CN106403821A - Displacement sensor, usage and manufacturing method thereof and interferometer - Google Patents

Abstract

The invention discloses a displacement sensor and its use, manufacturing method and an interferometer, wherein the displacement sensor includes: a semiconductor laser for generating a laser beam; a diffraction grating for converting a part of the laser beam The light is directly diffracted and then reflected to generate the first diffracted light; at the same time, it is used to diffract a part of the laser beam that passes through itself, reaches the object to be measured, and passes through itself again after being reflected by the object to be measured to form the second diffraction Light; the detector is located at the intersection of the first diffracted light to be measured and the preset diffracted light of the same order in the second diffracted light, and is used to measure the preset diffracted light of the same order in the first diffracted light and the second diffracted light The change of the interference intensity information between them; the information processor, connected with the detector, is used to read the interference intensity signal, and invert the displacement information of the object to be measured according to the interference intensity change information detected by the detector; the diffraction The grating is located between the semiconductor laser and the object to be measured.

Description

Displacement sensor, its use, manufacturing method and an interferometer

technical field

The present invention relates to the technical field of Micro Optic Electro Mechanical System (MOEMS), in particular to a displacement sensor.

Background technique

Displacement refers to the offset generated by the position of the object relative to the reference point. Among many physical quantities, displacement is easy to detect and obtain high-precision detection results compared with other quantities. Therefore, the mechanical quantity of the measured object is often converted into displacement to detect. For example, the acceleration is converted into the displacement of the mass block, and the expansion is converted into the displacement of the surface of the object. Small displacement measurement is the basis of measurement technologies such as pressure, acceleration, flow, temperature, vibration, etc. Large displacement measurement is the foundation of automated production lines (such as the movement of manipulators), industrial testing (such as expansion), and online monitoring (such as vibration).

The photoelectric displacement sensor converts the displacement information into optical information, which is reflected by the light intensity detected by the photodiode. The photoelectric displacement sensor has the advantages of non-contact measurement, fast test speed, high precision, small test point, etc., and has been widely researched and applied. Existing photoelectric displacement tests mainly include laser triangulation, Moiré fringe method, double-beam interferometry, and dual-frequency laser interferometry based on the Doppler effect. It is relatively complicated and cannot meet the requirements of small size, easy integration, high reliability and low power consumption in the development of modern industry.

The two-beam interferometry method is based on Michelson interferometer, and uses the change of two-beam interference intensity to reflect the information of displacement. The inversion of the displacement information of the measured object from the interference intensity has been widely studied, and the displacement measurement accuracy can reach more than one percent of the detection light wavelength by using the sinusoidal phase modulation method. In a two-beam interferometry system, the coherence length of the light source determines the maximum range that can be measured. Most of the light sources in existing large-range two-beam interferometry systems are provided by He-Ne lasers, but the He-Ne laser itself is relatively large, which fundamentally affects the volume of large-displacement two-beam interferometry systems.

Contents of the invention

In order to solve the existing technical problems, the embodiment of the present invention expects to provide a displacement sensor and an interferometer with the characteristics of miniaturization, easy integration, high reliability and low power consumption.

The technical scheme of the embodiment of the present invention is realized like this:

An embodiment of the present invention provides a displacement sensor, which includes:

Semiconductor lasers for generating laser beams;

The diffraction grating is used to directly diffract and then reflect a part of the light in the laser beam to generate the first diffracted light; at the same time, it is used to pass the laser beam through itself to reach the object to be measured, and after being reflected by the object to be measured Part of the light passing through itself is diffracted again to form the second diffracted light;

The detector is located at the intersection of the first diffracted light to be measured and the preset diffracted light of the same order in the second diffracted light, and is used to measure the difference between the first diffracted light and the preset diffracted light of the same order in the second diffracted light The change of the interference intensity information;

An information processor, connected to the detector, is used to read the interference intensity signal, and invert the displacement information of the object to be measured according to the interference intensity change information detected by the detector;

The diffraction grating is located between the semiconductor laser and the object to be measured.

