CN116428967A - A synchronously compensated three-degree-of-freedom laser interferometry device and method - Google Patents

Abstract

The invention discloses a synchronously compensated three-degree-of-freedom laser interferometry device and method, wherein the device includes: a laser emitting unit, a laser beam splitting unit, an interference signal generating unit, and a three-degree-of-freedom solving unit arranged in sequence; wherein, the laser The transmitting unit transmits the laser beam to the laser beam splitting unit; the laser beam splitting unit divides the laser beam into reference light and measuring light with different frequencies; the interference signal generating unit generates an interference signal according to the reference light and measuring light and outputs it to the three-degree-of-freedom solution The calculation unit; the three-degree-of-freedom calculation unit obtains the yaw angle, pitch angle and longitudinal displacement measurement value of the object to be measured according to the interference signal, and synchronously compensates the longitudinal displacement measurement value according to the yaw angle and pitch angle to obtain the actual value of the longitudinal displacement. The invention has a simple and compact structure, adopts a single beam to reduce adjustment errors, and can realize synchronous high-precision measurement of three degrees of freedom of longitudinal displacement, yaw angle and pitch angle of the object to be measured.

Description

A synchronously compensated three-degree-of-freedom laser interferometry device and method

technical field

The invention belongs to the technical field of precision measurement, and in particular relates to a synchronously compensated three-degree-of-freedom laser interferometry device and method.

Background technique

Measurement is the basis of all scientific research and industrial production, and precision measurement refers to measurement with millimeter or higher precision. In precision engineering such as high-end equipment manufacturing and semiconductor industry, nano-scale coordinate measuring machines are usually used to achieve mesoscopic ultra-precision measurement and control. With the development of high-end equipment manufacturing and precision metrology, the demand for measurement accuracy in ultra-precision coordinate measurement technology is increasing. higher.

Laser interferometry technology is a measurement technology that uses the laser wavelength as a scale to perceive displacement information through the frequency and phase changes of the interference spot. It has the advantages of high resolution, good traceability, fast response, and large measurement range. With the improvement of measurement accuracy requirements, the form of laser interferometry must move from single-degree-of-freedom displacement measurement to three-degree-of-freedom simultaneous measurement, so as to improve coordinate measurement accuracy through decoupling of three-degree-of-freedom measurement results.

The existing three-degree-of-freedom laser interferometry technology generally uses the parallel beam interferometry method, and its resolution can reach sub-nanometer level, but the three-degree-of-freedom periodic nonlinear error seriously limits the measurement accuracy, and the extreme control requirements of beam parallelism The complexity of the device structure also brings great challenges to the engineering realization. Therefore, the existing three-degree-of-freedom laser interferometry device cannot meet the needs of ultra-precision measurement.

Contents of the invention

The object of the present invention is to provide a synchronously compensated three-degree-of-freedom laser interferometry device and method to solve the technical problems of the existing three-degree-of-freedom laser interferometry device with complex structure, difficult adjustment and insufficient measurement accuracy.

The purpose of the present invention can be achieved through the following technical solutions:

A synchronously compensated three-degree-of-freedom laser interferometry device, comprising:

A laser emitting unit, a laser beam splitting unit, an interference signal generating unit, and a three-degree-of-freedom computing unit arranged in sequence, and the interference signal generating unit is communicatively connected to the three-degree-of-freedom computing unit;

Wherein, the laser emitting unit emits the laser beam to the laser beam splitting unit;

The laser beam splitting unit divides the laser beam into reference light and measurement light with different frequencies;

The interference signal generation unit generates an interference signal according to the reference light and the measurement light and outputs it to the three-degree-of-freedom solving unit;

The three-degree-of-freedom calculation unit obtains the yaw angle, pitch angle, and longitudinal displacement measurement value of the object to be measured according to the interference signal, and synchronizes the longitudinal displacement measurement value according to the yaw angle and the pitch angle The actual value of the longitudinal displacement of the object to be measured is obtained through compensation.

Optionally, the laser beam splitting unit includes:

An optical fiber splitter, a first sub-optical path and a second sub-optical path arranged in parallel behind the optical fiber splitter;

The fiber beam splitter divides the laser beam into a first sub-beam and a second sub-beam, the first sub-beam enters the first sub-optical path, and the second sub-beam enters the second sub-optical path ;

The first sub-optical path forms the reference light according to the first sub-beam, including a first acousto-optic frequency shifter, a first optical fiber, and a first collimating mirror arranged in sequence;

The second sub-optical path forms the measuring light according to the second sub-beam, including a second acousto-optic frequency shifter, a second optical fiber and a second collimating mirror arranged in sequence.

Optionally, the interference signal generation unit includes:

A beam-splitting prism, a target mirror and a photodetector arranged behind the beam-splitting prism, the target mirror is a mirror preset on the object to be measured;

The target mirror reflects the measuring light to the beam splitting prism; the beam splitting prism transmits the reference light to the photodetector, and reflects the measuring light reflected by the target mirror to the beam splitting prism. a photodetector; the photodetector generates an interference signal according to the reference light and the measurement light, and outputs the interference signal to the three-degree-of-freedom solving unit.

Optionally, the photodetector is a four-quadrant photodetector.

