CN115164733A - Picometer measuring system and method based on picometer optical comb - Google Patents
Picometer measuring system and method based on picometer optical comb Download PDFInfo
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- CN115164733A CN115164733A CN202210776991.7A CN202210776991A CN115164733A CN 115164733 A CN115164733 A CN 115164733A CN 202210776991 A CN202210776991 A CN 202210776991A CN 115164733 A CN115164733 A CN 115164733A
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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
- G01B11/02—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness
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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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- Length Measuring Devices By Optical Means (AREA)
Abstract
The invention discloses a system and a method for measuring leather and rice based on a leather and rice optical comb, wherein the measuring method comprises the following processes: the light emitted by the laser is divided into two beams by the beam splitter, and each beam sequentially passes through the reflector, the microscope objective, the pinhole filter and the collimating lens to generate a collimated and expanded light field; the light fields generated by the two beams of light are converged on an interference plane to generate an interference field with a period d; placing a holographic dry plate on an interference plane for first exposure; loading displacement information delta d of a picometer scale to cause periodic variation of an interference field; and carrying out secondary exposure on the holographic dry plate to obtain the picometer optical comb. Axial moire effect with picometer optical comb: illuminating a picometer optical comb with collimated expanded plane waves will produce moire interference fringes. Moire interference fringes are collected through a photoelectric detector, and the period T of the Moire interference fringes is calculated. And finally, reversely deducing the information delta d of the picometer scale to be measured through a formula.
Description
Technical Field
The invention relates to the technical field of picometer measurement, in particular to a picometer measurement system and method based on a picometer optical comb.
Background
With the rapid development of the precision machining industry, the machining precision has reached the nanometer level at present, and the manufacturing process of chips has been advanced to the 1nm level, for example. Therefore, the required measurement resolution is also increased, reaching the picometer level. The laser interferometer is a widely used displacement measuring device, but for displacement information of the picometer level, the manufacturing of the picometer level laser interferometer is very difficult, and the manufacturing method needs the most advanced optical, mechanical and electronic technology and simultaneously needs extremely high environmental requirements to accurately control factors such as temperature, humidity, air cleanliness and the like. In addition, the picometer laser interferometer is also easily influenced by the wavelength drift of the laser, the vibration isolation factor of the measuring platform and the like. Therefore, it is necessary to find other picometer-scale displacement measurements.
Zhou river et al [ prior art 1: zhou, comb, picometer interference apparatus and method, chinese Patent CN 110187424A [ P ] (2019) ] first proposed and manufactured picometer combs and observed the axial Moire interference effect of the picometer combs. The period of the Moire interference fringe generated after the picometer optical comb is irradiated by the plane wave is found to be in inverse proportion to the period difference value of the two exposures of the picometer optical comb, so that the picometer optical comb is very suitable for measuring displacement information with small scale.
Disclosure of Invention
The first objective of the present invention is to solve the above-mentioned drawbacks in the prior art, and provide a picometer measurement system and method based on a picometer optical comb, which avoids the high investment in manufacturing a picometer-level laser interferometer, and at the same time, can ensure the measurement accuracy, and greatly reduce the cost of the measurement system.
Another object of the present invention is to provide a method for performing measurements using the above system.
The first purpose of the invention can be achieved by adopting the following technical scheme:
a kind of picometer measurement system based on picometer optical comb, the said picometer measurement system includes: the device comprises a laser 1, a beam splitter 2, a reflector 3, a microscope objective 4, a pinhole filter 5, a collimating lens 6, a holographic dry plate 7, a photoelectric detector 8 and a computer 9; the laser beam emitted by the laser 1 is divided into two beams of light by the beam splitter 2, and the angles of the two beams of light are controlled by the reflector 3, so that the two beams of light can be converged on one plane to form a double-beam exposure system. Each beam of light is filtered, collimated and expanded through a microscope objective 4, a pinhole filter 5 and a collimating lens 6 in sequence, and converged on an interference plane to generate interference fringes, the holographic dry plate 7 is arranged on the interference plane for the first exposure, and displacement information of picometer scale is loaded on an interference field to cause periodic variation; carrying out secondary exposure on the holographic dry plate 7, and forming a picometer optical comb on the holographic dry plate 7;
a light beam emitted by a laser 1 sequentially passes through a microscope objective 4, a pinhole filter 5 and a collimating lens 6 to form a plane wave for collimating and expanding beams to irradiate a picometer optical comb on a holographic dry plate 7, and Moire interference fringes are generated along the propagation direction of the light beam due to the axial Moire effect; moire interference fringes are collected through a photoelectric detector 8 and transmitted to a computer 9 to calculate the period of the Moire interference fringes, and displacement information of a picometer scale is obtained according to a formula.
