CN112325803A - Common-path difference-based laser measurement method and device for change of included angle of polyhedral workpiece - Google Patents
Common-path difference-based laser measurement method and device for change of included angle of polyhedral workpiece Download PDFInfo
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Abstract
The invention provides a common-path difference-based laser measurement method and device for change of included angles of polyhedral workpieces. The device includes: laser emission unit, measuring unit, sensitive unit and zero calibration optical unit, the measuring unit includes: the device comprises a laser incident end, a collimating mirror, an isolator, a polarizer, a spectroscope, a focusing lens, a second polarizing spectroscope, a first detector and a second detector; the sensitive unit comprises a first polarizing beam splitter, a first reflecting mirror and a second reflecting mirror; the zero calibration optical unit consists of a third polarizing beam splitter, a third reflector, a fourth reflector and a guide rail. A beam of laser emitted by the laser passes through the collimating mirror and the polarizer to obtain two orthogonal polarized lights S and P, and the S and P are emitted along the same track after being transmitted by the spectroscope. The two signals of the S light and the P light are common signals from the measuring unit to the sensitive unit, so that the measuring error is reduced, and the change of the included angle of the precision workpiece in different states can be measured.
Description
Technical Field
The invention relates to the technical field of space geometric precision detection, in particular to a common-path difference-based laser measurement method and device for the change of an included angle of a polyhedral workpiece.
Background
With the development of precision manufacturing and processing technology, the requirement on the measurement precision of the change of the included angle of the polyhedral workpiece is continuously improved. The laser collimation measuring method is widely applied to the measurement of the change of the included angle of the polyhedral workpiece at present. However, laser light drifts due to the influence of many factors such as mechanical creep, air disturbance and laser self-change when the laser is spread in space, which brings errors to measurement. In order to suppress the above-mentioned errors caused by the light drift to the measurement, a common-path method is generally adopted. The common path method is to divide the laser beam into reference light and measuring light, because the two beams are in the same path in the transmission process, are separated at the sensitive unit end and are respectively reflected by the fixed reference surface and the measured surface, and then are in the same path continuously when returning to the measuring unit, therefore, the reference light only has the information of the light drift, the measuring light has the information of the light drift and the measured angle, and the drift compensation of the measuring light can be realized by detecting the drift condition of the reference light. The prior art methods for compensating for light drift include:
(1) the applicant discloses a common-path light drift real-time measurement and digital compensation method in a laser collimation system and a collimation method for automatically measuring a light drift angle, ZL 200410006321.9, and the method can reduce the influence of laser drift on a laser collimation or auto-collimation measurement result, and has the following defects: laser ray drift is obtained by means of a pyramid reflector or a cat eye lens, and the method is suitable for simultaneous measurement of laser multi-degree-of-freedom errors.
(2) In the invention patent 'two-dimensional photoelectric auto-collimation method and device for polarized light pyramid target common-path compensation' (ZL 201110021730.6) and 'two-dimensional photoelectric auto-collimation method and device for polarized light plane mirror reference common-path compensation' (ZL 201110021726. X), a method for controlling light drift in real time is provided, and a controller controls a two-dimensional light beam deflection device in real time according to drift reflected by a reference light beam to inhibit the drift coupled in a measuring light beam. The disadvantages of this method are: in the actual use process, the piezoelectric ceramic is adopted to control the deflection of the light beam, the compensation effect is influenced by the hysteresis characteristic, the creep characteristic and the temperature characteristic of the piezoelectric ceramic and the driving circuit of the piezoelectric ceramic, the response time of a piezoelectric ceramic control system is in the order of ms, certain hysteresis exists, and meanwhile, the introduction of a hardware part can increase the cost and the complexity of a measuring device.
In addition, in addition to light drift errors, circuit noise and mechanical stability of the measurement unit can introduce measurement errors during long-term measurements. This error is not compensated by the prior art methods of ray drift compensation, limiting the accuracy of the angle measurement.
Disclosure of Invention
The embodiment of the invention provides a common-path difference-based laser measurement method and device for the change of an included angle of a polyhedral workpiece, which aim to overcome the problems in the prior art.
In order to achieve the purpose, the invention adopts the following technical scheme.
