A large field of view kepler dispersion compensation method and compensation module

Abstract

The application provides a large field of view Kepler dispersion compensation method and a compensation module, comprising: dividing the Kepler dispersion compensation module into a front group and a rear group; determining the dispersion compensation requirement of the Kepler dispersion compensation module; determining the axial chromatic aberration requirement of the front group according to the wavelength range of the polychromatic light transmitted by the front group and the focal power of the front group, so as to design the parameters of the first and second combined lenses and the distance between the first and second combined lenses in combination with the axial chromatic aberration requirement of the front group, so that the absolute values of the focal powers of the first and second combined lenses are relatively low; determining the axial chromatic aberration requirement of the rear group according to the wavelength range of the polychromatic light transmitted by the rear group and the focal power of the rear group, so as to design the parameters of the third and fourth combined lenses and the distance between the third and fourth combined lenses in combination with the axial chromatic aberration requirement of the rear group, so that the absolute values of the focal powers of the third and fourth combined lenses are relatively low. The application can ensure that the Kepler dispersion compensation module can still correctly compensate for chromatic dispersion under a large field of view and does not introduce excessive monochromatic aberration.

Description

Technical Field

[0001] This invention belongs to the field of optical design, and more specifically, relates to a method and module for compensating Kepler dispersion over a large field of view. Background Technology

[0002] In recent years, diffraction scanning methods have been widely applied in high-throughput, high-precision ultrafast laser processing. Reports have emerged of using diffractive optical devices such as digital micromirror arrays, spatial light modulators, diffractive optical elements, and acousto-optic deflectors for ultrafast laser processing. However, ultrafast lasers exhibit angular dispersion when passing through diffractive optical devices, causing the focused spot to stretch and significantly reducing processing accuracy at the field of view edges. Therefore, it is necessary to compensate for angular dispersion at the field of view edges, thereby ensuring that the spot size reaches the diffraction limit throughout the entire field of view. Chinese patent document CN 104849837A reports a Kepler dispersion compensation module capable of compensating for angular dispersion at different field of view angles. Its compensation angle reaches ±2°, and its aperture reaches 6 mm. However, commercially available focusing objectives have a field of view angle of ±4.2° and an aperture of 12.6 mm. The compensation angle and aperture of existing compensation modules are smaller than those of focusing objectives, making it difficult to achieve complete angular dispersion compensation within the field of view of the focusing objective. Summary of the Invention

[0003] To address the shortcomings of existing technologies, the present invention aims to provide a large field-of-view Kepler dispersion compensation method and module, which solves the problem that existing Kepler dispersion compensation modules are unable to achieve complete compensation of character dispersion within a large field of view.

[0004] To achieve the above objectives, in a first aspect, the present invention provides a method for compensating for large field-of-view Kepler dispersion, comprising the following steps: The Kepler dispersion compensation module is divided into a front group and a rear group; wherein, the front group includes a first combined lens and a second combined lens, and the rear group includes a third combined lens and a fourth combined lens, and each combined lens includes at least one lens; Determine the dispersion compensation requirements of the Kepler dispersion compensation module, including: the wavelength range of the polychromatic light transmitted by the front group, the optical power of the front group, the wavelength range of the polychromatic light transmitted by the rear group, and the optical power of the rear group. The axial chromatic aberration requirement of the front group is determined based on the wavelength range of the polychromatic light transmitted by the front group and the optical power of the front group. The parameters of the first combined lens, the parameters of the second combined lens, and the spacing between the first and second combined lenses are designed in combination with the axial chromatic aberration requirement of the front group, so that the absolute values ​​of the optical power of the first and second combined lenses are relatively low. The parameters include optical power and Abbe number. The axial chromatic aberration requirement of the rear group is determined based on the wavelength range of the polychromatic light transmitted by the rear group and the optical power of the rear group. The parameters of the third and fourth combined lenses and the spacing between the third and fourth combined lenses are designed in combination with the axial chromatic aberration requirement of the rear group, so that the absolute values ​​of the optical power of the third and fourth combined lenses are relatively low. The design of the optical power of the combined lenses is used to ensure that the Kepler dispersion compensation module can still correctly compensate for chromatic aberration in a large field of view without introducing excessive monochromatic aberration.

