CN116299979A - Line scanning spectrum confocal dispersion objective lens - Google Patents
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- G02B13/00—Optical objectives specially designed for the purposes specified below
- G02B13/001—Miniaturised objectives for electronic devices, e.g. portable telephones, webcams, PDAs, small digital cameras
- G02B13/0055—Miniaturised objectives for electronic devices, e.g. portable telephones, webcams, PDAs, small digital cameras employing a special optical element
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- G02B13/00—Optical objectives specially designed for the purposes specified below
- G02B13/001—Miniaturised objectives for electronic devices, e.g. portable telephones, webcams, PDAs, small digital cameras
- G02B13/0015—Miniaturised objectives for electronic devices, e.g. portable telephones, webcams, PDAs, small digital cameras characterised by the lens design
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B13/00—Optical objectives specially designed for the purposes specified below
- G02B13/22—Telecentric objectives or lens systems
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- G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
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- G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
- G02B27/0025—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00 for optical correction, e.g. distorsion, aberration
- G02B27/0031—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00 for optical correction, e.g. distorsion, aberration for scanning purposes
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- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
- G02B27/0025—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00 for optical correction, e.g. distorsion, aberration
- G02B27/005—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00 for optical correction, e.g. distorsion, aberration for correction of secondary colour or higher-order chromatic aberrations
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Abstract
The invention discloses a line scanning spectrum confocal dispersion objective lens, which comprises: the linear light source incidence end and the receiving end, the dispersive objective lens front group optical system, the aperture diaphragm and the dispersive objective lens rear group optical system; wherein, the front group optical system of the dispersion objective lens is an achromatic optical system consisting of three groups of lenses, which collimates the incident light and transmits the light backward; the aperture diaphragm can adjust the clear aperture and control the luminous flux of the objective lens; the back group optical system of the dispersion objective lens is a hyperchromatic optical system composed of three groups of lenses, and the parallel light collimated by the front group optical system is focused on different focal planes according to the wavelength. The invention adopts a sectional double telecentric objective lens structure, can realize that converging light of each wavelength is perpendicular to the surface to be measured under different view fields, reduces measurement errors of off-axis view fields, and can replace a rear group optical system of the objective lens according to different test requirements, thereby realizing different measurement ranges and view fields.
Description
Technical Field
The invention relates to a line scanning spectrum confocal dispersion objective lens, which is particularly suitable for manufacturing precise instruments based on a spectrum confocal measurement principle, and measuring samples such as films, glass, circuit boards and the like.
Background
With the development of precision manufacturing industry, the requirement for workpiece detection is higher and higher. The spectral confocal measurement technology developed from the confocal measurement technology has wide application in industrial detection due to high detection efficiency, and particularly in measurement of transparent materials such as films, glass substrates and the like.
The spectral confocal measurement technology uses the axial chromatic aberration of an optical system to correspond wavelength information with spatial position codes. The reflected wavelength is detected by a spectrometer to determine the spatial position. Dispersive objectives capable of producing axial chromatic aberration are therefore critical to the implementation of spectral confocal measurement techniques.
In the existing spectral confocal measurement technology, a single-point dispersion objective lens is used as a main component. Although the axial focusing time is greatly reduced, the measuring efficiency is improved, the measuring efficiency is still limited by two-dimensional mechanical displacement when the surface is measured in a full field only by single-point measurement.
Disclosure of Invention
In order to further improve the measurement efficiency of the spectral confocal sensor, the invention provides the line scanning spectral confocal dispersion objective lens which can realize different measurement ranges and larger line fields of view, reduce the measurement error of the off-axis field of view and improve the transverse measurement efficiency of the spectral confocal sensor.