Optionally, the three-degree-of-freedom calculating unit synchronously compensates the longitudinal displacement measured value according to the yaw angle and the pitch angle to obtain the actual value of the longitudinal displacement of the object to be measured, including:

The three-degree-of-freedom calculation unit performs cosine error synchronous compensation on the measured longitudinal displacement according to the following formula to obtain the actual value of the longitudinal displacement of the object to be measured:

Among them, α _x is the yaw angle of the object to be measured, α _y is the pitch angle of the object to be measured, L is the measured value of the longitudinal displacement, and L′ is the actual value of the longitudinal displacement.

The present invention also provides a synchronously compensated three-degree-of-freedom laser interferometry method, using the synchronously compensated three-degree-of-freedom laser interferometry device for measurement, including:

Utilize the laser emitting unit to transmit the laser beam to the laser beam splitting unit;

dividing the laser beam into reference light and measuring light with different frequencies by using a laser beam splitting unit;

using an interference signal generation unit to generate an interference signal according to the reference light and the measurement light and outputting it to a three-degree-of-freedom solving unit;

Using a three-degree-of-freedom calculation unit to obtain the yaw angle, pitch angle, and longitudinal displacement measurement value of the object to be measured according to the interference signal, and synchronously compensate the longitudinal displacement measurement value according to the yaw angle and the pitch angle The actual value of the longitudinal displacement of the object to be measured is obtained.

Optionally, the laser beam splitting unit includes an optical fiber splitter, a first sub-optical path and a second sub-optical path arranged in parallel behind the optical fiber splitter, the first sub-optical path includes first acoustic sub-paths arranged in sequence An optical frequency shifter, a first optical fiber, and a first collimating mirror, the second sub-optical path includes a second acousto-optic frequency shifter, a second optical fiber, and a second collimating mirror arranged in sequence, and the laser beam splitting unit is used to separate the The laser beam is divided into reference light and measurement light with different frequencies, including:

The laser beam is divided into a first sub-beam and a second sub-beam by the fiber beam splitter, the first sub-beam enters the first sub-light path, and the second sub-beam enters the second sub-beam Optical path; the first sub-beam sequentially passes through the first acousto-optic frequency shifter, the first optical fiber and the first collimating mirror to form a reference light, and the second sub-beam sequentially passes through the second The measurement light is formed after the acousto-optic frequency shifter, the second optical fiber and the second collimating mirror.

Optionally, the interference signal generating unit includes a beam splitting prism, a target mirror arranged behind the beam splitting prism, and a photodetector, the target mirror is a mirror preset on the object to be measured, using The interference signal generation unit generates an interference signal according to the reference light and the measurement light and outputs it to the three-degree-of-freedom solving unit including:

using the target reflector to reflect the measurement light to the beam splitting prism;

transmitting the reference light to the photodetector by using the dichroic prism, and reflecting the measurement light reflected by the target reflector to the photodetector;

The photodetector is used to generate an interference signal according to the reference light and the measurement light, and the interference signal is output to the three-degree-of-freedom solving unit.

Optionally, the photodetector is a four-quadrant photodetector.

Optionally, using a three-degree-of-freedom calculating unit to perform synchronous compensation on the longitudinal displacement measurement value according to the yaw angle and the pitch angle to obtain the actual value of the longitudinal displacement of the object to be measured includes:

Using the three-degree-of-freedom calculation unit to perform cosine error synchronous compensation on the longitudinal displacement measurement value according to the following formula, to obtain the actual value of the longitudinal displacement of the object to be measured:

Among them, α _x is the yaw angle of the object to be measured, α _y is the pitch angle of the object to be measured, L is the measured value of the longitudinal displacement, and L′ is the actual value of the longitudinal displacement.

The invention provides a synchronously compensated three-degree-of-freedom laser interferometry device and method, comprising: a laser emitting unit, a laser beam splitting unit, an interference signal generating unit and a three-degree-of-freedom solving unit arranged in sequence, the interference signal generating The unit communicates with the three-degree-of-freedom calculation unit; wherein, the laser emitting unit transmits the laser beam to the laser beam splitting unit; the laser beam splitting unit divides the laser beam into reference beams with different frequencies and measuring light; the interference signal generating unit generates an interference signal according to the reference light and the measuring light and outputs it to the three-degree-of-freedom solving unit; the three-degree-of-freedom calculating unit obtains the Measure the yaw angle, pitch angle and longitudinal displacement measurement value of the object, and synchronously compensate the longitudinal displacement measurement value according to the yaw angle and the pitch angle to obtain the actual value of the longitudinal displacement of the object to be measured.

In view of this, the beneficial effects brought by the present invention are:

In the present invention, a laser beam splitting unit is used to divide a single laser beam emitted by a laser emitting unit into reference light and measuring light with different frequencies, and an interference signal is generated by an interference signal generating unit according to the reference light and measuring light. The two-dimensional deflection angle (yaw angle and pitch angle) and longitudinal displacement measurement value of the object to be measured are obtained from the signal, and the cosine error coupled in the longitudinal displacement measurement value is compensated in real time by using the two-dimensional deflection angle, so as to realize longitudinal displacement, deflection High-precision simultaneous measurement of roll and pitch angles. The invention has the advantages of simple and compact structure, using a single beam to reduce adjustment errors and high measurement accuracy, and is suitable for synchronous high-precision measurement of three-dimensional angles of longitudinal displacement and pitch and yaw two-dimensional angles in the displacement direction, and can Meet the needs of ultra-precision measurement.

