CN113607062A - Micro-actuator displacement and inclination angle measuring device and method - Google Patents
Micro-actuator displacement and inclination angle measuring device and method Download PDFInfo
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- CN113607062A CN113607062A CN202110882268.2A CN202110882268A CN113607062A CN 113607062 A CN113607062 A CN 113607062A CN 202110882268 A CN202110882268 A CN 202110882268A CN 113607062 A CN113607062 A CN 113607062A
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- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B11/00—Measuring arrangements characterised by the use of optical techniques
- G01B11/02—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B11/00—Measuring arrangements characterised by the use of optical techniques
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Abstract
The invention provides a micro-actuator displacement and inclination angle measuring device and method. The laser resonant cavity is composed of a fixed cavity mirror and an independent cavity mirror, an antireflection film-coated glass sheet is obliquely arranged between the independent cavity mirror and the laser gain tube along the laser axis, two weak light beams reflected by the surface of the glass sheet are incident to a plane reflector driven by an actuator, and the two weak light beams are coupled back to resonate to form bifurcated cavity laser feedback after being folded back. In the motion process of the actuator, a light intensity change stripe formed by laser feedback is received and recorded through a photoelectric detector, and the displacement and the inclination angle of the actuator are calculated according to the period and the envelope characteristic of the feedback stripe. The invention can simultaneously measure the displacement and the inclination angle of the micro-displacement actuator in the linear expansion and contraction process and evaluate the performance index of the micro-displacement actuator.
Description
Technical Field
The invention relates to the technical field of optical measurement, in particular to a micro-actuator displacement and inclination angle measuring device.
Background
The precisely controllable linear displacement has important application in various fields such as manufacturing, materials, scientific research and the like. With the increasing requirement for displacement accuracy, micro-displacement actuators driven by stepping motors or servo motors, piezoelectric ceramics, voice coil motors, etc. are developed gradually, and the performance index of the micro-displacement actuators determines the processing or measuring accuracy.
The actuator, driven by the power supply, may present a yaw angle with respect to the axis in addition to a linear elongation along the axis, mainly due to material and structural non-uniformities, already caused by the driving voltage differences. Therefore, in the working process of the actuator, on one hand, the resolution of the displacement variation along with the drive source (such as a voltage signal) is high, the linearity is good, and the displacement hysteresis is reduced as much as possible; on the other hand, the direction is good in the displacement process, and the inclination angle relative to the axis is reduced as much as possible.
In order to test the displacement performance and the inclination angle of different types of actuators, an interferometer which has higher precision and can trace to the laser wavelength is generally adopted. However, in the optical path of the interferometer, the components for measuring displacement and measuring inclination angle are independent, i.e. only one of the two components can be measured, and in practical application, if the piezoceramic actuator needs to simultaneously measure the inclination angle in the process of extension, the measurement cannot be performed through the interferometer. In addition, the displacement and inclination angle measurement components of the laser interferometer are large in size and weight, and the stress state of the components can be obviously changed in the driving process of the micro-displacement actuator, so that system errors are brought to measurement.
Disclosure of Invention
The present invention is directed to solving one of the above problems and providing a device capable of simultaneously measuring a micro tilt angle and a displacement change of a micro-actuator.
In order to achieve the purpose, the invention adopts the technical scheme that:
micro-actuator displacement and tilt measurement apparatus comprising:
laser gain tube: one end of the fixed cavity mirror is connected with the high-reflection film plated fixed cavity mirror, and the other end of the fixed cavity mirror is connected with the anti-reflection film plated glass window sheet;
independent chamber mirror: the laser gain tube mirror is arranged at an interval, one surface plated with the high reflection film faces one side of the glass window sheet and is arranged in parallel with the fixed cavity mirror to form a laser resonant cavity, and the laser resonant cavity and the fixed cavity are arranged at an interval, namely the length of the resonant cavity;
optical glass sheet: the gain tube is arranged between the gain tube glass window and the independent cavity mirror, is inclined at a certain angle with the laser beam in the resonant cavity, and comprises a first plane close to one side of the gain tube and a second plane close to one side of the independent cavity mirror, and the two planes are plated with antireflection films;
the actuator is arranged on a reflected light path of the laser passing through the optical glass sheet and is adjusted to generate micro-displacement along the direction of the laser beam;
a plane mirror: the two light primary paths reflected by the first plane and the second plane of the reflecting optical glass sheet return to the laser resonant cavity; a branched cavity attached to the laser resonant cavity is formed between the optical glass sheet and the plane reflector;
a photoelectric detector: the tail light detector is arranged on one side of the fixed cavity mirror, which is far away from the independent cavity mirror, and is used for detecting tail light output from the fixed cavity mirror and converting the tail light into an electric signal which changes along with time;
a data processing unit: the laser feedback stripe is measured according to the detected light intensity change curve when the laser branched cavity is fed back, and the displacement and the inclination angle of the actuator are calculated;
the displacement is the displacement of the actuator approaching or departing from the optical glass sheet along the direction of the laser axis in the branched cavity under the driving of the power supply, and the inclination angle is the angle change relative to the propagation direction of the laser axis.