The invention adopts the technical scheme for solving the technical problems that:
the invention relates to a line scanning spectrum confocal dispersion objective lens which is characterized by comprising the following components in sequence: the linear light source incidence end and the receiving end, the dispersive objective lens front group optical system, the aperture diaphragm and the dispersive objective lens rear group optical system;
the line light source incidence end and the receiving end comprise: a line light source incident port, a spectroscope and a reflected light receiving port; the size of the linear light source incidence port is the same as that of the reflective light receiving port, and the linear light source incidence port and the reflective light receiving port are in 90-degree relation and are respectively positioned on the incidence surface and the reflective surface of the spectroscope; the linear light source incidence port and the reflected light receiving port are both arranged on a front focal plane of the front group optical system of the dispersion objective lens;
the front group optical system of the dispersion objective lens is an object space telecentric infinity flat field correction achromatic optical system and consists of a first lens group, a second lens group and a third lens group;
the first lens group is a positive-power meniscus double-cemented lens formed by a first positive lens and a first negative lens, the concave surfaces of the first negative lens face the incidence direction of the linear light source, the first negative lens is made of an optical material with the dispersion coefficient smaller than a threshold delta, and the first positive lens is made of an optical material with the dispersion coefficient larger than the threshold delta; delta epsilon [35,45];
the combined focal power of the second lens group is positive and consists of a first single lens, a second single lens and a third single lens; and the first single lens and the third single lens are symmetrically distributed about the second single lens; the first single lens is a first positive focal power meniscus lens, and the concave surface of the first single lens faces the incidence direction of the linear light source; the second single lens is a biconcave lens with negative focal power, the third single lens is a meniscus lens with positive focal power, the convex surface of the third single lens faces the incidence direction of the linear light source, and the single lenses contained in the second lens group are all made of optical materials with dispersion coefficients larger than a threshold delta;
the third lens group is a positive-power meniscus double-cemented lens formed by a second positive lens and a second negative lens, the convex surface of the second positive lens faces the incidence direction of the linear light source, the second negative lens adopts an optical material with the dispersion coefficient smaller than a threshold delta, the second positive lens adopts an optical material with the dispersion coefficient larger than the threshold delta, and the third lens group and the first lens group are symmetrical with respect to the second single lens in space layout;
the aperture diaphragm is a circular aperture diaphragm with an adjustable clear aperture, and the aperture diaphragm is respectively overlapped with the back focal plane of the front group optical system of the dispersion objective and the front focal plane of the back group optical system of the dispersion objective; thereby forming an object space telecentric optical system by the aperture diaphragm and the front group optical system of the dispersion objective lens; forming an imaging side telecentric optical system by the aperture diaphragm and the dispersive objective rear group optical system; the front group optical system of the dispersion objective, the aperture diaphragm and the rear group optical system of the dispersion objective form a double telecentric optical system together;
the rear group optical system of the dispersion objective lens is an image space telecentric infinity flat field correction chromatic aberration-increasing optical system and is composed of a fourth lens group, a fifth lens group, a sixth lens group and plate protective glass in sequence;
the fourth lens group is a positive-power meniscus chromatic aberration-increasing double-cemented lens formed by a third positive lens and a third negative lens, the concave surface of the third negative lens faces the aperture diaphragm, the third negative lens adopts an optical material with the dispersion coefficient larger than the threshold delta, and the third positive lens adopts an optical material with the dispersion coefficient smaller than the threshold delta;
the combined focal power of the fifth lens group is positive, and the fifth lens group is a hyperchromatic optical system composed of a fourth single lens, a first double-cemented lens and a fifth single lens;
the fourth single lens is a third positive focal power meniscus lens, the concave surface of the fourth single lens faces the aperture diaphragm, and an optical material with the dispersion coefficient smaller than the threshold delta is adopted;
the first double-cemented lens is a biconcave achromatic double-cemented lens with negative focal power, which is composed of a fourth positive lens and a fourth negative lens, wherein the fourth negative lens adopts an optical material with a dispersion coefficient smaller than a threshold delta, and the fourth positive lens adopts an optical material with a dispersion coefficient larger than the threshold delta;
the fifth single lens is a fourth positive focal power meniscus lens, the convex surface of the fifth single lens faces the aperture diaphragm, and an optical material with the dispersion coefficient smaller than the threshold delta is adopted; the fourth single lens and the fifth single lens are respectively arranged at two sides of the first double-cemented lens;
the sixth lens group is a positive-power meniscus chromatic aberration-increasing double-cemented lens formed by a fifth positive lens and a fifth negative lens, the convex surface of the fifth positive lens faces the aperture diaphragm and adopts an optical material with a dispersion coefficient smaller than a threshold delta, the fifth negative lens adopts an optical material with a dispersion coefficient larger than the threshold delta, and the fourth lens group and the sixth lens group are symmetrical with respect to the first double-cemented lens in space layout;
the plate protection glass is plate glass with two parallel surfaces.
The invention also provides a structure of the line scanning spectrum confocal dispersion objective lens, which is characterized in that:
the first lens group, the first single lens, the second single lens, the third single lens and the third lens group uniformly share deflection angles of incident light rays generated by an optical system of the front group of the dispersion objective lens;
the fourth lens group, the fourth single lens, the first double-cemented lens, the fifth single lens and the sixth lens group uniformly share the deflection angle of the incident light ray generated by the optical system of the rear group of the dispersion objective lens.
The optical materials selected by the first lens group, the first single lens, the second single lens, the third single lens and the third lens group meet the flat field constraint condition shown in the formula (1):
in the formula (1), S IV-F Peztval field curvature, J, generated for the dispersive objective front group optical system F Is Lagrange invariant, phi of the dispersive objective lens front group optical system i An optical power of an ith lens in the dispersive objective lens front group optical system, n i Is the refractive index of the ith lens material in the dispersive objective lens front group optical system.