Description of drawings

Fig. 1 is the structural representation of measuring device of the present invention;

Fig. 2 is the measurement process schematic diagram of the embodiment of the present invention;

Fig. 3 is a schematic diagram of longitudinal displacement and two-dimensional deflection angles α _x , α _y in an embodiment of the present invention;

Figure 4 is a schematic diagram of differential wavefront sensing;

Fig. 5 is the schematic diagram of cosine error in the embodiment of the present invention;

Fig. 6 is the schematic flow sheet of measuring method of the present invention;

Among them, the frequency-stabilized laser-1, the fiber beam splitter-2, the second acousto-optic frequency shifter-3, the second optical fiber-4, the second collimator-5, the first acousto-optic frequency shifter-6, the second An optical fiber-7, a first collimating mirror-8, a beam splitting prism-9, a target mirror-10, a photoelectric detector-11, and a three-degree-of-freedom computing unit-12.

Detailed ways

Embodiments of the present invention provide a synchronously compensated three-degree-of-freedom laser interferometry device and method to solve the technical problems of complex structure, difficult adjustment, and insufficient measurement accuracy in existing three-degree-of-freedom laser interferometry devices.

In order to facilitate the understanding of the present invention, the present invention will be described more fully below with reference to the associated drawings. A preferred embodiment of the invention is shown in the drawings. However, the present invention can be embodied in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that the disclosure of the present invention will be thorough and complete.

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the technical field of the invention. The terms used herein in the description of the present invention are for the purpose of describing specific embodiments only, and are not intended to limit the present invention. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.

The use of nanometer coordinate measuring machines to achieve mesoscopic ultra-precise measurement and control is a major demand in precision engineering such as high-end equipment manufacturing and the semiconductor industry. Precision coordinate measurement technology has become one of the strategic commanding heights in the field of high-end equipment manufacturing and precision metrology. This poses a limit challenge to laser interferometry technology for three-degree-of-freedom displacement/angle synchronous measurement and measurement accuracy to break through the nano-pointing picometer level.

Laser interferometry technology has the advantages of high resolution, good traceability, fast response, and large measurement range. Compared with the traditional multi-beam three-degree-of-freedom laser interferometry method, the single-beam three-degree-of-freedom laser interferometry method has a simple system architecture. , No need for extreme control of multi-beam parallelism, etc., it is expected to play an important role in the field of multi-degree-of-freedom ultra-precision synchronous measurement.

With the improvement of precision requirements, it is also necessary to change the form of laser interferometry from single-degree-of-freedom displacement measurement to three-degree-of-freedom displacement/angle simultaneous measurement, so as to improve the coordinate measurement accuracy through the decoupling of three-degree-of-freedom measurement results. The reason is that the three-dimensional movement of the displacement stage is realized by the superposition of linear movements of different dimensions. Due to the inevitable non-ideality of the optical path and the guide rail itself, the linear movement must be accompanied by the attitude change and lateral displacement of the measured object, plus The non-ideality of the optical surface of the measured object will directly or indirectly cause the displacement and angle error of the measuring beam, and lead to a series of problems such as Abbe error and cosine error. Therefore, even if the displacement accuracy of the single-degree-of-freedom interferometry unit itself is already better than the nanometer level, the above-mentioned secondary effects caused by angle coupling will greatly restrict the actual coordinate measurement accuracy, and the displacement/angle of the three-degree-of-freedom Synchronize measurements for decoupling and correction.

At present, the three-degree-of-freedom laser interferometry technology cannot meet the above-mentioned ultra-precision measurement requirements. The commonly used parallel beam interferometry method can achieve sub-nanometer resolution, but the three-degree-of-freedom periodic nonlinear error seriously limits the measurement accuracy. Implementation poses major challenges. In contrast, the single-beam three-degree-of-freedom laser interferometry method has shown its advantages and potential because it breaks through the limitation of multi-beam in principle, and is expected to play an important role in the future three-degree-of-freedom measurement.

Three-degree-of-freedom laser interferometry methods can be divided into two categories: multi-beam and single-beam according to the number of beams used. The former is called parallel beam interferometry, which is currently the most widely used and most accurate three-degree-of-freedom laser interferometry method; the latter can be divided into single-beam heterodyne interferometry and single-beam homodyne interferometry according to the interference method. Two, the heterodyne method is called the differential wavefront interferometry method, which is mainly oriented to the detection of gravitational waves in space, and then it is simplified and introduced into the research of three-degree-of-freedom laser interferometry; the homodyne method is called the improved Tyman- The Green interferometry method, which improves the Tieman-Green interferometry method originally oriented to the surface detection of optical components, is used for multi-degree-of-freedom laser interferometry. At present, there are few related research works and it is still in its infancy. Although the parallel beam interferometry method has the advantages of high resolution, large measuring range, and good traceability, it still has limitations. It is currently unable to achieve three-degree-of-freedom ultra-precision measurement, which is prominently reflected in periodic nonlinearity. Error and beam parallelism etc.

In addition, the three-degree-of-freedom laser interferometry based on the parallel beam measurement method also has the following limitations in principle or application:

(1) In the parallel beam measurement method, the displacement measurements of the three measuring optical axes are relatively independent and the beams are separated by a certain distance. When the measurement distance is large, the turbulence in the air will cause different degrees of disturbance to each measurement beam, which will be directly reflected in the obvious angle measurement instability.

(2) The displacement measurement on each beam is three sets of relatively independent measurement data, and these three sets of relatively independent measurements require strict timing guarantees to give effective measurement results.

