CN113834421B - Imaging lens group and interferometer using same - Google Patents
Imaging lens group and interferometer using same Download PDFInfo
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- CN113834421B CN113834421B CN202111032064.6A CN202111032064A CN113834421B CN 113834421 B CN113834421 B CN 113834421B CN 202111032064 A CN202111032064 A CN 202111032064A CN 113834421 B CN113834421 B CN 113834421B
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- 238000003384 imaging method Methods 0.000 title claims abstract description 69
- 230000003287 optical effect Effects 0.000 claims abstract description 22
- 239000013078 crystal Substances 0.000 claims description 26
- 239000005338 frosted glass Substances 0.000 claims description 10
- 239000013307 optical fiber Substances 0.000 claims description 10
- 239000005337 ground glass Substances 0.000 claims description 8
- CPBQJMYROZQQJC-UHFFFAOYSA-N helium neon Chemical compound [He].[Ne] CPBQJMYROZQQJC-UHFFFAOYSA-N 0.000 claims description 8
- 238000000034 method Methods 0.000 claims description 8
- 238000005259 measurement Methods 0.000 claims description 7
- 238000001514 detection method Methods 0.000 description 3
- 238000013519 translation Methods 0.000 description 3
- 238000010586 diagram Methods 0.000 description 2
- 230000004075 alteration Effects 0.000 description 1
- 239000000969 carrier Substances 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 238000005305 interferometry Methods 0.000 description 1
- 230000001678 irradiating effect Effects 0.000 description 1
- 238000000691 measurement method Methods 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 238000012827 research and development Methods 0.000 description 1
- 230000035945 sensitivity Effects 0.000 description 1
- 238000004088 simulation Methods 0.000 description 1
- 238000012795 verification Methods 0.000 description 1
- 230000000007 visual effect Effects 0.000 description 1
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B9/00—Measuring instruments characterised by the use of optical techniques
- G01B9/02—Interferometers
- G01B9/02055—Reduction or prevention of errors; Testing; Calibration
Abstract
The invention discloses an imaging lens group and an interferometer applying the imaging lens group, wherein the imaging lens group comprises a first lens, a second lens and a third lens which are sequentially arranged from an object side to an image side along an optical axis, and the front surface and the rear surface of each three-sided lens are spherical surfaces. The interferometer using the imaging lens group utilizes the characteristic of double telecentric imaging, and uses the resolution plate to calibrate the resolution of the interferometer, so that the imaging of the interferometer is clearer, and the phase solving is more accurate.
Description
Technical Field
The invention belongs to the field of interference imaging, and particularly relates to an imaging lens group and an interferometer applying the imaging lens group.
Background
With the rapid development of science and technology, the optical element has very important roles in the fields of astronomical space flight, high-energy laser and the like, so that the surface shape detection of the optical element is also a very important link in the processing process. In a plurality of detection methods, the optical interference detection technology takes light waves as carriers, and has the characteristics of high measurement precision, high sensitivity, non-contact measurement and the like, and becomes a current research hot spot. In classical optical interferometry systems, the optical system architecture is largely divided into two main categories: a split-beam type and a common-beam type. The Fizeau interferometer is a typical representation of a common-light path type, has strong anti-interference capability and simple structure, and is widely applied to equipment research and development.
The conventional Fizeau interferometer has the problems that in actual surface shape measurement, phase resolving inaccuracy and the like are easy to occur, and the imaging resolution of the interferometer is low, so that an interferometer imaging lens group is provided, and the resolution of the Fizeau interferometer applying the imaging lens group is greatly improved by combining simulation and experimental result verification. In addition, for interferometer resolution measurement, the traditional measurement method uses a step plate, is complex to operate, is influenced by a phase solving algorithm, and cannot be visually displayed.
Disclosure of Invention
The invention aims to provide an imaging lens group and an interferometer using the imaging lens group, wherein the imaging lens group consisting of three lenses obviously improves the resolution of the interferometer and ensures the high precision of results in the actual measurement and phase solving processes.
The technical solution for realizing the purpose of the invention is as follows: an imaging lens group comprises a first lens, a second lens and a third lens which are sequentially arranged from an object side to an image side along an optical axis, wherein the front surface and the rear surface of the first lens are both convex surfaces, the front surface and the rear surface of the second lens are both concave surfaces, and the front surface and the rear surface of the third lens are both convex surfaces; and the front and rear surfaces of the first lens, the second lens and the third lens are spherical surfaces.