According to one aspect of the invention, a common-path difference-based laser measurement method for angle change of a polyhedral workpiece is provided, which comprises the following steps:
step 3, the reflected light of the first polarizing beam splitter is reflected by the first reflector and then changed into S ' light, the S ' light is reflected by the first polarizing beam splitter and then returns along the original light path, the S ' light is imaged on the sensitive surface of the first detector after being reflected by the beam splitter, focused by the focusing lens and reflected by the second polarizing beam splitter, and two-dimensional angle information of the first reflector containing the light angle drift amount error is calculated according to the imaging coordinate;
step 4, the transmitted light of the first polarizing beam splitter is reflected by a second reflecting mirror and carries two-dimensional angle information of the second reflecting mirror to be changed into P ' light, the P ' light is transmitted by the first polarizing beam splitter and returns along an original light path, the P ' light is reflected by the beam splitter, focused by a focusing lens and transmitted by the second polarizing beam splitter and is imaged on a sensitive surface of a second detector, and the two-dimensional angle information of the second reflecting mirror containing the light angle drift amount error is calculated according to imaging coordinates; the first reflector and the second reflector are respectively adhered to two surfaces of the polyhedral workpiece, and two-dimensional angles of two surface types of the polyhedral workpiece are respectively represented;
and 5, calculating to obtain the relative two-dimensional angle change information of the first reflector and the second reflector according to the two-dimensional angle information of the first reflector and the two-dimensional angle information of the second reflector containing the light angle drift amount error, wherein the relative two-dimensional angle change information represents the relative two-dimensional angle change of two surface types of the polyhedral workpiece.
Preferably, the calculating the two-dimensional angle information of the first reflector including the light angle drift error according to the imaging coordinates includes:
let the imaging coordinate be (x)1,y1) When the components of the light angle drift amount in the x-axis and the y-axis are α 'and β', respectively, and the focal length of the focusing lens is f, the two-dimensional angle information of the first reflecting mirror including the error of the light angle drift amount is α1+α′＝arctan(x1/2f)、β1+β′＝arctan(y2/2f)。
Preferably, the calculating the two-dimensional angle information of the second reflector including the light angle drift error according to the imaging coordinates includes:
let the imaging coordinate be (x)2,y2) The focal length of the focusing lens is f, and since the P 'light and the S' light are basically in the same path, the components of the ray angle drift in the two directions of the x axis and the y axis are respectively alpha 'and beta', and the two-dimensional angle change of the second reflector including the ray angle drift error is respectively alpha2+α′＝arctan(x2/2f)、β2+β′＝arctan(y2/2f)。
Preferably, the calculating to obtain the two-dimensional angle change information of the first mirror and the second mirror includes:
the relative two-dimensional angle variation of the first reflector is calculated by the following formula:
△α＝α2-α1＝arctan(x2/2f)-arctan(x1/2f)
the relative two-dimensional angle variation of the second reflector is calculated by the following formula:
△β＝β2-β1＝arctan(y2/2f)-arctan(y1(2 f). Preferably, the method further comprises:
step 6, moving a zero calibration optical unit composed of a third polarizing beam splitter, a third reflector and a fourth reflector to the middle of the beam splitter and the first polarizing beam splitter, so that S light and P light emitted along the same track are incident to the third polarizing beam splitter, and the S light is changed into S light after being reflected by the third polarizing beam splitter, the surface of the third reflector and the third polarizing beam splitter in sequence0The light P is transmitted by the third polarization beam splitter, the surface of the fourth reflector and the third polarization beam splitter in sequence and then becomes P0Light, S0Light and P0The light returns to the spectroscope along the same trajectory;
the first detector signal drift amount is calculated by the following formula:
αs＝arctan(xs/2f)、βs＝arctan(ys/2f)
the second detector signal drift amount is calculated by the following formula:
αp＝arctan(xp/2f)、βp＝arctan(yp/2f)
step 9, calculating to obtain relative two-dimensional angle change information of the first reflector and the second reflector for eliminating light angle drift, circuit drift and mechanical structure stability errors according to the two-dimensional angle information of the first reflector, the two-dimensional angle information of the second reflector, the signal drift amount of the first detector and the signal drift amount of the second detector;
the relative two-dimensional angle change information of the first reflector is calculated by the following formula:
△α＝(α2-αp)-(α1-αs)
＝arctan(x2/2f)-arctan(xp/2f)-arctan(x1/2f)+arctan(xs/2f)
the relative two-dimensional angle change information of the second reflector is calculated by the following formula:
△β＝(β2-βp)-(β1-βs)
＝arctan(y2/2f)-arctan(yp/2f)-arctan(y1/2f)+arctan(ys/2f)。
preferably, the method further comprises:
adding a pentagonal prism to the zero calibration optical unit, and driving the pentagonal prism to move by the guide rail;
in the step 6, the light emitted from the pentagonal prism 20 is moved to the middle of the beam splitter 7 and the first polarization beam splitter 13, so that the S light and the P light emitted along the same track change direction after passing through the pentagonal prism 20 and enter the third polarization beam splitter 16, and the S light is changed into the S light after being reflected by the third polarization beam splitter 16, the surface of the third reflector 17 and the third polarization beam splitter 16 in sequence0The light P is transmitted by the third PBS 16, reflected by the surface of the fourth reflector 18 and transmitted by the third PBS 16 in sequence, and then becomes P0Light, S0Light and P0The light follows the same trajectory, changes direction after passing through the penta prism 20, and returns to the beam splitter 7.