(3) The change of the angle of the mirror under test will change the angle of the reflected light. With the increase of this angle, the interference signal will change from bright and dark spots to light and dark stripes, thereby rapidly reducing the contrast of the interference signal. The angle measurement range is limited.

(4) The three-degree-of-freedom laser interferometry method currently lacks a true two-dimensional angle calibration and a complete error model derived from it.

Another representative method that can realize three-degree-of-freedom precision laser interferometry is Differential Wavefront Sensing (DWS), which is mainly oriented to the field of gravitational wave detection in deep space. The core idea is to use a position sensitive device (usually a four-quadrant detector) to differentially detect the phases of different regions (quadrants) in the interference signal, and then calculate the wavefront angle between the measurement light and the reference light. This method was originally proposed to solve a series of problems caused by the position and attitude errors of optical components in gravitational wave detection. With the rise of space exploration projects such as space gravitational wave detection and next-generation gravity field inversion, this technology is currently mainly used to solve the problem of interstellar baseline length measurement and its angular coupling error in the process of large-scale displacement measurement.

In the actual measurement process, the target to be measured cannot perform an ideal single-axis movement, and its movement process is often accompanied by attitude changes and lateral displacements. The resulting longitudinal displacement measurement error will greatly limit the single-degree-of-freedom laser interferometer. Measurement accuracy, in order to solve this problem and meet the high-precision measurement of various micro components, complex surfaces, microelectronic devices and precision optical components, the laser interferometry device has changed from single-degree-of-freedom displacement measurement to three-degree-of-freedom displacement-angle synchronization The direction of measurement is developing, and the displacement measurement results are corrected by measuring the two-dimensional angle information of the target to be measured to further improve the measurement accuracy. In order to compensate the measurement deviation, the rotation angle must be measured simultaneously, single-beam measurement based on fringe analysis or differential sensing technology uses only one measurement beam to simultaneously obtain the displacement and the rotation angle. The DWS technology in the differential sensing technology is more suitable for large-scale displacement measurement because it can obtain a larger angle measurement range.

The existing three-degree-of-freedom laser interferometry method has the limitations of numerous optical components, complex system structure, difficult adjustment, and the use of multiple beams, which is limited by the difficulty of further improving the accuracy of optical path adjustment errors. The present invention provides a synchronous The compensated three-degree-of-freedom laser interferometry device and method is a three-degree-of-freedom ultra-precision laser interferometry device and method based on cosine error synchronous compensation, and uses the obtained high-precision two-dimensional deflection angle of the target mirror to measure the longitudinal displacement Results The cosine error correction was carried out to realize the ultra-precise synchronous measurement of displacement, yaw angle and pitch angle. It has the advantages of simple and compact structure, using a single beam to reduce adjustment errors, and high measurement accuracy.

The purpose of the present invention is to overcome the limitations of the existing three-degree-of-freedom laser interferometry method, such as complex structure, difficult adjustment, and difficulty in further improving the accuracy of optical path adjustment errors due to the use of multiple beams. A high-precision three-degree-of-freedom measurement method for error synchronization compensation. The present invention uses differential wavefront sensing technology to measure displacement, and at the same time obtains the two-dimensional deflection angle caused by the inclination of the measuring mirror (target mirror) during the displacement measurement process, and utilizes the two-dimensional angle to couple in the longitudinal displacement measurement result The cosine error is compensated in real time, so as to realize the high-precision synchronous measurement of displacement, yaw angle and pitch angle.

Please refer to Fig. 1 and Fig. 2, the present invention provides a kind of embodiment of the three-degree-of-freedom laser interferometry device of synchronous compensation, comprising:

A laser emitting unit, a laser beam splitting unit, an interference signal generating unit, and a three-degree-of-freedom computing unit arranged in sequence, and the interference signal generating unit is communicatively connected to the three-degree-of-freedom computing unit;

Wherein, the laser emitting unit emits the laser beam to the laser beam splitting unit;

The laser beam splitting unit divides the laser beam into reference light and measurement light with different frequencies;

The interference signal generation unit generates an interference signal according to the reference light and the measurement light and outputs it to the three-degree-of-freedom solving unit;

The three-degree-of-freedom calculation unit obtains the yaw angle, pitch angle, and longitudinal displacement measurement value of the object to be measured according to the interference signal, and synchronizes the longitudinal displacement measurement value according to the yaw angle and the pitch angle The actual value of the longitudinal displacement of the object to be measured is obtained through compensation.

In this embodiment, the laser emitting unit emits the laser beam to the laser beam splitting unit. Preferably, the laser emitting unit may be a frequency-stabilized laser, and the frequency-stabilized laser emits a laser beam with a frequency f ₀ to the laser beam splitting unit.

Specifically, the laser beam splitting unit may include: an optical fiber splitter 2, a first sub-optical path and a second sub-optical path arranged in parallel behind the optical fiber splitter 2; wherein, the optical fiber splitter 2 divides the laser beam into the first A sub-beam and a second sub-beam, the first sub-beam enters the first sub-optical path, and the second sub-beam enters the second sub-optical path.

In a preferred embodiment, the function of the first sub-optical path is to form a reference light according to the first sub-beam, and the first sub-optical path may include a first acousto-optic frequency shifter 6, a first optical fiber 7 and a first collimating mirror 8 arranged in sequence The function of the second sub-optical path is to form measurement light according to the second sub-beam, and the second sub-optical path may include a second acousto-optic frequency shifter 3, a second optical fiber 4 and a second collimating mirror 5 arranged in sequence.