Further, the power level of the laser 1 determines the maximum detection distance of the moire fringes.
Further, the light beam emitted by the laser 1 is incident into the beam splitter 2. The beam splitter is a half-transmitting and half-reflecting mirror, and can uniformly split the laser beam emitted by the laser 1 into two beams which propagate along different directions, wherein one beam passes through the beam splitter 2 and propagates along the transmission direction, and the other beam is reflected by the beam splitter 2 and propagates along the reflection direction.
Further, the two light beams generated by the beam splitter 2 are reflected by the mirror 3 and converged on the interference plane. The reflector is provided with an adjusting knob, the deflection direction of the reflector can be finely adjusted, and the reflector can be used for controlling the included angle of two beams of light, so that the period d of an interference field is controlled.
Further, the holographic plate 7 is a substrate coated with photoresist, and the substrate 7 is placed on an interference plane for exposure to record interference field information.
Further, the picometer comb is formed by exposing the holographic dry plate 7 twice, and then developing, fixing and baking the holographic dry plate, and the period of the two exposures differs by picometer magnitude, so that the period of the interference field of the two exposures needs to be measured with picometer precision.
Further, the interference fringes generated after the picometer optical comb on the holographic dry plate 7 is irradiated by the laser beam are generated due to the axial Moire interference effect. The picometer optical comb is formed by twice exposure of two interference fields with small period difference, so that the picometer optical comb can be regarded as two slits which are very close to each other, when laser beams irradiate the two slits, because the distance between the two slits is small, an interference region can be generated at the overlapping part of diffraction light fields of the two slits, and Moire interference fringes propagate along the diffraction direction, so that the diffraction effect of the picometer optical comb is called as axial Moire effect.
Further, the moire interference fringe generated by the picometer optical comb on the holographic dry plate 7 is obtained by the following formula:
let reference light be expressed as
The object beams of the first and second exposures are denoted as
And
when two exposures are made, two target beams are respectively recorded on the hologram
O 2 (x, y) and reference beams
Generating an interference field after interference:
wherein R (x, y), O 1 (x，y)、O 2 (x, y) represents the intensities of the reference light and the object beams of the first and second exposures, respectively,
representing the phases of the reference light and the object beams of the first and second exposures, x and y representing the positions of the abscissa and ordinate, respectively, as the beams propagate;
thus, the light field recorded by a picometer optical comb is:
in the formula
For the background light intensity, the last term is the phase information of the interference field, and the light field periods of the two exposures are different by Δ d, because Δ d is controlled by the incident angle of the target beam, there is a difference Δ θ between the included angles of the two exposures. Δ θ is a small angle, so that the phase difference between the two exposure fields
Is very small, then
Is very large. This means that when the picometer comb is illuminated by a laser beam, a series of large period moire fringes will be generated due to the axial moire effect. This facilitates the acquisition and calculation of moire fringes.
Furthermore, the moire interference fringes have the characteristics of strong stability and high contrast, and are favorable for measuring and calculating the period of the fringes.
Further, the period T of the axial moire fringes produced by the picometer optical comb on the holographic dry plate 7 is defined by:
where d is the period of the exposure interference field at the first exposure and Δ d is the difference in the periods of the light fields at the two exposures.
Further, the period T of the moire fringes is inversely proportional to the difference Δ d between the periods of the two exposures, and the sensitivity of the measurement system is higher as the period T of the moire fringes is larger as the loaded displacement amount Δ d is smaller.