According to another aspect of the present invention, there is provided a laser measurement apparatus for a method for measuring a change in an included angle of a polyhedral workpiece based on common path difference, including: the device comprises a laser emitting unit, a measuring unit and a sensitive unit;
the laser emitting unit comprises a laser; or the device comprises a laser and an optical fiber, wherein the laser is flexibly connected with the measuring unit through a single optical fiber;
the measurement unit includes: the device comprises a laser incident end, a collimating mirror, an isolator, a polarizer, a spectroscope, a focusing lens, a second polarizing spectroscope, a first detector and a second detector; the laser beam splitter comprises a laser incidence end, a collimating mirror, an isolator, a polarizer and a beam splitter, wherein the laser incidence end, the collimating mirror, the isolator, the polarizer and the beam splitter are sequentially arranged along the direction of laser emitted from the laser incidence end, a focusing lens and a second polarizing beam splitter are sequentially arranged along the direction of laser reflected by the beam splitter and reflected by the beam splitter, the focusing lens is used for focusing and imaging the reflected measuring light S ' and the measuring light P ', the second polarizing beam splitter is used for splitting the common-path S ' and P ' light, and a first detector is arranged at an equivalent focal plane of the focusing lens reflected by the second polarizing beam splitter and used for collecting the S ' and calculating the light angle drift amount; the second detector is arranged at the equivalent focal plane of the focusing lens after being transmitted by the second polarizing beam splitter and is used for collecting the P' light and calculating the two-dimensional angle information of the second reflecting mirror containing the light angle drift amount error; the isolator is used for isolating the S 'light and the P' light reflected by the sensitive unit and transmitted by the spectroscope, and preventing the laser emission unit from being adversely affected.
The sensitive unit comprises a first polarizing beam splitter, a first reflecting mirror and a second reflecting mirror; the first polarizing beam splitter is used for splitting the S light and the P light which share the same path, the first reflector is used for reflecting the S light and forming a light beam which shares the path with the P light between the measuring unit and the sensitive unit, the change of the spot position of the S ' light measured by the first detector is changed into a measuring error introduced by the angle drift of the light, the second reflector is used for reflecting the P light, the change of the spot position of the P ' light measured by the second detector is changed into a two-dimensional angle of the second reflector which contains the error of the angle drift of the light, and the two-dimensional angle information of the second reflector is obtained by calculation according to the change of the spot position of the S ' light and the P.
Preferably, the apparatus further comprises:
the zero calibration optical unit consists of a third polarizing beam splitter, a third reflector, a fourth reflector and a guide rail, wherein when zero calibration is performed, a parallel light beam containing two orthogonal polarized lights S light and P light is emitted by the measuring unit, and the S light is changed into S light after being reflected by the third polarizing beam splitter, the surface of the third reflector and the third polarizing beam splitter in sequence0Light, S0The light returns to the measuring unit, is reflected by the beam splitter, focused by the focusing lens and reflected by the second polarizing beam splitter, and is collected and imaged by the first detector; the P light is transmitted by the third polarization spectroscope, the surface of the fourth reflector and the third polarization spectroscope in sequence and then becomes P0Light, P0The light returns to the measuring unit, is reflected by the spectroscope, is focused by the focusing lens and is transmitted by the second polarization spectroscope, and then is collected by the second detector for imaging; the measuring unit simultaneously collects the S light and the P light reflected by the zero calibration optical unit, and the measurement error caused by the mechanical structure of the measuring unit and the circuit noise is obtained after processing.