[0005] Optionally, the power allocation equation for the first group is: ; ; The two solutions to the above equation are: ; in, , v 11 and v 21 These are the Abbe numbers of the first and second combined lenses, respectively. φ 11 and φ 21 These are the optical powers of the first and second combined lenses, respectively. λ 11 and λ 21 These are the minimum and maximum wavelengths of the polychromatic light transmitted in the first group, respectively. λ 01 The center wavelength of the first group, φ 1 represents the optical power of the front group. d 1 represents the distance between the first and second combined lenses; φ 11 )1 and ( φ 11 )2 are the first and second solutions for the optical power of the first combined lens, respectively.

[0006] Optionally, the power allocation equation for the latter group is: ; ; The two solutions to the above equation are: ; in, , v 12 and v 22 These are the Abbe numbers of the third and fourth combined lenses, respectively. φ 12 and φ 22 These are the optical powers of the third and fourth combined lenses, respectively. λ 12 and λ 22 These are the minimum and maximum wavelengths of the polychromatic light transmitted in the latter group, respectively. λ 02 The center wavelength of the latter group, φ 2 represents the optical power of the rear group. d 2 represents the distance between the third and fourth combined lenses; φ 12 )1 and ( φ 12 )2 are the first and second solutions for the optical power of the third combined lens, respectively.

[0007] Optionally, the method further includes the following steps: The necessary condition for determining that the first set of optical power distribution equations has a solution is as follows: ; The necessary condition for the latter group of optical power distribution equations to have a solution is as follows: .

[0008] Optionally, the solution with the smaller absolute value among the optical power solutions is selected as the better design scheme to help control aberrations and further optimize the design based on the better design scheme.

[0009] Optionally, when designing the specific lens composition of the front or rear group, lenses with a large difference in Abbe number are selected to increase the... and The range of values ​​allows for greater design freedom.

[0010] Optionally, when designing the first to fourth combined lenses, the combined lens is first treated as a single lens, and the corresponding parameters are calculated. Then, the combined lens is split into multiple lens groups, and the surface radius and surface spacing of the split multiple lenses are numerically optimized to reduce the monochromatic aberration of the front or rear group. In the optimization process of the front group of multiple lenses, a symmetrical structure can be used to further reduce the monochromatic aberration of the front group.

[0011] In a second aspect, the present invention provides a large field-of-view Kepler dispersion compensation module designed using the method provided in the first aspect above, the compensation module comprising: a front group and a rear group; The front group, from the beam incident side to the exit side, includes: a first combined lens and a second combined lens; the first combined lens, from the beam incident side to the exit side, includes: a first lens, a second lens, and a third lens; the second combined lens, from the beam incident side to the exit side, includes: a fourth lens, a fifth lens, and a sixth lens. The rear group, from the beam incident side to the exit side, includes: a third combined lens and a fourth combined lens; the third combined lens includes: a seventh lens; the fourth combined lens, from the beam incident side to the exit side, includes: an eighth lens and a ninth lens.

[0012] Optionally, the glass material of the first lens, second lens, fourth lens, fifth lens, sixth lens, seventh lens and eighth lens is H-K9L optical glass; the glass material of the third lens and ninth lens is H-ZF88 optical glass.

[0013] Optionally, the first lens has a front surface radius of 21.66 mm and a surface spacing of 6.00 mm, and a rear surface radius of 65.21 mm and a surface spacing of 7.09 mm; the second lens has a front surface radius of 36.82 mm and a surface spacing of 2.75 mm, and a rear surface radius of 212.58 mm and a surface spacing of 8.13 mm; the third lens has a front surface radius of -30.32 mm and a surface spacing of 5.98 mm, and a rear surface radius of 19.12 mm and a surface spacing of 2.28 mm; the fourth lens has a front surface radius of 35.56 mm and a surface spacing of 3.25 mm, and a rear surface radius of -59.36 mm and a surface spacing of 13.59 mm; the fifth lens has a front surface radius of -140.62 mm and a surface spacing of 3.84 mm, and a rear surface radius of -33.11 mm and a surface spacing of 2.00 mm. mm; the front surface radius of the sixth lens is -24.04 mm, the surface spacing is 6.00 mm, the rear surface radius is -22.15 mm, and the surface spacing is 104.06 mm; The distance between the first and second combined lenses is 5.00 mm.