The other purpose of the invention can be achieved by adopting the following technical scheme:
a measuring method of a picometer measuring system based on a picometer optical comb comprises the following steps:
s1, a laser beam emitted by a laser 1 is divided into two beams of light through a beam splitter 2, and the angles of the two beams of light are controlled by a reflector 3 so that the two beams of light can be converged on a plane;
s2, two beams of light sequentially pass through a microscope objective 4, a pinhole filter 5 and a collimating lens 6 to form plane waves for collimating and expanding beams, and are converged on an interference plane to generate interference fringes with a period of d;
s3, placing the holographic dry plate 7 on an interference plane for first exposure;
s4, adjusting the included angle of the two beams of light by controlling the reflector 3, and loading displacement information delta d in a picometer scale on the interference field to enable the period of the interference field to be changed into d + delta d;
s5, placing the holographic dry plate 7 on an interference plane, carrying out secondary exposure, developing, fixing and baking, and forming a picometer optical comb on the holographic dry plate 7;
s6, a light beam emitted by the laser 1 sequentially passes through the microscope objective 4, the pinhole filter 5 and the collimating lens 6 to form a plane wave for collimating and expanding beams to irradiate a picometer optical comb on the holographic dry plate 7, and Moire interference fringes are generated;
s7, collecting the Moire interference fringes through a photoelectric detector 8, and transmitting the Moire interference fringes to a computer 9 to calculate the period T of the Moire interference fringes;
s8, according to the formula
And calculating displacement information delta d of the picometer scale to be measured.
Compared with the prior art, the invention has the following advantages and effects:
1. the light path required to be set up by the picometer measuring system based on the picometer optical comb is simple in structure and convenient to debug. The various devices required are common in the market place and are low cost.
2. Relationship between period T of Moire interference fringe and loaded displacement delta d in axial Moire interference effect
It can be seen that the displacement amount Δ d is inversely proportional to the period T of the moire fringes. When the displacement delta d is in the picometer magnitude, the period T reaches the millimeter magnitude, and detection is facilitated. Therefore, the measuring method based on the principle is very suitable for measuring in a picometer scale. The smaller the amount of displacement measured, the higher the sensitivity of the measurement system.
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the invention and do not constitute a limitation of the invention. In the drawings:
FIG. 1 is a schematic view of the present invention for making a picometer comb;
FIG. 2 is a schematic diagram of the moire fringes produced by the picometer optical comb of the present invention;
FIG. 3 is a test schematic of the present invention;
FIG. 4 is a schematic diagram of moire fringes collected by a photodetector according to the present invention;
figure 5 is a schematic representation of the moire fringe calculated in the computer of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Example 1
The embodiment discloses a picometer measuring system based on a picometer optical comb. Fig. 1 is a schematic diagram of the fabrication of the picometer optical comb in the present embodiment, and fig. 2 is a schematic diagram of the measurement of the moire interference fringes produced by the picometer optical comb in the present invention. A kind of picometer measurement system based on picometer optical comb includes: the device comprises a laser 1, a beam splitter 2, a reflector 3, a microscope objective 4, a pinhole filter 5, a collimating lens 6, a holographic dry plate 7, a photoelectric detector 8 and a computer 9; the laser beam emitted by the laser 1 is split into two beams of light by the beam splitter 2, and the two beams of light control the angle by the reflector 3 so that the two beams of light can be converged on one plane to form a double-beam exposure system. Each beam of light is filtered, collimated and expanded through a microscope objective 4, a pinhole filter 5 and a collimating lens 6 in sequence, and is converged on an interference plane to generate interference fringes with a period of d, the holographic dry plate 7 is arranged on the interference plane for the first exposure, then displacement information delta d with a picometer scale is loaded on an interference field through a fine adjustment reflector 3 to cause periodic change, the period of the interference fringes is changed into d + delta d, the holographic dry plate 7 is subjected to the second exposure, and then a picometer optical comb is formed on the holographic dry plate 7;
a light beam emitted by a laser 1 sequentially passes through a microscope objective 4, a pinhole filter 5 and a collimating lens 6 to form a plane wave which is collimated and expanded to irradiate a picometer optical comb on a holographic dry plate 7. FIG. 3 is a test schematic of the present invention, showing the generation of Moire fringes along the direction of beam propagation based on the axial Moire effect of a picometer optical comb; the moire interference fringes are collected by the photoelectric detector 8 and transmitted to the computer 9 to calculate the period T of the moire interference fringes according to the formula
Displacement information of the picometer scale is obtained.
