CN118816703B - An optical zoom Fizeau interferometer - Google Patents
An optical zoom Fizeau interferometer Download PDFInfo
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- CN118816703B CN118816703B CN202411297291.5A CN202411297291A CN118816703B CN 118816703 B CN118816703 B CN 118816703B CN 202411297291 A CN202411297291 A CN 202411297291A CN 118816703 B CN118816703 B CN 118816703B
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- 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
- G01B9/02015—Interferometers characterised by the beam path configuration
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B11/00—Measuring arrangements characterised by the use of optical techniques
- G01B11/24—Measuring arrangements characterised by the use of optical techniques for measuring contours or curvatures
- G01B11/2441—Measuring arrangements characterised by the use of optical techniques for measuring contours or curvatures using interferometry
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Abstract
本发明涉及一种光学变焦菲索干涉仪,包括：光源部，发出具有视场角的光线；第一光路方向，第一光路方向上依次设置有PBS分光镜、四分之一波片、前聚焦镜组、标准镜和被测物，所述前聚焦镜组具有变焦功能，光线经过所述四分之一波片后穿过前聚焦镜组，并准直照射到标准镜的参考面上或穿过标准镜照射到被测物上；第二光路方向，所述第二光路方向为第一光路方向相反方向。本发明通过变焦光学系统，改变干涉仪光学扩束系统的扩束比，局部放大干涉条纹，增加干涉条纹测量分辨率，再通过移动被测物，拼接出被测的整体面形，有效的解决了大翘曲光滑平面器件的面形测量问题。
The present invention relates to an optical zoom Fizeau interferometer, comprising: a light source part, which emits light with a field angle; a first optical path direction, in which a PBS spectrometer, a quarter wave plate, a front focusing lens group, a standard lens and an object to be measured are arranged in sequence, the front focusing lens group has a zoom function, the light passes through the quarter wave plate and then passes through the front focusing lens group, and is collimated and irradiated onto a reference surface of the standard lens or passes through the standard lens to irradiate onto the object to be measured; a second optical path direction, in which the second optical path direction is the opposite direction of the first optical path direction. The present invention changes the beam expansion ratio of the optical beam expansion system of the interferometer through a zoom optical system, locally amplifies interference fringes, increases the interference fringes measurement resolution, and then splices the overall surface shape of the object to be measured by moving the object to be measured, thereby effectively solving the surface shape measurement problem of a smooth plane device with large warping.
Description
Technical Field
The invention relates to the technical field of interferometers, in particular to an optical zoom Fizeau interferometer.
Background
The optical Fizeau interferometer is an optical instrument for measuring the optical path difference by utilizing the interference principle so as to measure the related physical quantity, any change of the optical path difference between two beams of coherent light can very sensitively cause the movement of interference fringes, and the optical path change of one beam of coherent light is caused by the change of the geometric path passed by the optical Fizeau interferometer or the refractive index of a medium, so that the interferometer measures the optical path difference by taking the wavelength of light waves as a unit, and the measurement accuracy is high, which is incomparable with other measurement methods.
With the advent of new surface shape measurement requirements, the measurement scheme of the conventional Fizeau interferometer has failed to meet the measurement requirements. The Fizeau dry optical interferometers in the prior art are all fixed-focus interferometer hosts, and the surface shape of the mirror surface is measured by matching with standard mirrors with different F numbers or planes according to different radiuses of the test lenses. However, the measurement of conventional Fizeau interferometers has certain limitations in measuring the shape of irregularly warped thin planar surfaces. When the irregular warping flat sheet is measured by using the plane standard mirror, the part with excessive warping can generate dense stripes, and when the interference stripes are too dense, the interferometer cannot calculate the surface shape distribution of the warping flat sheet by analyzing the stripes due to the limited size of camera pixels of the interferometer.
Disclosure of Invention
The invention aims to provide an optical zooming Fizeau interferometer.