In the above solution, the displacement sensor also includes:

The diffraction grating modulation and demodulation device is used for introducing periodic vibrations to the diffraction grating and demodulating the interference intensity information detected by the detector.

In the above solution, the displacement sensor also includes:

The reflected light collection device is used to collect the light reflected by the object to be measured, so that the intensity of the detected second diffracted light is equivalent to that of the preset same order diffracted light in the first diffracted light.

In the above solution, the semiconductor laser is a long coherence distance semiconductor laser.

The present invention also provides an interferometer, which includes:

Semiconductor lasers for generating laser beams;

The diffraction grating is used to directly diffract and then reflect a part of the light in the laser beam to generate the first diffracted light; at the same time, it is used to pass the laser beam through itself to reach the object to be measured, and after being reflected by the object to be measured Part of the light passing through itself is diffracted again to form the second diffracted light;

The detector is located at the intersection of the first diffracted light to be measured and the preset diffracted light of the same order in the second diffracted light, and is used to measure the difference between the first diffracted light and the preset diffracted light of the same order in the second diffracted light The change of the interference intensity information.

In the above scheme, the interferometer also includes:

The diffraction grating modulation and demodulation device is used for introducing periodic vibrations to the diffraction grating and demodulating the interference intensity information detected by the detector.

In the above scheme, the interferometer also includes:

The reflected light collection device is used to collect the light reflected by the object to be measured, so that the intensity of the detected second diffracted light is equivalent to that of the preset same order diffracted light in the first diffracted light.

In the above solution, the semiconductor laser is a long coherence distance semiconductor laser.

The present invention also provides a method for using a displacement sensor, the method comprising:

A semiconductor laser produces a laser beam;

The diffraction grating directly diffracts and then reflects a part of the laser beam to generate the first diffracted light; at the same time, the diffraction grating passes the laser beam through itself, reaches the object to be measured, and passes through it again after being reflected by the object to be measured. Part of its own light is diffracted into the second diffracted light;

The detector measures the change of the interference intensity information between the first diffracted light and the preset diffracted light of the same order in the second diffracted light;

The information processor reads the interference intensity signal, and inverts the displacement information of the object to be measured according to the change information of the interference intensity detected by the detector.

The present invention also provides a method for manufacturing a displacement sensor, the method comprising:

Use the micro-opto-electromechanical system MOEMS process to produce semiconductor lasers, diffraction gratings, detectors, information processors, and MOEMS components for grating modulation devices and reflected light collection devices;

Assembling the separated semiconductor laser, diffraction grating, photodetector, information processor, and the MOEMS element of the grating modulation device and the reflected light collection device according to any one of the above-mentioned displacement sensor structures; or

All or part of the MOEMS components of semiconductor lasers, diffraction gratings, photodetectors, information processors, grating modulation devices, and reflected light collection devices are integrated into a single chip.

The feature of the above-mentioned technical solution is that the detection light of the displacement sensor provided by the present invention can be provided by a semiconductor laser with a long coherence distance, unlike the existing dual-beam displacement measurement system, the detection light is provided by a He-Ne laser or the like. The displacement sensor invented in this way has the characteristics of miniaturization and easy integration. The maximum range measured by the sensor is half of the coherence distance of the semiconductor laser. With the continuous improvement of the long coherence distance semiconductor laser technology, the range of the invented displacement sensor can reach several meters or even farther.

Another feature of the above technical solution is that the method of generating coherent double beams is not realized by using different optical paths like Michelson interferometer, but by using the semi-reflective and semi-transparent properties of the diffraction grating to achieve light splitting. The direct reflection of the grating and the surface reflection of the object to be measured provide two beams of coherent light, and their optical path difference contains the displacement information of the object to be measured. The two beams of light that interfere with each other can be diffracted light of any order in the first diffracted light and the second diffracted light, such as 0th order, ±1st order, ±2nd order, etc. Their spatial directions are different, so different levels of diffracted light are used When coherent information is measured, the spatial positions of the corresponding detectors are also different.