[0014] Optionally, the seventh lens has a front surface radius of -41.20 mm and a surface spacing of 5.66 mm, and a rear surface radius of -63.57 mm and a surface spacing of 23.71 mm; the eighth lens has a front surface radius of -302.87 mm and a surface spacing of 1.00 mm, and a rear surface radius of 158.06 mm and a surface spacing of 0.58 mm; the ninth lens has a front surface radius of 248.50 mm and a surface spacing of 4.24 mm, and a rear surface radius of -99.42 mm and a surface spacing of 193.56 mm. The distance between the third and fourth combined lenses is 5.00 mm.

[0015] In summary, the technical solutions conceived by this invention have the following beneficial effects compared with the prior art: This invention provides a large field-of-view Kepler dispersion compensation method and module. The axial chromatic aberration requirement of the front group is determined based on the wavelength range of the polychromatic light transmitted and the optical power of the front group. The parameters and spacing of the first and second combined lenses are then designed in conjunction with this requirement, resulting in relatively low absolute values ​​of optical power for the first and second combined lenses. Similarly, the axial chromatic aberration requirement of the rear group is determined based on the wavelength range of the polychromatic light transmitted and the optical power of the rear group. The parameters and spacing of the third and fourth combined lenses are then designed in conjunction with this requirement, resulting in relatively low absolute values ​​of optical power for the third and fourth combined lenses. Based on the optical power allocation of the first, second, third, and fourth combined lenses, a split lens method is used to divide each of these lenses into multiple lenses. The surface radii and spacing of these multiple lenses are then numerically optimized to reduce monochromatic aberration in both the front and rear groups. A symmetrical structure can be used during the optimization process to further reduce monochromatic aberration in the front group. This invention ensures that the Kepler dispersion compensation module can correctly compensate for chromatic aberration in a large field of view without introducing excessive monochromatic aberration. Attached Figure Description

[0016] Figure 1 A flowchart of a large field-of-view Kepler dispersion compensation method provided in an embodiment of the present invention; Figure 2 This is a schematic diagram of the combined lens structure of the front group of the Kepler dispersion compensation module provided in an embodiment of the present invention; Figure 3 This is a schematic diagram of the combined lens structure of the rear group of the Kepler dispersion compensation module provided in an embodiment of the present invention; Figure 4 This is an optical structure diagram of a four-piece front assembly provided in an embodiment of the present invention; Figure 5 A dot diagram of the four-piece front assembly provided in an embodiment of the present invention; Figure 6 This is an optical structure diagram of a 6-piece front assembly provided in an embodiment of the present invention; Figure 7 A graph showing the variation of wavefront aberration RMS values ​​with field of view for a 6-piece front group provided in an embodiment of the present invention; Figure 8 This is an optical structure diagram of a three-piece rear assembly provided in an embodiment of the present invention; Figure 9 This is a dot diagram of the three-piece rear assembly provided in an embodiment of the present invention; Figure 10 An optical structure diagram of a 9-chip Kepler dispersion compensation module provided in an embodiment of the present invention; Figure 11 A dot plot of polychromatic light with chromatic dispersion at 510 nm to 520 nm provided for embodiments of the present invention; Figure 12 A dot plot of polychromatic light at 510 nm to 520 nm after chromatic aberration compensation provided in an embodiment of the present invention; In all the accompanying drawings, the same reference numerals are used to denote the same elements or structures, wherein: 101-110 are respectively: the front focal plane of a 4-element front group, the first surface of a first lens, the second surface of a first lens, the first surface of a second lens, the second surface of a second lens, the first surface of a third lens, the second surface of a third lens, the first surface of a fourth lens, the second surface of a fourth lens, and the rear focal plane of a 4-element front group; 201-214 are respectively: the front focal plane of a 6-element front group, the first surface of a first lens, the second surface of a first lens, the first surface of a second lens, the second surface of a second lens, the first surface of a third lens, the second surface of a third lens, the first surface of a fourth lens, the second surface of a fourth lens, the first surface of a fifth lens, the second surface of a fifth lens, the first surface of a sixth lens, the second surface of a sixth lens, and the rear focal plane of a 6-element front group; 301-308 are respectively: the front focal plane of a 3-element rear group, the first surface of a first lens, the second surface of a first lens, the first surface of a second lens, the second surface of a second lens, the first surface of a third lens, the second surface of a third lens, and the rear focal plane of a 3-element rear group. Detailed Implementation

[0017] For ease of understanding, the English abbreviations and related technical terms used in the embodiments of the present invention will be explained and described below.

[0018] The embodiments of the present invention will now be described with reference to the accompanying drawings.