In some embodiments of the invention, the data processing unit is configured to calculate the actuator displacement Δ L as follows:
ΔL＝λ/2(M+m)；
wherein, λ is the laser wavelength, M is the feedback stripe integer part, M is the feedback stripe decimal part obtained according to the light intensity variation phase, and the feedback stripe decimal part is obtained according to the light intensity variation curve detected by the photoelectric detector;
the data processing unit is configured to calculate the tilt angle of the actuator as follows
Wherein: d is a light beam ErAnd a light beam Er'The distance between the two chambers is epsilon, a bifurcated cavity length difference coefficient caused by micro-actuator displacement and inclination angle is epsilon, and N is a period number of half-wavelength fluctuation under one long-period envelope in a light intensity change curve in the actuator expansion and contraction process; 10800 is a radian to angle conversion factor;
Erfor emitting laser through the gain tube, on the first plane F of the optical glass sheet1After being reflected to the plane mirror, the light is transmitted to the plane mirror and then reflected back to the laser resonant cavity by the plane mirror; er'For emitting laser through the gain tube, on the first plane F of the optical glass sheet1Refracted to a second plane F2Through the second plane F2Reflected to a first plane F1Then passes through a first plane F1And refracting the optical glass sheet, transmitting the optical glass sheet to the plane reflector, and reflecting the light returned to the resonant cavity by the plane reflector.
In some embodiments of the present invention, there is further provided a method for measuring displacement and tilt angle of a micro-actuator, using the above-mentioned testing apparatus, including the following steps:
calculating actuator displacement Δ L: obtaining an integer part M and a decimal part M of the laser feedback stripes according to the image of the photoelectric detector;
ΔL＝λ/2(M+m)；
calculating tilt angle of actuator
The method comprises the following steps:
wherein: d is a light beam ErAnd a light beam Er'The distance between the two chambers is epsilon, a bifurcated cavity length difference coefficient caused by micro-actuator displacement and inclination angle is epsilon, and N is a period number of half-wavelength fluctuation under one long-period envelope in a light intensity change curve in the actuator expansion and contraction process; 10800 is a radian to angle conversion factor;
Erfor emitting laser light through the gain tube, at the first side of the optical glass sheetA plane F1After being reflected to the plane mirror, the light is transmitted to the plane mirror and then reflected back to the laser resonant cavity by the plane mirror; er'For emitting laser through the gain tube, on the first plane F of the optical glass sheet1Refracted to a second plane F2Through the second plane F2Reflected to a first plane F1Then passes through a first plane F1And refracting the optical glass sheet, transmitting the optical glass sheet to the plane reflector, and reflecting the light returned to the resonant cavity by the plane reflector.
In some embodiments of the invention, the method further comprises:
obtaining tilt data for a first set of actuators at a first angle calculation;
rotating the actuator by 90 degrees, and repeating the calculation step of the inclination angle of the actuator;
obtaining tilt data for a second set of actuators at a second angle calculation;
and combining the first set of tilt angle data and the second set of tilt angle data to obtain an actual tilt angle and a tilt direction during the displacement of the actuator.
Compared with the prior art, the invention has the advantages and positive effects that:
(1) the invention can simultaneously measure the displacement and the inclination angle of the micro-displacement actuator in the linear extension process and evaluate the performance index of actuation.
(2) The invention can calculate the displacement and the inclination angle of the actuator by calculating the number of the feedback stripes in the measuring process, and has high linearity; the magnitudes of actuator displacement and tilt can be correlated to the laser wavelength, enabling the measurement to be traced to the reference for length, the laser wavelength.