Example 2
The embodiment discloses a method for measuring the picometers by using a picometer measuring system based on a picometer optical comb, which comprises the following steps:
s1, a laser 1 is used for emitting laser beams, the laser beams are divided into two beams of light through a beam splitter 2, and the angles of the two beams of light are controlled through a reflector 3, so that the two beams of light can be converged on a plane. Each beam of light is filtered, collimated and expanded by the microscope objective 4, the pinhole filter 5 and the collimating lens 6 in turn, and converged on an interference plane to generate an initial interference field with the period of d =833.333 nm.
S2, placing the holographic dry plate 7 on an interference plane for first exposure.
S3, changing the included angle of the two beams through the reflector 3, so that the fringe period of the interference field is changed by delta d compared with the initial value. The holographic plate 7 is placed on the interference plane for a second exposure.
And S4, developing, fixing and baking the holographic dry plate 7 subjected to the two-time exposure to generate a picometer optical comb on the holographic dry plate 7.
And S5, forming a plane wave for collimating and expanding by using a light beam emitted by the laser 1 to irradiate the picometer optical comb on the holographic dry plate 7 through the microscope objective 4, the pinhole filter 5 and the collimating lens 6 in sequence. Moire interference fringes are generated along the direction of beam propagation by the axial moire effect of the picometer optical comb. The moire fringes as shown in fig. 4 are collected by the photodetector 8.
S6, transmitting the collected moire fringes to a computer 9 to calculate the period T of the moire fringes, and FIG. 5 is a schematic diagram of the moire fringes calculated by the computer to calculate the period T of the moire fringes.
S7, substituting the period T of the Moire interference fringes and the period d of the interference field in the first exposure into a formula
And finally calculating the displacement delta d of the picometer scale to be measured.
Table 1 shows a series of parameters in this embodiment 2, where the period of the first exposure is d =833.333nm, the displacement of the picometer scale to be measured is Δ d, and the period of the moire interference fringe is T.
The displacement Δ d on the picometer scale is calculated by the following equation:
TABLE 1 comparison table of measured displacement Δ d corresponding to periods T of different Moire interference fringes
| T(μm) | d(nm) | Δd(pm) |
| 3.473 | 833.333 | 200 |
| 3.859 | 833.333 | 180 |
| 4.341 | 833.333 | 160 |
| 4.961 | 833.333 | 140 |
| 5.788 | 833.333 | 120 |
| 6.945 | 833.333 | 100 |
As can be seen from table 1, the measured period T of the moire fringes increases rapidly and largely with decreasing amount of displacement Δ d to be measured, which means that the sensitivity of the measuring system is high, i.e. the period of the detected moire fringes becomes more pronounced for smaller amounts of change. In summary, the picometer measuring system based on the picometer optical comb disclosed in the above embodiments has the advantages of simple structure, convenience in measurement and high sensitivity, is very suitable for measuring picometer scale information, and has an important application prospect.
The above embodiments are preferred embodiments of the present invention, but the present invention is not limited to the above embodiments, and any other changes, modifications, substitutions, combinations, and simplifications which do not depart from the spirit and principle of the present invention should be construed as equivalents thereof, and all such modifications are intended to be included in the scope of the present invention.
