Achromatic F-theta Telecentric Scanning Field Lens for Low Coherence Interferometry

Abstract

The present invention relates to an achromatic F‑theta telecentric scanning field mirror for low-coherence interference detection, and relates to the technical field of scanning field mirror optical design. The achromatic F‑theta telecentric scanning field mirror of the present invention comprises: a front mirror group and a rear mirror group arranged in sequence along the optical axis direction from the entrance pupil position; the front mirror group comprises: a first lens, a second lens, and a third lens arranged in sequence along the optical axis direction; the rear mirror group comprises: a fourth lens, a fifth lens, a sixth lens, and a seventh lens arranged in sequence along the optical axis direction. In the achromatic F‑theta telecentric scanning field mirror of the present invention, in terms of chromatic aberration control and geometric aberration correction, the front and rear mirror groups are relatively independent, and the combined effect enables the whole system to obtain better achromatic and aberration correction effects. In terms of F‑theta distortion balance, the front and rear mirror groups cooperate with each other to maximize the F‑theta distortion cancellation.

Description

Technical Field

[0001] The invention relates to the technical field of scanning field mirror optical design, and in particular to an achromatic F-theta telecentric scanning field mirror for low-coherence interference detection. Background Art

[0002] Optical surface processing usually goes through three stages: milling, grinding, and polishing. Corresponding to different processing stages, the surface detection method used to guide processing usually transitions from contour detection with micron-level accuracy to interference detection with nanometer-level accuracy. As for the grinding stage, due to the high roughness of the surface during processing (PV value of several microns to tens of microns), it is difficult to form effective optical reflection. At present, there is no effective non-contact optical detection method for surface detection of components at this stage. In addition, modern optical systems have higher and higher requirements for the quality of optical components. Only examining the surface quality and surface accuracy of optical components cannot meet the growing performance requirements of optical systems. Subsurface defects have become another important indicator for evaluating the quality of optical components. Given that brittle fracture during large-removal cutting and grinding processes is the main source of subsurface defects, the grinding stage will be a critical period for suppressing existing subsurface defects and controlling the regeneration of subsurface defects, and achieving high-precision detection of subsurface defects is one of the top priorities.

[0003] The low-coherence interference tomography method can be used to conveniently realize the synchronous detection of the surface shape and sub-surface defects of optical components during the grinding process. Among them, the low-coherence interference tomography system based on the beam scanning method can flexibly realize the in-situ non-destructive detection of the components under test. At the same time, the system sampling frequency can reach up to 100 kHz, and combined with the sub-aperture splicing detection technology, it can realize efficient detection in parallel with the grinding process of large-aperture optical components. The reasonable construction of the beam scanning low-coherence interference tomography system requires the targeted design and development of the core component, the achromatic F-theta telecentric scanning field mirror. Summary of the invention

[0004] In view of the above, an object of the present invention is to provide an achromatic F-theta telecentric scanning field lens for low coherence interferometric detection.

[0005] In order to solve the above technical problems, the technical solutions of the present invention are as follows:

[0006] An achromatic F-theta telecentric scanning field lens for low-coherence interference detection comprises: a front lens group and a rear lens group arranged in sequence along the optical axis direction from an entrance pupil position;

[0007] The front lens group includes: a first lens, a second lens, and a third lens arranged in sequence along the optical axis; wherein the first lens is a positive power lens, the second lens is a negative power lens, and the third lens is a positive power lens;

[0008] The rear lens group includes: a fourth lens, a fifth lens, a sixth lens, and a seventh lens, which are sequentially arranged along the optical axis direction; wherein the fourth lens is a positive power lens, the fifth lens is a negative power lens, the sixth lens is a positive power lens, and the seventh lens is a positive power lens;

[0009] Along the incident direction of light, the light entrance surface and the light exit surface of the first lens are the first curved surface and the second curved surface, respectively; the light entrance surface and the light exit surface of the second lens are the third curved surface and the fourth curved surface, respectively; the light entrance surface and the light exit surface of the third lens are the fifth curved surface and the sixth curved surface, respectively; the light entrance surface and the light exit surface of the fourth lens are the seventh curved surface and the eighth curved surface, respectively; the light entrance surface and the light exit surface of the fifth lens are the ninth curved surface and the tenth curved surface, respectively; the light entrance surface and the light exit surface of the sixth lens are the eleventh curved surface and the twelfth curved surface, respectively; and the light entrance surface and the light exit surface of the seventh lens are the thirteenth curved surface and the fourteenth curved surface, respectively;

