CN114910016B

CN114910016B - White light interference signal reconstruction device

Info

Publication number: CN114910016B
Application number: CN202210467326.XA
Authority: CN
Inventors: 张和君
Original assignee: Chotest Technology Inc
Current assignee: Chotest Technology Inc
Priority date: 2022-04-29
Filing date: 2022-04-29
Publication date: 2024-04-12
Anticipated expiration: 2042-04-29
Also published as: CN118328886A; CN118328887A; CN114910016A

Abstract

The present disclosure describes a reconstruction device for white light interference signals, comprising a generation module, a beam splitting module, an interference objective lens, and a data processing module, wherein the generation module is used for generating a target beam comprising a first beam and a second beam, the beam splitting module comprises a first beam splitting unit and a second beam splitting unit, the first beam splitting unit is configured to receive the target beam and reflect the target beam to the interference objective lens, the target beam forms a target reflected beam at the interference objective lens, the second beam splitting unit is configured to receive the target reflected beam transmitted through the first beam splitting unit, and decouple the target reflected beam into a first reflected beam matched with the first beam and a second reflected beam matched with the second beam; the data processing module is configured to obtain an initial height of the target point based on the first reflected light beam and to compensate the initial height based on the second reflected light beam. According to the present disclosure, the measurement height of the target point can be compensated to improve the measurement accuracy of the target point.

Description

White light interference signal reconstruction device

Technical Field

The present disclosure relates to an intelligent manufacturing equipment industry, and in particular, to a white light interference signal reconstruction device.

Background

With the increasing development of ultra-precise processing technology, ultra-precise detection technology is also becoming more important. The optical measurement method is widely applied to the field of optical measurement by virtue of low cost and high precision. Among them, the optical measurement system based on the interference principle has the advantages of high precision and high resolution, and is often used for accurate measurement of physical quantities. The white light interferometer is ultra-precise measurement equipment based on a white light interferometry technology, and the measurement precision and accuracy of the ultra-precise measurement equipment are obviously affected by the environment. In general, environmental effects include both industrial environmental effects and natural environmental effects, wherein an industrial environmental effect refers to vibrations caused by people and the surrounding environment, so that low-frequency vibrations are generated on the ground and transmitted to the interferometer; the natural environment influence means that the interferometer generates certain vibration due to changes of the natural environment, such as air flow, temperature change, etc. Both of the above vibrations due to environmental influences are environmental vibrations. When environmental vibration exists, white light interference fringes generated based on a white light interferometer are easy to shake, for example interference fringe images are mutually overlapped, deformed, trimmed, blurred or burr and the like, so that a larger error exists in a measurement result; furthermore, the large amplitude of the fluctuation of the plurality of pattern fringes can cause the interference fringes to be not observed and cannot be measured.

In the prior art, the influence of environmental vibration on a white light interference measurement result is generally reduced by adopting technologies such as mechanical vibration isolation, synchronous phase shift interference and the like, and a bearing platform with good shock resistance, high rigidity and the like is designed from the mechanical structure perspective by adopting the mechanical vibration isolation technology so as to reduce the influence of environmental vibration factors on white light interference microscopic imaging. However, the structural anti-vibration design makes the equipment appear huge and heavy, has lower measurement accuracy, has limited contribution to white light interference signal reconstruction, and cannot effectively reconstruct microscopic 3D morphology of a sample under some environmental noise with large vibration, ultralow frequency and high frequency. In four space positions, four CCDs are used to collect interference patterns of each frame with pi/2 phase difference at the same time so as to reduce influence of environmental vibration on phase shift. The method has high requirements on consistency of photoelectric properties of the CCD and various optical devices, and the measuring system has complex structure, high control difficulty and high price.

Disclosure of Invention

The present disclosure has been made in view of the above-mentioned conventional art, and an object thereof is to provide a white light interference signal reconstruction device capable of compensating a measurement height of a target point to improve measurement accuracy of the target point.

The present disclosure provides a reconstruction device of a white light interference signal, the reconstruction device measuring a height of a target point of an object to be measured based on the white light interference signal and reconstructing the object to be measured based on a compensating interference signal and the height of the target point, the reconstruction device generating module, a beam splitting module, an interference objective lens, and a data processing module, the generating module being configured to generate a target beam including a first beam forming the white light interference signal and a second beam forming the compensating interference signal, the beam splitting module including a first beam splitting unit configured to receive the target beam and reflect the target beam to the interference objective lens, the target beam forming a target reflected beam at the interference objective lens, the second beam splitting unit configured to receive the target reflected beam transmitted via the first beam splitting unit and to decouple the target reflected beam into a first reflected beam matching the first beam and a second reflected beam matching the second beam; the data processing module is configured to obtain an initial height of the target point based on the first reflected light beam and to compensate the initial height based on the second reflected light beam. In this case, according to the reconstruction device of the present disclosure, the initial height of the target point can be obtained based on the first light beam, and the initial height can be compensated based on the second light beam, whereby the overall measurement accuracy of the reconstruction device can be improved, and further the reconstruction accuracy of the reconstruction device can be improved.

In addition, in the reconstruction device according to the present invention, optionally, the reconstruction device further includes a receiving module including a first receiving unit configured to receive the first reflected light beam transmitted through the second light splitting unit and a second receiving unit; the second receiving unit is configured to receive a second reflected light beam reflected via the second light splitting unit. In this case, the reconstruction means can obtain the initial height of the target point based on the first reflected light beam received by the first receiving unit, and can compensate the initial height based on the second reflected light beam received by the second receiving unit.

In addition, in the reconstruction device according to the present invention, the generation module may include a first light source for generating a first light beam, a second light source for generating a second light beam, and a third spectroscopic unit for coupling the first light beam and the second light beam as a target light beam. In this case, the first beam and the second beam can be coupled into one beam (i.e., the target beam), which is advantageous for improving the propagation stability of the beams, and the reconstruction means can obtain the initial height of the target point based on the first beam in the target beam, which is compensated based on the second beam in the target beam.

In addition, in the reconstruction device according to the present invention, optionally, the interference objective lens includes a fourth spectroscopic unit configured to receive the target beam and decompose the target beam into a first sub-target beam reflected to the reference unit and a second sub-target beam transmitted to the target point; the first sub-target beam is reflected to the reference unit via the fourth beam splitting unit and is reflected by the reference unit to form a first sub-target reflected beam; the second sub-target beam is transmitted to the target point via the fourth beam splitting unit and reflected by the target point to form a second sub-target reflected beam, and the first sub-target reflected beam and the second sub-target reflected beam form a target reflected beam. In this case, when the target beam enters the interference objective lens and reaches the fourth spectroscopic unit, the fourth spectroscopic unit can decompose the target beam into a first sub-target beam and a second sub-target beam, the first sub-target beam is reflected via the interference objective lens internal structure to form a first sub-target reflected beam, the second sub-target beam is reflected via the target point to form a second sub-target reflected beam, and the fourth spectroscopic unit can combine the first sub-target reflected beam and the second sub-target reflected beam into a target reflected beam, whereby the reconstruction device can obtain an initial height of the target point and compensate the initial height based on interference signals of the first sub-target reflected beam and the second sub-target reflected beam in the target reflected beam.

In addition, in the reconstruction device according to the present invention, optionally, a driving module is further included, and the driving module is configured to adjust the relative positions of the interference objective lens and the target point. In this case, the relative positions of the interference objective lens and the target point can be changed to obtain the zero optical path difference position corresponding to the target point, and the reconstruction device can obtain the initial height of the target point and compensate the initial height.

In the reconstruction device according to the present invention, the generation module may further include a first lens unit and a second lens unit disposed between the third spectroscopic unit and the first spectroscopic unit. In this case, the target beam can be converged into a beam after passing through the first lens unit and then transmitted to the second lens unit, and the second lens unit converts the converged target beam into collimated light and transmits the collimated light to the first beam splitting unit, so that the divergence of the target beam can be reduced and the energy loss of the target beam can be reduced.

In the reconstruction device according to the present invention, the receiving module may further include a third lens unit disposed between the second beam splitting unit and the first receiving unit, and a fourth lens unit disposed between the second beam splitting unit and the second receiving unit. In this case, the third lens unit can focus the first reflected light beam on the first receiving unit, and the fourth lens unit can focus the second reflected light beam on the second receiving unit.