[0019] This invention provides a method for allocating optical power and optical design results for a large field-of-view Kepler dispersion compensation module, offering a solution for large field-of-view Kepler dispersion compensation.

[0020] Figure 1 This is a flowchart of a large field-of-view Kepler dispersion compensation method provided in an embodiment of the present invention; as follows: Figure 1 As shown, it includes the following steps: S101, the Kepler dispersion compensation module is divided into a front group and a rear group; wherein, the front group includes a first combined lens and a second combined lens, and the rear group includes a third combined lens and a fourth combined lens, and each combined lens includes at least one lens; S102, Determine the dispersion compensation requirements of the Kepler dispersion compensation module, which include: the wavelength range of the polychromatic light transmitted by the front group, the optical power of the front group, the wavelength range of the polychromatic light transmitted by the rear group, and the optical power of the rear group. S103, determine the axial chromatic aberration requirement of the front group based on the wavelength range of the polychromatic light transmitted by the front group and the optical power of the front group, and design the parameters of the first combined lens, the parameters of the second combined lens, and the spacing between the first and second combined lenses in combination with the axial chromatic aberration requirement of the front group, so that the absolute values ​​of the optical power of the first combined lens and the second combined lens are relatively low; wherein, the parameters include optical power and Abbe number. S104. Based on the wavelength range of the polychromatic light transmitted by the rear group and the optical power of the rear group, the axial chromatic aberration requirement of the rear group is determined. The parameters of the third combined lens, the parameters of the fourth combined lens, and the spacing between the third and fourth combined lenses are designed in combination with the axial chromatic aberration requirement of the rear group, so that the absolute values ​​of the optical power of the third and fourth combined lenses are relatively low. The design of the optical power of the combined lenses is used to ensure that the Kepler dispersion compensation module can still correctly compensate for chromatic aberration in a large field of view without introducing excessive monochromatic aberration.

[0021] Understandably, when designing the two combined lenses in the first group, the combined lens is first treated as a single lens, and its corresponding parameters are calculated. Then, the first combined lens is split into a first multi-lens group, which contains multiple lenses, and its optical power is the same as that of the first combined lens. Subsequently, the second combined lens is split into a second multi-lens group, which also contains multiple lenses, and its optical power is the same as that of the second combined lens. Numerical optimization of the surface radius and surface spacing of the split multi-lens groups is performed to reduce monochromatic aberration in the first group. During the optimization process, a symmetrical structure can be used to further reduce monochromatic aberration in the first group.

[0022] Understandably, when designing the two combined lenses in the latter group, the combined lens is first treated as a single lens, and its corresponding parameters are calculated. Then, the third combined lens is split into a third multi-lens group, which contains multiple lenses, and its optical power is the same as that of the third combined lens. Subsequently, the fourth combined lens is split into a fourth multi-lens group, which also contains multiple lenses, and its optical power is the same as that of the fourth combined lens. Numerical optimization of the surface radius and spacing of the split multi-lens groups is then performed to reduce monochromatic aberration in the latter group.

[0023] It should be noted that the large field of view mentioned in this invention refers to a field of view with a field angle of ±4.2° and beyond.

[0024] Specifically, we first introduce the optical power allocation method of the large field-of-view Kepler dispersion compensation module. The Kepler dispersion compensation module consists of a front group and a rear group, both of which are composed of combined lenses. On the one hand, the structure of the combined lens of the front group is as follows: Figure 2 As shown, it contains two thin lenses L 11 With L 21 Their optical power and Abbe number are respectively φ 11 , v 11 and φ 21 , v 21 The optical power of the combined lens is φ 1; The distance between the lenses is d 1; The heights of the peripheral rays passing through the two lenses are respectively h 11 , h 21 The aperture angles of the edge rays are respectively , The axial chromatic aberration of the combined lens is: (1); Where, n' 21 Let L be the refractive index of the image space of the thin lens L21, since L 21 The medium of the image space is air, therefore n' 21 =1; C i1 For thin lens L i1 The chromatic aberration coefficient, which is related to the height of the incident light. h i1 Optical power φ i1 With Abbe number v i1 related: (2); Among them, aperture angle , Edge light height h 11、 h 21 Optical power of combined lenses φ 1. All three conditions must be met: (3); Optical power of combined lenses φ 1. Optical power of thin lens φ 11 , φ 21 and spacing d The relationship of 1 is: (4); The axial chromatic aberration of the combined lens is obtained by combining equations (1) to (4). for: (5); The color difference requirement for the front group is: (6); in, λ 01 The center wavelength, λ 11 to λ 21 ( λ 11 < λ 01 < λ 21 () represents the wavelength range of polychromatic light.