Another feature of the above technical solution is that a modulation system can be introduced into the diffraction grating. Introduce periodic vibration to the diffraction grating, and then demodulate the interference intensity information detected by the detector; this can effectively suppress and reduce noise and improve measurement accuracy.

In addition, each component of the displacement sensor and interferometer provided by the present invention can be produced by using MOEMS technology, therefore, the displacement sensor and interferometer provided by the present invention have the characteristics of miniaturization and easy integration.

Description of drawings

FIG. 1 is a schematic diagram of the composition and structure of a displacement sensor provided by an embodiment of the present invention;

FIG. 2 is a schematic flowchart of a method for using a displacement sensor provided by an embodiment of the present invention;

Fig. 3 is a schematic diagram of light propagation during the working process of the displacement sensor provided by the embodiment of the present invention.

detailed description

In order to illustrate the embodiments and technical solutions of the present invention more clearly, the technical solutions of the present invention will be described in more detail below in conjunction with the accompanying drawings and embodiments. Obviously, the described embodiments are part of the embodiments of the present invention, not all of them. Example. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts fall within the protection scope of the present invention.

Fig. 1 is a schematic structural diagram of a displacement sensor provided by an embodiment of the present invention. As shown in Fig. 1, the displacement sensor includes:

A semiconductor laser 101, used to generate a laser beam;

The diffraction grating 102 is used to directly diffract and reflect a part of the light in the laser beam to generate the first diffracted light; at the same time, it is used to pass the laser beam through itself, reach the object to be measured, and be reflected by the object to be measured After that, a part of the light passing through itself is diffracted again to form the second diffracted light;

The detector 103 is located at the intersection of the first diffracted light to be measured and the preset diffracted light of the same order in the second diffracted light, and is used to measure the difference between the first diffracted light and the preset diffracted light of the same order in the second diffracted light The change of the interference intensity information between

An information processor 104, connected to the detector, is used to read the interference intensity signal, and invert the displacement information of the object to be measured according to the interference intensity change information detected by the detector;

The diffraction grating is located between the semiconductor laser and the object to be measured.

Specifically, in the above-mentioned displacement sensor, the semiconductor laser 101 can be a semiconductor laser with a long coherence distance, so that the displacement sensor can measure a relatively large displacement, and the range of the displacement sensor is half of the coherence distance of the semiconductor laser. With the continuous advancement of semiconductor laser technology, the range of the invented displacement sensor can reach several meters or even farther.

In addition, in the above-mentioned displacement sensor, the diffraction grating 102 may be implemented as a semi-reflective and semi-transparent grating for laser light.

Further, in the above-mentioned displacement sensor, the detector 103 can be a photodetector; the position of the detector 103 is related to the laser wavelength emitted by the semiconductor laser 101, the period of the diffraction grating 102, and the diffracted light to be measured to interfere. Regarding the order, when the period of the diffraction grating and the laser wavelength are determined, the direction of each diffraction order in the diffracted light is determined, and the position of the detector is determined by the direction of the diffraction order to be measured and the distance between the detection surface and the diffraction grating . Therefore, it is necessary to pre-set which order of diffracted light to measure. In practical applications, it can be set to measure level 0, ±1, ±2, etc. according to the specific situation, that is, the above-mentioned diffracted light of the same order can be measured It is the diffracted light of 0th order, ±1st order, and ±2nd order.

In addition, in the above-mentioned displacement sensor, the information processor 104 can be composed of a central processing unit (CPU), a microprocessor (MPU), a digital signal processor (DSP), or a field programmable gate array located in the displacement sensor in practical applications. (FPGA) implementation.

Further, the above-mentioned displacement sensor may also include:

The diffraction grating modulation and demodulation device 105 is used to introduce periodic vibrations to the diffraction grating and demodulate the interference intensity information detected by the detector.