Drawings
FIG. 1 is a schematic diagram of an actuator displacement and tilt angle measuring device according to the present invention;
FIG. 2 is a schematic diagram of the optical path of the displacement and tilt measuring device of the actuator of the present invention;
FIG. 3 is a state diagram of the actuator without displacement;
FIG. 4 is a state diagram of displacement of the actuator with tilt;
FIG. 5 is a graph of displacement of the actuator along the laser axis with the laser intensity at the tilt position.
In the above figures:
1. the device comprises a laser gain tube, 2 parts of a fixed cavity mirror, 3 parts of an anti-reflection window sheet, 4 parts of an independent cavity mirror, 5 parts of a glass sheet, 6 parts of an actuator, 7 parts of a plane mirror, 8 parts of a photoelectric detector and 9 parts of a data processing unit.
Detailed Description
The invention is described in detail below by way of exemplary embodiments. It should be understood, however, that elements, structures and features of one embodiment may be beneficially incorporated in other embodiments without further recitation.
In the description of the present invention, it should be noted that the terms "upper", "lower", "front", "rear", and the like indicate orientations or positional relationships based on positional relationships shown in the drawings, and are only for convenience in describing the present invention and simplifying the description, but do not indicate or imply that the referred device or element must have a specific orientation, be constructed in a specific orientation, and be operated, and thus, should not be construed as limiting the present invention.
It will be understood that when an element is referred to as being "disposed on," "connected to," or "secured to" another element, it can be directly on the other element or be indirectly on the other element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or be indirectly connected to the other element. Furthermore, the terms "first" and "second" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.
The invention provides a micro-actuator displacement and inclination angle measuring device, which can be a micro-displacement actuator such as piezoelectric ceramics and a voice coil motor.
Referring to fig. 3 and 4, the direction of laser propagation from left to right is illustrated, which is defined as the initial propagation direction of laser light, and the displacement described herein refers to the displacement of the actuator 6 toward or away from the optical glass sheet along the laser axis in the bifurcated cavity under the driving of the power supply, and is represented as the upward or downward direction shown in fig. 3; the tilt angle referred to herein means the angular change of the actuator with respect to the propagation direction of the laser axis, and is represented by the swing direction shown in fig. 4. The reason why the actuator generates displacement and inclination angle is: when the actuator 6 applies voltage, each end face of the actuator generates elongation, and the elongation movement is performed towards the initial propagation direction of the laser; however, due to the non-uniformity of the material and structure of the actuator 6, the elongation motion generated by the actuator 6 is non-uniform, and thus, the tilt angle is generated.
The structure of the measuring device is shown in fig. 1, and comprises:
laser gain tube 1: one end of the fixed cavity mirror 2 is connected with the high-reflection film plated, and the other end of the fixed cavity mirror 3 is connected with the anti-reflection film plated glass window sheet; the light-emitting direction of the light-emitting device faces the independent cavity mirror 4; the diameter of the capillary tube in the gain tube 1 is small, and light deviating from the diameter range of the capillary tube cannot return through the gain tube 1;
independent chamber mirror 4: the laser gain tube mirror 1 is arranged at an interval, one surface plated with a high reflection film faces one side of the glass window sheet and is arranged in parallel with the fixed cavity mirror 2 to form a laser resonant cavity, and the interval between the laser resonant cavity and the fixed cavity mirror is L0The distance between the two is the cavity length of the resonant cavity;
optical glass sheet 5: is arranged between the gain tube glass window 3 and the independent cavity mirror 4 and is inclined at a certain angle with the laser beam in the resonant cavity, specifically, the normal direction of the gain tube glass window is at an angle theta relative to the light-emitting direction of the gain tube, the thickness of the gain tube glass window is d, and the gain tube glass window comprises a first plane F close to one side of the gain tube 11And a second plane F adjacent to one side of the independent cavity mirror2Plating antireflection films on the two planes; the laser is reflected after being irradiated to the optical glass sheet 3, and the actuator 6 is arranged on a reflection light path of the laser passing through the optical glass sheet; in some embodiments, antireflection films may be disposed on both sides of the optical glass sheet 3, and after the antireflection films are disposed, the reflection coefficient of light may be reduced, and the reflection amount of light after passing through the optical glass sheet 3 may be reduced; the optical glass sheet 5 is positioned in the resonant cavity and forms an angle theta with the laser, and the angle can be selected according to requirements and can be set to be 45 degrees for example;