In addition, in the reconstruction device according to the present invention, optionally, the bandwidth of the first light beam is not less than a first preset value, and the bandwidth of the second light beam is not greater than a second preset value, where the first preset value is not less than the second preset value. In this case, the first light beam and the second light beam span a sufficiently long interval so that the first light beam and the second light beam can have a higher isolation, and thus the influence of the second light beam on the first light beam during measurement can be reduced.

In addition, in the reconstruction device according to the present invention, the data processing module may further include a timing synchronization unit configured to transmit a control signal to the first receiving unit and the second receiving unit to synchronize the first receiving unit and the second receiving unit to receive the first reflected light beam and the second reflected light beam. In this case, the first receiving unit and the second receiving unit can synchronously receive the optical signal, whereby the vibration information monitored by the compensation optical path can be synchronized with the measurement information of the measurement optical path, further improving the overall measurement accuracy of the reconstruction device.

In addition, in the reconstruction device according to the present invention, optionally, the time for which the first receiving unit responds to one optical signal is not less than the response time for which the second receiving unit responds to one optical signal. In this case, the sampling integration time of the second receiving unit may be much lower than that of the first receiving unit, so that the vibration information monitored by the compensation light path can reflect the environmental vibration more accurately.

According to the present disclosure, it is possible to provide a reconstruction device that compensates a measurement height of a target point to improve measurement accuracy of the target point.

Drawings

The present disclosure will now be explained in further detail by way of example only with reference to the accompanying drawings.

Fig. 1 is a schematic view showing an application scenario of a white light interference signal reconstruction device according to the present disclosure.

Fig. 2 is a block diagram showing a construction of a reconstruction device of a white light interference signal according to the present disclosure.

Fig. 3 is a schematic diagram showing the total optical path of a reconstruction device of white light interference signals according to the present disclosure.

Fig. 4 is a schematic diagram showing an internal structure of an interference objective lens according to the present disclosure.

Fig. 5 is a schematic diagram showing a measurement optical path to which the present disclosure relates.

Fig. 6 is a schematic diagram illustrating white light interference signals and scanning strokes related to the present disclosure.

Fig. 7 is a schematic diagram showing a compensation optical path to which the present disclosure relates.

Fig. 8 is a schematic diagram illustrating the compensation interference signal and scan stroke related to the present disclosure.

Fig. 9 is a schematic diagram showing the synchronous reception of optical signals by the measurement optical path and the compensation optical path according to the present disclosure.

Fig. 10 is a schematic diagram illustrating another embodiment of the total optical path of a reconstruction device for white light interference signals according to the present disclosure.

Fig. 11 is a flow chart illustrating a compensation method according to the present disclosure.

Fig. 12 is a schematic diagram showing scan times and scan strokes of a plurality of target points according to the present disclosure.

Fig. 13 is a flow chart illustrating a reconstruction method according to the present disclosure.

Fig. 14a is a schematic view showing a three-dimensional surface morphology obtained by three-dimensionally reconstructing an object to be measured based on a conventional apparatus and method under a first condition.

Fig. 14b is a schematic diagram showing a three-dimensional surface morphology obtained by three-dimensionally reconstructing an object to be measured under a first condition by the reconstruction apparatus and the reconstruction method according to the present disclosure.

Fig. 15a is a schematic view showing a three-dimensional surface morphology obtained by three-dimensionally reconstructing an object to be measured based on a conventional apparatus and method under a second condition.

Fig. 15b is a schematic view showing a three-dimensional surface morphology obtained by three-dimensionally reconstructing an object to be measured under a second condition by the reconstruction apparatus and the reconstruction method according to the present disclosure.

Detailed Description

Hereinafter, preferred embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. In the following description, the same members are denoted by the same reference numerals, and overlapping description thereof is omitted. In addition, the drawings are schematic, and the ratio of the sizes of the components to each other, the shapes of the components, and the like may be different from actual ones.

It should be noted that the terms "comprises" and "comprising," and any variations thereof, in this disclosure, such as a process, method, apparatus, article, or apparatus that comprises or has a list of steps or elements is not necessarily limited to those steps or elements expressly listed or inherent to such process, method, article, or apparatus, but may include or have other steps or elements not expressly listed or inherent to such process, method, article, or apparatus.

In addition, headings and the like referred to in the following description of the disclosure are not intended to limit the disclosure or scope thereof, but rather are merely indicative of reading. Such subtitles are not to be understood as being used for segmenting the content of the article, nor should the content under the subtitle be limited only to the scope of the subtitle.

The present disclosure relates to a reconstruction device for white light interference signals, which may also be referred to as a device or a reconstruction device in some cases. In some examples, the reconstruction device of the white light interference signal related to the present disclosure may also be referred to as a reconstruction device with a dual optical path, a reconstruction device with a dual light source, a device for reconstructing an object to be measured based on the white light interference signal, a reconstruction device with a compensation function, or a reconstruction device with an anti-vibration function.

According to the reconstruction device of the present disclosure, the initial height of the target point can be obtained based on the first light beam, and the initial height is compensated based on the second light beam, so that the comprehensive measurement accuracy of the reconstruction device can be improved, and the reconstruction accuracy of the reconstruction device can be improved.

The reconstruction device according to the present embodiment will be described in detail below with reference to the accompanying drawings.

Fig. 1 is a schematic diagram showing an application scenario of a white light interference signal reconstruction device 10 according to the present disclosure. Fig. 2 is a block diagram showing the structure of the white light interference signal reconstruction device 10 according to the present disclosure.

In some examples, the reconstruction device 10 may measure the height of the target point 21 of the object based on the white light interferometry signal. In some examples, the reconstruction device 10 may compensate for the height of the target point 21 based on the compensated interference signal. Thereby, the height data of the target point 21 can be more accurate.

In some examples, the reconstruction device 10 may reconstruct the object to be measured based on the height of the target point 21. In other examples, the reconstruction device 10 may reconstruct the object to be measured based on the height of the compensated target point 21. Thus, the reconstructed data of the object to be measured can be more accurate.

In some examples, the reconstruction device 10 may measure the height of the target point 21 of the object based on the white light interferometry signal and reconstruct the object based on the compensating interferometry signal and the height of the target point 21.

Referring to fig. 1, the reconstruction apparatus 10 according to the present embodiment may be used to measure an initial height of a target point 21 (described later) of an object 20, and may compensate the initial height to obtain a compensated integrated measurement height. This can improve the overall measurement accuracy of the reconstruction device 10.

In some examples, the reconstruction device 10 may reconstruct the three-dimensional surface topography of the object 20.

In the present embodiment, the reconstruction apparatus 10 may include a generation module 100, a spectroscopy module 200, an interference objective 300, and a data processing module 400 (see fig. 2).

Wherein the generation module 100 may be used to generate a light beam, and the light beam may reach the interference objective 300 via the beam splitting module 200. Then, after the light beam is reflected by the interference objective 300 and the object 20 to be measured, an interference light beam can be formed at the interference objective 300, and the data processing module 400 obtains the initial height of the target point 21 of the object 20 to be measured based on the interference light beam and compensates the initial height to obtain the integrated measurement height. Further, the reconstruction device 10 may reconstruct the three-dimensional surface topography of the object 20.

In some examples, the analyte 20 may be referred to as a sample. The sample can be a semiconductor, a 3C electronic glass screen, a micro-nano material, an automobile part, or an ultra-precise device such as a MEMS device. In some examples, the sample may be a device applied in the field of aerospace or defense, military, etc.

In some examples, the measurement point at which the reconstruction apparatus 10 measures the object 20 may be referred to as the target point 21. I.e. the reconstruction means 10 can be used to measure the height of the target point 21. The target point 21 may be a point, a line, or an area. In some examples, the analyte 20 may include at least one target point 21. Measuring one target point 21 may obtain the height of one target point 21, and measuring a plurality of target points 21 may obtain the heights of a plurality of target points 21. In this case, if only the height of one target point 21 needs to be obtained, the reconstruction device 10 needs to measure only one target point 21; when the reconstruction device 10 measures the plurality of target points 21 of the object 20, the three-dimensional surface topography of the object 20 can be reconstructed based on the heights of the plurality of target points 21. In some examples, the height may be a surface height of the test object 20.

Fig. 3 is a schematic diagram showing the overall optical path of the white light interference signal reconstruction device 10 according to the present disclosure.