[0025] Combining equations (5) and (6), we obtain the following equation for the distribution of optical power in the first group: (7); in, The two solutions to equation (7) are: (8).

[0026] On the other hand, the rear group's combined lens structure, such as Figure 3 As shown, it contains two thin lenses L 12 With L 22 Their optical power and Abbe number are respectively φ 12 , v 12 and φ 22 , v22 The optical power of the combined lens is φ 2; the distance between the lenses is d 2; The heights of the peripheral rays passing through the two lenses are respectively h 12 , h 22 The aperture angles of the edge rays are respectively , Axial chromatic aberration of combined lenses for: (9); The color difference requirements for the later group are: (10); Referring to equations (9) and (10), the power distribution equation for the latter group is obtained as follows: (11); in, The two solutions to equation (11) are: (12).

[0027] The necessary and sufficient conditions for equations (7) and (12) to have solutions are respectively: (13); Using equations (1) to (13), the optical power allocation of the front and rear lens groups can be realized respectively. Based on this, the optical design results of the large field-of-view Kepler dispersion compensation module can be obtained through optimization design.

[0028] Next, we will introduce the design results of the large field-of-view Kepler dispersion compensation module.

[0029] The structure of the four-piece front assembly, obtained after optical design optimization, is as follows: Figure 4 As shown, this lens group is an image-side telecentric system with an entrance pupil diameter of 12.6 mm and a maximum field of view of 3°. The dot plots of this lens group at field of view angles of 0°, 2.2°, and 3° are shown below. Figure 5 As shown, the root mean square (RMS) radii of the light spot are 0.61 μm, 1.28 μm, and 1.93 μm, respectively, all smaller than the Airy disk radius, indicating that the spot size meets the diffraction limit requirement. The optical parameters of the 4-element front group are shown in Table 1.

[0030] Table 1. Parameters of the 4-piece front assembly

[0031] For a 4-element front group, at a field of view of 4.2°, the RMS value of the edge wave aberration reaches 0.32λ, which is not only 10 times higher than the RMS value at 3°, but also significantly exceeds the diffraction limit. This is because the light reaches the first surface at an excessive height, introducing more astigmatism. At this point, it is difficult to optimize the spot quality using a split lens approach; therefore, a symmetrical structure is attempted for optimization. The method involves inserting an H-K9 lens at the rear of the 4-element front group, forming a symmetrical structure with the H-K9 lens at the front. The optimized 6-element front group structure is shown below. Figure 6 As shown, this lens group is an image-side telecentric system with an entrance pupil diameter of 12.6 mm and a maximum field of view of 4.2°. The RMS value of the wavefront aberration of this lens group as a function of the field of view is shown in the curve. Figure 7 As shown, the RMS value at the edge of the field of view decreases to 0.018 λ, and the largest aberration occurs at a field of view angle of 3.8°, with an RMS value of 0.031 λ. Compared with the 4-element front group, the 6-element front group has a larger compensation range and smaller wavefront aberration. The optical parameters of this lens group are shown in Table 2.

[0032] Table 2. Parameters of the 6-piece front assembly

[0033] The structure of the three-piece rear assembly, obtained after optical design optimization, is as follows: Figure 8 As shown, the entrance pupil diameter of this lens group is 12.6 mm, and the maximum field of view is 4.2°. The dot plots of this lens group at field of view angles of 0°, 2.97°, and 4.2° are shown below. Figure 9 As shown, the RMS radii of the light spots are 1.67 μm, 1.47 μm, and 1.83 μm, respectively, all smaller than the Airy disk radius, indicating that the spot size meets the diffraction limit requirement. The optical parameters of the 3-piece rear array are shown in Table 3.