In order to solve the technical problem, the present invention provides an optical zoom Fizeau interferometer, comprising:
a light source unit which emits light having an angle of view;
The device comprises a first light path direction, wherein a PBS spectroscope, a quarter wave plate, a front focusing lens group, a standard lens and an object to be measured are sequentially arranged in the first light path direction, the front focusing lens group has a zooming function, and light rays pass through the front focusing lens group after passing through the quarter wave plate and are collimated to irradiate on a reference surface of the standard lens or pass through the standard lens to irradiate on the object to be measured;
The second light path direction is opposite to the first light path direction, wherein a part of light rays are reflected by the reference surface of the standard mirror, irradiate onto the rear focusing mirror along the second light path direction and enter the camera, and the other part of light rays penetrate through the standard mirror to irradiate onto the measured object, enter the camera along the second light path direction, are collected by the camera collecting system, interfere with each other to generate interference fringes, and the resolution of the measured object is smaller than or equal to the interval between the interference fringes by adjusting the focal lengths of the front focusing mirror group and the rear focusing mirror.
Further, the front focusing lens group comprises two positive lenses and a negative lens positioned in the middle of the two positive lenses, the positive lenses and the negative lenses can move back and forth along the optical axis direction, the focal length f1 of the front focusing lens group is adjusted, and the light transmission caliber of the front focusing lens group is D1.
Further, the rear focusing mirror can move back and forth along the optical axis direction, the focal length f2 of the rear focusing mirror is adjusted, and the light transmission caliber of the rear focusing mirror is D2.
Further, the resolution calculation formula is:,
wherein S1 is the resolution of the measured object, D2 is the aperture of the rear focusing mirror, f1 is the focal length of the front focusing mirror group, N is the pixel number of the camera, and f2 is the focal length of the rear focusing mirror.
Further, the interval calculation formula of the interference fringes is Δp=λ/2wn, wherein Δp is the interval of the interference fringes, λ is the wavelength of the polarization-dependent light source, w is the inclination angle between the measured surface of the measured object and the reference surface of the standard mirror, and n is the refractive index of air.
Further, the light source unit is a semiconductor laser.
The invention has the beneficial effects that the beam expansion ratio of the interferometer optical beam expansion system is changed through the zooming optical system, interference fringes are locally amplified, the measurement resolution of the interference fringes is increased, and the measured integral surface shape is spliced through moving a measured object, so that the surface shape measurement problem of a large-warpage smooth plane device is effectively solved.
Drawings
The invention will be further described with reference to the drawings and examples.
FIG. 1 is a schematic block diagram of an optical zoom Fizeau interferometer of the present invention;
fig. 2 is a schematic structural view of a movable lens of the optical zoom fein interferometer of the present invention.
In the figure:
1. standard mirror, 2 front focusing lens group, 21, positive lens, 22, negative lens, 3, quarter wave plate, 4, PBS spectroscope, 5, rear focusing lens, 6, camera, 7, light source part, 8, data processor, 9, measured object.
Detailed Description
The invention will now be described in further detail with reference to the accompanying drawings. The drawings are simplified schematic representations which merely illustrate the basic structure of the invention and therefore show only the structures which are relevant to the invention.
An optical zoom Fizeau interferometer according to the present invention includes a light source 7 for emitting light having a field angle, the light source 7 being a semiconductor laser, as shown in FIGS. 1 to 2.
The light source section 7 emits light having a certain angle of view, which is an angle range covered by the light emitted from the light source, using a semiconductor laser, which is important for the entire interference system to be able to irradiate and cover the entire surface of the object 9 to be measured, has a high degree of monochromaticity, coherence, is able to generate linearly polarized light, and can convert the linearly polarized light into circularly polarized light by an additional component.