As described above, the reconstruction apparatus 10 may include the generation module 100, the spectroscopy module 200, the interference objective 300, and the data processing module 400. Referring to fig. 3, in the reconstruction device 10 according to the present embodiment, the generation module 100 may be used to generate the target light beam L1. The light splitting module 200 may include a first light splitting unit 210 and a second light splitting unit 220. The first light splitting unit 210 may be used to receive the target beam L1 and reflect the target beam L1 to the interference objective 300. The interference objective lens 300 may be used to form the target reflected light beam L1 'and transmit the target reflected light beam L1' to the data processing module 400 via the first and second light splitting units 210 and 220. The data processing module 400 may obtain the initial height of the target point 21 based on the target reflected light beam L1' and may compensate for the initial height.

In some examples, there may be an error in the height of the target point 21 measured with a single beam due to the presence of ambient vibrations. Accordingly, the initial height to which the present disclosure relates may refer to a measurement result due to the presence of environmental vibrations, with a large error in the initial height obtained. Compensating for the initial height may refer to reducing errors due to environmental vibrations. In some examples, the height after compensating for the initial height may be referred to as a combined measured height. That is, the reconstruction device 10 according to the present embodiment can improve the measurement accuracy of the target point 21.

In some examples, the above-described errors may refer to errors in a scanning direction, which may be seen in fig. 3 (the direction in which Z is pointed in fig. 3). In other words, the displacement amount (or translational amount) of the target point 21 in the scanning direction is caused by the environmental vibration.

As described above, the generation module 100 may be used to generate the target beam L1. The target light beam L1 may include a first light beam L10 and a second light beam L20. In some examples, the reconstruction apparatus 10 may be based on the first light beam L10 to obtain an initial height of the target point 21, and the second light beam L20 to compensate for the initial height. For example, the reconstruction device 10 may monitor vibration information of the target point 21 based on the second light beam L20 to compensate for the initial height to obtain the integrated measurement height. In this case, the reconstruction device 10 measures the target point 21 based on two light beams, and can improve the measurement accuracy of the height of the target point 21.

In some examples, the generation module 100 may include a first light source 110. The first light source 110 may be used to generate a first light beam L10. The generation module 100 may include a second light source 120. The second light source 120 may be used to generate a second light beam L20. The first light beam L10 and the second light beam L20 may be coupled into a target light beam L1. In this case, the first light beam L10 and the second light beam L20 may be coupled and combined into a single light beam (i.e., the target light beam L1), which is beneficial to improving propagation stability of the light beams.

In some examples, the bandwidth of the first light beam L10 generated by the first light source 110 may be not less than the first preset value. The first preset value may be not less than 100nm. In some examples, light having a bandwidth not less than the first preset value may be referred to as broadband light. Since the coherence of broadband light is poor, the coherence length is low, and thus the interference phenomenon thereof becomes more remarkable at a position where the optical path difference is shorter. In this case, the position where the optical path difference is shortest may be obtained based on the intensity of the interference phenomenon of the first light beam L10, and the initial height of the target point 21 may be obtained based on the position where the optical path difference is shortest.

In some examples, the scan stroke when the reconstruction device 10 measures one target point 21 may be not less than the coherence length of the first light beam L10. In this case, the interference signal formed when the first light beam L10 interferes can be displayed entirely.

In some examples, the first light beam L10 generated by the first light source 110 may be white light. The first light source 110 may act as a scanning light source for the measurement process. In some examples, the first light beam L10 generated by the first light source 110 may have a wavelength of 400nm-700nm, for example, 400nm, 450nm, 500nm, 550nm, 6000nm, 650nm, or 700nm. In this case, it can be convenient for the reconstruction device 10 to obtain image information of the surface of the object 20 to be measured during the measurement.

In some examples, the interference signal formed when the first light beam L10 interferes may be referred to as a white light interference signal. In some examples, the interference signal formed by the first reflected light beam L10' may also be referred to as white light interference signal hereinafter.

In some examples, the bandwidth of the second light beam L20 generated by the second light source 120 may be not greater than the second preset value. In some examples, the first preset value may be not less than the second preset value. For example, the second preset value may be 50nm. In some examples, light having a bandwidth no greater than a second preset value may be referred to as narrowband light. In this case, since the coherence length of the narrowband light is long, the second light beam L20 can form an interference signal in the entire scanning stroke of measuring one target point 21.

In some examples, the vibration of the target point 21 may be monitored based on the second light beam L20. In other words, vibration information (i.e., an error due to environmental vibration) of the target point 21 during measurement can be obtained based on the second light beam L20. Thereby, the initial height can be compensated based on the second light beam L20.

In some examples, the second light beam L20 generated by the second light source 120 may be infrared light. In some examples, the wavelength of the second light beam L20 generated by the second light source 120 may be not less than 900nm, for example, the wavelength of the second light beam L20 may be 950nm, 980nm, 1000nm, or the like. In this case, the wavelength bands spanned by the first light beam L10 and the second light beam L20 have a sufficiently long interval so that the first light beam L10 and the second light beam L20 can have a higher isolation, and thus the influence of the second light beam L20 on the first light beam L10 during the measurement process can be reduced.

In some examples, the interference signal formed when the second light beam L20 interferes may be referred to as a compensating interference signal. In some examples, the interference signal formed by the second reflected light beam L20' may also be referred to as a compensating interference signal hereinafter.

In some examples, the generation module 100 may further include a third light splitting unit 130. The third light splitting unit 130 may be used to couple the first light beam L10 and the second light beam L20 as the target light beam L1. In this case, the first light beam L10 and the second light beam L20 can be coupled into one beam (i.e., the target light beam L1), and the reconstruction device 10 can obtain the initial height of the target point 21 based on the first light beam L10 in the target light beam L1, compensating for the initial height based on the second light beam L20 in the target light beam L1.

In some examples, the third light splitting unit 130 may be a dichroic light splitting sheet. The third light splitting unit 130 may be disposed at 45 ° to the central axis of the first light source 110, and the central axis of the second light source 120 may be perpendicular to the central axis of the first light source 110. The dichroic beamsplitter may reflect or transmit the light beam based on its wavelength selection. In the present embodiment, the third light splitting unit 130 may be used to transmit the first light beam L10, and the third light splitting unit 130 may be used to reflect the second light beam L20. Therefore, the first light beam L10 and the second light beam L20 can be coupled into the target light beam L1 after reaching the third light splitting unit 130.

In some examples, the generation module 100 may include a combined light source for emitting the first light beam L10 and the second light beam L20. That is, the generation module 100 may include one light source for emitting the target light beam L1, wherein the target light beam L1 includes the first light beam L10 and the second light beam L20. In other words, a combined light source may be used to emit the first light beam L10 and the second light beam L20. In this case, the generating module 100 may not include the third light splitting unit 130 for coupling the first light beam L10 and the second light beam L20, so that the effect that the first light beam L10 and the second light beam L20 are on the same optical path can be achieved.

In some examples, the target light beam L1 generated by the generation module 100 may be received by the spectroscopy module 200. The spectroscopic module 200 may be used to change the propagation direction of the target light beam L1. As described above, the spectroscopic module 200 may include the first spectroscopic unit 210. The first light splitting unit 210 may be used to receive the target light beam L1. The first light splitting unit 210 may be used to reflect the target light beam L1. In some examples, the first light splitting unit 210 may be configured to receive the target light beam L1 and reflect the target light beam L1. Thereby, the target light beam L1 can further change the propagation direction of the target light beam L1 based on the setting of the first spectroscopic unit 210.

In some examples, the generation module 100 may further include a first lens unit 140 and a second lens unit 150. And the first lens unit 140 and the second lens unit 150 may be disposed between the third light splitting unit 130 and the first light splitting unit 210. The first lens unit 140 may be a converging lens having a function of converging light beams, and the second lens unit 150 may be a collimating lens for converting light beams into collimated light. In this case, the target light beam L1 can be converged into a beam after passing through the first lens unit 140 and then transmitted to the second lens unit 150, and the second lens unit 150 converts the converged target light beam L1 into collimated light and transmits the collimated light to the first beam splitting unit 210, whereby divergence of the target light beam L1 can be reduced and thus energy loss of the target light beam L1 can be reduced.

In some examples, the generation module 100 may not include the first lens unit 140 and the second lens unit 150.