Preferably, the apparatus further comprises:
the zero calibration optical unit consists of a third polarizing spectroscope, a third reflector, a fourth reflector, a guide rail and a pentagonal prism, and the pentagonal prism is arranged along the guide rail during zero calibrationMoving to the middle of the spectroscope and the first polarizing spectroscope, emitting a parallel light beam containing two orthogonal polarized lights S and P by the measuring unit, changing the direction of the parallel light beam after passing through the pentagonal prism, and entering a third polarizing spectroscope, wherein the S light is changed into S light after being reflected by the third polarizing spectroscope, the surface of the third reflector and the third polarizing spectroscope in sequence0Light, S0The direction of the light is changed after passing through the pentagonal prism, the light returns to the measuring unit and is collected and imaged by the first detector after being reflected by the beam splitter, focused by the focusing lens and reflected by the second polarizing beam splitter in sequence; the P light is transmitted by the third polarization spectroscope, the surface of the fourth reflector and the third polarization spectroscope in sequence and then becomes P0Light, P0The light changes direction after passing through the pentagonal prism, returns to the measuring unit, is reflected by the beam splitter, focused by the focusing lens and transmitted by the second polarizing beam splitter in sequence, and is collected and imaged by the second detector; the measuring unit simultaneously collects S reflected by the zero calibration optical unit0Light and P0The light is processed to obtain the measurement error caused by the mechanical structure of the measurement unit and the circuit noise. Preferably, the sensitive unit structure is adjusted according to the position difference of the measured surface, and when the two measured surfaces are not mutually vertical, an auxiliary module is added, so that the first reflecting mirror and the second reflecting mirror are mutually vertical;
preferably, the first mirror is changed to a reflective film plated on the surface of the first polarizing beamsplitter.
According to the technical scheme provided by the embodiment of the invention, the two paths of signals of the S light and the P light in the embodiment of the invention are common signals from the measuring unit to the sensitive unit, and the influence of light ray drift caused by various factors on a measuring angle result is greatly reduced by adopting differential processing, so that the measuring stability and reliability are obviously improved; meanwhile, differential digital signal processing is adopted, so that the cost is reduced, the real-time performance of common-path differential processing is improved, and the real-time processing response time is less than 1 microsecond. . The zero calibration optical unit can reduce circuit noise and measurement errors caused by a mechanical structure of the measurement unit during long-term measurement, and can realize measurement of the change of an included angle of a precision workpiece in different states. Due to the adoption of the real-time common-path difference and automatic zero calibration method, the light angle drift of the measuring device can be controlled to be less than 0.1 second for a long time (24 hours), and the requirements of measuring the change of the included angle of the workpiece with high precision and high stability are met.
Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.
Fig. 1 is a diagram of a measurement state structure of a common-path difference-based laser measurement device for measuring changes in included angles of a polyhedral workpiece according to a first embodiment of the present invention;
fig. 2 is a light path diagram of a sensing unit according to an embodiment of the present invention;
fig. 3 is a structural diagram of a zeroing state of a laser measuring device for an included angle of a polyhedral workpiece based on common-path difference according to an embodiment of the present invention;
FIG. 4 is a diagram of an optical path of a zeroing optical unit according to an embodiment of the present invention;
fig. 5 is a light path diagram of a sensing unit according to a second embodiment of the present invention;
fig. 6 is a light path diagram of a sensing unit according to a third embodiment of the present invention;
fig. 7 is a light path diagram of a sensing unit according to a fourth embodiment of the present invention;
fig. 8 is an optical path diagram of a zeroing optical unit according to a fifth embodiment of the present invention;
fig. 9 is a structural diagram of a measurement state of a two-dimensional small-angle change laser measurement device based on common-path difference according to a sixth embodiment of the present invention;
fig. 10 is a structural diagram of a zero calibration state of a two-dimensional small-angle change laser measurement device based on common-path difference according to a sixth embodiment of the present invention;
fig. 11 is an optical path diagram of a zeroing optical unit according to a sixth embodiment of the present invention.
Detailed Description
Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the accompanying drawings are illustrative only for the purpose of explaining the present invention, and are not to be construed as limiting the present invention.