Specifically, the diffraction grating modulation and demodulation device 105 can be realized by methods such as piezoelectric modulation. The purpose of the diffraction grating modulation and demodulation device is to suppress the noise in the measurement process. The signal-to-noise ratio of the detection signal is improved, thereby improving the displacement measurement accuracy.

Further, the above-mentioned displacement sensor may also include:

The reflected light collecting device 106 is used to collect the light reflected by the object to be measured, so that the intensity of the detected second diffracted light is equivalent to that of the preset same order diffracted light in the first diffracted light.

Specifically, the reflected light collection device 106 can be realized by a lens or other methods. The purpose of the reflected light collection device 106 is to make more light reflected by the object to be measured participate in coherence. Ideally, the intensity of the two beams of light participating in the coherence is equal.

The displacement sensor provided by the present invention, if the information processor 104 is removed, the remaining part itself is an interferometer. Therefore, the present invention also provides an interferometer, which includes:

Semiconductor lasers for generating laser beams;

The diffraction grating is used to directly diffract and then reflect a part of the light in the laser beam to generate the first diffracted light; at the same time, it is used to pass the laser beam through itself to reach the object to be measured, and after being reflected by the object to be measured Part of the light passing through itself is diffracted again to form the second diffracted light;

The detector is located at the intersection of the first diffracted light to be measured and the preset diffracted light of the same order in the second diffracted light, and is used to measure the difference between the first diffracted light and the preset diffracted light of the same order in the second diffracted light The change of the interference intensity information.

Further, the above-mentioned interferometer also includes:

The diffraction grating modulation and demodulation device is used for introducing periodic vibrations to the diffraction grating and demodulating the interference intensity information detected by the detector.

Further, the above-mentioned interferometer also includes:

The reflected light collection device is used to collect the light reflected by the object to be measured, so that the intensity of the detected second diffracted light is equivalent to that of the preset same order diffracted light in the first diffracted light.

Further, in the above interferometer, the semiconductor laser is a long coherence distance semiconductor laser.

Fig. 2 is a schematic flow chart of the method for using the displacement sensor provided by the present invention. As shown in Fig. 2, the method includes:

Step 201, the semiconductor laser generates a laser beam;

Step 202, the diffraction grating directly diffracts and then reflects a part of the laser beam to generate the first diffracted light; at the same time, the diffraction grating passes the laser beam through itself to the object to be measured, and after being reflected by the object to be measured Part of the light passing through itself is diffracted again to form the second diffracted light;

Specifically, as shown in Figure 3, when the laser beam emitted by the semiconductor laser is incident on the surface of the diffraction grating, a part of the laser beam is directly diffracted by the diffraction grating and then reflected to generate the first diffracted light. The first diffracted light contains a series of diffraction orders, Such as 0 level, ±1 level, ±2 level, etc.; at the same time, a part of the laser beam passes through the diffraction grating to reach the object to be measured, and after being reflected by the object to be measured, it passes through the diffraction grating again and diffracts into the second diffracted light. The second diffracted light also includes a series of diffraction orders, such as 0 order, ±1 order, ±2 order and so on.

Step 203, the detector measures the change of the interference intensity information between the first diffracted light and the diffracted light of the same preset order in the second diffracted light;

Specifically, adjust the diffraction grating so that the reflective surface of the object to be measured is parallel to the reflective surface of the grating, as shown in Figure 3, at this time, the space between the first diffracted light and the preset diffracted light of the same diffraction order in the second diffracted light In the same direction, they will interfere. The detector is adjusted so that the detector is located at the intersection of the same preset diffraction order of the first diffracted light and the second diffracted light, as shown in FIG. 3 . In this way, the detector can measure the change information of the interference intensity between the first diffracted light and the second diffracted light.

Here, the preset same diffraction order refers to that the preset order of the first diffracted light and the second diffracted light is the same as 0th order, the same as ±1st order, the same as ±2nd order, etc.