The light beam passes through the front focusing lens group 2 after passing through the quarter wave plate 3, and is collimated and irradiated onto a reference surface of the standard lens 1 or irradiated onto the measured object 9 through the standard lens 1;
The second light path direction is opposite to the first light path direction, wherein a part of light is reflected by the reference surface of the standard mirror 1, irradiates onto the rear focusing mirror 5 along the second light path direction and enters the camera 6, another part of light irradiates onto the measured object 9 through the standard mirror 1, enters the camera 6 along the second light path direction, is collected by the camera 6 collecting system, interference fringes are generated by mutual interference of the reflected light of the measured object 9 and the reflected light information of the reference surface of the standard mirror 1, and the resolution of the measured object 9 is smaller than or equal to the interval between the interference fringes by adjusting the focal lengths of the front focusing mirror group 2 and the rear focusing mirror 5.
In the first light path direction, the system is sequentially provided with a PBS spectroscope 4 for separating incident polarized light, ensuring that only light with a specific polarization state enters, and the entered light passes through a quarter wave plate 3, converting the state of the polarized light to adapt to the subsequent interference process, wherein the light passes through the quarter wave plate 3 and then enters a front focusing lens group 2, the front focusing lens group 2 has a zooming function, the focusing state of the light can be adjusted to adapt to different measurement requirements, the front focusing lens group 2 can be adjusted to accurately control the focusing and collimation of the light irradiated to a standard lens 1 or a measured object 9, the standard lens 1 can provide a reference reflecting surface, so that the light emitted from the front focusing lens group 2 can be accurately reflected or passed, the position of the measured object 9 is arranged behind the standard lens 1, and the reflected light is received, and the reflection or the passing of the light is influenced according to the surface characteristics of the light.
The second light path direction is opposite to the first light path direction, part of light is reflected from the reference surface of the standard mirror 1, the other part of light passes through the standard mirror 1 to directly irradiate the measured object 9, and then is reflected back into the light path, the rear focusing mirror 5 receives two paths of reflected light and guides the two paths of reflected light into the camera 6, and the rear focusing mirror 5 also has an adjustable focal length so as to optimize imaging quality and adjust the definition of interference fringes.
The measured object 9 can vertically move along the optical axis direction of the interferometer, the polarized coherent light source emits light with a certain angle of view, the polarization state direction of the polarized coherent light source is adjusted, the polarized light can be reflected after passing through the PBS spectroscope 4, the light can be changed into circularly polarized light after passing through the quarter wave plate 3, the circularly polarized light can be collimated and irradiated onto the reference surface of the standard mirror 1 through the front focusing mirror group 2, a part of the light is reflected by the reference surface of the standard mirror 1, after passing through the front focusing mirror group 2 and the quarter wave plate 3, the polarization state of the light can be changed into polarized light perpendicular to the incident light of the polarized coherent light source, the light can be transmitted through the PBS spectroscope 4 and enter the camera 6 through the rear focusing mirror 5, the other part of the light irradiated onto the reference surface of the standard mirror 1 can be irradiated onto the measured object 9 after passing through the standard mirror 1 and reflected back along the same light path reflected by the standard surface of the front standard mirror 1, interference fringes are generated by mutual interference of the reflected light information of the measured object 9 and the reflected light information of the reference surface of the standard mirror 1, the interference fringes are generated through the motion control and the camera 6 acquisition system, the interferometer information is subjected to item transfer and the acquisition of the information of the interferometer information is processed through the data processor 8, and the surface information of the measured object 9 is obtained.
The interval calculation formula of the interference fringes is delta p=lambda/2 wn, wherein delta p is the interval of the interference fringes, lambda is the wavelength of a polarization-related light source, w is the inclination angle between the measured surface of the measured object 9 and the reference surface of the standard mirror 1, and n is the refractive index of air.
The front focusing lens group 2 comprises two positive lenses 21 and a negative lens 22 positioned in the middle of the two positive lenses 21, the positive lenses 21 and the negative lenses 22 can move back and forth along the optical axis direction, the focal length f1 of the front focusing lens group 2 is regulated, the light passing caliber of the front focusing lens group 2 is D1, the rear focusing lens 5 can move back and forth along the optical axis direction, the focal length f2 of the rear focusing lens 5 is regulated, the light passing caliber of the rear focusing lens 5 is D2, and the resolution calculation formula is as follows:,
where S1 is the resolution of the object 9, D2 is the aperture of the rear focusing mirror 5, f1 is the focal length of the front focusing mirror group 2, N is the number of pixels of the camera 6 (for example, the number of pixels of the camera 6 is n·n), and f2 is the focal length of the rear focusing mirror 5.