[0010] The curvature radius of the first curved surface is -33.0±5%mm, the curvature radius of the second curved surface is -32.0±5%mm; the curvature radius of the third curved surface is -33.0±5%mm, the curvature radius of the fourth curved surface is -70.0±5%mm; the curvature radius of the fifth curved surface is -2450.0±5%mm, the curvature radius of the sixth curved surface is -110.0±5%mm; the curvature radius of the seventh curved surface is 3700.0±5%mm, the curvature radius of the eighth curved surface is 10 ... The curvature radius of the curved surface is -160.0±5%mm; the curvature radius of the 9th curved surface is -210.0±5%mm, the curvature radius of the 10th curved surface is 325.0±5%mm; the curvature radius of the 11th curved surface is 725.0±5%mm, the curvature radius of the 12th curved surface is -230.0±5%mm; the curvature radius of the 13th curved surface is 390.0±5%mm, the curvature radius of the 14th curved surface is -895.0±5%mm;

[0011] The center thickness d1 of the first lens is 15.0±5% mm, the center thickness d2 of the second lens is 14.0±5% mm, the center thickness d3 of the third lens is 15.5±5% mm, the center thickness d4 of the fourth lens is 22.5±5% mm, the center thickness d5 of the fifth lens is 7.0±5% mm, the center thickness d6 of the sixth lens is 22.0±5% mm, and the center thickness d7 of the seventh lens is 17.0±5% mm;

[0012] The distance of the air gap between the first lens and the second lens on the optical axis is 10.0±5% mm, the distance of the air gap between the second lens and the third lens on the optical axis is 5.0±5% mm, the distance of the air gap between the third lens and the fourth lens on the optical axis is 90.0±5% mm, the distance of the air gap between the fourth lens and the fifth lens on the optical axis is 9.0±5% mm, the distance of the air gap between the fifth lens and the sixth lens on the optical axis is 9.0±5% mm, and the distance of the air gap between the sixth lens and the seventh lens on the optical axis is 5.0±5% mm.

[0013] In the above technical solution, the glass material used for the first lens is H-ZPK7, the glass material used for the second lens is H-QK3L, the glass material used for the third lens is H-BAK5, the glass material used for the fourth lens is H-ZPK7, the glass material used for the fifth lens is H-ZF71, the glass material used for the sixth lens is H-ZPK7, and the glass material used for the seventh lens is H-ZPK7.

[0014] In the above technical solution, the curvature radius of the first curved surface is -33.766mm, the curvature radius of the second curved surface is -32.670mm, the curvature radius of the third curved surface is -33.000mm, the curvature radius of the fourth curved surface is -70.150mm, the curvature radius of the fifth curved surface is -2460.700mm, the curvature radius of the sixth curved surface is -109.310mm, and the curvature radius of the seventh curved surface is 3726.400mm. m, the curvature radius of the 8th surface is -162.650mm, the curvature radius of the 9th surface is -211.723mm, the curvature radius of the 10th surface is 326.761mm, the curvature radius of the 11th surface is 725.000mm, the curvature radius of the 12th surface is -231.200mm, the curvature radius of the 13th surface is 391.770mm, and the curvature radius of the 14th surface is -894.000mm.

[0015] In the above technical solution, the center thickness d1 of the first lens is 15.0 mm, the center thickness d2 of the second lens is 14.2 mm, the center thickness d3 of the third lens is 15.4 mm, the center thickness d4 of the fourth lens is 22.4 mm, the center thickness d5 of the fifth lens is 7.0 mm, the center thickness d6 of the sixth lens is 21.8 mm, and the center thickness d7 of the seventh lens is 16.8 mm.

[0016] In the above technical solution, the entrance pupil size is 10 mm, the entrance pupil is located on the object focal plane of the field lens, and the center of the entrance pupil coincides with the optical axis.

[0017] In the above technical solution, the distance l1 between the entrance pupil and the first curved surface of the first lens on the optical axis is 50.0 mm, the distance l2 between the second curved surface of the first lens and the third curved surface of the second lens on the optical axis is 10.0 mm, the distance l3 between the fourth curved surface of the second lens and the fifth curved surface of the third lens on the optical axis is 5.0 mm, the distance l4 between the sixth curved surface of the third lens and the seventh curved surface of the fourth lens on the optical axis is 91.2 mm, the distance l5 between the eighth curved surface of the fourth lens and the ninth curved surface of the fifth lens on the optical axis is 9.4 mm, the distance l6 between the tenth curved surface of the fifth lens and the eleventh curved surface of the sixth lens on the optical axis is 9.3 mm, the distance l7 between the twelfth curved surface of the sixth lens and the thirteenth curved surface of the seventh lens on the optical axis is 5.0 mm, and the distance between the fourteenth curved surface of the seventh lens and the focal plane on the optical axis is the back intercept S of the field lens, S=200.0 mm.

[0018] The present invention has the following beneficial effects:

[0019] The achromatic F-theta telecentric scanning field mirror for low-coherence interference detection of the present invention has relatively compact arrangement of the positions of the lenses, forming two groups of front and rear concentrated distribution forms in space, which is convenient for installation and debugging.