As used herein, the singular forms "a", "an", "the" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and/or "comprising," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. It will be understood that when an element is referred to as being "connected" or "coupled" to another element, it can be directly connected or coupled to the other element or intervening elements may also be present. Further, "connected" or "coupled" as used herein may include wirelessly connected or coupled. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.
It will be understood by those skilled in the art that, unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the prior art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.
For the convenience of understanding the embodiments of the present invention, the following description will be further explained by taking several specific embodiments as examples in conjunction with the drawings, and the embodiments are not to be construed as limiting the embodiments of the present invention.
The embodiment of the invention provides a common-path difference-based laser measurement method and device for the change of an included angle of a polyhedral workpiece, which can realize the measurement of the change of the included angle of a precise workpiece in different states.
The embodiment of the invention provides a common-path difference-based laser measurement method for the change of an included angle of a polyhedral workpiece, which comprises the following steps:
step 3, the reflected light of the first polarization spectroscope obtained in the step 2 is reflected by the first reflector and then changed into S ' light, the S ' light is reflected by the first polarization spectroscope and then returns along the original light path, the S ' light is reflected by the spectroscope, focused by the focusing lens and reflected by the second polarization spectroscope and then imaged on a sensitive surface of the first detector, and two-dimensional angle information of the first reflector containing the light angle drift amount error can be calculated according to imaging coordinates;
let the imaging coordinate be (x)1,y1) The components of the light angle drift amount in the x-axis and the y-axis are α 'and β', respectively, and the focal length of the focusing lens is f, then the two-dimensional angle information of the first reflector including the light angle drift amount error is: alpha is alpha1+α′＝arctan(x1/2f)、β1+β′＝arctan(y2/2f)
Step 4, the transmitted light of the first polarizing beam splitter obtained in the step 2 is reflected by a second reflecting mirror and carries two-dimensional angle information of the second reflecting mirror, the transmitted light is changed into P ' light, the P ' light is returned along an original light path after being transmitted by the first polarizing beam splitter, the P ' light is imaged on a sensitive surface of a second detector after being reflected by the beam splitter, focused by a focusing lens and transmitted by the second polarizing beam splitter, and the two-dimensional angle information of the second reflecting mirror containing the light angle drift amount error can be calculated according to imaging coordinates;
let the imaging coordinate be (x)2,y2) The focal length of the focusing lens is f, and since the P 'light and the S' light are basically in the same path, the components of the ray angle drift in the two directions of the x axis and the y axis are respectively alpha 'and beta', and the two-dimensional angle change of the second reflector including the ray angle drift error is respectively alpha2+α′＝arctan(x2/2f)、β2+β′＝arctan(y2/2f)；
the relative two-dimensional angle variation of the first reflector and the second reflector is calculated by the following two formulas respectively:
△α＝α2-α1＝arctan(x2/2f)-arctan(x1/2f)
△β＝β2-β1＝arctan(y2/2f)-arctan(y1/2f)
step 6, moving a zero calibration optical unit composed of a third polarizing beam splitter, a third reflector and a fourth reflector to the middle of the beam splitter and the first polarizing beam splitter, so that the S light and the P light emitted along the same track and obtained in the step (1) are incident to the third polarizing beam splitter, and the S light is reflected by the third polarizing beam splitter, the surface of the third reflector and the third polarizing beam splitter and then is changed into S light0The light P is transmitted by the third PBS, reflected by the surface of the fourth reflector and transmitted by the third PBS to become P0Light, S0Light and P0The light returns to the spectroscope along the same trajectory;
s acquired in step 7 and step (6)0After the light is reflected by the beam splitter, focused by the focusing lens and reflected by the second polarizing beam splitter, the light is reflected by the beam splitterThe first detector acquires imaging, and the signal drift amount of the first detector can be calculated according to imaging coordinates, wherein the signal drift amount of the first detector comprises the circuit drift amount of the first detector and S0Errors introduced by mechanical structural stability of the optics through which the light passes;
the first detector signal drift amount is calculated by the following formula:
αs＝arctan(xs/2f)、βs＝arctan(ys/2f)
the second detector signal drift amount is calculated by the following formula:
αp＝arctan(xp/2f)、βp＝arctan(yp/2f)
step 9, according to the two-dimensional angle information of the first reflector obtained in the step 3, the two-dimensional angle information of the second reflector obtained in the step 4, the signal drift amount of the first detector obtained in the step 7 and the signal drift amount of the second detector obtained in the step 8, the relative two-dimensional angle change information of the first reflector and the second reflector for eliminating the light angle drift, the circuit drift and the mechanical structure stability error can be obtained through calculation;
the relative two-dimensional angle change information of the first reflector and the second reflector is calculated by the following two formulas respectively:
△α＝(α2-αp)-(α1-αs)
＝arctan(x2/2f)-arctan(xp/2f)-arctan(x1/2f)+arctan(xs/2f)
△β＝(β2-βp)-(β1-βs)
＝arctan(y2/2f)-arctan(yp/2f)-arctan(y1/2f)+arctan(ys/2f)
and step 10, the first reflector and the second reflector respectively represent two-dimensional angles of two surface types of the polyhedral workpiece, and the two-dimensional angle change information between the first reflector and the second reflector represents the relative two-dimensional angle change of the two surface types of the polyhedral workpiece.