the actuator 6 is arranged on a reflected light path of the laser passing through the optical glass sheet and is adjusted to generate micro-displacement along the direction of the laser beam;
plane mirror 7: arranged to be actuatedThe end face of the device facing one side of the optical glass sheet 5 is arranged in parallel to the initial propagation direction of the laser; first plane F of reflective optical glass sheet1And a second plane F2Two reflected light beams return to the laser resonant cavity in a primary path; a branched cavity attached to the laser resonant cavity is formed between the optical glass sheet 5 and the plane reflector 7, and the length of the branched cavity is lbThe length is defined as the distance between the incident point of the laser light incident on the optical glass sheet 5 from the end of the gain tube 1 and the plane mirror 7; when the actuator 6 is rotated, the length of the bifurcation cavity will change; the direction of the laser reflected to the plane reflector 7 by the optical glass sheet 3 is the laser axis transmission direction;
the photodetector 8: the tail light detector is arranged on one side of the fixed cavity mirror, which is far away from the independent cavity mirror, and is used for detecting tail light output from the fixed cavity mirror and converting the tail light into an electric signal which changes along with time;
the data processing unit 9: and the photoelectric detector 8 is connected with the laser feedback stripe and is used for measuring the laser feedback stripe according to the detected light intensity change curve when the laser branched cavity is fed back, and calculating the displacement and the inclination angle of the actuator 6.
The data processing unit calculates the displacement Δ L of the actuator 6 based on the following method:
ΔL＝λ/2(M+m)；
wherein, λ is the laser wavelength, M is the feedback stripe integer part, M is the feedback stripe decimal part obtained according to the light intensity variation phase, and the feedback stripe decimal part is obtained according to the light intensity variation curve detected by the photoelectric detector;
the data processing unit is configured to calculate the tilt angle of the actuator as follows
Wherein: d is a light beam ErAnd a light beam Er'The distance between the two is the length difference coefficient of the branched cavity caused by the displacement and the inclination angle of the micro-actuator, and is the inclination angle of the actuator
And the displacement delta L determines a small amount, and N is the periodicity of half-wavelength fluctuation under a long period envelope in a light intensity change curve in the expansion and contraction process of the actuator; 10800 is a transform factor for radian conversion to an angle in units;
Erfor laser passing through gain tube, on the first plane F of optical glass sheet1After being reflected to the plane mirror, the light is transmitted to the plane mirror and then reflected back to the laser resonant cavity by the plane mirror; er'For emitting laser through the gain tube, at a first plane F of the optical glass sheet 51Refracted to a second plane F2Through the second plane F2Reflected to a first plane F1Then passes through a first plane F1And refracting the optical glass sheet, transmitting the optical glass sheet to the plane reflector, and reflecting the light returned to the resonant cavity by the plane reflector.
The following describes the principles of the present invention in detail.
The resonant cavity of the standing wave laser consists of a fixed cavity mirror 2 and an independent cavity mirror 4, and the oscillating optical field meets the resonance condition. When the output laser is reflected by the optical surface outside the resonant cavity, the output laser returns to the resonant cavity and is overlapped with the oscillating optical field to form interference, namely laser feedback or self-mixing interference. When the external optical reflection surface (usually a mirror with a specific reflectivity) changes, the phase of the feedback light returning to the resonant cavity is correspondingly changed, which can cause the laser intensity to change to form a feedback stripe.
An optical glass sheet 5 is placed in the laser resonant cavity, the optical glass sheet inclines along the laser axis to enable part of light in the cavity to be reflected to the outside of the laser, a plane reflector 7 is arranged on the reflected light path to enable the light to be incident back to the resonant cavity along the original path, laser feedback is formed similarly, and the laser intensity is changed.
Because the optical glass sheet 5 in the cavity and the plane reflector 7 outside the cavity form a branched cavity structure independent of the laser resonant cavity, the reflectivity of the surface of the element is low, two beams of incident light formed by the branched cavity can not influence laser oscillation, but the output light intensity can be changed, and a laser feedback effect is generated. When the off-cavity plane mirror 7 is displaced in the laser direction, the light intensity changes periodically. According to the laser physics, the light intensity of the laser changes for one period every time the plane mirror 7 of the branched cavity moves for one half of the wavelength of the light, and a feedback stripe is formed. When the reflector is driven by the actuator with linear displacement, the number of feedback stripes is measured, and the displacement of the micro actuator can be obtained.