[0020] The achromatic F-theta telecentric scanning field mirror for low-coherence interference detection of the present invention has two front and rear mirror groups with respective focused functions. The three lenses of the front mirror group are mainly responsible for the task of transmitting large-angle light beams, and the four lenses of the rear mirror group are mainly responsible for the task of adjusting the telecentricity of each field of view on the image side.

[0021] The achromatic F-theta telecentric scanning field mirror for low-coherence interference detection of the present invention has relatively independent front and rear mirror groups in terms of chromatic aberration control and geometric aberration correction, and the combined effect enables the entire system to obtain better achromatic and aberration correction effects.

[0022] The achromatic F-theta telecentric scanning field mirror for low-coherence interference detection of the present invention has the front and rear mirror groups cooperate with each other in terms of F-theta distortion balance, thereby achieving F-theta distortion cancellation to the maximum extent. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0024] Figure 1 A schematic diagram of the deviation of the vector height test generated when the scanning beam pointing is not fixed;

[0025] Figure 2 Schematic diagram of the geometric relationship between the scanning beam pointing deviation and the arrow height deviation;

[0026] Figure 3 Schematic diagram of field curvature in beam scanning;

[0027] Figure 4 A schematic structural diagram of an achromatic F-theta telecentric scanning field mirror provided in an embodiment of the present invention;

[0028] Figure 5 A focal plane point diagram obtained by processing the achromatic F-theta telecentric scanning field lens provided in an embodiment of the present invention using simulation software;

[0029] Figure 6 A focal plane magnification chromatic aberration diagram obtained by processing the achromatic F-theta telecentric scanning field lens provided in an embodiment of the present invention using simulation software;

[0030] Figure 7 The axial chromatic aberration distribution diagram is obtained by processing the achromatic F-theta telecentric scanning field lens provided in the embodiment of the present invention using simulation software;

[0031] Figure 8 A color focus shift curve diagram obtained by processing the achromatic F-theta telecentric scanning field lens provided in an embodiment of the present invention using simulation software;

[0032] Fig. 9 The F-theta distortion diagram is obtained by processing the achromatic F-theta telecentric scanning field mirror provided by the embodiment of the present invention using simulation software;

[0033] Fig.10 A field curvature diagram obtained by processing the achromatic F-theta telecentric scanning field lens provided in an embodiment of the present invention using simulation software;

[0034] Fig.11 The MTF curve diagram is obtained by processing the achromatic F-theta telecentric scanning field lens provided in the embodiment of the present invention using simulation software.

[0035] The reference numerals in the figures indicate:

[0036] 1-first lens, 2-second lens, 3-third lens, 4-fourth lens, 5-fifth lens, 6-sixth lens, 7-seventh lens. DETAILED DESCRIPTION

[0037] The inventive concept of the present invention is: in the reasonable construction of the beam scanning low coherence interference tomography system, it is necessary to carry out targeted design and development of the core component, the achromatic F-theta telecentric scanning field mirror, and the relevant index requirements involved are as follows:

[0038] 1) Working spectrum:

[0039] In addition to the various types of glass materials traditionally used to manufacture transmissive optical elements, special zero-expansion glass, metal, SiC and other materials are also used to manufacture the mirror body of reflective optical elements. Light waves in the near-infrared spectrum have good penetrability for all of the above-mentioned materials, and as the working light waves of the low-coherence interference tomography system, they have good material universality. In addition, the wider the spectrum width, the higher the accuracy of the low-coherence interference tomography. Combined with the detection requirements, it is preferred to take a spectrum width range of 1100nm-1500nm, a total of 400nm.

[0040] 2) Numerical aperture:

[0041] In low-coherence interferometric detection, the scanning field mirror is responsible for both focusing the illumination light field and collecting the backscattered light. The numerical aperture of the scanning field mirror must meet the requirements of the beam convergence depth being greater than or equal to the axial vector range and having sufficient signal strength within the axial vector range. Combined with the detection requirements, it is preferred to determine that the numerical aperture of the scanning field mirror design is greater than 0.02.

[0042] 3) Scanning field of view:

[0043] The low-coherence interference detection system combined with the sub-aperture stitching detection system can be used for the simultaneous detection of surface shape and sub-surface defects in the grinding stage of large-aperture optical components. In order to ensure detection efficiency and reduce the number of sub-aperture stitching times, it is preferred that the coverage range of a single sub-aperture is set to 100 mm square.