Referring to fig. 3, in the reconstruction device 10 according to the present embodiment, the first spectroscopic unit 210 may reflect the target light beam L1 to the interference objective 300 after receiving the target light beam L1. The interference objective lens 300 may be used to generate a target reflected beam L1'. The target reflected light beam L1' includes a light beam reflected by the target point 21 of the object 20 and a light beam reflected by the interference objective lens 300.

Fig. 4 is a schematic diagram showing an internal structure of an interference objective lens 300 according to the present disclosure.

Referring to fig. 4, in some examples, the interference objective 300 may include a fourth spectroscopic unit 310 and a reference unit 320. The fourth light splitting unit 310 may be configured to receive the target light beam L1 and split the target light beam L1 into a first sub-target light beam L30 and a second sub-target light beam L40. In some examples, the fourth light splitting unit 310 may be further configured to reflect the first sub-target beam L30 to the reference unit 320 and transmit the second sub-target beam L40 to the target point 21.

In some examples, the first sub-target beam may be reflected to the reference unit 320 via the fourth spectroscopic unit and reflected by the reference unit 320 to form a first sub-target reflected beam L30'. In some examples, the second sub-target beam L40 may be transmitted to the target point 21 via the fourth spectroscopic unit 310 and reflected by the target point 21 to form a second sub-target reflected beam L40'.

In some examples, the first sub-target reflected beam L30' and the second sub-target reflected beam L40' may form a target reflected beam L1'. In particular, the fourth light splitting unit 310 may be further configured to combine the first sub-target reflected light beam L30' and the second sub-target reflected light beam L40' to form a target reflected light beam L1'. In other words, the target reflected light beam L1' may include the first sub-target reflected light beam L30' and the second sub-target reflected light beam L40'.

In some examples, the first sub-target reflected beam L30 'and the second sub-target reflected beam L40' may form interference, and the reconstruction apparatus 10 may obtain an initial height of the target point 21 based on the white light interference signal formed by the first sub-target reflected beam L30 'and the second sub-target reflected beam L40' and compensate the initial height to improve the measurement accuracy of the reconstruction apparatus 10.

Hereinafter, for convenience of understanding, the total optical path of the target beam L1 is divided into a measurement optical path and a compensation optical path, and how to obtain the initial height of the target point 21 based on the first beam L10 and compensate the initial height based on the second beam L20 is described in detail with respect to the measurement optical path and the compensation optical path, respectively.

Referring to fig. 5, the first light beam L10 generated by the first light source 110 may reach the interference objective lens 300 after being reflected by the first light splitting unit 210, and the fourth light splitting unit 310 of the interference objective lens 300 may split the first light beam L10 into a first sub-beam and a second sub-beam. The specific principle can be referred to in fig. 4, and will not be described herein. The first sub-beam may be reflected to the reference unit 320 via the fourth beam splitting unit 310, and the reference unit 320 may receive and reflect the first sub-beam to form a first sub-reflected beam. The second sub-beam may be transmitted to the target point 21 via the fourth beam splitting unit 310, and the target point 21 may receive and reflect the second sub-beam to form a second sub-reflected beam. And the fourth light splitting unit 310 may combine the first sub-reflected light beam and the second sub-reflected light beam into a first reflected light beam L10'.

In some examples, the first sub-reflected beam and the second sub-reflected beam in the first reflected beam L10' may have an optical path difference. Accordingly, the first sub-reflected light beam and the second sub-reflected light beam can interfere, and the reconstruction device 10 can obtain the initial height of the target point 21 based on the interference signal (white light interference signal) of the first reflected light beam L10'.

Note that the first sub-target beam L30 may include a first sub-beam, and the first sub-target reflected beam L30' may include a first sub-reflected beam. The second sub-target beam L40 may include a second sub-beam, and the second sub-target reflected beam L40' may include a second sub-reflected beam.

Since the first light beam L10 may be white light, the coherence length of the white light is short. When the optical path difference between the first sub-reflected beam and the second sub-reflected beam is not greater than the coherence length of the first beam L10, the first sub-reflected beam and the second sub-reflected beam may interfere to generate interference fringes. In some examples, when the optical path difference between the first sub-reflected beam and the second sub-reflected beam is zero, the intensity of the white light interference signal may reach a maximum value, and the reconstruction apparatus 10 may obtain the initial height of the target point 21 based on the white light interference signal at this time.

The above-described zero optical path difference may mean that the vertical distance between the fourth spectroscopic unit 310 and the reference unit 320 is equal to the vertical distance between the fourth spectroscopic unit 310 and the target point 21. In other words, when the vertical distance between the fourth spectroscopic unit 310 and the reference unit 320 is equal to the vertical distance between the fourth spectroscopic unit 310 and the target point 21, the optical path difference of the first sub-reflected light beam and the second sub-reflected light beam may be zero.

In some examples, the reconstruction device 10 may further include a drive module 500. The drive module 500 may be configured to adjust the relative positions of the interference objective 300 and the target point 21. In some examples, the drive module 500 may adjust the interference objective 300 away from or near the target point 21. In other examples, the drive module 500 may adjust the target point 21 away from or towards the interference objective 300. In this case, the relative positions of the interference objective lens 300 and the target point 21 can be changed so that the zero optical path difference position corresponding to the target point 21 can be obtained, and the reconstruction device 10 can obtain the initial height of the target point 21.

In some examples, the reconstruction apparatus 10 may further include a carrier module 600. The carrying module 600 may be used to carry the object 20 to be measured. That is, the driving module 500 may be configured to drive the relative position between the interference objective lens 300 and the carrier module 600.

In some examples, the drive module 500 may control the relative positions of the interference objective 300 and the carrier module 600 based on control signals sent by the reconstruction device 10. In other examples, the drive module 500 may be manual.

Fig. 6 is a schematic diagram showing white light interference signals and scanning strokes related to the present disclosure.

Where I may represent the light intensity and z may represent the scanning stroke.

In some examples, the scan stroke may refer to a relative displacement of the interference objective 300 and the target point 21. I.e. the scanning length in the vertical direction. In some examples, the scan travel may refer to an optical path difference between the first sub-target reflected beam and the second sub-target reflected beam L40'. I.e. the optical path difference between the first sub-reflected beam and the second sub-reflected beam. Or an optical path difference between the third sub-reflected beam and the fourth sub-reflected beam later.

Referring to fig. 6, in some examples, at the zero path difference position of the first sub-reflected beam and the second sub-reflected beam, the white light interference signal collected by the measurement light path may be modulated by a gaussian envelope.

In some examples, the scan stroke may be greater than the coherence length of the first light beam L10. In this case, the white light interference signal formed by the first reflected light beam L10' can be displayed entirely, and thus the interference peak can be obtained based on the entire white light interference signal, whereby the reconstruction device 10 can obtain the initial height of the target point 21 based on the interference peak.

Referring to fig. 7, the second light beam L20 generated by the second light source 120 may reach the interference objective lens 300 after being reflected by the first light splitting unit 210, and the fourth light splitting unit 310 of the interference objective lens 300 may split the second light beam L20 into the third sub-beam and the fourth sub-beam. The specific principle can be referred to in fig. 4, and will not be described herein. Wherein the third sub-beam may be reflected to the reference unit 320 via the fourth beam-splitting unit 310, and the reference unit 320 may receive and reflect the third sub-beam to form a third sub-reflected beam. The fourth sub-beam may be transmitted to the target point 21 via the fourth beam-splitting unit 310, and the target point 21 may receive and reflect the fourth sub-beam to form a fourth sub-reflected beam. And the fourth light splitting unit 310 may combine the third sub-reflected light beam and the fourth sub-reflected light beam into a second reflected light beam L20'.

In some examples, the third sub-reflected beam and the fourth sub-reflected beam in the second reflected beam L20' may have an optical path difference. Thus, the third sub-reflected light beam and the fourth sub-reflected light beam can interfere. As described above, the coherence length of the second light beam L20 is long. Thus, the second reflected light beam L20' can form a compensating interference signal throughout the scanning stroke, i.e. at a zero path difference position larger than the first reflected light beam L10', the second reflected light beam L20' can still form interference. Thereby, the reconstruction device 10 can compensate for the initial height. In other words, corresponding phase information can be provided throughout the scanning stroke (see fig. 8). In some examples, the compensated interference signal of the second reflected light beam L20' over the entire scanning stroke may be based to obtain a measurement error due to environmental vibrations, and the initial height may be compensated based on the measurement error to improve the overall measurement accuracy of the reconstruction device 10. In some examples, the compensating interference signal of the compensating optical path may be referred to as a vibration monitoring signal.

