spaced 20 micrometers apart. The microstructures on these surfaces are distributed on an aspherical substrate. The height of the microstructure on the substrate of lens one is H1 = 6.894 μm; the height of the microstructure on the substrate of lens two is H2 = 5.692 μm. Both the front and rear surfaces of lens eight are freeform surfaces.

[0149] The surface phase coefficients of the microstructures are shown in Table 10 below:

[0150] Table 10

[0151] Serial Number Phase coefficient L1S2 L2S1 1 <![CDATA[A1]]> 57.196 -111.560 2 <![CDATA[A2]]> 16.172 -1.120 3 <![CDATA[A3]]> -0.578 -2.176 4 <![CDATA[A4]]> 0.266 0.121 5 <![CDATA[A5]]> -0.011 -0.021 6 <![CDATA[A6]]> 0 0

[0152] Note: The normalized radius corresponding to the phase coefficient is 1.0 mm.

[0153] The substrate for the diffraction microstructure is an aspherical surface, and the corresponding aspherical coefficients are shown in Table 11 below:

[0154] Table 11

[0155]

[0156]

[0157] Both the front and rear surfaces of lens eight are freeform surfaces, and the freeform surface coefficients are shown in Table 12 below:

[0158] Table 12

[0159] Serial Number Higher-order coefficients L8S1 L8S2 1 <![CDATA[b 20 ]]> 0.0067005051 0.026960233 2 <![CDATA[b 02 ]]> 0.007809433 0.028802494 3 <![CDATA[b 04 ]]> -0.03170201 -0.020051313 4 <![CDATA[b 22 ]]> -0.063531541 -0.040110896 5 <![CDATA[b 40 ]]> -0.031319437 -0.019785553 6 <![CDATA[b 60 ]]> 0.0047642861 0.0027600547 7 <![CDATA[b 42 ]]> 0.014484004 0.0082693794 8 <![CDATA[b 24 ]]> 0.014482641 0.0082769294 9 <![CDATA[b 06 ]]> 0.0048222179 0.0027654127 10 ... ... ...

[0160] Note: The normalized radius is 1.0 mm.

[0161] The embodiments described above provide a detailed explanation of the technical solutions and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, additions, and equivalent substitutions made within the scope of the principles of the present invention should be included within the protection scope of the present invention.

Claims

1. An optical imaging system comprising a plurality of optical elements arranged along an optical path, characterized in that, The surfaces of several optical elements include freeform surfaces, diffractive microstructure surfaces, and metasurfaces; among them, the diffractive microstructure surfaces are arranged in pairs; The equation of the freeform surface is: Where: z(x,y) is the optical surface sagitta; k is the conic coefficient; c is the radius of curvature; r is the radius of height along the optical axis. 2 =x 2 +y 2 A i These are the polynomial coefficients, E i (x, y) is a polynomial; the freeform surface described is a bisymmetric structure, and the polynomial E i In (x,y), the coefficients of the odd-degree terms of x and y are 0, as follows: Among them, A i These are polynomial coefficients; In each pair of diffraction microstructures, two layers of diffraction microstructures are arranged on a planar, spherical, aspherical, or freeform surface substrate of an optical element made of materials with different refractive indices. The gap between the two layers of diffraction microstructures is air or other light-transmitting filling medium. The spacing δ between the two layers of diffraction microstructures is 1–20 μm, and the phase distributions of the diffraction microstructures are as follows: and Z A (ρ), Z B (ρ) represents the microstructure morphology of the two diffraction microstructure surfaces; n A (λ) and n B (λ) represents the refractive index of the optical element made of the two materials; the heights of the two diffraction microstructures are H1 and H2, respectively, and the heights of the diffraction microstructures satisfy the following condition: Where, λ 01 , λ 02 For the design wavelength, n A (λ 01 ), n A (λ 02 ) and n B (λ 01 ), n B (λ 02 ( ) is the design wavelength λ 01 , λ 02 The corresponding refractive indices of the two optical elements made of two different materials; The metasurface is an artificial two-dimensional material with nanoscale elliptical cylinders, cuboids or irregular shapes as basic units, set on a planar or curved substrate, including transmissive or reflective metasurfaces.

2. A camera lens, characterized in that, The camera lens has a field of view (FOV) of >90° and uses the optical imaging system of claim 1. The optical imaging system includes at least three lenses as optical elements. The surfaces of all lenses include at least one freeform surface and at least one pair of diffractive microstructure surfaces and one metasurface.

3. The camera lens according to claim 2, characterized in that, The optical imaging system comprises, in sequence, a first lens, a second lens, a third lens, a fourth lens, a fifth lens, and a sixth lens along the optical axis from the object side to the image side; The first lens has negative optical power, the second lens has negative optical power, the third lens has positive optical power, the fourth lens has negative optical power, the fifth lens has negative optical power, and the sixth lens has positive optical power; all surfaces of the first to the sixth lenses include at least one freeform surface, and at least one pair of diffractive microstructure surfaces and one metasurface.

4. A camera lens, characterized in that, The camera lens has a field of view (FOV) of less than 30°. The optical imaging system described in claim 1 includes at least one lens and at least one prism containing a refractive surface and a reflective surface. The surfaces of all lenses contain at least one freeform surface and at least one pair of diffractive microstructure surfaces and a metasurface.

5. The camera lens according to claim 4, characterized in that, The optical imaging system described above includes, in sequence from the object side to the image side along the optical axis, a first lens, a second prism, and a third lens; The first lens has positive optical power, the second prism has two transmission surfaces and three reflection surfaces, and the third lens has negative optical power. The second surface of the first lens is adjacent to the first transmission surface of the second prism, with a spacing of 1 to 20 μm, and the surface shapes are the same; the second surface of the first lens and the first transmission surface of the second prism are diffraction microstructure surfaces; the three reflecting surfaces of the second prism are freeform surfaces. The second reflecting surface of the second prism is located in the optical path of the first reflecting surface of the second prism, and the third reflecting surface of the second prism is located in the optical path of the second reflecting surface of the second prism; the central normals of the first reflecting surface, the second reflecting surface, and the third reflecting surface of the second prism all intersect.

6. A camera lens, characterized in that, The field of view (FOV) of the camera lens satisfies 30°≤FOV≤90°. The optical imaging system described in claim 1 includes at least four lenses as optical elements. The surfaces of all lenses contain at least two freeform surfaces, and at least a pair of diffractive microstructure surfaces and a metasurface.

7. The camera lens according to claim 6, characterized in that, The optical imaging system comprises, in sequence from the object side to the image side along the optical axis, a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens, and an eighth lens; Among them, the first lens has positive optical power, the second lens has negative optical power, the third lens has positive optical power, the fourth lens has optical power, the fifth lens has optical power, the sixth lens has positive optical power, the seventh lens has negative optical power, and the eighth lens has negative optical power. All surfaces of the first to eighth lenses contain at least two freeform surfaces, and at least a pair of diffractive microstructure surfaces and a metasurface.

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