[0044] 4) Telecentricity:

[0045] After using the low-coherence interference detection system to regularly obtain the vector height change information of multiple sampling points in a certain area on the measured surface element, the surface shape of the measured area can be reconstructed through the relevant algorithm. Figure 1 As shown in the figure, during the beam scanning sampling process, the actual sampling point position obtained by the scanning beam with pointing deviation will be offset from the ideal sampling point position obtained by the scanning beam with fixed pointing. Taking the zero optical path difference position between the sample arm and the reference arm as the reference, the sampling point position offset caused by the uncertain beam pointing deviation will introduce the vector height measurement error. The larger the measurement error, the lower the accuracy of the reconstructed surface data. In order to realize the scanning of the fixed pointing beam, the scanning field mirror must be in the telecentric scanning form. Accordingly, the scanning beam pointing deviation can be converted into the telecentricity deviation. Figure 1 represents the γ beam pointing deviation.

[0046] Since the actual optical system is not perfect, especially the wide-band system, except for the zero field of view on the axis, the telecentricity of the convergent beams in different spectral bands in the remaining fields of view are different. Figure 2As shown in the figure, when the beam pointing deviation is small, in the curved surface detection, it can be considered that the actual sampling point and the ideal sampling point are on a small surface element with a fixed steepness, and there are only two situations: the steepness is upward and the steepness is downward. From the geometric relationship in the figure, it can be obtained that the relationship between the test vector height deviation Δs and the beam pointing deviation γ can be described by formula (1), where α is the surface element steepness at the corresponding position, and s is the true value of the vector height measured when there is no ideal pointing deviation.

[0047]

[0048] From the above formula, when the beam pointing deviation is controlled within the range of 0.1°, the test sag deviation can be less than 2μm in the surface detection with a steepness variation range of ±15°, which basically meets the surface detection accuracy requirements of the conventional surface grinding stage. Therefore, it is determined that the full field telecentricity deviation of the designed telecentric scanning field mirror is less than 0.1°.

[0049] 5) F-theta distortion:

[0050] Generally speaking, the image height y of the scanning field mirror is linearly related to the tangent value tanθ of the scanning galvanometer deflection angle θ. In order to simplify the deflection control requirements of the scanning galvanometer, a quantitative distortion amount is introduced in the design of the scanning field mirror to make the image height y of the scanning field mirror and the deflection angle θ of the scanning galvanometer satisfy a linear relationship: y=f·θ, where f is the focal length of the scanning field mirror. In the design, the existing F-theta distortion will still cause the lateral positioning accuracy of the scanning field mirror to decrease as the field of view increases during use. The corresponding positioning error can be compensated by adjusting the deflection angle of the scanning galvanometer at the corresponding position. In order to minimize the lateral positioning compensation in the actual scanning sampling, it is preferably determined that the relative distortion of the required scanning field mirror F-theta of the full field of view is less than 0.05%.

[0051] 6) Field curvature:

[0052] like Figure 3 As shown in the figure, according to the results of geometric optical tracing, during the full-field scanning process, the inherent field curvature of the optical system will cause a certain axial deviation between the focus positions of the edge field of view and the central field of view in the sagittal / meridian direction, and the actual focus positions of each field of view in the sagittal / meridian direction are distributed on a curved surface I, rather than on an ideal plane I'. During the actual scanning and sampling process, the axial difference in the focus positions of different fields of view will lead to uneven distribution of axial signal intensities of different fields of view, which will affect the detection quality of the system. In order to minimize this effect, it is preferred to determine that the full-field sagittal / meridian field curvature of the scanning field mirror is less than 1 mm.

[0053] The relevant technical indicator requirements are summarized as follows:

[0054] Working spectrum: 1100nm-1500nm;

[0055] Numerical aperture: greater than 0.02;

[0056] Scanning field of view: can cover 100×100mm 2 square area;

[0057] Telecentricity: The telecentricity deviation of the entire field of view is less than 0.1°;

[0058] F-theta distortion: The relative distortion of F-theta in the whole field of view is less than 0.05%;

[0059] Field curvature: The sagittal / meridian curvature of the entire field of view is less than 1mm.

[0060] Based on this, the present invention provides an achromatic F-theta telecentric scanning field mirror for low coherence interference detection.

[0061] First, it is determined that the entrance pupil size range of the achromatic F-theta telecentric scanning field lens provided by the present invention is 10±10% mm, and the focal length range of the field lens is 200±10% mm, so as to meet the index requirement of "numerical aperture greater than 0.02".

[0062] Secondly, the maximum field of view of the achromatic F-theta telecentric scanning field mirror provided by the present invention is determined to be a φ150mm circular domain, so as to meet the requirement of the index "covering 100×100mm 2 Square area".

[0063] The achromatic F-theta telecentric scanning field lens provided by the present invention comprises: a front lens group and a rear lens group, which are sequentially arranged along the optical axis direction from the entrance pupil position. The front lens group is composed of three lenses, which are sequentially arranged along the optical axis direction: a first lens, a second lens, and a third lens, wherein the first lens is a positive power lens, the second lens is a negative power lens, and the third lens is a positive power lens. The rear lens group is composed of four lenses, which are sequentially arranged along the optical axis direction: a fourth lens, a fifth lens, a sixth lens, and a seventh lens, wherein the fourth lens is a positive power lens, the fifth lens is a negative power lens, the sixth lens is a positive power lens, and the seventh lens is a positive power lens.