It should be noted that the first sub-target beam L30 may include a third sub-beam, and the first sub-target reflected beam L30' may include a third sub-reflected beam. The second sub-target beam L40 may include a fourth sub-beam, and the second sub-target reflected beam L40' may include a fourth sub-reflected beam.

From the foregoing, it can be appreciated that the target reflected light beam L1' can include a first reflected light beam L10' and a second reflected light beam L20'.

Referring back to fig. 3, in the total optical path of the reconstruction device 10 according to the present embodiment, the first sub-target reflected light beam L30 'and the second sub-target reflected light beam L40' may have an optical path difference. That is, the first sub-target reflected beam L30' and the second sub-target reflected beam L40' included in the target reflected beam L1' may form a white light interference signal enveloped by a gaussian and a compensation interference signal over the entire scanning stroke. In this case, when the target beam L1 reaches the fourth spectroscopic unit 310 after entering the interference objective 300, the fourth spectroscopic unit 310 can decompose the target beam L1 into the first sub-target beam L30 and the second sub-target beam L40, the first sub-target beam L30 being reflected via the internal structure of the interference objective 300 to form the first sub-target reflected beam L30', the second sub-target beam L40 being reflected via the target point 21 to form the second sub-target reflected beam L40', the fourth spectroscopic unit 310 can also combine the first sub-target reflected beam L30 'and the second sub-target reflected beam L40' into the target reflected beam L1', whereby the reconstruction device 10 can obtain the initial height of the target point 21 based on the interference signals of the first sub-target reflected beam L30' and the second sub-target reflected beam L40 'in the target reflected beam L1', and compensate the initial height.

In some examples, the relative positions of the interference objective lens 300 and the target point 21 may be adjusted such that the optical path difference of the first sub-target reflected beam L30 'and the second sub-target reflected beam L40' is zero. In this case, during the adjustment, the reconstruction device 10 can determine the position where the zero optical path difference occurs based on the change in the white light interference signal. I.e. the white light interference signal reaches a peak value, when the optical path difference between the first sub-target reflected light beam L30 'and the second sub-target reflected light beam L40' is zero, the reconstruction device 10 can obtain the initial height of the target point 21 based on the corresponding white light interference signal at this time.

In some examples, the scan stroke may be greater than the coherence length of the first light beam L10. In this case, in addition to allowing the white light interference signal of the first light beam L10 to be displayed completely, a compensation interference signal of the second light beam L20 over the entire scanning stroke can be obtained, whereby the initial height of the target point 21 can be obtained and compensated for to improve the overall measurement accuracy of the reconstruction device 10.

It should be noted that the first sub-target beam L30 and the first beam L10 do not correspond. The first sub-target beam L30 includes a portion of the first beam L10 and a portion of the second beam L20. Similarly, the second sub-target beam L40 includes a portion of the first beam L10 and a portion of the second beam L20.

As described above, the reconstruction device 10 may also include a drive module 500. In some examples, the driving module 500 may be configured to adjust the relative distance between the carrier module 600 and the interference objective lens 300 so that the optical path differences between the plurality of target points 21 included on the surface of the object 20 and the reference unit 320 of the interference objective lens 300 are sequentially zero. In this case, the reconstruction device 10 can obtain the heights of the plurality of target points 21 based on the interference signals of the plurality of target points 21, and can reconstruct the three-dimensional surface topography of the object 20.

As described above, the light splitting module 200 may include the second light splitting unit 220. The second light splitting unit 220 may be disposed in the same direction as the first light splitting unit 210. The second light splitting unit 220 may be a dichroic light splitting sheet. In some examples, the target reflected light beam L1' may reach the second light splitting unit 220 via the first light splitting unit 210 after exiting through the interference objective lens 300. In other words, the second light splitting unit 220 may be configured to receive the target reflected light beam L1' transmitted through the first light splitting unit 210.

In the reconstruction device 10 according to the present embodiment, the second beam splitting unit 220 may be further configured to decouple the target reflected light beam L1' into the first reflected light beam L10' and the second reflected light beam L20'. Wherein the first reflected light beam L10 'may be matched with the first light beam L10 and the second reflected light beam L20' may be matched with the second light beam L20. Since the dichroic beamsplitter may reflect or transmit the light beam based on its wavelength selection, the first reflected light beam L10' may be transmitted via the second beamsplitter 220 and the second reflective element may be reflected via the second beamsplitter 220.

The reconstruction device 10 according to the present embodiment may further include a receiving module 700. The receiving module 700 may be configured to receive the first reflected light beam L10 'and the second reflected light beam L20'.

In some examples, the receiving module 700 may include a first receiving unit 710 and a second receiving unit 720. Wherein the first receiving unit 710 may be configured to receive the first reflected light beam L10 'transmitted through the second light splitting unit 220, and the second receiving unit 720 may be configured to reflect the second reflected light beam L20' through the second light splitting unit 220. In this case, the reconstruction apparatus 10 can obtain the initial height of the target point 21 based on the first reflected light beam L10 'received by the first receiving unit 710, and can compensate the initial height based on the second reflected light beam L20' received by the second receiving unit 720.

In some examples, the first receiving unit 710 may be a CDD camera or a CMOS camera. Thereby, the first receiving unit 710 can convert the received first reflected light beam L10' into a first electrical signal.

In some examples, the second receiving unit 720 may be a photodetector. Preferably, the second receiving unit 720 may be a point photodetector. The second receiving unit 720 may convert the received second reflected light beam L20' into a second electrical signal. In some examples, a point photodetector may have the advantage of high speed, large dynamic range received signals. In this case, using the point photodetector as the second receiving unit 720 enables the reconstruction device 10 to quickly and accurately receive the light intensity variation information of the target point 21 in the process of measuring the target point 21.

In some examples, the first electrical signal may be an interference signal of the first reflected light beam L10 '(i.e., a white light interference signal) and the second electrical signal may be an interference signal of the second reflected light beam L20' (i.e., a compensating interference signal).

In some examples, the receiving module 700 further includes a third lens unit 730 disposed between the second light splitting unit 220 and the first receiving unit 710, and a fourth lens unit 740 disposed between the second light splitting unit 220 and the second receiving unit 720. In some examples, the third lens unit 730 and the fourth lens unit 740 may be a converging lens having a converging light beam function. In this case, the third lens unit 730 can focus the first reflected light beam L10 'on the first receiving unit 710, and the fourth lens unit 740 can focus the second reflected light beam L20' on the second receiving unit 720.

In some examples, the receiving module 700 may also not include the third lens unit 730 and the fourth lens unit 740.

In some examples, the receiving module 700 may include a combined receiving unit for receiving the first reflected light beam L10 'and the second reflected light beam L20'. That is, the combined receiving unit may also be used to receive the second reflected light beam L20 'while receiving the first reflected light beam L10'. Also, the combining module may be used to simultaneously implement the functions of the first receiving unit 710 and the second receiving unit 720 described above. In this case, the reconstruction device 10 may not include the second spectroscopic unit 220 and can also achieve the above-described function, i.e., obtain the initial height of the target point 21 and compensate for the initial height.

In some examples, when the receiving module 700 is configured to receive the first reflected light beam L10' and the second reflected light beam Fan Guangshu as a combined receiving unit, the receiving module 700 may include only one lens unit or may not include a lens unit.

In the reconstruction device 10 according to the present embodiment, the reconstruction device 10 may further include a data processing module 400. The data processing module 400 may be configured to obtain an initial height of the target point 21 based on the first reflected light beam L10 'and compensate the initial height based on the second reflected light beam L20'.

In some examples, the first reflected light beam L10 'and the second reflected light beam L20' may be received by the receiving module 700, and the receiving module 700 may receive the first reflected light beam L10 'and convert the first reflected light beam L10' into a first electrical signal, receive the second reflected light beam L20 'and convert the second reflected light beam L20' into a second electrical signal, and transmit the second electrical signal to the data processing module 400. The data processing module 400 obtains an initial height of the target point 21 based on the first electrical signal, and compensates the initial height based on the second electrical signal.