Axial chromatic aberration generated by the first lens group, the first single lens, the second single lens, the third single lens and the third lens group meets the constraint condition shown in the formula (2):
in the formula (2), L chF For the dispersion ofAxial chromatic aberration, y, produced by an objective lens front group optical system i For the incident height of the light ray on the ith lens in the optical system of the front group of the dispersion objective lens i V is the optical power of the ith lens in the dispersive objective lens front group optical system i Abbe number, u, of the ith lens material in the dispersive objective lens front group optical system F5 Is the angle of the aperture of the incident beam.
The optical materials selected by the fourth lens group, the fourth single lens, the first double-cemented lens, the fifth single lens and the sixth lens group meet the flat field constraint condition shown in the formula (3):
in the formula (3), S IV-B Peztval field curvature, J, generated for the dispersive objective post-group optical system B Is Lagrange invariant, phi of the dispersive objective lens rear group optical system j An optical power of a j-th lens in the dispersive objective lens rear group optical system, n j Is the refractive index of the j-th lens material in the dispersive objective lens rear group optical system.
The sum of the axial chromatic aberration generated by the fourth lens group, the fourth single lens, the first double-cemented lens, the fifth single lens and the sixth lens group is the axial chromatic aberration of the dispersion objective lens, so as to form a measuring range of the dispersion objective lens, and the constraint condition shown in the formula (4) is satisfied:
in the formula (4), L chB Axial chromatic aberration generated for the dispersive objective lens rear group optical system, L ch Axial chromatic aberration, y, generated for said dispersive objective j For the incident height of the light ray on the j-th lens in the optical system of the rear group of the dispersion objective lens j The optical power of the j-th lens in the rear group optical system of the dispersion objective lens is v j Abbe number, u, of the j-th lens material in the dispersive objective lens back group optical system B5 To converge the beam aperture angle, phi 3a Is the focal power phi of the fourth positive lens in the first double-cemented lens 3b V for the fourth negative lens power in the first doublet lens 3a Abbe number, v of optical material used for fourth positive lens in the first double-cemented lens 3b Abbe number of the optical material used for the fourth negative lens in the first double cemented lens.
Compared with the prior art, the invention has the beneficial effects that:
1. the invention adopts a double telecentric objective lens structure, can ensure that the convergence measuring light of each view field is vertical to the surface to be measured, and reduces the energy loss caused by inclined reflection.
2. The invention adopts a sectional objective structure, the objective front group optical system is set as an infinite flat field correction achromatic optical system, the objective rear group optical system is set as an infinite flat field correction achromatic optical system as a fixed part, and the objective rear group optical system can be replaced according to different test requirements as an adjustable part, so that different measuring ranges and measuring fields can be obtained.
3. The invention adopts a symmetrical optical structure, is beneficial to correcting various off-axis aberrations and improves the measuring effect.
4. The invention adopts the aperture diaphragm with adjustable aperture, and can adjust the light flux of the dispersion objective lens according to the reflection condition of the measured surface so as to realize the best measurement effect.
Drawings
FIG. 1 is a block diagram of a line scanning spectral confocal dispersion objective of the present invention;
FIG. 2 is a graph showing the measurement ranges formed by the dispersive objective lens according to the present invention;
reference numerals in the drawings: a 1-line light source incidence end and a receiving end; 2 a dispersive objective lens front group optical system; 3, an aperture diaphragm; 4 a dispersive objective lens back group optical system; a 5-wire light source incident port; a beam splitter; a 7-wire light source receiving port; 8 a first lens group; 9 a second lens group; 10 a third lens group; 11 a first single lens; 12 a second single lens; 13 a third single lens; 14 a fourth lens group; 15 a fifth lens group; 16 a sixth lens group; 17 plate protection glass; 18 fourth single lens; a first doublet lens 19; 20 a fifth single lens; 21 measurement range.