[0064] In order to meet the requirement of achromatization for the entire spectrum of 1100nm-1500nm, preferably, the glass material used for the first lens is H-ZPK7, the glass material used for the second lens is H-QK3L, the glass material used for the third lens is H-BAK5, the glass material used for the fourth lens is H-ZPK7, the glass material used for the fifth lens is H-ZF71, the glass material used for the sixth lens is H-ZPK7, and the glass material used for the seventh lens is H-ZPK7. The above four materials are all existing commercially available products with reasonable costs.

[0065] In order to comprehensively meet the requirements of telecentricity, F-theta distortion, and field curvature, reduce the geometric aberrations of each field of view, and optimize the achromatic effect, optionally, the radius of curvature of the light incident surface of the first lens is -33.0±5%, the radius of curvature of the light exit surface of the first lens is -32.0±5%, the radius of curvature of the light incident surface of the second lens is -33.0±5%, the radius of curvature of the light exit surface of the second lens is -70.0±5%, the radius of curvature of the light incident surface of the third lens is -2450.0±5%, and the radius of curvature of the light exit surface of the third lens is -110.0±5%, The curvature radius of the light incident surface of the fourth lens is 3700.0±5%, the curvature radius of the light exiting surface of the fourth lens is -160.0±5%, the curvature radius of the light incident surface of the fifth lens is -210.0±5%, the curvature radius of the light exiting surface of the fifth lens is 325.0±5%, the curvature radius of the light incident surface of the sixth lens is 725.0±5%, the curvature radius of the light exiting surface of the sixth lens is -230.0±5%, the curvature radius of the light incident surface of the seventh lens is 390.0±5%, and the curvature radius of the light exiting surface of the seventh lens is -895.0±5%. The units of the above radii of curvature are all mm.

[0066] Further, the center thickness of the first lens is 15.0±5%, the center thickness of the second lens is 14.0±5%, the center thickness of the third lens is 15.5±5%, the center thickness of the fourth lens is 22.5±5%, the center thickness of the fifth lens is 7.0±5%, the center thickness of the sixth lens is 22.0±5%, and the center thickness of the seventh lens is 17.0±5%. The units of the above center thicknesses are all mm.

[0067] Furthermore, the distance of the air gap between the first lens and the second lens on the optical axis is 10.0±5%, the distance of the air gap between the second lens and the third lens on the optical axis is 5.0±5%, the distance of the air gap between the third lens and the fourth lens on the optical axis is 90.0±5%, the distance of the air gap between the fourth lens and the fifth lens on the optical axis is 9.0±5%, the distance of the air gap between the fifth lens and the sixth lens on the optical axis is 9.0±5%, and the distance of the air gap between the sixth lens and the seventh lens on the optical axis is 5.0±5%. The units of the above distances are all mm.

[0068] The present invention is described in detail below with reference to the accompanying drawings.

[0069] like Figure 4As shown, the achromatic F-theta telecentric scanning field lens for low-coherence interference detection provided by the embodiment of the present invention comprises a first lens 1, a second lens 2, a third lens 3, a fourth lens 4, a fifth lens 5, a sixth lens 6, and a seventh lens 7 which are sequentially arranged along the optical axis direction from the entrance pupil position. Among them, the first lens 1 is a positive power lens, the second lens 2 is a negative power lens, and the third lens 3 is a positive power lens, and the three form a front lens group; the fourth lens 4 is a positive power lens, the fifth lens 5 is a negative power lens, the sixth lens 6 is a positive power lens, and the seventh lens 7 is a positive power lens, and the four form a rear lens group.

[0070] The glass material used for the first lens 1 is H-ZPK7, the glass material used for the second lens 2 is H-QK3L, the glass material used for the third lens 3 is H-BAK5, the glass material used for the fourth lens 4 is H-ZPK7, the glass material used for the fifth lens 5 is H-ZF71, the glass material used for the sixth lens 6 is H-ZPK7, and the glass material used for the seventh lens 7 is H-ZPK7.

[0071] Along the light incident direction, the light incident surface and the light exit surface of the first lens 1 are the first curved surface and the second curved surface, respectively; the light incident surface and the light exit surface of the second lens 2 are the third curved surface and the fourth curved surface, respectively; the light incident surface and the light exit surface of the third lens 3 are the fifth curved surface and the sixth curved surface, respectively; the light incident surface and the light exit surface of the fourth lens 4 are the seventh curved surface and the eighth curved surface, respectively; the light incident surface and the light exit surface of the fifth lens 5 are the ninth curved surface and the tenth curved surface, respectively; the light incident surface and the light exit surface of the sixth lens 6 are the eleventh curved surface and the twelfth curved surface, respectively; and the light incident surface and the light exit surface of the seventh lens 7 are the thirteenth curved surface and the fourteenth curved surface, respectively.