In some examples, the data processing module 400 may include a timing synchronization unit 410. The timing synchronization unit 410 may be configured to transmit a control signal to the first receiving unit 710 to cause the first receiving unit 710 to receive the first reflected light beam L10', and transmit a control signal to the second receiving unit 720 to cause the second receiving unit 720 to receive the second reflected light beam L20'. In some examples, the timing synchronization unit 410 may be configured to transmit a control signal to the first and second receiving units 710 and 720 to cause the first and second receiving units 710 and 720 to synchronously receive the first and second reflected light beams L10 'and L20'. In this case, the first receiving unit 710 and the second receiving unit 720 can synchronously receive the optical signal, and thus, vibration information monitored by the compensation optical path can be synchronized with measurement information of the measurement optical path, further improving the overall measurement accuracy of the reconstruction device 10.

Referring to fig. 9, in some examples, the control signal may be a frame synchronization pulse, and the instant synchronization unit 410 synchronizes the first and second receiving units 710 and 720 with a timing at which the first and second receiving units 710 and 720 turn on receiving the optical signal by transmitting the frame synchronization pulse. Also, the time interval per frame may be the same. One data information (i.e., white light interference signal and compensation interference signal) of the target point 21 can be obtained per frame. In other examples, multiple data information for target point 21 may be obtained per frame. In some examples, N frames of data information may be acquired to reconstruct the three-dimensional surface topography of the test object 20. N may be an even number.

In some examples, the same timing synchronization unit 410 is used to control the first receiving unit 710 and the second receiving unit 720 to trigger sampling synchronously, so that interference signals of the compensating optical path and the measuring optical path can be synchronized, and vibration information monitored by the compensating optical path can be synchronized with an initial height obtained by the measuring optical path.

In some examples, to reduce the impact of environmental vibrations on measurement accuracy, the rate at which the first receiving unit 710 and the second receiving unit 720 receive optical signals may be increased as much as possible. As described above, the first receiving unit 710 may be a CDD camera or a CMOS camera, and the second receiving unit 720 may be a point photodetector. The frame rate of the first receiving unit 710 may be 50HZ-1KHZ and the second receiving unit 720The frame rate may be 1MHZ-1GHZ. Thus, the sampling rate of the second receiving unit 720 may be much greater than the sampling rate of the first receiving unit 710. That is, the time for which the first receiving unit 710 responds to one optical signal may be not less than the response time for which the second receiving unit 720 responds to one optical signal. Let the first receiving unit 710 receive an optical signal for a time τ ₁ The second receiving unit 720 receives an optical signal for a time τ ₂ In combination with the Frame synchronization pulses (Frame 1, frame2, frame3 … …), a timing diagram of synchronous acquisition of optical signals by the measurement optical path and the compensation optical path may be as shown in fig. 9. In this case, the sampling integration time of the second receiving unit 720 may be far lower than that of the first receiving unit 710, so that the vibration information of the compensation light path monitoring can more accurately reflect the environmental vibration.

Referring to fig. 3, in some examples, the data processing module 400 may further include a data acquisition unit 420 and a computing unit 430. The data acquisition unit 420 may be in signal connection with the second receiving unit 720, and the second electrical signal of the second receiving unit 720 may be transmitted to the calculating unit 430 via the data acquisition unit 420. The control signal transmitted from the timing synchronization unit 410 may be transmitted to the second receiving unit 720 via the data acquisition unit 420.

In some examples, the data acquisition unit 420 may not be included.

In some examples, the first receiving unit 710 may be directly in signal connection with the computing unit 430. The calculation unit 430 may obtain the initial height of the target point 21 based on the received first electrical signal, and may compensate the initial height based on the received second electrical signal to improve the overall measurement accuracy of the reconstruction device 10.

The present disclosure also provides a measurement system with compensation function, which may include any of the above-mentioned reconstruction devices 10 and an object 20 to be measured, and the reconstruction device 10 may be used to measure and compensate an initial height of the target point 21 of the object 20 to be measured. In some examples, the reconstruction apparatus 10 may also measure the initial heights of the plurality of target points 21 of the object 20 and compensate for the initial heights of the plurality of target points 21 to reconstruct the three-dimensional surface topography of the object 20.

Fig. 10 is a schematic diagram illustrating another embodiment of the total optical path of the white light interference signal reconstruction device 10 according to the present disclosure.

Referring to fig. 10, in some examples, the reconstruction apparatus 10 may include a plurality of second receiving units 720. In some examples, the number of second receiving units 720 may be not less than 3. For example, 3, 4, 5, etc. second receiving units 720 may be included. As shown in fig. 10, a second receiving unit 720a, a second receiving unit 720b, and a second receiving unit 720c may be included. In some examples, when the reconstruction apparatus 10 includes a plurality of second receiving units 720, the plurality of second receiving units 720 may monitor vibration information of the plurality of target points 21, and may synthesize the vibration plane based on the plurality of vibration information. In this case, the reconstruction device 10 can realize not only a function of compensating for the initial height of the target point 21 but also a function of compensating for the angular change of the target point 21.

In other words, when one second receiving unit 720 is included, the reconstruction device 10 is able to obtain translational noise characterizing the target point 21. When a plurality of second receiving units 720 are included, the reconstruction apparatus 10 can obtain the angular swing noise characterizing the target point 21.

The present disclosure also provides a compensation method, which is a method for compensating an error due to vibration. In some examples, the compensation method may be applied to any of the reconstruction devices 10 described above. In other examples, the compensation method may be applied to other devices that require correction of errors, without limitation.

The compensation method according to the present disclosure will be described in detail below with reference to the reconstruction device 10, and the reconstruction device 10 will be further described in addition to the compensation method according to the present disclosure.

The compensation method provided by the present disclosure may include obtaining a target reflected light beam L1' based on the target light beam L1 (step S200).

In step S200, first, the generating module 100 may generate the target beam L1. The target light beam L1 may include a first light beam L10 and a second light beam L20. Then, the target light beam L1 generated by the generating module 100 may reach the interference objective lens 300 via reflection of the first light splitting unit 210. While the interference objective lens 300 may decompose the target light beam L1 into a first sub-target light beam L30 and a second sub-target light beam L40, the first sub-target light beam L30 may be reflected via the internal structure of the interference objective lens 300 to form a first sub-target reflected light beam L30', and the second sub-target light beam L40 may reach the target point 21 of the object 20 via the interference objective lens 300 and be reflected by the target point 21 to form a second sub-target reflected light beam L40'. Finally, the first sub-target reflected light beam L30' and the second sub-target reflected light beam L40' may be combined into a target reflected light beam L1' at the interference objective 300.

The first sub-target beam L30 may include a portion of the first beam L10 and a portion of the second beam L20, and the second sub-target beam L40 may also include a portion of the first beam L10 and a portion of the second beam L20. Correspondingly, the first sub-target reflected light beam L30' may include a portion of the first reflected light beam L10' and a portion of the second reflected light beam L20', and the second sub-target reflected light beam L40' may include a portion of the first reflected light beam L10' and a portion of the second reflected light.

In some examples, the first reflected light beam L10 'may form a white light interference signal and the second reflected light beam L20' may form a compensating interference signal.

The compensation method provided by the present disclosure may include adjusting the relative positions of the interference objective lens 300 and the object 20 to cause the first sub-target reflected light beam L30 'and the second sub-target reflected light beam L40' to interfere (step S400).

In some examples, the relative positions of the interference objective lens 300 and the object 20 may be adjusted to cause the first sub-target reflected light beam L30 'and the second sub-target reflected light beam L40' to interfere.

In some examples, the relative positions of the interference objective lens 300 and the object 20 may be adjusted such that the optical path difference between the first sub-target reflected light beam L30 'and the second sub-target reflected light beam L40' is zero. When the optical path difference is zero, the interference phenomenon that can be formed by the first reflected light beam L10' out of the first sub-target reflected light beam L30' and the second sub-target reflected light beam L40' is strongest. The initial height may be obtained based on the white light interference signal at this time.

In some examples, the coherence length of the first light beam L10 may be greater due to the scan stroke. The coherence length of the second light beam L20 is longer and the second reflected light beam L20' can interfere over the whole scanning stroke.

The compensation method provided by the present disclosure may include receiving the first reflected light beam L10 'and the second reflected light beam L20' to obtain a first electrical signal matched with the first reflected light beam L10 'and a second electrical signal matched with the second reflected light beam L20' (step S600).