Detailed Description
In this embodiment, as shown in fig. 1, a sectional type double telecentric objective lens structure is adopted for a line scanning spectrum confocal dispersion objective lens, so that the converging light of each wavelength under different fields of view is perpendicular to the surface to be measured, the measurement error of the off-axis field of view can be reduced, and in addition, the sectional type objective lens structure can replace the rear group optical system of the objective lens according to different test requirements, thereby realizing different measurement ranges and fields of view. Specifically, the line scanning spectrum confocal dispersion objective consists of a line light source incidence end and a receiving end 1, a dispersion objective front group optical system 2, an aperture diaphragm 3 and a dispersion objective rear group optical system 4;
as shown in fig. 1, the linear light source incident end and receiving end 1 includes: the linear light source incidence port 5, the spectroscope 6 and the reflected light receiving port 7 can be a linear light source formed by a one-dimensional optical fiber array and closely connected with a multi-point light source side by side or a linear light source generated by a slit; the beam splitter 6 is usually a beam splitter prism or a sheet beam splitter, the beam splitting ratio of the beam splitter 6 can be set by itself, and the transmittance of the beam splitter is usually adopted: the reflectance was 50:50, which allows maximum light energy utilization, and which can be adjusted according to specific measurement requirements, for example, to suppress background noise of the incident light, the transmittance of the beam splitter 6, for example, the transmittance, can be improved: the reflectance was 75:25, so that most of the incident light participates in the measurement process, and the reflected confocal spectrum energy is reduced, which is suitable for the case of high side reflectivity; the size of the linear light source incidence port 5 is the same as that of the reflective light receiving port 7, and the linear light source incidence port 5 and the reflective light receiving port 7 are in 90 DEG relation and are respectively positioned on the incidence surface and the reflective surface of the spectroscope 6; the line light source incidence port 5 and the reflected light receiving port 7 have the same conjugate point, so that the line light source incidence port 5 and the reflected light receiving port 7 can be mutually converted, and in the actual use process, the line light source and the corresponding receiver can be flexibly installed according to the on-site light path arrangement condition; the linear light source incidence port 5 and the reflected light receiving port 7 are arranged on the front focal plane of the front group optical system 2 of the dispersion objective lens;
as shown in fig. 1, the dispersive objective lens front group optical system 2 is an object side telecentric infinity flat field correction achromatic optical system, and is composed of a first lens group 8, a second lens group 9, and a third lens group 10; the dispersive objective lens front group optical system 2 subjected to infinity flat field correction can collimate and emit divergent light incident from any field of view of the linear light source incident port 5, and the divergent light is incident to the dispersive objective lens rear group optical system 4 through the aperture diaphragm 3; the front group optical system 2 of the dispersion objective is also a group of achromatic optical systems, so that the multi-color light incident from the linear light source incident port 5 can be well collimated and enter the rear group optical system 4 of the dispersion objective;
the first lens group 8 is a positive-power meniscus double-cemented lens formed by a first positive lens and a first negative lens, the concave surfaces of the first negative lens face the incidence direction of the linear light source, the concave surfaces of the lens face the incidence light, the reflection of light on the interface of air and glass can be reduced, the generation of stray light is reduced, and the lens with a meniscus structure is beneficial to correcting spherical aberration; the first negative lens uses an optical material having a dispersion coefficient smaller than a threshold Δ, for example: flint glass, heavy flint glass, and some lanthanide glasses; the first positive lens is made of an optical material with a dispersion coefficient larger than a threshold delta; for example: crown glasses, dense crown glasses, and some lanthanide glasses; delta epsilon [35,45];
the combined focal power of the second lens group 9 is positive, and the lens is composed of a first single lens 11, a second single lens 12 and a third single lens 13, and the structure of separating positive and negative lenses is beneficial to correcting spherical aberration and axial chromatic aberration; the first single lens 11 and the third single lens 13 are symmetrically distributed about the second single lens 12, and the symmetrically distributed structure is beneficial to correcting coma aberration, astigmatism, distortion and vertical axis chromatic aberration introduced by an off-axis visual field; the first single lens 11 is a first positive focal power meniscus lens, and the concave surface faces the incidence direction of the linear light source; the second single lens 12 is a biconcave lens with negative focal power, the third single lens 13 is a meniscus lens with positive focal power, the convex surface faces the incident direction of the linear light source, and the single lenses included in the second lens group 9 are made of optical materials with dispersion coefficient larger than a threshold delta, for example: crown glasses, dense crown glasses, and some lanthanide glasses, wherein the second single lens 12 of negative power may be made of a glass material having a slightly higher dispersive power than the first single lens 11 and the third single lens 13, which is more advantageous for correcting axial chromatic aberration;
the third lens group 10 is a positive power meniscus double cemented lens composed of a second positive lens and a second negative lens, the convex surface of the second positive lens faces the incidence direction of the linear light source, the second negative lens adopts an optical material with a dispersion coefficient smaller than a threshold value delta, the second positive lens adopts an optical material with a dispersion coefficient larger than the threshold value delta, and the third lens group 10 and the first lens group 8 are symmetrical about the second single lens 12 in space layout; the symmetrical structure is beneficial to correcting various aberrations introduced by off-axis view field rays;
the dispersive objective lens front group optical system 2 is an achromatic optical system, and therefore the optical materials selected for the first lens group 8, the first single lens 11, the second single lens 12, the third single lens 13, and the third lens group 10 satisfy the flat field constraint condition shown in formula (1):
in the formula (1), S IV-F Peztval field curvature, J, generated for dispersive objective front group optical system 2 F Is Lagrange invariant, phi of the dispersive objective lens front group optical system 2 i Is the optical power of the ith lens in the dispersive objective lens front group optical system 2, n i For the refractive index of the i-th lens material in the dispersive objective front group optical system 2, the flat image field is critical for the line scanning spectral confocal measurement system, and can ensure the consistency of the measured peaks under different fields.