[0034] Table 3. Parameters of the 3-piece rear assembly

[0035] The optical structure of a 9-element Kepler dispersion compensation module, consisting of a 6-element front group and a 3-element rear group, is as follows: Figure 10 As shown, this lens assembly has a 12.6 mm aperture and a 4.2° compensation angle. The dispersion compensation performance of this lens assembly is as follows: Figure 11 and Figure 12 As shown. Figure 11 This indicates that in a focalless image space, polychromatic light with a wavelength range of 510 nm to 520 nm passes through a scribe line with a period d of... The dot plot after the diffraction optics device shows that the beam angle at the center wavelength of 515 nm reaches 4.2° and the angular dispersion of the beam reaches 1.44 mrad, which is much larger than the Airy disk size shown by the black circle, which has a radius of 0.05 mrad. Figure 12 The image shows a dot plot after dispersion compensation using a 9-element Kepler dispersion compensation module, with all light spots distributed within the Airy disk. The RMS radius of the light spot is 0.013 mrad, only 26.7% of the Airy disk radius, indicating that the 9-element Kepler dispersion compensation module can correctly compensate for chromatic aberration at a field of view of 4.2° without introducing excessive monochromatic aberration, thus meeting the usage requirements.

[0036] In a specific embodiment, using equations (1) to (13), the optical power allocation of the front lens group and the rear lens group can be realized respectively. The specific implementation process is as follows: H-ZF88 glass is preferred. v =227.5) and H-K9L glass ( v =854.6) These two materials with significantly different Abbe numbers are used to increase the value in equation (13). and The range of possible values ​​allows for greater design freedom. d 1 = 5 mm φ 1 = 0.006 mm -1 As a condition for solving equation (7), choose d 2 = 5 mm φ 2 = 0.006 mm -1 As a condition for solving equation (13), the solution results of the first and second groups are shown in Table 4 and Table 5, respectively.

[0037] As the preferred option, the first group has four solutions, among which L 11 L 21 The first set of solutions using H-ZF88 and H-K9L glass respectively has the smallest absolute value of optical power, which is beneficial for controlling aberrations. Therefore, this set of solutions is used for further optimization design of the previous set.

[0038] Table 4. Results of the calculation of the first group of optical powers

[0039] As the preferred option, the latter group has four solutions, among which L 12 L 22 The second set of solutions, which uses H-K9 and H-ZF88L glass respectively, has the smallest absolute value of optical power. Therefore, this set of solutions is used for further optimization design of the subsequent sets.

[0040] Table 5. Results of the calculation of the optical power of the rear group

[0041] The design results of the large field-of-view Kepler dispersion compensation module are as follows: As a preferred embodiment, a four-piece front assembly structure is as follows: Figure 4 As shown, this lens assembly is an image-side telecentric system. Surface 101 is the front focal plane of the lens assembly. Incident light enters from surface 102, passes through surfaces 102 to 109 sequentially, and focuses on the rear focal plane 110. The entrance pupil of the lens assembly is located on the front focal plane 101, and its diameter is 12.6 mm. The field of view of the lens assembly is ±3°. The dot plots of this lens assembly at field of view angles of 0°, 2.2°, and 3° are shown below. Figure 5 As shown, the RMS radii of the light spots are 0.61 μm, 1.28 μm, and 1.93 μm, respectively, all smaller than the Airy disk radius, indicating that the spot size meets the diffraction limit requirement. The optical parameters of the 4-piece front group are shown in Table 1.

[0042] As a preferred embodiment, a 6-piece front assembly structure is as follows: Figure 6 As shown, this lens assembly is an image-side telecentric system. Surface 201 is the front focal plane of the lens assembly. Incident light enters from surface 202, passes through surfaces 202 to 213 sequentially, and focuses on the rear focal plane 214. The entrance pupil of the lens assembly is located on the front focal plane 201, and its diameter is 12.6 mm. The field of view of the lens assembly is ±4.2°. The RMS value of the wavefront aberration of this lens assembly as a function of the field of view is shown in the curve. Figure 7 As shown, the RMS value at the edge of the field of view decreases to 0.018 λ, and the largest aberration occurs at a field of view angle of 3.8°, with an RMS value of 0.031 λ. Compared with the 4-element front group, the 6-element front group has a larger compensation range and smaller wavefront aberration. The optical parameters of this lens group are shown in Table 2.

[0043] As a preferred embodiment, a three-piece rear assembly structure is as follows: Figure 8 As shown, this lens assembly is an image-side telecentric system. Surface 301 is the front focal plane of the lens assembly. Incident light enters from surface 302, passes through surfaces 302 to 307 sequentially, and focuses on the rear focal plane 308. The entrance pupil of the lens assembly is located on the front focal plane 301, and its diameter is 12.6 mm. The field of view of the lens assembly is ±4.2°. The dot plots of this lens assembly at field of view angles of 0°, 2.97°, and 4.2° are shown below. Figure 9 As shown, the RMS radii of the light spots are 1.67 μm, 1.47 μm, and 1.83 μm, respectively, all smaller than the Airy disk radius, indicating that the spot size meets the diffraction limit requirement. The optical parameters of the 3-piece rear array are shown in Table 3.