In some examples, the receiving module 700 may include a first receiving unit 710 and a second receiving unit 720. The target reflected light beam L1' may exit through the interference objective lens 300 and reach the second light splitting unit 220 through the first light splitting unit 210. The second light splitting unit 220 may decouple the target reflected light beam L1' into a first reflected light beam L10' transmitted through the first light splitting unit 210 and a second reflected light beam L20' reflected through the first light splitting unit 210.

In some examples, the first receiving unit 710 may receive the first reflected light beam L10'. In some examples, the first receiving unit 710 may convert the first reflected light beam L10' from an optical signal into an electrical signal (i.e., a first electrical signal). Similarly, the second receiving unit 720 may receive the second reflected light beam L20 'and convert the second reflected light beam L20' from an optical signal to an electrical signal (i.e., a second electrical signal).

In some examples, the first electrical signal may be a white light interference signal. The second electrical signal may be a compensating interference signal.

In some examples, the moments at which the first receiving unit 710 and the second receiving unit 720 receive the optical signals may be the same. In other words, the measurement light path and the compensation light path may collect the optical signal simultaneously. In some examples, the first receiving unit 710 and the second receiving unit 720 may be controlled to synchronously receive the first reflected light beam L10 'and the second reflected light beam L20' based on the timing synchronization unit 410 transmitting the control signal.

The compensation method provided by the present disclosure may include obtaining an initial height of the target point 21 based on the first electrical signal and compensating the initial height based on the second electrical signal (step S800).

Fig. 12 is a schematic diagram showing scan times and scan strokes of a plurality of target points 21 according to the present disclosure. Where t may be the scan time and z may be the scan stroke.

As described above, the object 20 may include a plurality of target points 21. In some examples, the object 20 to be measured may be measured in the scanning direction at a constant speed, and the data of the plurality of target points 21 may be acquired at uniform time intervals to obtain the initial heights of the plurality of target points 21.

Referring to fig. 12, in some examples, the white light interference signal acquired by the measurement light path may include scan non-uniformity errors due to ambient vibration, which may cause the scan motion to deviate from linearity due to the presence of ambient vibration. In some examples, the scan travel of the target point 21 may be linear with scan time if there is no ambient vibration.

As shown in fig. 12, z is a relative displacement between the object 20 to be measured and the interference objective lens 300, essentially corresponding to an optical path difference between the first sub-target reflected light beam L30 'and the second sub-target reflected light beam L40'. Ideally, the heights obtained based on the plurality of data of the acquired target point 21 may be distributed on a straight line. However, since the presence of the environmental vibrations may cause a deviation between the nominal position at the acquisition time and the actual position of the target point 21 (initial height position), the data points in the figure may be represented as deviations of the actual position of the target point 21 from a straight line. Epsilon ₁ 、ε ₂ 、ε ₃ Epsilon ₄ The error (which may be referred to as a position error or a height error) due to environmental vibrations at each acquisition instant may be represented. The compensation method according to the present disclosure may calculate the above-mentioned error in a quantifiable form, thereby compensating for the initial height of the target point 21.

The following details and derives how the error due to the environmental vibration is obtained.

In some examples, the intensity model of the compensated interference signal of the second reflected light beam L20' may be expressed as formula (1):

I(t)＝A+Bcos[θ+φ(t)] (1)

where θ may be the wavefront phase, φ (t) may be the time-varying phase shift, and A and B may be the DC term coefficient and the AC term coefficient, respectively. I (t) may be the light intensity, t being the scan time.

If the second receiving unit 710 collects the compensation interference signals from the kth frame to the p-th frame, the interference light intensities of the kth frame and the p-th frame may be formula (2) and formula (3), respectively:

I _k ＝A+Bcos(θ) (2)

wherein I is _k May be the light intensity of the second reflected light beam L20' at the kth frame, I _p May be the intensity of the second reflected light beam L10' at the p-th frame,may be a phase increment.

In some examples, equation (2) and equation (3) may be further derived to obtain the wavefront phase θ of the target point 21 of the object 20, equation (4):

/>

in some examples, the phase shift delta between two frames may be taken as("four-step phase shift method"), then the wavefront phase θ:

in some examples, the phase truth value at the target point 21 of the second receiving unit 720 may be made θ, since the value range of the tangent function is [ -pi/2, +pi _/2] The period of the function is pi, and the function is based on the light intensity sequence (I ₁ ，I ₂ ，I ₃ ，L I _N ) The interference phase shift of adjacent frames can be calculated:

frames 1-2: θ ₁ ＝θ+δ ₁

Frames 3-4: θ ₂ ＝Mod _π (θ+π+δ ₂ )＝θ+δ ₂

Frames 5-6: θ ₃ ＝Mod _π (θ+2π+δ ₃ )＝θ+δ ₃

…

Kth-1 to k frame: θ _k ＝Mod _π (θ+2π+δ _k/2 )＝θ+δ _k/2

…

N-1 to N frames: θ _N/2 ＝Mod _π (θ+2π+δ _N/2 )＝θ+δ _N/2

Where k=1, 2, …, N/2,δ _k is an additional amount of phase shift caused by vibration noise between the 2k-1 to 2k frames.

In some examples, the above N/2 versions may be added and averaged to yield equation (6):

when the frame rate of acquisition is sufficiently high, the averaged vibration contribution may be near zero:

therefore, the wavefront phase of the surface of the second receiving unit 720 corresponding to the target point 21 of the object 20 can be expressed by the formula (7):

wherein N is the total number of frames acquired, θ _k Indicating the phase change of the target point in the adjacent frame (frames 2k-1 to 2 k),thus, an accurate wavefront phase can be obtained.

In step S800, an error due to environmental vibration may be calculated based on the above-described accurate wavefront phase. In some examples, the error due to environmental vibrations may be referred to as vibration disturbances.

In some examples, the amount of phase shift added to the vibration noise in each frame j may be calculated based on equation (8):

wherein I is _j Is to compensate the light intensity of the interference signal in the j frame, I _j-1 Is the light intensity of the compensating interference signal in the j-1 th frame, a is the direct current term coefficient of the intensity model of the compensating interference signal, and θ is the wavefront phase of the second receiving unit 720 corresponding to the target point 21.

In some examples, the first frame is the initial frame and the phase change due to vibration may be zero, i.e., delta _j =0. Thus, the phase change of the target point 21 due to the vibration in each frame can be obtained based on the formula (8).

In some examples, when a plurality of (gtoreq 3) second receiving units 720 are arranged, different Z-direction translation amounts can be detected on a plurality of target points 21 at the same time, and thus a vibration plane can be fitted, and besides, the translation noise of the target points 21 can be characterized, the angle swing noise of the target points 21 can be also characterized.

In step S800, the initial target point 21 may also be set based on equation (8)The initial height is compensated. In some examples, the vibration of each frame j may be calculated based on the monitoring signal, the vibration of the jth frame causing a phase change of delta _j Correspondingly, the displacement induced in the z-direction can be represented by equation (9):

wherein lambda is _monitor May be the center wavelength of the second light beam L20.

In some examples, the integrated measurement height may be obtained by superimposing the initial height with the vibration disturbance. The integrated measurement height may be obtained, for example, by adding compensation information to the vibration disturbance. Thus, after the vibration disturbance is obtained, the integrated measurement height of the target point 21 can be obtained based on the rule of superposition.

Assuming that the white light interference signal of the first reflected light beam L10' is at the j-th frame, the sequence z is at the z-position _j The sample data at the target point 21 is (z _j ,I _j ) The actual sampling position (the position of the object 20 to be measured) can be z in consideration of displacement due to environmental vibration _j +ε _j Thus, the sampled data can be corrected as:

as can be seen from the above, the uncompensated target spot 21 sampling data may be a regular sequence of positions (initial heights) or a time sequence. However, by calculating the error due to the environmental vibration and compensating the error to the initial height, an irregular, but accurate, sampling of the position sequence (integrated measurement height) or time sequence can be obtained.

In some examples, the compensation method may obtain the integrated measured heights of the plurality of target points 21 of the object 20 based on the above steps.

In summary, the compensation method can obtain the initial height of the target point 21 based on the white light interference signal generated by the first reflected light beam L10'. The initial height may be compensated based on the compensated interference signal of the second reflected light beam L20' throughout the scanning stroke. The compensated initial height may be the integrated measured height.