Wherein the F number F of the imaging lens group 1 F number F with collimating lens in interferometer 2 The method meets the following conditions: f (F) 1 ＝F 2 。
The surface shape parameters of the front and rear surfaces of the first, second and third lenses are as follows:
an interferometer applying the imaging lens group comprises a helium-neon laser, an optical fiber, a beam expander lens group, a beam splitter prism, a collimating lens, a standard reference flat crystal, a piece to be measured, an aperture diaphragm, an imaging lens group, rotary ground glass, a zoom lens group and a CCD camera; the first optical axis of the common optical path is sequentially provided with a piece to be detected, a standard reference flat crystal, a collimating lens, a beam splitting prism, an aperture diaphragm, an imaging lens group, rotary ground glass, a zoom lens group and a CCD camera. The light beam emitted by the helium-neon laser enters the beam expanding lens group through the optical fiber, is reflected to the collimating lens by the beam splitting prism after being expanded by the beam expanding lens group, collimated light of the collimating lens is transmitted to the to-be-detected piece through the standard reference planar crystal, and the light beam carrying the surface shape information of the to-be-detected piece and the surface shape information of the standard reference planar crystal reaches the target surface of the CCD camera after passing through the standard reference planar crystal, the collimating lens, the beam splitting prism, the aperture diaphragm, the imaging lens group, the rotary frosted glass and the zoom lens group along the first optical axis of the common optical path.
Compared with the prior art, the invention has the remarkable advantages that:
(1) The MTF of the imaging lens group is more than 70% at the spatial frequency of 60lp/mm, and the imaging lens group has small field curvature and distortion.
(2) According to the imaging characteristics of double telecentricity of the interference light path, the resolution of the interferometer is calibrated by using a resolution plate, so that the method is more visual and is easy to operate.
(3) The Fizeau interferometer using the imaging lens group of the invention greatly improves the imaging resolution and has more accurate result in phase solving.
Drawings
FIG. 1 is a light path diagram of an interferometer employing an imaging lens set of the present invention.
Fig. 2 is a light path diagram of an imaging lens assembly according to the present invention.
Fig. 3 is an MTF graph of an imaging lens set of the present invention.
Fig. 4 is a graph of curvature of field and distortion of an image plane of the imaging lens assembly of the present invention.
FIG. 5 is a graph of the results of an interferometric imaging optical path of a USAF1951 resolution plate in an embodiment.
Detailed Description
The invention is described in further detail below with reference to the accompanying drawings.
Referring to fig. 2, an imaging lens assembly includes a first lens 13, a second lens 14 and a third lens 15 disposed in order from an object side to an image side along an optical axis, wherein front and rear surfaces of the first lens 13 are convex, front and rear surfaces of the second lens 14 are concave, and front and rear surfaces of the third lens 15 are convex; the front and rear surfaces of the first lens 13, the second lens 14, and the third lens 15 are spherical.
Further, the first lens 13 and the third lens 15 are lenses of positive refractive power, and the second lens 14 is a lens of negative refractive power.
Further, the overall focal length of the imaging lens group 9 is f, and the focal length of the first lens 13 is f1, and satisfies the following conditions: 2.03< f/f1<2.27.
Further, the overall focal length of the imaging lens group 9 is f, and the focal length of the second lens 14 is f2, and satisfies the following conditions: -4.81< f/f2< -4.43.
Further, the overall focal length of the imaging lens group 9 is f, and the focal length of the third lens 15 is f3, and satisfies the following conditions: 2.04< f/f3<2.32.
The surface shape parameters of the front and rear surfaces of the first, second and third lenses 13, 14 and 15 are as follows:
f-number F of the imaging lens group 9 1 F number F with collimator lens 5 in interferometer 2 The method meets the following conditions: f (F) 1 ＝F 2 。
In combination with fig. 2, 3 and 4, the MTF of the imaging lens group is greater than 70% at a spatial frequency of 60lp/mm, and the imaging lens group has little curvature of field and distortion.
Referring to fig. 1, an interferometer applying the imaging lens group of the present invention includes a helium-neon laser 1, an optical fiber 2, a beam expander group 3, a beam splitter prism 4, a collimator lens 5, a standard reference flat crystal 6, a piece 7 to be measured, an aperture diaphragm 8, an imaging lens group 9, a rotary frosted glass 10, a zoom lens group 11 and a CCD camera 12; the first optical axis of the common optical path is sequentially provided with a piece to be detected 7, a standard reference flat crystal 6, a collimating lens 5, a beam splitting prism 4, an aperture diaphragm 8, an imaging lens group 9, rotary ground glass 10, a zoom lens group 11 and a CCD camera 12. The light beam emitted by the helium-neon laser 1 enters the beam expander group 3 through the optical fiber 2, is reflected to the collimating lens 5 by the beam splitter prism 4 after being expanded by the beam expander group 3, collimated light of the collimating lens 5 reaches the piece 7 to be detected after passing through the standard reference flat crystal 6, and the light beam carrying the surface shape information of the piece 7 to be detected and the surface shape information of the standard reference flat crystal 6 reaches the target surface of the CCD camera 12 after passing through the standard reference flat crystal 6, the collimating lens 5, the beam splitter prism 4, the aperture diaphragm 8, the imaging lens group 9, the rotary ground glass 10 and the zoom lens group 11 along the first optical axis of the common optical path.