Further, the diffraction grating can be periodically vibrated by the diffraction grating modulation and demodulation device, and the interference intensity change information detected by the detector can be demodulated to suppress the noise in the measurement process.

Step 204, the information processor reads the interference intensity signal, and inverts the displacement information of the object to be measured according to the interference intensity change information detected by the detector;

Specifically, as shown in FIG. 3 , the optical path difference between the first diffracted light and the second diffracted light that interferes at this time is determined by the distance between the reflection surface of the diffraction grating and the reflection surface of the object to be measured, which is different from the traditional The method of measuring the displacement information of the Michelson interferometer is the same, and the information processor can invert the displacement information of the moving object after passing through the existing processing circuit and executing the existing processing algorithm according to the change information of the interference intensity.

The present invention also provides a method for manufacturing the above-mentioned displacement sensor, the method comprising:

Use the micro-opto-electromechanical system MOEMS process to produce semiconductor lasers, diffraction gratings, detectors, information processors, and MOEMS components for grating modulation devices and reflected light collection devices;

Assembling the separated semiconductor laser, diffraction grating, photodetector, information processor, and the MOEMS element of the grating modulation device and the reflected light collection device according to any one of the above-mentioned displacement sensor structures; or

All or part of the MOEMS components of semiconductor lasers, diffraction gratings, photodetectors, information processors, grating modulation devices, and reflected light collection devices are integrated into a single chip.

Specifically, the separated semiconductor laser, diffraction grating, grating modulation device, reflected light collection device, photodetector, information processor, etc. are assembled with reference to Figure 1 to form the invented displacement sensor; or

Using the existing MOEMS process to integrate all or part of the MOEMS components of semiconductor lasers, diffraction gratings, photodetectors, information processors, grating modulation devices, and reflected light collection devices into a single chip, a fully integrated Or semi-integrated MOEMS displacement sensor.

The feature of the above-mentioned technical solution is that the detection light of the displacement sensor provided by the present invention can be provided by a semiconductor laser with a long coherence distance, unlike the existing dual-beam displacement measurement system, the detection light is provided by a He-Ne laser or the like. The displacement sensor invented in this way has the characteristics of miniaturization and easy integration. The maximum range measured by the sensor is half of the coherence distance of the semiconductor laser. With the continuous improvement of the long coherence distance semiconductor laser technology, the range of the invented displacement sensor can reach several meters or even farther.

Another feature of the above technical solution is that the method of generating coherent double beams is not realized by using different optical paths like Michelson interferometer, but by using the semi-reflective and semi-transparent properties of the diffraction grating to achieve light splitting. The direct reflection of the grating and the surface reflection of the object to be measured provide two beams of coherent light, and their optical path difference contains the displacement information of the object to be measured. The two beams of light that interfere with each other can be diffracted light of any order in the first diffracted light and the second diffracted light, such as 0th order, ±1st order, ±2nd order, etc. Their spatial directions are different, so different levels of diffracted light are used When coherent information is measured, the spatial positions of the corresponding detectors are also different.

Another feature of the above technical solution is that a modulation system can be introduced into the diffraction grating. Introduce periodic vibration to the diffraction grating, and then demodulate the interference intensity information detected by the detector; this can effectively suppress and reduce noise and improve measurement accuracy.

In terms of manufacturing methods, it can be built through separate component patches, or it can be integrated. When building through separate component patches, separate semiconductor lasers, diffraction gratings, grating modulation devices, reflected light collection devices, photodetectors, information processors, etc. are assembled with reference to Figure 1 to form the invented displacement sensor. Since the manufacture of each component in the invented displacement sensor is compatible with the existing MOEMS process, all MOEMS processes can also be used to produce a monolithically integrated displacement sensor.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the protection scope of the present invention.