The present disclosure also provides a reconstruction method for reconstructing the three-dimensional morphology of the object 20 to be measured, hereinafter referred to as reconstruction method. In some examples, the reconstruction method may include step S200, step S400, step S600, and step S800 of the compensation method described above. And will not be described in detail herein.

In some examples, the reconstruction method may further include reconstructing a three-dimensional topography of the object 20 based on the combined measured heights of the plurality of target points 21 (step S1000).

In step S1000, the object 20 to be measured may be further subjected to three-dimensional reconstruction to obtain a phase diagram of the three-dimensional surface morphology of the object 20 to be measured.

In some examples, the object 20 may be reconstructed in three dimensions based on the plurality of corrected sample data. In some examples, the plurality of corrected sample data may be processed by a non-uniform sample analysis method, for example, the signal reconstruction may be performed on the object 20 by a non-uniform DFT to obtain a phase diagram of the three-dimensional surface topography of the object 20.

Fig. 14a is a schematic view showing a three-dimensional surface topography obtained by three-dimensionally reconstructing the object 20 to be measured based on a conventional apparatus and method under a first condition. Fig. 14b is a schematic diagram showing a three-dimensional surface morphology obtained by three-dimensionally reconstructing the object 20 under the first condition by the reconstruction apparatus 10 and the reconstruction method according to the present disclosure.

Referring to fig. 14a and 14b, in some examples, the analyte 20 may be a polished glass with a roughness sa=1.5 nm. Under the condition that the environmental vibration is not greater than 5nm (first condition), the three-dimensional surface morphology obtained by performing three-dimensional reconstruction on the object 20 to be measured through the conventional apparatus and method may be shown in fig. 14a, and the three-dimensional surface morphology obtained by performing three-dimensional reconstruction on the object 20 to be measured through the reconstruction apparatus 10 and the reconstruction method according to the present disclosure may be shown in fig. 14 b.

In some examples, the three-dimensional reconstruction of the test object 20 based on conventional apparatus and methods may result in a surface roughness of 4.501nm and a repeatability of 0.033. The surface roughness obtained by three-dimensionally reconstructing the object 20 to be measured based on the reconstruction device 10 and the compensation method according to the present disclosure may be 1.546nm, and the repeatability may be 1.438.

As can be seen from fig. 14a and 14b, in the case of small environmental vibration, the conventional apparatus and the reconstruction apparatus 10 have no visual effect on the reconstruction of the object 20 to be measured, and the measured value of the conventional apparatus is slightly larger and the repeatability is slightly deteriorated by the surface roughness index analysis.

Fig. 15a is a schematic view showing a three-dimensional surface topography obtained by three-dimensionally reconstructing the object 20 to be measured based on the conventional apparatus and method under the second condition. Fig. 15b is a schematic diagram showing a three-dimensional surface topography obtained by three-dimensionally reconstructing the object 20 under the second condition by the reconstruction apparatus 10 and the compensation method according to the present disclosure.

In some examples, the condition of ambient vibration of about 20nm is referred to as a second condition. In some examples, the surface roughness resulting from three-dimensional reconstruction of the test object 20 based on conventional apparatus and methods may be 7.049nm and the repeatability may be 0.003. The surface roughness obtained by three-dimensionally reconstructing the object 20 to be measured based on the reconstruction device 10 and the compensation method according to the present disclosure may be 1.560nm, and the repeatability may be 0.004.

As can be seen from fig. 15a and 15b, when the environmental vibration amplitude is large, if the conventional reconstruction device 10 is adopted, the reconstructed picture can obviously observe the stripes introduced by the vibration, and meanwhile, the obtained roughness value is larger, and particularly, the repeatability is seriously deteriorated due to the disturbance of random noise; when the reconstruction apparatus 10 and the reconstruction method of the present disclosure are employed, the measured surface roughness, repeatability index and the result in a low noise environment are substantially consistent.

According to the present disclosure, the measurement error due to the environmental vibration can be reduced by the compensation optical path, thereby improving the measurement accuracy of the reconstruction device 10. And the reconstruction device 10 according to the present disclosure can integrate the total optical path into one device, so as to improve the integration level of the reconstruction device 1, and effectively solve the problems of huge volume, huge weight, and the like in the prior art. Meanwhile, the invention also provides a compensation method and a reconstruction method, by the compensation method, errors generated by environmental vibration can be calculated in a quantifiable mode, and then the initial height can be compensated. The compensation method and the reconstruction method can obtain comprehensive measurement precision of a plurality of target points 21 of the object 20 to be measured, and further reconstruct three-dimensional surface morphology of the object 20 to be measured with higher precision.

While the disclosure has been described in detail in connection with the drawings and examples, it is to be understood that the foregoing description is not intended to limit the disclosure in any way. Modifications and variations of the present disclosure may be made as desired by those skilled in the art without departing from the true spirit and scope of the disclosure, and such modifications and variations fall within the scope of the disclosure.

Claims

1. A reconstruction device for white light interference signals, wherein the reconstruction device measures heights of a plurality of target points of an object to be measured based on the white light interference signals and reconstructs the object to be measured based on compensating interference signals and the heights of the plurality of target points, the reconstruction device comprises a generating module, a beam splitting module, an interference objective lens, a receiving module and a data processing module, the generating module is used for generating a target beam comprising a first beam forming the white light interference signals and a second beam forming the compensating interference signals, the beam splitting module comprises a first beam splitting unit and a second beam splitting unit, the first beam splitting unit is configured to receive the target beam and reflect the target beam to the interference objective lens, the target beam forms a target reflected beam at the interference objective lens, and the second beam splitting unit is configured to receive the target reflected beam transmitted through the first beam splitting unit and decouple the target reflected beam into a first reflected beam matched with the first beam and a second reflected beam matched with the second beam; the receiving module comprises a first receiving unit and a plurality of second receiving units, wherein the first receiving unit is used for receiving a first reflected light beam, and the second receiving units are used for receiving a second reflected light beam; the data processing module is configured to acquire initial heights of a plurality of target points based on the first reflected light beams, calculate and acquire height errors of the plurality of target points based on compensation interference signals of the second reflected light beams received by the plurality of second reflecting units in the whole scanning stroke, and synthesize a vibration plane based on the height errors of the plurality of target points; and compensating the initial height based on the height error, compensating for an angular change of the target point based on the vibration plane.

2. The reconstruction device according to claim 1, wherein,

the first receiving unit is configured to receive the first reflected light beam transmitted through the second light splitting unit; the second receiving unit is configured to receive a second reflected light beam reflected via the second light splitting unit.

3. The reconstruction device according to claim 1, wherein,

the generation module includes a first light source for generating a first light beam, a second light source for generating a second light beam, and a third light splitting unit for coupling the first light beam and the second light beam as a target light beam.

4. The reconstruction device according to claim 1, wherein,

the interference objective comprises a fourth light splitting unit and a reference unit,

the fourth beam splitting unit is configured to receive the target beam and split the target beam into a first sub-target beam reflected to the reference unit and a second sub-target beam transmitted to the target point;

the first sub-target beam is reflected to the reference unit via the fourth beam splitting unit and is reflected by the reference unit to form a first sub-target reflected beam;

the second sub-target beam is transmitted to the target point via the fourth beam splitting unit and reflected by the target point to form a second sub-target reflected beam, and the first sub-target reflected beam and the second sub-target reflected beam form a target reflected beam.

5. The reconstruction device according to claim 1, wherein,

a drive module is also included, the drive module configured to adjust a relative position of the interference objective and the target point.

6. The reconstruction device according to claim 3, wherein,

the generation module further includes a first lens unit and a second lens unit disposed between the third light splitting unit and the first light splitting unit.

7. The reconstruction device according to claim 2, wherein,

the receiving module further includes a third lens unit disposed between the second light splitting unit and the first receiving unit, and a fourth lens unit disposed between the second light splitting unit and the second receiving unit.

8. The reconstruction device according to claim 1, wherein,

the bandwidth of the first light beam is not smaller than a first preset value, the bandwidth of the second light beam is not larger than a second preset value, and the first preset value is not smaller than the second preset value.

9. The reconstruction device according to claim 1, wherein,

the data processing module includes a timing synchronization unit configured to send a control signal to the first and second receiving units to synchronize the first and second receiving units to receive the first and second reflected light beams.

10. The reconstruction device according to claim 1 or 9, wherein,

the time of the first receiving unit responding to an optical signal is not less than the response time of the second receiving unit responding to an optical signal.