Claims (8)
1. A kind of picometer measurement system based on optical comb of picometer, characterized by, the said picometer measurement system includes: the device comprises a laser (1), a beam splitter (2), a reflector (3), a microscope objective (4), a pinhole filter (5), a collimating lens (6), a holographic dry plate (7), a photoelectric detector (8) and a computer (9); the laser beam emitted by the laser (1) is divided into two beams of light by the beam splitter (2), and the two beams of light can be converged on a plane by controlling the angle by the reflector (3); each beam of light is converged on an interference plane to generate interference fringes through a microscope objective (4), a pinhole filter (5) and a collimating lens (6) in sequence, the holographic dry plate (7) is arranged on the interference plane for the first exposure, and displacement information of a picometer scale is loaded on an interference field to cause periodic variation; carrying out secondary exposure on the holographic dry plate (5), and forming a picometer optical comb on the holographic dry plate;
a light beam emitted by a laser (1) passes through a microscope objective (4), a pinhole filter (5) and a collimating lens (6) in sequence to form a plane wave for collimating and expanding beams to irradiate a picometer optical comb on a holographic dry plate (7) and generate Moire interference fringes; moire interference fringes are collected through a photoelectric detector (8), transmitted to a computer (9) to calculate the period of the Moire interference fringes, and displacement information of a picometer scale is obtained according to a formula.
2. The picometer measurement system based on a picometer optical comb according to claim 1, characterized in that the beam splitter (2) is a half-mirror.
3. The picometer measurement system based on the picometer optical comb according to claim 1, characterized in that the mirror (3) controls the period d of the interference field by controlling the angle between the two beams.
4. A picometer measurement system based on a picometer optical comb according to claim 1, characterized in that the holographic dry plate (7) is a photoresist-coated substrate.
5. The picometer measurement system based on the picometer optical comb according to the claim 1, characterized in that, the picometer optical comb is formed by two exposures, which is formed by developing, fixing and baking after the holographic dry plate (7) is exposed twice, and the period of the interference field of the two exposures needs to be measured with picometer precision because the period of the two exposures differs by picometer magnitude.
6. The picometer measurement method based on the picometer optical comb according to the claim 1, characterized in that the interference fringes generated after the picometer optical comb on the holographic dry plate (7) is irradiated by laser beam are generated due to axial Moire interference effect.
7. A picometer measurement method based on a picometer optical comb according to claim 1, characterized in that the moire interference fringes produced by the picometer optical comb on the holographic dry plate (7) are obtained by the following formula:
let the reference light be
The target beams of the first exposure and the second exposure are respectively
And
wherein R (x, y), O 1 (x,y)、O 2 (x, y) represents the intensities of the reference light and the object beams of the first and second exposures, respectively,
representing the phases of the reference light and the object beams of the first and second exposures, x and y representing the positions of the abscissa and ordinate, respectively, as the beams propagate;
when two exposures are made, two target beams are respectively recorded on the hologram
And a reference beam
Generating an interference field after interference:
thus, the light field recorded by a picometer optical comb is:
(ii) 2 Cy R (x, y) (+) 2 +|O 1 (x,y)| 2 +|O 2 (x,y)| 2 For background light intensity, the last term is phase information of the interference field, and the period of the light field of the two exposures is different by Δ d, because Δ d is controlled by the incident angle of the target beam, there is an included angle difference Δ θ between the two exposures.
8. The method as claimed in any one of claims 1 to 7, comprising the steps of:
s1, a laser beam emitted by a laser (1) is divided into two beams of light through a beam splitter (2), and the two beams of light are controlled by an angle of a reflector (3) to be converged on a plane;
s2, two beams of light sequentially pass through a microscope objective (4), a pinhole filter (5) and a collimating lens (6) to form a plane wave expanded by collimation, and the plane wave is converged on an interference plane to generate interference fringes with a period of d;
s3, placing the holographic dry plate (7) on an interference plane for first exposure;
s4, adjusting the included angle of the two beams of light by controlling the reflector (3) to load displacement information delta d with a picometer scale on the interference field, so that the period of the interference field is changed into d + delta d;
s5, placing the holographic dry plate (7) on an interference plane, carrying out secondary exposure, developing, fixing and baking, and forming a picometer optical comb on the holographic dry plate (7);
s6, a light beam emitted by the laser (1) sequentially passes through the microscope objective (4), the pinhole filter (5) and the collimating lens (6) to form a plane wave for collimating and expanding beams to irradiate a picometer optical comb on the holographic dry plate (7) and generate Moire interference fringes;
s7, collecting the Moire interference fringes through a photoelectric detector (8), and transmitting the Moire interference fringes to a computer (9) to calculate the period T of the Moire interference fringes;
s8, according to the formula
And calculating displacement information delta d of the picometer scale to be measured.
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