Specifically, the optical path propagation of the laser light after passing through the actuator displacement and tilt angle measuring device is schematically shown in fig. 2. Hereinafter, a method for measuring the tilt angle and the displacement of the micro-actuator using the device provided by the present invention will be described with reference to the accompanying drawings.
The initial light wave emitted by the fixed cavity mirror 2 is transmitted towards the right side of the figure, and the complex amplitude of the electric field vector of the initial light wave is E0The electric field vector complex amplitude is changed into E after the right propagation in the resonant cavity is a positive direction and is amplified by the laser gain tube 1 and attenuated by the anti-reflection window sheet 3i。
Because two surfaces before intracavity optical glass piece 5 back can all reflect laser, actually the branching chamber has two bundles of parallel laser:
one beam is ErEmitting laser light E for gain tube 1iFirst plane F of optical glass sheet 51After being reflected to the plane reflector 7, the light is transmitted to the plane reflector 7 and refracted back by the plane reflector 7;
one beam is Er'Emitting laser light E for gain tube 1iFirst plane F of optical glass sheet 51Refracted to a second plane F2Through the second plane F2Reflected to a first plane F1Then passes through a first plane F1The light refracted out of the optical glass sheet 5 is transmitted to the plane reflector 7, and then is refracted back by the plane reflector 7.
Reflected light ErAnd Er'Is reflected by the plane mirror 7 and returns to the first plane F1And a second plane F2After once refraction and reflection, three paths of light beams are generated respectively:
Er: is first plane F1Reflecting to form reflected light ErrThe reflected light returns along the capillary gain tube; along a first plane F1Refracting and further along a second plane F2Refracted and pass through a second plane F2The light is passed out to form refracted light Ert(ii) a Is first plane F1Refracting and further along a second plane F2Reflected by the first plane F1Refracted and pass through a first plane F1Then the light passes out to form a return light Err'；
Er': is first plane F1Reflecting to form reflected light Er'r(ii) a Along a first plane F1Refracting and further along a second plane F2Refracted and pass through a second plane F2The light is passed out to form refracted light Er't(ii) a Is first plane F1Refracting and further along a second plane F2Reflected by the first plane F1Refracted and pass through a first plane F1Then the light passes out to form a return light Er'r'The reflected light returns along the capillary gain tube.
Since the diameter of the capillary in the gain tube 1 is small, the above-mentioned Err'、Er'tAnd not back to the gain chamber. Meanwhile, the reflection coefficient of the surface of the optical glass sheet 5 is very small due to the antireflection coating, so that only two times of reflected light and less than two times of reflected light on the two surfaces of the optical glass sheet 5 are considered, the intensity of high-order reflected light is too small to be ignored, and only E is consideredrr、Er'r'And returns to the gain chamber.
The folding back of the optical path from the fixed cavity mirror 2 to the independent cavity mirror 4 is as follows.
EiTransmitted light E from optical glass sheet 5tAfter propagating to the independent cavity mirror 4, the electric field vector complex amplitude is changed into E1The original path returns to pass through the optical glass sheet 5 again, and after being reflected and transmitted by the two surfaces, the primary reflected light respectively follows the original ErtAnd Er't，Err'Cannot enter the laser gain tube 1, only the transmitted light E2Can be returned to the fixed cavity mirror 2 via the capillary.
In summary, in the optical path, the light returning to the resonant cavity includes: err、Er'r'、E2。
The principle of estimation for calculating the displacement and tilt of the micro-actuator is as follows.
It is known that: refraction of airA rate of n0Refractive index of glass n1The incident angle of the laser in the resonant cavity reaching the glass sheet 5 is thetaiAngle of reflection θrθ, the angle of refraction is:
θt＝arcsin(n0/n1·sinθ)。
e can be calculated based on the above-mentioned indexrAnd Er'Optical path difference to the plane mirror 7:
then Err、Er'r'The optical path difference returning to the incident point is: 2 Delta l.
Then Err、Er'r'The phase delay amount of (d) is: 2 Δ Φ ═ 4 pi Δ l/λ.
Further, the electric field vector complex amplitude of each light returning to the resonant cavity after passing through the independent cavity mirror 4, the optical glass sheet 5 and the plane reflector 7 can be calculated as follows:
where g is the gain coefficient of the active medium, laTo activate the effective length of the medium (He-Ne laser capillary gain tube), glaThe one-way gain is obtained by the laser passing through the gain tube once in the resonant cavity, L' is the equivalent physical cavity length of the laser resonant cavity, and k is the wave vector: k 2 pi/λ.