In specific implementation, the first lens group 8, the first single lens 11, the second single lens 12, the third single lens 13 and the third lens group 10 uniformly share the deflection angle of the incident light ray generated by the optical system 2 of the front group of the dispersion objective lens;
axial chromatic aberration generated by the first lens group 8, the first single lens 11, the second single lens 12, the third single lens 13, and the third lens group 10 satisfies the constraint condition shown in formula (2):
in the formula (2), L chF Axial chromatic aberration, y, produced for a dispersive objective front group optical system 2 i For the incident height of the light ray on the ith lens in the dispersive objective lens front group optical system 2, phi i The optical power of the ith lens in the dispersive objective lens front group optical system 2, v i Abbe number, u, of the ith lens material in the dispersive objective lens front group optical system 2 F5 For the incident beam aperture angle, axial chromatic aberration generated by the first single lens 11, the second single lens 12, the third single lens 13 after determining the material is fixed, and residual chromatic aberration can be eliminated by generating opposite axial chromatic aberration by the first lens group 8 and the third lens group 10; the axial chromatic aberration which can be generated by the single lens is determined by the focal power of the lens and the material, when the focal power of the lens is determined, the axial chromatic aberration which can be generated by the single lens is determined by the Abbe number of the material, and the types of the optical materials are limited, if the front group optical system 2 of the dispersive objective lens is formed by the single lens, the phenomenon that the axial chromatic aberration cannot be eliminated is possibly generated, so that two groups of double cemented lenses are used, and the double cemented lenses can realize the axial chromatic aberration in a larger range by adjusting the focal power of the positive lens and the type of the material, so that the double cemented lenses have strong applicability.
The aperture diaphragm 3 is a circular aperture diaphragm with an adjustable clear aperture, the light passing amount and the light entering amount of the dispersion objective can be controlled by adjusting the clear aperture of the aperture diaphragm 3, the clear aperture of the aperture diaphragm 3 is reduced for some measured surfaces with higher reflectivity, the light passing amount of the dispersion objective is reduced, the corresponding spectrum detector or spectrometer can be prevented from being saturated, the clear aperture of the aperture diaphragm 3 is increased for the side surface with lower reflectivity, the light passing amount of the dispersion objective is adjusted to be high, and the peak intensity of a measured spectrum is improved; the aperture diaphragm 3 is respectively overlapped with the back focal plane of the front group optical system 2 of the dispersion objective lens and the front focal plane of the back group optical system 4 of the dispersion objective lens; when the incident ray source is a one-dimensional optical fiber array, the cone angle of the light beam emitted by each optical fiber is not influenced by a rear optical system, and when the dispersive objective lens front group optical system 2, the linear light source formed by the whole row of the one-dimensional optical fibers is the object telecentric; an imaging side telecentric optical system is formed by the aperture diaphragm 3 and the dispersive objective lens rear group optical system 4, the imaging side telecentric optical system ensures that the convergence measuring light of each view field can be the same as the on-axis view field, as shown in a part (a) in fig. 2, is vertical to the measured surface and is incident, meanwhile, ensures the consistency of the corresponding transverse measuring range of each wavelength, avoids the deviation of the transverse measuring range introduced by a non-telecentric optical system, and can utilize the measuring light to the greatest extent, as shown in a part (b) in fig. 2, so as to realize the optimal measuring effect; the front group optical system 2 of the dispersion objective, the aperture diaphragm 3 and the rear group optical system 4 of the dispersion objective form a double telecentric optical system together;
as shown in fig. 1, the post-dispersing-objective optical system 4 is an image-space telecentric infinity field correction chromatic aberration-increasing optical system, the post-dispersing-objective optical system 4 can focus parallel incident light with different incident angles on the same focal plane after infinity field correction, meanwhile, the post-dispersing-objective optical system 4 is a chromatic aberration-increasing system, can focus complex-color light containing multiple wavelengths on different focal planes in an incremental wavelength manner, and focuses light with different fields of view with the same wavelength on the same focal plane, and forms measuring focal planes with various wavelengths within a range in a preset manner, as shown in a part (a) in fig. 2; and is composed of a fourth lens group 14, a fifth lens group 15, a sixth lens group 16 and a plate protection glass 17 in this order; the plate protection glass 17 does not deflect the light, so there is no aberration contribution, especially the axial chromatic aberration that the dispersive objective is most concerned with; the front group optical system 2 of the dispersive objective is an achromatic system, so that the axial chromatic aberration of the dispersive objective is generated by the rear group optical system, and the axial chromatic aberration required to be generated by the rear group optical system 4 of the dispersive objective can be distributed to the fourth lens group, the fifth lens group and the sixth lens group approximately according to the proportion of the focal power of each lens group;