[0044] As a preferred embodiment, a lens assembly structure for a 9-element Kepler dispersion compensation module, consisting of the aforementioned 6-element front group and the aforementioned 3-element rear group, is as follows: Figure 10As shown, this lens assembly has a 12.6mm aperture and a 4.2° compensation angle. It should be noted that... Figure 10 The arrangement order of the middle and rear groups is relatively... Figure 8 The arrangement order is reversed, that is, the position and front and back surfaces of the lenses are reversed. The optical parameters of the rear group after the reversal are shown in Table 6.

[0045] Table 6. Parameters of the 3-piece rear assembly after inversion

[0046] Figure 10 The dispersion compensation performance of the lens group shown is as follows: Figure 11 and Figure 12 As shown. Figure 11 This indicates that in a focalless image space, polychromatic light with a wavelength range of 510 nm to 520 nm passes through a scribe line with a period d of... The dot plot after the diffraction optics device shows that the beam angle at the center wavelength of 515 nm reaches 4.2° and the angular dispersion of the beam reaches 1.44 mrad, which is much larger than the size of the Airy disk shown by the black circle, which has a radius of 0.05 mrad. Figure 12 The image shows a dot plot after dispersion compensation using a 9-element Kepler dispersion compensation module, with all light spots distributed within the Airy disk. The RMS radius of the light spot is 0.013 mrad, only 26.7% of the Airy disk radius, indicating that the 9-element Kepler dispersion compensation module can correctly compensate for chromatic aberration at a field of view of 4.2° without introducing excessive monochromatic aberration, thus meeting the usage requirements.

[0047] It should be understood that expressions such as "comprising" and "may include" used in this invention indicate the presence of the disclosed functions, operations, or constituent elements, and do not limit one or more additional functions, operations, and constituent elements. In this invention, terms such as "comprising" and / or "having" are to be interpreted as indicating a particular characteristic, number, operation, constituent element, component, or combination thereof, but not to exclude the possibility of the presence or addition of one or more other characteristics, numbers, operations, constituent elements, components, or combinations thereof.

[0048] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A large field of view Kepler dispersion compensation method, characterized in that, Includes the following steps: The Kepler dispersion compensation module is divided into a front group and a rear group; wherein, the front group includes a first combined lens and a second combined lens, and the rear group includes a third combined lens and a fourth combined lens, and each combined lens includes at least one lens; Determine the dispersion compensation requirements of the Kepler dispersion compensation module, including: the wavelength range of the polychromatic light transmitted by the front group, the optical power of the front group, the wavelength range of the polychromatic light transmitted by the rear group, and the optical power of the rear group. The equation for the distribution of optical power in the first group is as follows: ； ； The two solutions to the first set of power distribution equations are: ； in, , v 11 and v 21 These are the Abbe numbers of the first and second combined lenses, respectively. φ 11 and φ 21 These are the optical powers of the first and second combined lenses, respectively. λ 11 and λ 21 These are the minimum and maximum wavelengths of the polychromatic light transmitted in the first group, respectively. λ 01 The center wavelength of the first group, φ 1 represents the optical power of the front group. d 1 represents the distance between the first and second combined lenses; φ 11 )1 and ( φ 11 )2 are the first and second solutions for the optical power of the first combined lens, respectively; The power distribution equation for the latter group is as follows: ； ； The two solutions to the power distribution equation of the latter group are: ； in, , v 12 and v 22 These are the Abbe numbers of the third and fourth combined lenses, respectively. φ 12 and φ 22 These are the optical powers of the third and fourth combined lenses, respectively. λ 12 and λ 22 These are the minimum and maximum wavelengths of the polychromatic light transmitted in the latter group, respectively. λ 02 The center wavelength of the latter group, φ 2 represents the optical power of the rear group. d 2 represents the distance between the third and fourth combined lenses; φ 12 )1 and ( φ 12 )2 are the first and second solutions for the optical power of the third combined lens, respectively; The axial chromatic aberration requirement of the front group is determined based on the wavelength range of the polychromatic light transmitted by the front group and the optical power of the front group. The parameters of the first combined lens, the parameters of the second combined lens, and the spacing between the first and second combined lenses are designed in combination with the axial chromatic aberration requirement of the front group, so that the absolute values ​​of the optical power of the first and second combined lenses are relatively low. The parameters include optical power and Abbe number. The axial chromatic aberration requirement of the rear group is determined based on the wavelength range of the polychromatic light transmitted by the rear group and the optical power of the rear group. The parameters of the third and fourth combined lenses and the spacing between the third and fourth combined lenses are designed in combination with the axial chromatic aberration requirement of the rear group, so that the absolute values ​​of the optical power of the third and fourth combined lenses are relatively low. The design of the optical power of the combined lenses is used to ensure that the Kepler dispersion compensation module can still correctly compensate for chromatic aberration in a large field of view without introducing excessive monochromatic aberration.