In the process of calculating the equivalent physical cavity length of the laser resonant cavity, the refractive indexes of the laser gain medium, the anti-reflection window sheet 3 and the optical glass sheet 5 are considered, and the following steps are obtained:
then according to the self consistent condition, the light field from the fixed cavity mirror 2 goes back and forth a circle in the cavity, and after returning to the fixed cavity mirror 2, the light field should be consistent with the initial state, then there are:
E0＝E2+Err+Er'r'；
namely:
meanwhile, for the optical glass sheet 7 with the antireflection film coated on the surface, the reflectivity is far less than 1, and the transmissivity is approximately equal to 1. By simplifying equation (3) and eliminating higher order small quantities, the laser gain can be expressed as:
wherein:
l1＝l+lb-L'，l2＝l+lb+Δl-L'。
when the length of the bifurcation cavity is lbIn the change, the laser intensity generates sinusoidal modulation with a period of λ 2, that is, when the plane mirror 7 is driven by the actuator, the laser intensity changes by one period (feedback fringe) every time λ 2 is displaced, and then the total displacement Δ L (linear elongation) of the actuator is:
ΔL＝λ/2(M+m)； (5)
wherein, M is the integral part of the feedback stripe, and M is the decimal part of the feedback stripe obtained according to the phase of the light intensity change. The light wave image obtained by reference detection can be obtained by the data processing unit 9, the whole period number is M, and the part less than one period is converted into a fractional part M according to the phase.
The actuators 6 are energized so that the extensions of the points on the end surfaces thereof are not uniform, and the plane mirror 7 has a small yaw angle with respect to the surface normal
After passing through the reflector 7, the two light beams are alongThe displacement amounts in the respective axial directions are not equal, and a difference exists between them. According to l in formula (4)1And l2The following steps are changed:
l1′＝l+(1-ε/2)lb-ΔL-L′,l2′＝l+(1+ε/2)lb-ΔL+Δl-L′； (6)
by substituting equation (6) for equation (4), the variation curve of the laser intensity formed during the displacement of the actuator 6 can be calculated as shown in fig. 5.
It can be seen that as the actuator 6 is displaced, the bifurcated lumen length lbInstead, a long-period envelope appears on the light intensity fluctuation curve with a period λ 2. The average displacement of the actuator 6 can be obtained in accordance with the light intensity fluctuation period, instead of equation (5). And the size of the deflection angle in the elongation process of the actuator 6 is calculated according to the half-wavelength fluctuation cycle number N under one long-period envelope in the light intensity curve:
thereby, the linear extension Δ L of the actuator 6 and the yaw angle in the x-axis direction can be obtained simultaneously
Obtaining tilt data for a first set of actuators at a first angle calculation;
rotating the actuator by 90 degrees, and repeating the calculation step of the inclination angle of the actuator;
obtaining tilt data for a second set of actuators at a second angle calculation;
and combining the first set of tilt angle data and the second set of tilt angle data to obtain an actual tilt angle and a tilt direction during the displacement of the actuator.
For example, the actuator 6 may be rotated 90 ° relative to the laser axis, and continuing the above test, the pitch angle ζ in the y-direction may be obtained. Combining two angles of inclination
And ζ, can be actuatedThe actual angle of inclination and the direction of inclination of the device 6 during elongation.
The above description is only a preferred embodiment of the present invention, and not intended to limit the present invention in other forms, and any person skilled in the art may apply the above modifications or changes to the equivalent embodiments with equivalent changes, without departing from the technical spirit of the present invention, and any simple modification, equivalent change and change made to the above embodiments according to the technical spirit of the present invention still belong to the protection scope of the technical spirit of the present invention.