It should be noted that the frequency shift amounts of the first acousto-optic frequency shifter 6 and the second acousto-optic frequency shifter 3 are different. In an embodiment of the present invention, the frequency shift amount of the first AO frequency shifter 6 is f1, and the frequency shift amount of the second AO frequency shifter 3 is f ₂ , f ₁ ≠ f ₂ .

The laser beam with a frequency of f ₀ is divided into two sub-beams, the first sub-beam and the second sub-beam after passing through the fiber beam splitter 2. The first sub-beam enters the first sub-optical path to form a reference light, and the second sub-beam enters the second Two sub-light paths are used to form measurement light. It should be noted that it is also possible that the second sub-beam enters the first sub-optical path to form the reference light, and the first sub-beam enters the second sub-optical path to form the measurement light.

In a preferred embodiment, the first sub-beam enters the first sub-optical path, and after successively passing through the first acousto-optic frequency shifter 6 with a frequency shift of f1, the first optical fiber 7 and the first collimating mirror 8, the formed frequency is _f0 +f ₁ reference light; the second sub-beam enters the second sub-optical path, and after passing through the second acousto-optic frequency shifter 3 with a frequency shift of f ₂ , the second optical fiber 4 and the second collimator 5, the frequency is formed is the measuring light of f ₀ +f ₂ .

In this embodiment, before the measurement, the target reflector 10 is pre-installed on the target object to be measured (referred to as the object to be measured), and the measurement light has an included angle with the reference light after being reflected by the movable target reflector 10 (also It is called deflection angle) θ, and the two beams are combined to form a heterodyne interference signal. The measurement light and the reference light are coherently mixed on the surface of the photodetector 11 (such as a four-quadrant photodetector), and the forming frequency is |f ₁ -f ₂ | beat frequency signal (interference signal), read the output signal of the four-quadrant photodetector 11.

Differential wavefront sensing technology is used for displacement measurement, and at the same time, the two-dimensional deflection angle caused by the tilt of the measuring mirror (target mirror) is obtained during the displacement measurement process, and the cosine error coupled in the longitudinal displacement measurement result is calculated by using the two-dimensional angle Real-time compensation is performed to realize high-precision simultaneous measurement of displacement, yaw angle and pitch angle.

It should be noted that the target reflector 10 is preset on the object to be measured and moves together with the object to be measured, therefore, the three-degree-of-freedom measurement value of the target reflector 10 can be equivalent to the three-degree-of-freedom measurement of the object to be measured value.

In this embodiment, please refer to FIG. 3 and FIG. 4. The three-degree-of-freedom calculation unit 12 obtains the interference signal output by the photodetector 11, and performs calculations based on the interference signal to obtain the yaw angle α _x and the pitch angle α of the object to be measured. _y and the longitudinal displacement measurement value L, that is, the three-degree-of-freedom measurement value of the object to be measured is obtained, as shown in formula (1); then, the longitudinal displacement measurement value is synchronously compensated according to the yaw angle and the pitch angle, and the object to be measured is obtained The actual value of the longitudinal displacement.

Among them, L is the longitudinal displacement measurement value, the unit is m; α _x is the yaw angle, the unit is rad; α _y is the pitch angle, the unit is rad; ∝ is proportional to, φ _A , φ _B , φ _C , φ _D is the phase shift detected by each quadrant in the four-quadrant photodetector 11, and the unit is rad; δ _x is a preset yaw angle scaling factor, and δ _y is a preset pitch angle scaling factor.

It should be noted that the two scale factors δ _x and δ _y are obtained through calibration before the experiment, and the accuracy is determined by the measurement accuracy of the scale factor and the phase measurement accuracy, which belong to the content of differential wavefront sensing technology and will not be discussed here. repeat.

Please refer to FIG. 3 , the three-degree-of-freedom calculating unit 12 calculates the deflection angle θ between the measurement light and the reference light by using formula (2) according to the obtained two-dimensional deflection angles α _x , α _y of the target mirror 10:

Please refer to FIG. 5 , after calculating the deflection angle θ between the measurement light and the reference light, the three-degree-of-freedom calculation unit 12 further calculates the longitudinal displacement between the four-quadrant photodetector 11 and the target mirror 10 according to the deflection angle θ The actual value (actual distance) L', as shown in formula (3):

Of course, formula (2) and formula (3) can also be combined to obtain formula (4), and the three-degree-of-freedom solving unit 12 obtains the yaw angle α _x , the pitch angle α _y and the measured value of the longitudinal displacement of the object to be measured After L, use the formula (4) to correct the cosine error of the longitudinal displacement measurement value, and perform synchronous compensation on the longitudinal displacement measurement value, and solve the actual value L′ of the longitudinal displacement of the object to be measured:

That is, the three-degree-of-freedom calculation unit 12 uses the obtained high-precision two-dimensional deflection angles α _x and α _y of the target mirror 10 to perform cosine error correction on the longitudinal displacement measurement result L to obtain the high-precision two-dimensional deflection angle α of the target mirror 10 The measurement results of three degrees of freedom of _x , α _y and the actual value of longitudinal displacement L′ realize the ultra-precise simultaneous measurement of the yaw angle, pitch angle and longitudinal displacement of the object to be measured (target mirror 10).