When no circuit or mechanical zero calibration is needed, the relative two-dimensional angle change information of two surface types of the polyhedral workpiece can be obtained only through the steps (1) to (5).
The embodiment of the invention provides a measuring device of a laser measuring method for the change of an included angle of a polyhedral workpiece based on common-path difference, which comprises the following steps: the device comprises a laser emitting unit, a measuring unit, a sensitive unit, a zero calibration optical unit and the like. The first reflecting mirror and the second reflecting mirror are respectively adhered to two surfaces of the polyhedral workpiece, so that the relative two-dimensional angle change of the two surfaces of the polyhedral workpiece can be represented through the relative two-dimensional angle change of the two reflecting mirrors.
The laser emitting unit includes a laser; preferably, the laser emitting unit can also be composed of a laser and an optical fiber, and the laser is flexibly connected with the measuring unit through a single optical fiber.
The measuring unit comprises a laser incidence end, a collimating mirror, an isolator, a polarizer, a spectroscope, a focusing lens, a second polarizing spectroscope, a first detector and a second detector; the laser beam splitter comprises a laser incidence end, a collimating mirror, an isolator, a polarizer and a beam splitter, wherein the laser incidence end, the collimating mirror, the isolator, the polarizer and the beam splitter are sequentially arranged along the direction of laser emitted from the laser incidence end, the focusing lens and the second polarizing beam splitter are sequentially arranged along the direction of laser reflected by the beam splitter and reflected by the beam splitter, the focusing lens is used for focusing and imaging the reflected measuring light S ' and the measuring light P ', the second polarizing beam splitter is used for splitting the common-path S ' and P ' light, and the first detector is arranged at an equivalent focal plane of the focusing lens reflected by the second polarizing beam splitter and used for collecting the S ' and calculating the light angle drift amount; the second detector is arranged at the equivalent focal plane of the focusing lens after being transmitted by the second polarizing beam splitter and is used for collecting the P' light and calculating the two-dimensional angle information of the second reflecting mirror containing the light angle drift amount error; the isolator is used for isolating the S 'light and the P' light reflected by the sensitive unit and transmitted by the spectroscope, and preventing the laser emission unit from being adversely affected.
The sensitive unit comprises a first polarizing beam splitter, a first reflecting mirror and a second reflecting mirror; the first polarizing beam splitter is used for splitting the S light and the P light which share the same path, the first reflector is used for reflecting the S light and forming a light beam which shares the path with the P light between the measuring unit and the sensitive unit, the position of the S ' light spot finally measured by the first detector is changed into a measuring error introduced by light angle drift due to fixed position of the first reflector, the second reflector is used for reflecting the P light, the light direction of the reflected light P ' is changed due to two-dimensional angle change of the second reflector, the position change of the P ' light spot finally measured by the second detector comprises the two-dimensional angle change of the second reflector of the light angle drift error, and second-dimensional angle information can be obtained through calculation according to the position change of the S ' light and the light P ' light spot.