[0072] The curvature radius of the first curved surface is -33.766mm, the curvature radius of the second curved surface is -32.670mm, the curvature radius of the third curved surface is -33.000mm, the curvature radius of the fourth curved surface is -70.150mm, the curvature radius of the fifth curved surface is -2460.700mm, the curvature radius of the sixth curved surface is -109.310mm, the curvature radius of the seventh curved surface is 3726.400mm, and the curvature radius of the eighth curved surface is -109.310mm. The radius of curvature of the surface is -162.650mm, the radius of curvature of the 9th surface is -211.723mm, the radius of curvature of the 10th surface is 326.761mm, the radius of curvature of the 11th surface is 725.000mm, the radius of curvature of the 12th surface is -231.200mm, the radius of curvature of the 13th surface is 391.770mm, and the radius of curvature of the 14th surface is -894.000mm.

[0073] The center thickness d1 of the first lens 1 is 15.0 mm, the center thickness d2 of the second lens 2 is 14.2 mm, the center thickness d3 of the third lens 3 is 15.4 mm, the center thickness d4 of the fourth lens 4 is 22.4 mm, the center thickness d5 of the fifth lens 5 is 7.0 mm, the center thickness d6 of the sixth lens 6 is 21.8 mm, and the center thickness d7 of the seventh lens 7 is 16.8 mm.

[0074] The entrance pupil size is 10mm. The entrance pupil is located on the object focal plane of the field lens. The center of the entrance pupil coincides with the optical axis. The distance l1 between the entrance pupil and the first curved surface of the first lens 1 on the optical axis is 50.0mm. The distance l2 between the second curved surface of the first lens 1 and the third curved surface of the second lens 2 on the optical axis is 10.0mm. The distance l3 between the fourth curved surface of the second lens 2 and the fifth curved surface of the third lens 3 on the optical axis is 5.0mm. The distance l4 between the sixth curved surface of the third lens 3 and the seventh curved surface of the fourth lens 4 on the optical axis is 10.0mm. The distance l4 is 91.2mm, the distance l5 between the 8th curved surface of the fourth lens 4 and the 9th curved surface of the fifth lens 5 on the optical axis is 9.4mm, the distance l6 between the 10th curved surface of the fifth lens 5 and the 11th curved surface of the sixth lens 6 on the optical axis is 9.3mm, the distance l7 between the 12th curved surface of the sixth lens 6 and the 13th curved surface of the seventh lens 7 on the optical axis is 5.0mm, and the distance between the 14th curved surface of the seventh lens 7 and the focal plane on the optical axis, i.e., the back intercept S of the field lens is 200.0mm.

[0075] The relevant optical parameters of the achromatic F-theta telecentric scanning field lens given in the above embodiment are summarized in Table 1. In this embodiment, the achromatic F-theta telecentric scanning field lens composed of the above lenses according to the relevant preferred parameter combination achieves the following optical indicators:

[0076] 1) Achromatic spectrum: 1100nm-1500nm;

[0077] 2) Entrance pupil size: 10mm;

[0078] 3) Focal length: 200mm;

[0079] 4) Scanning field of view: φ150mm;

[0080] 5) Telecentricity in the entire field of view: less than 0.03° (results are shown in Table 2);

[0081] 6) Full field of view F-theta distortion: Relative distortion is less than 0.01% (see the results Fig. 9 );

[0082] 7) Full field sagittal / meridian curvature: less than 0.5 mm (see results Fig.10 ).

[0083] Table 1 Optical parameters of the achromatic F-theta telecentric scanning field mirror of the embodiment

[0084]

[0085] Table 2 Statistical table of telecentricity of the achromatic F-theta telecentric scanning field mirror at the focal plane of different wavelength beams in the embodiment

[0086]

[0087] like Figure 5 As shown, the geometric aberrations of the achromatic F-theta telecentric scanning field mirror of the embodiment are all within the diffraction limit (circle composed of black solid lines in the figure) within the field of view of the light waves of different wavelengths in the spectral range of 1100nm to 1500nm.

[0088] like Figure 6 As shown, the achromatic F-theta telecentric scanning field mirror of the embodiment is designed so that the lateral chromatic aberration of light waves of different wavelengths in the spectral range of 1100nm to 1500nm within the field of view is less than the diffraction limit range (within the range defined by the two dotted lines in the figure).