It can be understood that the actual values of the yaw angle, pitch angle and longitudinal displacement of the object to be measured are finally obtained by using the three-degree-of-freedom calculating unit 12 . The four-quadrant photodetector in this embodiment adopts differential wavefront sensing technology, which can simultaneously measure the longitudinal displacement information and the two-dimensional angle deflection information of the target reflector, and the measured two-dimensional deflection angle of the target reflector is used for longitudinal displacement The cosine error correction is carried out on the measurement results, which further improves the measurement accuracy of the longitudinal displacement and realizes the simultaneous ultra-precision measurement of the three degrees of freedom of the object to be measured.

The synchronously compensated three-degree-of-freedom laser interferometry device provided in this embodiment uses a laser beam splitting unit to divide a single laser beam emitted by a laser emitting unit into reference light and measuring light with different frequencies, and the interference signal generating unit according to the reference light and measurement light The measurement light generates an interference signal, and the three-degree-of-freedom calculation unit obtains the two-dimensional deflection angle (yaw angle and pitch angle) and the measured value of the longitudinal displacement of the object to be measured according to the interference signal, and uses the two-dimensional deflection angle to calculate the measured value of the longitudinal displacement The coupled cosine error is compensated in real time, so as to realize the high-precision simultaneous measurement of longitudinal displacement, yaw angle and pitch angle. The invention has the advantages of simple and compact structure, using a single beam to reduce adjustment errors and high measurement accuracy, and is suitable for synchronous high-precision measurement of three-dimensional angles of longitudinal displacement and pitch and yaw two-dimensional angles in the displacement direction, and can Meet the needs of ultra-precision measurement.

Please refer to Fig. 6, the present invention also provides an embodiment of a synchronously compensated three-degree-of-freedom laser interferometry method, using the synchronously compensated three-degree-of-freedom laser interferometry device for measurement, including:

Utilize the laser emitting unit to transmit the laser beam to the laser beam splitting unit;

dividing the laser beam into reference light and measuring light with different frequencies by using a laser beam splitting unit;

using an interference signal generation unit to generate an interference signal according to the reference light and the measurement light and outputting it to a three-degree-of-freedom solving unit;

Using a three-degree-of-freedom calculation unit to obtain the yaw angle, pitch angle, and longitudinal displacement measurement value of the object to be measured according to the interference signal, and synchronously compensate the longitudinal displacement measurement value according to the yaw angle and the pitch angle The actual value of the longitudinal displacement of the object to be measured is obtained.

In this embodiment, the laser beam splitting unit includes a fiber beam splitter 2, a first sub-optical path and a second sub-optical path arranged in parallel behind the fiber optic splitter 2, and the first sub-optical path includes first acousto-optic frequency shifting arranged in sequence 6, the first optical fiber 7 and the first collimating mirror 8, the second sub-optical path includes the second acousto-optic frequency shifter 3, the second optical fiber 4 and the second collimating mirror 5 arranged in sequence, and the laser beam splitting unit is used to divide the The laser beam is divided into reference light and measuring light with different frequencies including:

Fiber beam splitter 2 is used to divide the laser beam into a first sub-beam and a second sub-beam, the first sub-beam enters the first sub-optical path, and the second sub-beam enters the second sub-optical path; the first sub-beam passes through the first acoustic After the optical frequency shifter 6, the first optical fiber 7 and the first collimating mirror 8, the reference light is formed, and the second sub-beam is formed after passing through the second acousto-optic frequency shifter 3, the second optical fiber 4 and the second collimating mirror 5 in sequence Measure light.

In one embodiment of the present invention, the interference signal generating unit includes a beam splitting prism 9, a target mirror 10 arranged behind the beam splitting prism 9, and a photodetector 11, and the target mirror 10 is a mirror preset on the object to be measured , using the interference signal generation unit to generate the interference signal according to the reference light and the measurement light and outputting it to the three-degree-of-freedom solving unit includes:

Utilize target reflector 10 to reflect measurement light to beam splitting prism 9;

Use the dichroic prism 9 to transmit the reference light to the photodetector 11, and reflect the measurement light reflected by the target reflector 10 to the photodetector 11;

The interference signal is generated by the photodetector 11 according to the reference light and the measurement light, and the interference signal is output to the three-degree-of-freedom solving unit 12 .

Preferably, the photodetector 11 in this embodiment is a four-quadrant photodetector.

In one embodiment of the present invention, using the three-degree-of-freedom calculating unit 12 to perform synchronous compensation on the longitudinal displacement measurement value according to the yaw angle and the pitch angle to obtain the actual value of the longitudinal displacement of the object to be measured includes:

Using the three-degree-of-freedom calculation unit 12 to perform cosine error synchronous compensation on the longitudinal displacement measurement value according to the following formula, the actual value of the longitudinal displacement of the object to be measured is obtained:

Among them, α _x is the yaw angle of the object to be measured, α _y is the pitch angle of the object to be measured, L is the measured value of the longitudinal displacement, and L′ is the actual value of the longitudinal displacement.

The measurement method provided by the present invention is a high-precision three-degree-of-freedom measurement method based on cosine error synchronous compensation. The specific steps of the method are as follows:

Step 1. The frequency-stabilized laser outputs a laser beam with a frequency f _0. The laser beam is divided into two beams and passes through different acousto-optic frequency shifters respectively. After frequency shifting, the output frequency is f ₀ + f ₁ reference light and the frequency is f Measuring light at ₀ +f ₂ .