the fourth lens group 14 is a positive-power meniscus chromatic aberration-increasing double-cemented lens composed of a third positive lens and a third negative lens, wherein the concave surface of the third negative lens faces the aperture stop 3, the third negative lens adopts an optical material with a dispersion coefficient larger than a threshold delta, and the third positive lens adopts an optical material with a dispersion coefficient smaller than the threshold delta; the arrangement of the optical materials is just opposite to that of the achromatic lens, and the distribution and the arrangement of the optical power are favorable for increasing the axial chromatic aberration generated by the lens, but the chromatic dispersion performance of the optical materials selected by the positive lens is not excessively large, and if the negative lens glued with the positive lens is not excessively large, the negative lens can become a plane mirror and is invalid; the meniscus lens form is advantageous for correcting spherical aberration of the optical system;
the fifth lens group 15 has positive combined power and is a chromatic aberration increasing optical system composed of a fourth single lens 18, a first double cemented lens 19, and a fifth single lens 20;
the fourth single lens 18 is a third positive power meniscus lens, the concave surface of the fourth single lens faces the aperture diaphragm 3, and an optical material with the dispersion coefficient smaller than a threshold delta is adopted;
the first biconvex lens 19 is a biconcave achromatic biconvex lens with negative power, which is composed of a fourth positive lens and a fourth negative lens, wherein the fourth negative lens adopts an optical material with a dispersion coefficient smaller than a threshold delta, and the fourth positive lens adopts an optical material with a dispersion coefficient larger than the threshold delta; because the negative focal power lens generates negative axial chromatic aberration, the axial chromatic aberration is not beneficial to the optical system to increase, the negative focal power lens in the fifth lens group 15 is arranged as an achromatic cemented lens, and because the single lens introduces negative axial chromatic aberration no matter what material is used, the chromatic aberration task of other lens groups can be increased, so that the lens is arranged as an achromatic double cemented lens, and the influence of the negative lens on the axial chromatic aberration is reduced to the greatest extent;
the fifth single lens 20 is a fourth positive power meniscus lens, the convex surface of the fifth single lens faces the aperture stop 3, and an optical material with the dispersion coefficient smaller than a threshold delta is adopted; the fourth single lens 18 and the fifth single lens 20 are respectively arranged at two sides of the first double cemented lens 19, and the symmetrically distributed structure is also beneficial to correcting aberration introduced by the off-axis visual field;
the fifth lens group 15 is a chromatic aberration increasing optical system, and the axial chromatic aberration that can be contributed by the fourth single lens 18 and the fifth single lens 20 is related to the optical power and the optical material selected, but the optical power is not excessively large, otherwise, larger spherical aberration is introduced, and correction is difficult, so that in order to ensure that enough axial chromatic aberration can be generated, the fourth single lens 18 and the fifth single lens 20 are made of optical materials with the dispersion coefficient smaller than a threshold delta;
the sixth lens group 16 is a positive power meniscus chromatic aberration-increasing double cemented lens composed of a fifth positive lens and a fifth negative lens, the convex surface of the fifth positive lens faces the aperture stop 3, and an optical material with a dispersion coefficient smaller than a threshold delta is adopted, the fifth negative lens adopts an optical material with a dispersion coefficient larger than the threshold delta, the fourth lens group 14 and the sixth lens group 16 are symmetrical about the first double cemented lens 19 in terms of space layout, and the symmetrical structure is beneficial to correcting various aberrations introduced by off-axis view rays;
the optical materials selected for the fourth lens group 14, the fourth single lens 18, the first doublet lens 19, the fifth single lens 20, and the sixth lens group 16 satisfy the flat field constraint condition shown in formula (3):
in the formula (3), S IV-B Peztval field curvature, J, generated for dispersive objective lens rear group optical system 4 B Is Lagrange invariant, phi of the dispersive objective lens rear group optical system 4 j Optical power, n, of the j-th lens in the dispersive objective lens rear group optical system 4 j Is the refractive index of the j-th lens material in the dispersive objective lens rear group optical system 4.
The fourth lens group 14, the fourth single lens 18, the first double cemented lens 19, the fifth single lens 20 and the sixth lens group 16 uniformly share the deflection angle of the incident light beam generated by the dispersive objective lens rear group optical system 4;
the deflection angles of the light rays are uniformly distributed on each lens, so that the deflection angles of the light rays generated on the surfaces of each group of lenses are reduced, the tolerance sensitivity of each lens can be reduced to the greatest extent, and meanwhile, the spherical aberration of the optical system can be corrected.
The sum of the axial chromatic aberration generated by the fourth lens group 14, the fourth single lens 18, the first doublet lens 19, the fifth single lens 20 and the sixth lens group 16 is the axial chromatic aberration of the dispersive objective lens, forming a measuring range 21 of the dispersive objective lens, and satisfying the constraint condition shown in formula (4):
in the formula (4), L chB Axial chromatic aberration L generated for dispersive objective lens rear group optical system 4 ch For axial chromatic aberration generated by dispersive objectives, i.e. measuring range of dispersive objective, y j For the incident height of the light ray on the j-th lens in the dispersive objective lens rear group optical system 4, phi j The optical power, v, of the j-th lens in the dispersive objective lens rear group optical system 4 j Abbe number, u, of the j-th lens material in the dispersive objective lens rear group optical system 4 B5 To converge the beam aperture angle, phi 3a Is the fourth positive lens power, phi, in the first doublet 19 3b Is the fourth negative lens power, v, in the first doublet 19 3a The abbe number, v, of the optical material used for the fourth positive lens in the first doublet 19 3b Abbe number of the optical material used for the fourth negative lens in the first doublet lens 19.