Further, the rotary frosted glass 10 is rotated by a stepping motor, and the zoom lens group 11 is focused and zoomed by a control handle.
In the light path adjustment process, the imaging lens group 9, the rotary ground glass 10 and the zoom lens group 11 are all used for adjusting the imaging position through a two-dimensional translation table.
When the interferometer applying the imaging lens group of the invention is used for measuring the imaging resolution of the system, the to-be-measured piece 7 adopts a resolution plate, and the specific steps are as follows:
the output end of the helium-neon laser 1 is coupled into an optical fiber 2 through a coupler, standard spherical waves emitted by the optical fiber 2 are expanded by a beam expander group 3, and collimated light is obtained through a beam splitter prism 4 and a collimating lens 5 in sequence.
And step two, the collimated light irradiates on the USAF1951 resolution plate through a standard reference flat crystal 6.
And thirdly, the reflected light of the USAF1951 resolution plate is imaged on the rough surface of the rotary frosted glass 10 once through the standard reference flat crystal 6, the collimating lens 5, the beam splitting prism 4, the aperture diaphragm 8 and the imaging lens group 9, and in the process, the axial distance of the rotary frosted glass 10 is adjusted by utilizing the two-dimensional translation table, so that the rough surface is positioned at the rear intercept of the imaging lens group 9.
And step four, adjusting the distance between the variable magnification lens group 11 and the rotary frosted glass 10 by utilizing a two-dimensional translation table, so that the frosted surface of the rotary frosted glass 10 is positioned at the flange distance position of the variable magnification lens group 11.
And fifthly, adjusting the distance between the CCD camera 12 and the zoom lens group 11, and adjusting the zoom lens group 11 by using a control handle until the image is clearly formed on the CCD camera 12.
Further, the double telecentric imaging light path adopted in the measurement comprises a two-time imaging relationship. The light reflected by the resolution plate of USAF1951 is imaged on the rough surface of the rotary frosted glass 10 once through the standard reference flat crystal 6, the collimating lens 5, the beam splitting prism 4, the aperture diaphragm 8 and the imaging lens group 9, and the primary image and object satisfy the following relationship:
where y is the object size, y 'is the image size, x is the focal length of the collimating lens 5, and x' is the focal length of the imaging lens group 9.
The zoom lens group 11 consists of a certain focus lens and a zoom lens, can realize continuous zoom of 0.72-4.35, and forms a primary image on the target surface of the CCD camera 12 in a secondary imaging mode. The primary and secondary images satisfy the following relationship:
where y 'is the size of the primary image, y "is the size of the secondary image, x' is the focal length of the zoom lens, and x" is the focal length of the fixed focus lens.
When the interferometer applying the imaging lens group of the invention is used for measuring the surface shape to be measured, the to-be-measured piece 7 adopts the to-be-measured flat crystal, and the specific steps are as follows:
and step A, the output end of the helium-neon laser 1 is coupled into an optical fiber 2 through a coupler, standard spherical waves emitted by the optical fiber 2 are expanded by a beam expander group 3, and collimated light is obtained through a beam splitter prism 4 and a collimating lens 5 in sequence.
And B, irradiating the collimated light on the flat crystal to be detected through a standard reference flat crystal 6.
And C, reflected light carrying the surface shape information of the to-be-detected planar crystal passes through the standard reference planar crystal 6, the collimating lens 5, the beam splitting prism 4, the aperture diaphragm 8, the imaging lens group 9, the rotary frosted glass 10 and the zoom lens group 11, reaches the target surface of the CCD camera 12, and interferes with the reference light carrying the surface shape information of the standard reference planar crystal 6.
And D, carrying out phase solving according to the interference pattern acquired by the CCD camera 12.
With reference to fig. 1 and 5, the imaging resolution of a system employing an interferometer of the present imaging lens set is significantly improved.
In summary, the present invention provides an imaging lens set with high resolution and small aberration, which greatly improves the interference imaging resolution of the interferometer. Compared with the traditional Fizeau interferometer, the Fizeau interferometer using the imaging lens group has the advantages that imaging is clearer, and phase solving is more accurate.