Step 2: Install the target reflector 10 on the target object to be measured, the target reflector 10 moves together with the target object, the measurement light has an angle θ with the reference light after being reflected by the movable target reflector 10, the combination of the two The beam forms the heterodyne interference signal, the measurement light and the reference light are coherently mixed on the surface of the four-quadrant photodetector to form a beat frequency signal with a frequency of |f ₁ -f ₂ |, and the output signal of the four-quadrant photodetector is read.

Step 3, using the three-degree-of-freedom calculation unit to solve the output signal of the four-quadrant photodetector to obtain the measured values of the two-dimensional deflection angles α _x , α _y and the longitudinal displacement L of the target mirror 10;

Calculate the deflection angle θ between the measurement light and the reference light according to the obtained two-dimensional deflection angles α _x , α _y of the target mirror 10;

Further according to the deflection angle θ of the measuring light and the reference light, the actual distance L' between the four-quadrant photodetector and the target reflector 10 is solved;

That is, use the obtained high-precision two-dimensional deflection angles α _x , α _y of the target mirror 10 to perform cosine error correction on the longitudinal displacement measurement result L, and obtain the high-precision two-dimensional deflection angles α _x , α _y and the longitudinal displacement of the target mirror 10 The measurement results of three degrees of freedom of L′ realize the ultra-precise simultaneous measurement of the yaw angle, pitch angle and displacement of the target mirror 10 .

The purpose of the present invention is to overcome the limitations of the existing three-degree-of-freedom laser interferometry method, such as complex structure, difficult adjustment, and difficulty in further improving the accuracy of optical path adjustment errors due to the use of multiple beams. A high-precision three-degree-of-freedom measurement method for error synchronization compensation. This method uses differential wavefront sensing technology for displacement measurement, and at the same time obtains the two-dimensional deflection angle caused by the inclination of the measuring mirror (target mirror) during the displacement measurement process, and uses the two-dimensional angle to analyze the coupling in the longitudinal displacement measurement results. The cosine error is compensated in real time, so as to realize the high-precision synchronous measurement of displacement, yaw angle and pitch angle.

The present invention has following characteristics and beneficial effect:

The differential wavefront sensing technology can simultaneously measure the longitudinal displacement information and the two-dimensional angle deflection information of the target mirror. At the same time, the cosine error correction is carried out on the longitudinal displacement measurement result through the measured two-dimensional deflection angle of the target mirror, which further improves the Displacement measurement accuracy, realizing three-degree-of-freedom synchronous precision measurement, has the advantages of simple and compact structure, using a single beam to reduce adjustment errors, and high measurement accuracy. The invention is suitable for the synchronous high-precision measurement of the three-dimensional angles of longitudinal displacement and pitch and yaw two-dimensional angles in the displacement direction.

Those skilled in the art can clearly understand that for the convenience and brevity of the description, the specific working process of the above-described system, device and unit can refer to the corresponding process in the foregoing method embodiment, which will not be repeated here.

In the embodiments provided in this application, it should be understood that the disclosed systems, devices and methods may be implemented in other ways. For example, the device embodiments described above are only illustrative. For example, the division of the units is only a logical function division. In actual implementation, there may be other division methods. For example, multiple units or components can be combined or May be integrated into another system, or some features may be ignored, or not implemented. In another point, the mutual coupling or direct coupling or communication connection shown or discussed may be through some interfaces, and the indirect coupling or communication connection of devices or units may be in electrical, mechanical or other forms.

The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place, or may be distributed to multiple network units. Part or all of the units can be selected according to actual needs to achieve the purpose of the solution of this embodiment.

In addition, each functional unit in each embodiment of the present invention may be integrated into one processing unit, each unit may exist separately physically, or two or more units may be integrated into one unit. The above-mentioned integrated units can be implemented in the form of hardware or in the form of software functional units.

If the integrated unit is realized in the form of a software function unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on such an understanding, the essence of the technical solution of the present invention or the part that contributes to the prior art or all or part of the technical solution can be embodied in the form of a software product, and the computer software product is stored in a storage medium , including several instructions to make a computer device (which may be a personal computer, a server, or a network device, etc.) execute all or part of the steps of the method described in each embodiment of the present invention. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), magnetic disk or optical disk, and other media that can store program codes.

The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: it can still be described in the foregoing embodiments Modifications are made to the recorded technical solutions, or equivalent replacements are made to some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims (10)