The plate protection glass 17 is double-sided parallel plate glass, and the plate protection glass 17 does not influence the image quality of the system, so that the abrasion-resistant optical glass is adopted, and the rear group optical system is protected from being damaged.
Claims (6)
1. A line scanning spectral confocal dispersion objective lens, comprising, in order: the linear light source incidence end and the receiving end (1), the dispersive objective lens front group optical system (2), the aperture diaphragm (3) and the dispersive objective lens rear group optical system (4);
the line light source incidence end and the receiving end (1) comprise: a line light source incidence port (5), a spectroscope (6) and a reflected light receiving port (7); the size of the linear light source incidence port (5) is the same as that of the reflective light receiving port (7), the linear light source incidence port (5) and the reflective light receiving port (7) are in 90-degree relation, and are respectively positioned on the incidence surface and the reflective surface of the spectroscope (6); the linear light source incidence port (5) and the reflected light receiving port (7) are both arranged on the front focal plane of the dispersive objective front group optical system (2);
the front group optical system (2) of the dispersion objective lens is an object space telecentric infinity flat field correction achromatic optical system and is composed of a first lens group (8), a second lens group (9) and a third lens group (10);
the first lens group (8) is a positive-power meniscus double-cemented lens formed by a first positive lens and a first negative lens, the concave surfaces of the first negative lens face the incidence direction of the linear light source, the first negative lens is made of an optical material with the dispersion coefficient smaller than a threshold delta, and the first positive lens is made of an optical material with the dispersion coefficient larger than the threshold delta; delta epsilon [35,45];
the combined focal power of the second lens group (9) is positive, and the lens consists of a first single lens (11), a second single lens (12) and a third single lens (13); and the first single lens (11) and the third single lens (13) are symmetrically distributed about the second single lens (12); the first single lens (11) is a first positive focal power meniscus lens, and the concave surface of the first single lens faces the incidence direction of the linear light source; the second single lens (12) is a biconcave lens with negative focal power, the third single lens (13) is a meniscus lens with positive focal power, the convex surface of the third single lens faces the incidence direction of the linear light source, and the single lenses contained in the second lens group (9) are all made of optical materials with the dispersion coefficient larger than a threshold delta;
the third lens group (10) is a positive-power meniscus double-cemented lens formed by a second positive lens and a second negative lens, the convex surface of the second positive lens faces the incidence direction of the linear light source, the second negative lens adopts optical materials with the dispersion coefficient smaller than a threshold delta, the second positive lens adopts optical materials with the dispersion coefficient larger than the threshold delta, and the third lens group (10) and the first lens group (8) are symmetrical with respect to the second single lens (12) in space layout;
the aperture diaphragm (3) is a circular aperture diaphragm with an adjustable clear aperture, and the aperture diaphragm (3) is respectively overlapped with the back focal plane of the front group optical system (2) of the dispersion objective and the front focal plane of the back group optical system (4) of the dispersion objective; thereby forming an object space telecentric optical system by the aperture diaphragm (3) and the dispersive objective lens front group optical system (2); an imaging side telecentric optical system is formed by the aperture diaphragm (3) and the dispersive objective lens rear group optical system (4); the front group optical system (2) of the dispersion objective, the aperture diaphragm (3) and the rear group optical system (4) of the dispersion objective form a double telecentric optical system together;
the rear group optical system (4) of the dispersion objective lens is an image space telecentric infinity flat field correction chromatic aberration-increasing optical system and is sequentially composed of a fourth lens group (14), a fifth lens group (15), a sixth lens group (16) and plate protection glass (17);
the fourth lens group (14) is a positive-power meniscus chromatic aberration-increasing double-cemented lens formed by a third positive lens and a third negative lens, the concave surface of the third negative lens faces the aperture diaphragm (3), the third negative lens is made of an optical material with a dispersion coefficient larger than the threshold delta, and the third positive lens is made of an optical material with a dispersion coefficient smaller than the threshold delta;
the combined focal power of the fifth lens group (15) is positive, and the fifth lens group is a color difference increasing optical system composed of a fourth single lens (18), a first double-cemented lens (19) and a fifth single lens (20);
the fourth single lens (18) is a third positive focal power meniscus lens, the concave surface of the fourth single lens faces the aperture diaphragm (3), and an optical material with the dispersion coefficient smaller than the threshold delta is adopted;
the first double-cemented lens (19) is a biconcave achromatic double-cemented lens with negative focal power, which is composed of a fourth positive lens and a fourth negative lens, wherein the fourth negative lens adopts an optical material with a dispersion coefficient smaller than a threshold delta, and the fourth positive lens adopts an optical material with a dispersion coefficient larger than the threshold delta;
the fifth single lens (20) is a fourth positive focal power meniscus lens, the convex surface of the fifth single lens faces the aperture diaphragm (3), and an optical material with the dispersion coefficient smaller than the threshold delta is adopted; the fourth single lens (18) and the fifth single lens (20) are respectively arranged at two sides of the first double-cemented lens (19);
the sixth lens group (16) is a positive-power meniscus chromatic aberration-increasing double-cemented lens composed of a fifth positive lens and a fifth negative lens, wherein the convex surface of the fifth positive lens faces the aperture stop (3) and adopts an optical material with a dispersion coefficient smaller than a threshold value delta, the fifth negative lens adopts an optical material with a dispersion coefficient larger than the threshold value delta, and the fourth lens group (14) and the sixth lens group (16) are symmetrical with respect to the first double-cemented lens (19) in space layout;
the plate protection glass (17) is plate glass with two parallel surfaces.