[0089] like Figure 7 As shown, within the pupil range of the achromatic F-theta telecentric scanning field mirror in the embodiment, the axial chromatic aberration distribution between light waves of different wavelengths in the 1100nm to 1500nm spectral range on each aperture band is highly consistent, and the maximum axial chromatic aberration between different aperture bands is about 0.5mm, which is within the focal depth range of the system (the theoretical calculated value is 2mm).

[0090] like Figure 8 As shown, the maximum chromatic focus shift of the achromatic F-theta telecentric scanning field mirror of the embodiment is about 22 μm, which is much smaller than the focal depth range of the system (the theoretical calculated value is 2 mm).

[0091] like Fig. 9 As shown, the maximum F-theta distortion of the achromatic F-theta telecentric scanning field lens of the embodiment is about 0.008%. Fig.10 As shown, the maximum field curvature of the achromatic F-theta telecentric scanning field mirror in the embodiment is less than 0.5 mm, which meets the corresponding design index requirements.

[0092] like Fig.11 As shown, the MTF curves of each field of view of the achromatic F-theta telecentric scanning field mirror in the embodiment are close to the diffraction limit, which comprehensively reflects that the system chromatic aberration control and aberration correction effects are good.

[0093] The achromatic F-theta telecentric scanning field mirror for low-coherence interference detection of the present invention has relatively compact arrangement of the positions of the lenses, forming two groups of front and rear concentrated distribution forms in space, which is convenient for installation and debugging.

[0094] The achromatic F-theta telecentric scanning field mirror for low-coherence interference detection of the present invention has two front and rear mirror groups with respective focused functions. The three lenses of the front mirror group are mainly responsible for the task of transmitting large-angle light beams, and the four lenses of the rear mirror group are mainly responsible for the task of adjusting the telecentricity of each field of view on the image side.

[0095] The achromatic F-theta telecentric scanning field mirror for low-coherence interference detection of the present invention has relatively independent front and rear mirror groups in terms of chromatic aberration control and geometric aberration correction, and the combined effect enables the entire system to obtain better achromatic and aberration correction effects.

[0096] The achromatic F-theta telecentric scanning field mirror for low-coherence interference detection of the present invention has the front and rear mirror groups cooperate with each other in terms of F-theta distortion balance, thereby achieving F-theta distortion cancellation to the maximum extent.

[0097] Obviously, the above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived therefrom are still within the scope of protection of the invention.

Claims

1. Achromatic F-theta telecentric scanning field lens for low coherence interferometric detection, characterized in that: include: A front lens group and a rear lens group are arranged in sequence along the optical axis starting from the entrance pupil position; The front lens group comprises: a first lens (1), a second lens (2), and a third lens (3) which are arranged in sequence along the optical axis direction; wherein the first lens (1) is a positive power lens, the second lens (2) is a negative power lens, and the third lens (3) is a positive power lens; The rear lens group comprises: a fourth lens (4), a fifth lens (5), a sixth lens (6), and a seventh lens (7) which are arranged in sequence along the optical axis direction; wherein the fourth lens (4) is a positive power lens, the fifth lens (5) is a negative power lens, the sixth lens (6) is a positive power lens, and the seventh lens (7) is a positive power lens; Along the incident direction of light, the light entrance surface and the light exit surface of the first lens (1) are the first curved surface and the second curved surface, respectively; the light entrance surface and the light exit surface of the second lens (2) are the third curved surface and the fourth curved surface, respectively; the light entrance surface and the light exit surface of the third lens (3) are the fifth curved surface and the sixth curved surface, respectively; the light entrance surface and the light exit surface of the fourth lens (4) are the seventh curved surface and the eighth curved surface, respectively; the light entrance surface and the light exit surface of the fifth lens (5) are the ninth curved surface and the tenth curved surface, respectively; the light entrance surface and the light exit surface of the sixth lens (6) are the eleventh curved surface and the twelfth curved surface, respectively; and the light entrance surface and the light exit surface of the seventh lens (7) are the thirteenth curved surface and the fourteenth curved surface, respectively; The curvature radius of the first curved surface is -33.0±5%mm, the curvature radius of the second curved surface is -32.0±5%mm; the curvature radius of the third curved surface is -33.0±5%mm, the curvature radius of the fourth curved surface is -70.0±5%mm; the curvature radius of the fifth curved surface is -2450.0±5%mm, the curvature radius of the sixth curved surface is -110.0±5%mm; the curvature radius of the seventh curved surface is 3700.0±5%mm, the curvature radius of the eighth curved surface is 10 ... The curvature radius of the curved surface is -160.0±5%mm; the curvature radius of the 9th curved surface is -210.0±5%mm, the curvature radius of the 10th curved surface is 325.0±5%mm; the curvature radius of the 11th curved surface is 725.0±5%mm, the curvature radius of the 12th curved surface is -230.0±5%mm; the curvature radius of the 13th curved surface is 390.0±5%mm, the curvature radius of the 14th curved surface is -895.0±5%mm; The center thickness d1 of the first lens (1) is 15.0±5% mm, the center thickness d2 of the second lens (2) is 14.0±5% mm, the center thickness d3 of the third lens (3) is 15.5±5% mm, the center thickness d4 of the fourth lens (4) is 22.5±5% mm, the center thickness d5 of the fifth lens (5) is 7.0±5% mm, the center thickness d6 of the sixth lens (6) is 22.0±5% mm, and the center thickness d7 of the seventh lens (7) is 17.0±5% mm; The distance between the first lens (1) and the second lens (2) on the optical axis is 10.0±5% mm, the distance between the second lens (2) and the third lens (3) on the optical axis is 5.0±5% mm, the distance between the third lens (3) and the fourth lens (4) on the optical axis is 90.0±5% mm, the distance between the fourth lens (4) and the fifth lens (5) on the optical axis is 9.0±5% mm, the distance between the fifth lens (5) and the sixth lens (6) on the optical axis is 9.0±5% mm, and the distance between the sixth lens (6) and the seventh lens (7) on the optical axis is 5.0±5% mm.