Claims (7)
1. An interferometer, characterized in that: the device comprises a helium-neon laser (1), an optical fiber (2), a beam expander group (3), a beam splitter prism (4), a collimating lens (5), a standard reference flat crystal (6), a piece to be tested (7), an aperture diaphragm (8), an imaging lens group (9), rotary ground glass (10), a zoom lens group (11) and a CCD camera (12); the first optical axis of the common optical path is sequentially provided with a piece to be detected (7), a standard reference flat crystal (6), a collimating lens (5), a beam splitting prism (4), an aperture diaphragm (8), an imaging lens group (9), rotary ground glass (10), a zoom lens group (11) and a CCD camera (12); the light beam emitted by the helium-neon laser (1) enters a beam expanding lens group (3) through an optical fiber (2), is reflected to a collimating lens (5) by a beam splitting prism (4) after being expanded by the beam expanding lens group (3), collimated light of the collimating lens (5) is transmitted to a piece (7) to be detected after passing through a standard reference flat crystal (6), and the light beam carrying the surface shape information of the piece (7) to be detected and the surface shape information of the standard reference flat crystal (6) passes through the standard reference flat crystal (6), the collimating lens (5), the beam splitting prism (4), an aperture diaphragm (8), an imaging lens group (9), rotary ground glass (10) and a zoom lens group (11) along a first optical axis of a common optical path and then reaches the target surface of a CCD camera (12);
the imaging lens group (9) comprises a first lens (13), a second lens (14) and a third lens (15) which are sequentially arranged from an object side to an image side along an optical axis, wherein the front surface and the rear surface of the first lens (13) are both convex surfaces, the front surface and the rear surface of the second lens (14) are both concave surfaces, and the front surface and the rear surface of the third lens (15) are both convex surfaces; the front and rear surfaces of the first lens (13), the second lens (14) and the third lens (15) are spherical surfaces;
the overall focal length of the imaging lens group (9) is f, the focal length of the first lens (13) is f1, and the following conditions are satisfied: 2.03< f/f1<2.27;
the focal length of the second lens (14) is f2, and the following conditions are satisfied: -4.81< f/f2< -4.43;
the focal length of the third lens (15) is f3, and the following condition is satisfied: 2.04< f/f3<2.32.
2. An interferometer according to claim 1, wherein: the surface shape parameters of the front and rear surfaces of the first lens (13), the second lens (14) and the third lens (15) are as follows:
3. an interferometer according to claim 1, wherein: the first lens (13) and the third lens (15) are lenses of positive refractive power, and the second lens (14) is a lens of negative refractive power.
4. An interferometer according to claim 1, wherein: the saidF number F of imaging lens group (9) 1 F number F with collimating lens (5) in interferometer 2 The method meets the following conditions: f (F) 1 ＝F 2 。
5. An interferometer according to claim 1, wherein: the rotary frosted glass (10) is rotated by a stepping motor, and the zoom lens group (11) is focused and zoomed by a control handle.
6. An interferometer according to claim 1, wherein: when used for interference system resolution measurement, the part to be measured (7) adopts a resolution plate.
7. An interferometer according to claim 1, wherein: when the device is used for measuring the surface shape of the flat crystal to be measured, the flat crystal to be measured is adopted by the piece to be measured (7).
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Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2000275006A (en) * | 1999-03-26 | 2000-10-06 | Fuji Photo Optical Co Ltd | Image formation lens for interferometer apparatus |
| JP2008309668A (en) * | 2007-06-15 | 2008-12-25 | Opcell Co Ltd | Laser scanning interferometer |
| CN103197382A (en) * | 2013-03-01 | 2013-07-10 | 南京理工大学 | Optical fiber derived type interferometer laser light source system |
| CN105423951A (en) * | 2015-12-22 | 2016-03-23 | 中国科学院长春光学精密机械与物理研究所 | Etalon of convex reference surface with long radius of curvature |
| CN107631687A (en) * | 2017-08-31 | 2018-01-26 | 南京理工大学 | Point source dystopy expands simultaneous phase-shifting fizeau interferometer and its measuring method |
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- 2021-09-03 CN CN202111032064.6A patent/CN113834421B/en active Active
Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2000275006A (en) * | 1999-03-26 | 2000-10-06 | Fuji Photo Optical Co Ltd | Image formation lens for interferometer apparatus |
| JP2008309668A (en) * | 2007-06-15 | 2008-12-25 | Opcell Co Ltd | Laser scanning interferometer |
| CN103197382A (en) * | 2013-03-01 | 2013-07-10 | 南京理工大学 | Optical fiber derived type interferometer laser light source system |
| CN105423951A (en) * | 2015-12-22 | 2016-03-23 | 中国科学院长春光学精密机械与物理研究所 | Etalon of convex reference surface with long radius of curvature |
| CN107631687A (en) * | 2017-08-31 | 2018-01-26 | 南京理工大学 | Point source dystopy expands simultaneous phase-shifting fizeau interferometer and its measuring method |
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