Claims (10)

1. a kind of displacement transducer is it is characterised in that institute's displacement sensors include：

Semiconductor laser, for producing laser beam；

Diffraction grating, for reflecting the direct diffraction of a part of light in described laser beam again, produces first Diffraction light；It is simultaneously used for pass through itself in described laser beam, reaching object under test, and through object under test Again pass through a part of optical diffraction of itself after reflection, form the second diffraction light；

Detector, in the first diffraction light to be measured and the second diffraction light, the diffraction light of default same stages time crosses Place is strong for measuring the interference between the diffraction light of default same stages time in the first diffraction light and the second diffraction light Degree change information；

Message handler, is connected with described detector, for reading interference strength signal, is visited according to detector The change of the interference strength information surveyed, is finally inversed by the displacement information of object under test；

Described diffraction grating is located between semiconductor laser and object under test.

2. displacement transducer according to claim 1 is it is characterised in that institute's displacement sensors also wrap Include：

Diffraction grating modulation-demodulation device, periodically vibrates for introducing to diffraction grating, and to detection The interference strength information that device detects is demodulated.

3. displacement transducer according to claim 1 and 2 is it is characterised in that institute's displacement sensors Also include：

Reflection light collecting device, for the light through object under test reflection for the collection so that being detected the second diffraction light Suitable with the intensity of the diffraction light of same stages time default in the first diffraction light.

4. the displacement transducer according to any one of claims 1 to 3 is it is characterised in that described partly lead Body laser is long coherence apart from semiconductor laser.

5. a kind of interferometer is it is characterised in that described interferometer includes：

Semiconductor laser, for producing laser beam；

Diffraction grating, for reflecting the direct diffraction of a part of light in described laser beam again, produces first Diffraction light；It is simultaneously used for pass through itself in described laser beam, reaching object under test, and through object under test Again pass through a part of optical diffraction of itself after reflection, form the second diffraction light；

Detector, in the first diffraction light to be measured and the second diffraction light, the diffraction light of default same stages time crosses Place is strong for measuring the interference between the diffraction light of default same stages time in the first diffraction light and the second diffraction light The change of degree information.

6. interferometer according to claim 5 is it is characterised in that described interferometer also includes：

Diffraction grating modulation-demodulation device, periodically vibrates for introducing to diffraction grating, and to detection The interference strength information that device detects is demodulated.

7. interferometer according to claim 5 is it is characterised in that described interferometer also includes：

Reflection light collecting device, for the light through object under test reflection for the collection so that being detected the second diffraction light Suitable with the intensity of the diffraction light of same stages time default in the first diffraction light.

8. the interferometer according to any one of claim 5 to 7 is it is characterised in that described quasiconductor swashs Light device is long coherence apart from semiconductor laser.

9. a kind of using method of displacement transducer is it is characterised in that the method includes：

Semiconductor laser produces laser beam；

The direct diffraction of a part of light in described laser beam is reflected by diffraction grating again, produces the first diffraction light； Diffraction grating will pass through itself, reach object under test in described laser beam simultaneously, and through object under test reflection Again pass through a part of light of itself afterwards, be diffracted to the second diffraction light；

Interference between the diffraction light of default same stages time in detector measurement first diffraction light and the second diffraction light The change of strength information；

Message handler reads interference strength signal, the interference strength change information being detected according to detector, instead The displacement information of performance object under test.

10. a kind of manufacture method of displacement transducer is it is characterised in that the method includes：

Using Micro-Opto-Electro-Mechanical Systems MOEMS technique productions semiconductor laser, diffraction grating, detector, Message handler, and the MOEMS element of Grating Modulation device, reflection light collecting device；

By detached semiconductor laser, diffraction grating, photodetector, message handler, and grating Modulating device, the MOEMS element of reflection light collecting device are according to according to any one of Claims 1-4 institute The displacement sensor structure assembling stated；Or

By semiconductor laser, diffraction grating, photodetector, message handler, and Grating Modulation dress Put, reflect all or part of element in the MOEMS element of light collecting device to be integrated in a monolithic.