The front focusing lens group 2 comprises two positive lenses 21 and one negative lens 22 which can move along the optical axis direction, so that the front focusing lens group 2 not only can adjust the focusing depth of light rays, but also can change the coverage range of light beams to match the surfaces of the objects 9 to be measured with different sizes and curvatures.
The rear focusing lens 5 can also move back and forth along the optical axis direction, and the focal length f2 is adjusted, so that the definition and fringe contrast of an interference image can be optimized, and the light transmission aperture D2 of the rear focusing lens 5 directly influences the resolution of an imaging system.
The front focusing lens group 2 has a light transmission aperture D1, a focal length f1, the rear focusing lens group 5 has a light transmission aperture D2, a focal length f2, a formula d1/d2=f1/f 2, the number of pixels of the camera 6 is n·n, and the resolution s2=d2/N of the camera 6, so that the resolution s1= (d2·f1)/(n·f2) of the measured surface of the measured object 9.
When the warp of the object 9 is too large, the tilt angle w is too large, and the interference fringe interval Δp is further reduced, and when the interference fringe interval Δp is smaller than the resolution S1 of the object 9, the interference fringes cannot be resolved and resolved by the camera 6, so that the denser interference fringes can be seen only when the resolution S1 is reduced.
According to the formula s1= (d2·f1)/(n·f2), when the focal length f1 is reduced or the focal length f2 is increased, S1 may be reduced.
In the actual operation process, the focal length f2 of the rear focusing lens 5 can be changed, or both of the focal lengths f1 and f2 are changed, when the focal length f1 or f2 is changed, in order to ensure that the target surface of the camera 6 is fully utilized, the light passing D2 of the rear focusing lens 5 is kept unchanged, when the focal length f1 is reduced or f2 is increased, the light passing D1 of the front focusing lens group 2 is reduced, the size of the measured object 9 is also reduced, and the whole surface shape of the measured object 9 can be measured by splicing by vertically moving the measured object 9 along the optical axis direction.
In the second embodiment, the aperture of the object 9 is equal to the light transmission aperture D1 of the front focusing lens group 2 by 300mm, the focal length f1=1000mm of the front focusing lens group 2, the warp of the object 9 by 0.2mm, the pixel number of the camera 6 by 1000, the pixel size by 3×3 μm, the target size of the camera 6 by 3mm, the light transmission aperture D2 of the rear focusing lens 5 by 3mm, and the focal length f2=f1/100=10mm of the rear focusing lens 5.
The warp of the object 9 to be measured was 0.2mm, based on the trigonometric function R 2=1502+(R-0.2)2
And the formula sin (w) =150/R, where R is the approximate radius of curvature of the warp of the object 9, w is the maximum angle between the object 9 and the reference plane of the standard mirror 1, the tilt angle w is 0.15 degrees obtained by the two formulas, assuming that the wavelength λ=633 nm emitted by the polarized coherent light source, according to the formula Δp=λ/2wn, the fringe interval Δp= 120.89 μm, and according to the formulas d1/d2=f1/f 2 and s1= (d2·f1)/(n·f2), d1/d2=300/3=100 times can be obtained, then at this camera 6 pixel size of 3×3 μm, the resolution s1=d1·3 μm/d2=300 μm of the object 9, because S1> Δp, the interferometer fringes of the interval Δp= 120.89 μm cannot be resolved by the camera 6.