Claims (4)
1. Micro-actuator displacement and inclination measuring device characterized in that includes:
laser gain tube: one end of the fixed cavity mirror is connected with the high-reflection film plated fixed cavity mirror, and the other end of the fixed cavity mirror is connected with the anti-reflection film plated glass window sheet;
independent chamber mirror: the laser gain tube mirror is arranged at an interval, one surface plated with the high reflection film faces one side of the glass window sheet and is arranged in parallel with the fixed cavity mirror to form a laser resonant cavity, and the laser resonant cavity and the fixed cavity are arranged at an interval, namely the length of the resonant cavity;
optical glass sheet: the gain tube is arranged between the gain tube glass window and the independent cavity mirror, is inclined at a certain angle with the laser beam in the resonant cavity, and comprises a first plane close to one side of the gain tube and a second plane close to one side of the independent cavity mirror, and the two planes are plated with antireflection films;
the actuator is arranged on a reflected light path of the laser passing through the optical glass sheet and is adjusted to generate micro-displacement along the direction of the laser beam;
a plane mirror: the two light primary paths reflected by the first plane and the second plane of the reflecting optical glass sheet return to the laser resonant cavity; a branched cavity attached to the laser resonant cavity is formed between the optical glass sheet and the plane reflector;
a photoelectric detector: the tail light detector is arranged on one side of the fixed cavity mirror, which is far away from the independent cavity mirror, and is used for detecting tail light output from the fixed cavity mirror and converting the tail light into an electric signal which changes along with time;
a data processing unit: the laser feedback stripe is measured according to the detected light intensity change curve when the laser branched cavity is fed back, and the displacement and the inclination angle of the actuator are calculated;
the displacement is the displacement of the actuator approaching or departing from the optical glass sheet along the direction of the laser axis in the branched cavity under the driving of the power supply, and the inclination angle is the angle change relative to the propagation direction of the laser axis.
2. A micro-actuator displacement and tilt angle measuring device according to claim 1, wherein:
the data processing unit is configured to calculate the actuator displacement Δ L as follows:
ΔL＝λ/2(M+m)；
wherein, λ is the laser wavelength, M is the feedback stripe integer part, M is the feedback stripe decimal part obtained according to the light intensity variation phase, and the feedback stripe decimal part is obtained according to the light intensity variation curve detected by the photoelectric detector;
the data processing unit is configured to calculate the tilt angle θ of the actuator as follows:
wherein: d is a light beam ErAnd a light beam Er'The distance between the two chambers is epsilon, a bifurcated cavity length difference coefficient caused by micro-actuator displacement and inclination angle is epsilon, and N is a period number of half-wavelength fluctuation under one long-period envelope in a light intensity change curve in the actuator expansion and contraction process; 10800 is a radian to angle conversion factor;
Erfor emitting laser through the gain tube, on the first plane F of the optical glass sheet1After being reflected to the plane mirror, the light is transmitted to the plane mirror and then reflected back to the laser resonant cavity by the plane mirror; er'For emitting laser through the gain tube, on the first plane F of the optical glass sheet1Refracted to a second plane F2Through the second plane F2Reflected to a first plane F1Then passes through a first plane F1Refract the optical glass sheet to transmit to the planeAnd the light returning to the resonant cavity is reflected by the plane mirror at the reflector.
3. A method of measuring the displacement and tilt of a micro-actuator using the test apparatus of claim 2, comprising the steps of:
calculating actuator displacement Δ L: obtaining an integer part M and a decimal part M of the laser feedback stripes according to the image of the photoelectric detector;
ΔL＝λ/2(M+m)；
calculating the inclination angle theta of the actuator:
wherein: d is a light beam ErAnd a light beam Er'The distance between the two chambers is epsilon, a bifurcated cavity length difference coefficient caused by micro-actuator displacement and inclination angle is epsilon, and N is a period number of half-wavelength fluctuation under one long-period envelope in a light intensity change curve in the actuator expansion and contraction process; 10800 is a radian to angle conversion factor;
Erfor emitting laser through the gain tube, on the first plane F of the optical glass sheet1After being reflected to the plane mirror, the light is transmitted to the plane mirror and then reflected back to the laser resonant cavity by the plane mirror; er'For emitting laser through the gain tube, on the first plane F of the optical glass sheet1Refracted to a second plane F2Through the second plane F2Reflected to a first plane F1Then passes through a first plane F1And refracting the optical glass sheet, transmitting the optical glass sheet to the plane reflector, and reflecting the light returned to the resonant cavity by the plane reflector.
4. A method of micro-actuator displacement and tilt measurement according to claim 3, further comprising:
obtaining tilt data for a first set of actuators at a first angle calculation;
rotating the actuator by 90 degrees, and repeating the calculation step of the inclination angle of the actuator;
obtaining tilt data for a second set of actuators at a second angle calculation;
and combining the first set of tilt angle data and the second set of tilt angle data to obtain an actual tilt angle and a tilt direction during the displacement of the actuator.
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