1. A three-degree-of-freedom laser interferometry device for synchronous compensation, characterized in that it comprises: A laser emitting unit, a laser beam splitting unit, an interference signal generating unit, and a three-degree-of-freedom computing unit arranged in sequence, and the interference signal generating unit is communicatively connected to the three-degree-of-freedom computing unit; Wherein, the laser emitting unit emits the laser beam to the laser beam splitting unit; The laser beam splitting unit divides the laser beam into reference light and measurement light with different frequencies; The interference signal generation unit generates an interference signal according to the reference light and the measurement light and outputs it to the three-degree-of-freedom solving unit; The three-degree-of-freedom calculation unit obtains the yaw angle, pitch angle, and longitudinal displacement measurement value of the object to be measured according to the interference signal, and synchronizes the longitudinal displacement measurement value according to the yaw angle and the pitch angle The actual value of the longitudinal displacement of the object to be measured is obtained through compensation. 2. The three-degree-of-freedom laser interferometry device for synchronous compensation according to claim 1, wherein the laser beam splitting unit comprises: An optical fiber splitter, a first sub-optical path and a second sub-optical path arranged in parallel behind the optical fiber splitter; The fiber beam splitter divides the laser beam into a first sub-beam and a second sub-beam, the first sub-beam enters the first sub-optical path, and the second sub-beam enters the second sub-optical path ; The first sub-optical path forms the reference light according to the first sub-beam, including a first acousto-optic frequency shifter, a first optical fiber, and a first collimating mirror arranged in sequence; The second sub-optical path forms the measurement light according to the second sub-beam, including a second acousto-optic frequency shifter, a second optical fiber, and a second collimator arranged in sequence, and the first acousto-optic frequency shifter It is different from the frequency shift amount of the second acousto-optic frequency shifter. 3. the three-degree-of-freedom laser interferometry device of synchronous compensation according to claim 1, is characterized in that, described interference signal generation unit comprises: A beam-splitting prism, a target mirror and a photodetector arranged behind the beam-splitting prism, the target mirror is a mirror preset on the object to be measured; The target mirror reflects the measuring light to the beam splitting prism; the beam splitting prism transmits the reference light to the photodetector, and reflects the measuring light reflected by the target mirror to the beam splitting prism. a photodetector; the photodetector generates an interference signal according to the reference light and the measurement light, and outputs the interference signal to the three-degree-of-freedom solving unit. 4 . The synchronously compensated three-degree-of-freedom laser interferometry device according to claim 3 , wherein the photodetector is a four-quadrant photodetector. 5. The synchronously compensated three-degree-of-freedom laser interferometry device according to claim 1, wherein the three-degree-of-freedom calculating unit performs a measurement of the longitudinal displacement according to the yaw angle and the pitch angle Performing synchronous compensation to obtain the actual value of the longitudinal displacement of the object to be measured includes: The three-degree-of-freedom calculation unit performs cosine error synchronous compensation on the measured longitudinal displacement according to the following formula to obtain the actual value of the longitudinal displacement of the object to be measured:

Among them, α _x is the yaw angle of the object to be measured, α _y is the pitch angle of the object to be measured, L is the measured value of the longitudinal displacement, and L′ is the actual value of the longitudinal displacement. 6. a three-degree-of-freedom laser interferometry method of synchronous compensation, is characterized in that, utilizes the three-degree-of-freedom laser interferometry device of synchronous compensation as any one of claims 1 to 5 to measure, comprising: Utilize the laser emitting unit to transmit the laser beam to the laser beam splitting unit; dividing the laser beam into reference light and measuring light with different frequencies by using a laser beam splitting unit; using an interference signal generation unit to generate an interference signal according to the reference light and the measurement light and outputting it to a three-degree-of-freedom solving unit; Using a three-degree-of-freedom calculation unit to obtain the yaw angle, pitch angle, and longitudinal displacement measurement value of the object to be measured according to the interference signal, and synchronously compensate the longitudinal displacement measurement value according to the yaw angle and the pitch angle The actual value of the longitudinal displacement of the object to be measured is obtained. 7. The three-degree-of-freedom laser interferometry method of synchronous compensation according to claim 6 is characterized in that, the laser beam splitting unit comprises an optical fiber beam splitter, a first sub-unit that is arranged in parallel behind the optical fiber beam splitter An optical path and a second sub-optical path, the first sub-optical path includes a first acousto-optic frequency shifter, a first optical fiber, and a first collimating mirror arranged in sequence, and the second sub-optical path includes a second acousto-optic frequency shifter arranged in sequence A frequency converter, a second optical fiber and a second collimating mirror, using a laser beam splitting unit to divide the laser beam into reference light and measurement light with different frequencies include: The laser beam is divided into a first sub-beam and a second sub-beam by the fiber beam splitter, the first sub-beam enters the first sub-light path, and the second sub-beam enters the second sub-beam Optical path; the first sub-beam sequentially passes through the first acousto-optic frequency shifter, the first optical fiber and the first collimating mirror to form a reference light, and the second sub-beam sequentially passes through the second The measurement light is formed after the acousto-optic frequency shifter, the second optical fiber and the second collimating mirror. 8. the three-degree-of-freedom laser interferometry method of synchronous compensation according to claim 6, is characterized in that, described interference signal generating unit comprises beam splitting prism, is arranged on the target mirror and photodetector behind described beam splitting prism, The target mirror is a mirror preset on the object to be measured, and the interference signal generated by the interference signal generation unit according to the reference light and the measurement light and output to the three-degree-of-freedom calculation unit includes: using the target reflector to reflect the measurement light to the beam splitting prism; transmitting the reference light to the photodetector by using the dichroic prism, and reflecting the measurement light reflected by the target reflector to the photodetector; The photodetector is used to generate an interference signal according to the reference light and the measurement light, and the interference signal is output to the three-degree-of-freedom solving unit. 9. The three-degree-of-freedom laser interferometry method with synchronous compensation according to claim 8, wherein the photodetector is a four-quadrant photodetector. 10. The three-degree-of-freedom laser interferometry method for synchronous compensation according to claim 6, wherein a three-degree-of-freedom calculation unit is used to perform a measurement on the longitudinal displacement measurement value according to the yaw angle and the pitch angle Synchronous compensation to obtain the actual value of the longitudinal displacement of the object to be measured includes: Using the three-degree-of-freedom calculation unit to perform cosine error synchronous compensation on the longitudinal displacement measurement value according to the following formula, to obtain the actual value of the longitudinal displacement of the object to be measured:

Among them, α _x is the yaw angle of the object to be measured, α _y is the pitch angle of the object to be measured, L is the measured value of the longitudinal displacement, and L′ is the actual value of the longitudinal displacement.

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