At this time, by moving the lens of the front focusing lens group 2, changing the focal length f1 of the front focusing lens group 2, so that the focal length of the front focusing lens group 2 becomes f1=200 mm, and D1/d2=f1/f2=200/10=20, and then the aperture d1=d2·20=60 mm of the front focusing lens group 2 at this time, the resolution s1= (d2·f1)/(n·f2) =3×20=60 μm, and because S1< Δp, the camera 6 can resolve interference fringes with a Δp interval width and resolve surface shape data within a 60mm diameter range, and at this time, because the aperture of the front focusing lens group becomes 60mm due to zooming, it is necessary to move and scan the measured sample to splice the whole 300mm aperture data, and form the whole 300mm aperture surface shape data, thereby realizing the surface shape data measurement of large warp dense interference fringes, and the focal length of the front focusing lens group 2 can be flexibly adjusted to have complex shapes and high warp density measured objects 9, and can be applied to large interference fringes, and high dimensional measurement accuracy is ensured, in particular, and high dimensional measurement is not challenging and high in the measurement is ensured.
With the above-described preferred embodiments according to the present invention as an illustration, the above-described descriptions can be used by persons skilled in the relevant art to make various changes and modifications without departing from the scope of the technical idea of the present invention. The technical scope of the present invention is not limited to the description, but must be determined according to the scope of claims.
Claims (5)
1. An optical zoom Fizeau interferometer is disclosed, characterized by comprising the following steps:
a light source unit (7) that emits light having an angle of view;
The device comprises a first light path direction, wherein a PBS spectroscope (4), a quarter wave plate (3), a front focusing lens group (2), a standard lens (1) and a measured object (9) are sequentially arranged in the first light path direction, the front focusing lens group (2) has a zooming function, and light passes through the front focusing lens group (2) after passing through the quarter wave plate (3) and is collimated and irradiated onto a reference surface of the standard lens (1) or irradiated onto the measured object (9) after passing through the standard lens (1);
The device comprises a front focusing mirror (5), a rear focusing mirror (5), a camera (6), a standard mirror (1), a camera (6) and a camera (9), wherein the second light path direction is opposite to the first light path direction, a part of light is reflected by the reference surface of the standard mirror (1), irradiates onto the rear focusing mirror (5) along the first light path direction, irradiates onto a measured object (9) through the standard mirror (1), enters the camera (6) along the second light path direction, is collected by the camera (6) collecting system, and generates interference fringes by mutual interference between the reflected light of the measured object (9) and the reflected light information of the reference surface of the standard mirror (1), and the resolution of the measured object (9) is smaller than or equal to the interval between the interference fringes by adjusting the focal length of the front focusing mirror group (2) and the rear focusing mirror (5);
the resolution calculation formula is as follows:
,
Wherein S1 is the resolution of the object (9), D2 is the aperture of the rear focusing mirror (5), f1 is the focal length of the front focusing mirror, N is the pixel number of the camera (6), and f2 is the focal length of the rear focusing mirror (5).
2. An optical zoom Fizeau interferometer according to claim 1,
The front focusing lens group (2) comprises two positive lenses (21) and a negative lens (22) positioned in the middle of the two positive lenses (21), the positive lenses (21) and the negative lenses (22) can move back and forth along the optical axis direction, the focal length f1 of the front focusing lens group (2) is adjusted, and the light transmission caliber of the front focusing lens group (2) is D1.
3. An optical zoom Fizeau interferometer according to claim 2,
The rear focusing mirror (5) can move back and forth along the optical axis direction, the focal length f2 of the rear focusing mirror (5) is adjusted, and the light transmission caliber of the rear focusing mirror (5) is D2.
4. An optical zoom Fizeau interferometer according to claim 3,
The interval calculation formula of the interference fringes is delta p=lambda/2 wn, wherein delta p is the interval of the interference fringes, lambda is the wavelength of a polarization-dependent light source (7), w is the inclination angle between the measured surface of a measured object (9) and the reference surface of a standard mirror (1), and n is the refractive index of air.
5. An optical zoom Fizeau interferometer according to claim 4, wherein,
The light source unit (7) is a semiconductor laser.
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