2. The method of claim 1, wherein, It also includes the following steps: The necessary condition for determining that the first set of optical power distribution equations has a solution is as follows: ； The necessary condition for the latter group of optical power distribution equations to have a solution is as follows: 。 3. The method of claim 1, wherein, When designing the specific lens groups of the front group or the rear group, lenses with a large difference in Abbe number are selected to increase the range of values of , thereby achieving higher design freedom.

4. The method of claim 1, wherein, When designing the first to fourth combined lenses, the combined lens is first treated as a single lens, and the corresponding parameters are calculated. Then, the combined lens is split into multiple lens groups. The surface radius and surface spacing of the split multiple lenses are numerically optimized to reduce the monochromatic aberration of the front or rear group. In the optimization process of the front group of multiple lenses, a symmetrical structure is used to further reduce the monochromatic aberration of the front group.

5. A large field Kepler dispersion compensation module designed by the method of any one of claims 1 to 4. include: The front group and the back group; The front group, from the beam incident side to the exit side, includes: a first combined lens and a second combined lens; the first combined lens, from the beam incident side to the exit side, includes: a first lens, a second lens, and a third lens; the second combined lens, from the beam incident side to the exit side, includes: a fourth lens, a fifth lens, and a sixth lens. The rear group, from the beam incident side to the exit side, includes: a third combined lens and a fourth combined lens; the third combined lens includes: a seventh lens; the fourth combined lens, from the beam incident side to the exit side, includes: an eighth lens and a ninth lens.

6. The compensation module of claim 5, wherein, The first, second, fourth, fifth, sixth, seventh, and eighth lenses are made of H-K9L optical glass; the third and ninth lenses are made of H-ZF88 optical glass.

7. The compensation module according to claim 5 or 6, characterized in that The first lens has a front surface radius of 21.66 mm and a surface spacing of 6.00 mm, and a rear surface radius of 65.21 mm and a surface spacing of 7.09 mm. The second lens has a front surface radius of 36.82 mm and a surface spacing of 2.75 mm, and a rear surface radius of 212.58 mm and a surface spacing of 8.13 mm. The third lens has a front surface radius of -30.32 mm and a surface spacing of 5.98 mm, and a rear surface radius of 19.12 mm and a surface spacing of 2.28 mm. The fourth lens has a front surface radius of 35.56 mm and a surface spacing of 3.25 mm, and a rear surface radius of -59.36 mm and a surface spacing of 13.59 mm. The fifth lens has a front surface radius of -140.62 mm and a surface spacing of 3.84 mm, and a rear surface radius of -33.11 mm and a surface spacing of 2.00 mm. mm; the front surface radius of the sixth lens is -24.04 mm, the surface spacing is 6.00 mm, the rear surface radius is -22.15 mm, and the surface spacing is 104.06 mm; The distance between the first combined lens and the second combined lens is 5.00 mm; The seventh lens has a front surface radius of -41.20 mm and a surface spacing of 5.66 mm, and a rear surface radius of -63.57 mm and a surface spacing of 23.71 mm; the eighth lens has a front surface radius of -302.87 mm and a surface spacing of 1.00 mm, and a rear surface radius of 158.06 mm and a surface spacing of 0.58 mm; the ninth lens has a front surface radius of 248.50 mm and a surface spacing of 4.24 mm, and a rear surface radius of -99.42 mm and a surface spacing of 193.56 mm. The distance between the third and fourth combined lenses is 5.00 mm.

Images