2. A line scanning spectral confocal dispersing objective according to claim 1, wherein:
the first lens group (8), the first single lens (11), the second single lens (12), the third single lens (13) and the third lens group (10) uniformly share deflection angles of incident light rays generated by the front group optical system (2) of the dispersion objective lens;
the fourth lens group (14), the fourth single lens (18), the first double-cemented lens (19), the fifth single lens (20) and the sixth lens group (16) uniformly share the deflection angle of the incident light rays generated by the rear group optical system (4) of the dispersive objective lens.
3. A line scanning spectral confocal dispersing objective according to claim 1, wherein:
the optical materials selected by the first lens group (8), the first single lens (11), the second single lens (12), the third single lens (13) and the third lens group (10) meet the flat field constraint condition shown in the formula (1):
in the formula (1), S IV-F Peztval field curvature, J, generated for the dispersive objective pre-group optical system (2) F Is Lagrange invariant, phi, of the dispersive objective lens front group optical system (2) i For the optical power of the ith lens in the dispersive objective lens front group optical system (2), n i Is the refractive index of the ith lens material in the dispersive objective lens front group optical system (2)Emissivity of the material.
4. A line scanning spectral confocal dispersing objective according to claim 1, wherein:
axial chromatic aberration generated by the first lens group (8), the first single lens (11), the second single lens (12), the third single lens (13) and the third lens group (10) meets the constraint condition shown in the formula (2):
in the formula (2), L chF Axial chromatic aberration, y, produced for said dispersive objective front group optical system (2) i For the incident height phi of the light ray on the ith lens in the dispersion objective lens front group optical system (2) i Is the optical power, v, of the ith lens in the dispersive objective lens front group optical system (2) i Abbe number, u, of the ith lens material in the dispersive objective lens front group optical system (2) F5 Is the angle of the aperture of the incident beam.
5. A line scanning spectral confocal dispersing objective according to claim 1, wherein:
the optical materials selected by the fourth lens group (14), the fourth single lens (18), the first double-cemented lens (19), the fifth single lens (20) and the sixth lens group (16) meet the flat field constraint condition shown in the formula (3):
in the formula (3), S IV-B Peztval field curvature, J, generated for the dispersive objective post-group optical system (4) B Is Lagrange invariant, phi, of the dispersive objective lens back group optical system (4) j Is the optical power of the j-th lens in the dispersive objective lens rear group optical system (4), n j Is the refractive index of the j-th lens material in the dispersive objective lens rear group optical system (4).
6. A line scanning spectral confocal dispersing objective according to claim 1, wherein:
the sum of axial chromatic aberration generated by the fourth lens group (14), the fourth single lens (18), the first double-cemented lens (19), the fifth single lens (20) and the sixth lens group (16) is the axial chromatic aberration of the dispersion objective lens, so that a measuring range (21) of the dispersion objective lens is formed, and the constraint condition shown in the formula (4) is satisfied:
in the formula (4), L chB Axial chromatic aberration, L, for the dispersive objective lens rear group optical system (4) ch Axial chromatic aberration, y, generated for said dispersive objective j For the incident height of the light ray on the j-th lens in the dispersion objective lens rear group optical system (4), phi j Is the optical power, v, of the j-th lens in the dispersive objective lens rear group optical system (4) j Abbe number, u, of the j-th lens material in the dispersive objective lens back group optical system (4) B5 To converge the beam aperture angle, phi 3a For the fourth positive lens power, phi, in the first doublet (19) 3b For the fourth negative lens power, v, in the first doublet (19) 3a Abbe number, v of optical material used for fourth positive lens in the first double-cemented lens (19) 3b An abbe number of an optical material used for a fourth negative lens in the first double cemented lens (19).
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| CN117031698B (en) * | 2023-09-11 | 2024-06-11 | 中国科学技术大学 | Multispectral wide-angle lens |
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