2. The achromatic F-theta telecentric scanning field lens for low coherence interferometric detection according to claim 1, characterized in that: The glass material used for the first lens (1) is H-ZPK7, the glass material used for the second lens (2) is H-QK3L, the glass material used for the third lens (3) is H-BAK5, the glass material used for the fourth lens (4) is H-ZPK7, the glass material used for the fifth lens (5) is H-ZF71, the glass material used for the sixth lens (6) is H-ZPK7, and the glass material used for the seventh lens (7) is H-ZPK7.

3. The achromatic F-theta telecentric scanning field lens for low coherence interferometric detection according to claim 1 or 2, characterized in that: The curvature radius of the first curved surface is -33.766mm, the curvature radius of the second curved surface is -32.670mm, the curvature radius of the third curved surface is -33.000mm, the curvature radius of the fourth curved surface is -70.150mm, the curvature radius of the fifth curved surface is -2460.700mm, the curvature radius of the sixth curved surface is -109.310mm, the curvature radius of the seventh curved surface is 3726.400mm, and the curvature radius of the eighth curved surface is -109.310mm. The radius of curvature of the surface is -162.650mm, the radius of curvature of the 9th surface is -211.723mm, the radius of curvature of the 10th surface is 326.761mm, the radius of curvature of the 11th surface is 725.000mm, the radius of curvature of the 12th surface is -231.200mm, the radius of curvature of the 13th surface is 391.770mm, and the radius of curvature of the 14th surface is -894.000mm.

4. The achromatic F-theta telecentric scanning field lens for low coherence interferometric detection according to claim 3, characterized in that: The center thickness of the first lens (1) is d1=15.0 mm, the center thickness of the second lens (2) is d2=14.2 mm, the center thickness of the third lens (3) is d3=15.4 mm, the center thickness of the fourth lens (4) is d4=22.4 mm, the center thickness of the fifth lens (5) is d5=7.0 mm, the center thickness of the sixth lens (6) is d6=21.8 mm, and the center thickness of the seventh lens (7) is d7=16.8 mm.

5. The achromatic F-theta telecentric scanning field lens for low coherence interferometric detection according to claim 3, characterized in that: The entrance pupil size is 10mm, the entrance pupil is located on the object focal plane of the field lens, and the center of the entrance pupil coincides with the optical axis.

6. The achromatic F-theta telecentric scanning field lens for low coherence interferometric detection according to claim 3, characterized in that: The distance l1 between the entrance pupil and the first curved surface of the first lens (1) on the optical axis is 50.0 mm, the distance l2 between the second curved surface of the first lens (1) and the third curved surface of the second lens (2) on the optical axis is 10.0 mm, the distance l3 between the fourth curved surface of the second lens (2) and the fifth curved surface of the third lens (3) on the optical axis is 5.0 mm, the distance l4 between the sixth curved surface of the third lens (3) and the seventh curved surface of the fourth lens (4) on the optical axis is 91.2 mm, and the distance l5 between the sixth curved surface of the third lens (3) and the seventh curved surface of the fourth lens (4) on the optical axis is 10.0 mm. ) and the 9th curved surface of the fifth lens (5) on the optical axis is 9.4 mm, the distance l5 between the 10th curved surface of the fifth lens (5) and the 11th curved surface of the sixth lens (6) on the optical axis is 9.3 mm, the distance l7 between the 12th curved surface of the sixth lens (6) and the 13th curved surface of the seventh lens (7) on the optical axis is 5.0 mm, and the distance between the 14th curved surface of the seventh lens (7) and the focal plane on the optical axis is the field lens back intercept S, S=200.0 mm.

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