The zero calibration optical unit consists of a third polarizing beam splitter, a third reflector, a fourth reflector and a guide rail. When the time zero is corrected, a parallel light beam containing two orthogonal polarized lights S and P is emitted by the measuring unit, and the S light is changed into S after being reflected by the third polarizing beam splitter and the third polarizing beam splitter reflected by the surface of the third reflector0Light, S0The light returns to the measuring unit, is reflected by the spectroscope, focused by the focusing lens and reflected by the second polarizing spectroscope, and is collected and imaged by the first detector; the P light is transmitted by the third polarization beam splitter, the surface of the fourth reflector and the third polarization beam splitter and then becomes P0Light, P0The light returns to the measuring unit, is reflected by the spectroscope, is focused by the focusing lens and is transmitted by the second polarization spectroscope, and then is collected by the second detector for imaging; the measuring unit simultaneously collects the S light and the P light reflected by the zero calibration optical unit, and the measurement error caused by the mechanical structure of the measuring unit and the circuit noise is obtained after processing.
Example one
The processing procedure of the common-path difference-based laser measurement method for the change of the included angle of the polyhedral workpiece includes the following steps:
step 3, the reflected light of the first polarizing beam splitter 13 obtained in the step 2 is reflected by the first reflector 14 and then changed into S ' light, the S ' light is reflected by the first polarizing beam splitter 13 and then returns along the original light path, the S ' light is reflected by the beam splitter 7, focused by the focusing lens 8 and reflected by the second polarizing beam splitter 9 and then imaged on the sensitive surface of the first detector 10, and the two-dimensional angle information of the first reflector 14 containing the light angle drift amount error can be calculated according to the imaging coordinate;
let the imaging coordinate be (x)1,y1) When the focal length of the focusing lens 8 is f, the components of the ray angle drift in the x-axis and the y-axis become α 'and β', respectively, the two-dimensional angle information of the first mirror 14 including the error of the ray angle drift is: alpha is alpha1+α′＝arctan(x1/2f)、β1+β′＝arctan(y2/2f)
Step 4, the transmitted light of the first polarizing beam splitter 13 obtained in the step 2 is reflected by the second reflecting mirror 15 and carries two-dimensional angle information of the second reflecting mirror 15 to become P ' light, the P ' light is transmitted by the first polarizing beam splitter 13 and then returns along an original light path, the P ' light is reflected by the beam splitter 7, focused by the focusing lens 8 and transmitted by the second polarizing beam splitter 9 to be imaged on a sensitive surface of the second detector 11, and the two-dimensional angle information of the second reflecting mirror containing the light angle drift amount error can be calculated according to imaging coordinates;
let the imaging coordinate be (x)2,y2) The focusing lens 8 has a focal length f, and since the P 'light is substantially in the same path as the S' light, the light isThe components of the angle drift in the x-axis and y-axis directions are respectively alpha 'and beta', and the two-dimensional angle change of the second reflector including the light angle drift error is respectively alpha2+α′＝arctan(x2/2f)、β2+β′＝arctan(y2/2f)；
the two-dimensional angle variation of the first reflector 14 and the second reflector 15 is calculated by the following two formulas:
△α＝α2-α1＝arctan(x2/2f)-arctan(x1/2f)
△β＝β2-β1＝arctan(y2/2f)-arctan(y1/2f)
step 6, moving a zeroing optical unit composed of a third polarizing beam splitter 16, a third reflector 17 and a fourth reflector 18 to the middle of the beam splitter 7 and the first polarizing beam splitter 13, so that the S light and the P light emitted along the same track and obtained in the step (1) are incident to the third polarizing beam splitter 16, and the S light is reflected by the third polarizing beam splitter 16, the surface of the third reflector 17 and the third polarizing beam splitter 16 in sequence and then is changed into S light0The light P is transmitted by the third PBS 16, reflected by the surface of the fourth reflector 18 and transmitted by the third PBS 16 in sequence, and then becomes P0Light, S0Light and P0The light returns to the beam splitter 7 along the same trajectory;
s acquired in step 7 and step (6)0After light is reflected by the spectroscope 7, focused by the focusing lens 8 and reflected by the second polarizing spectroscope 9, imaging is acquired by the first detector 10, the signal drift amount of the first detector 10 can be calculated according to imaging coordinates, and the signal drift amount of the first detector 10 comprises the circuit drift amount of the first detector 10 and S0Errors introduced by mechanical structural stability of the optics through which the light passes;
the amount of signal drift of the first detector 10 is calculated by the following equation:
αs＝arctan(xs/2f)、βs＝arctan(ys/2f)
the signal drift amount of the second detector 11 is calculated by the following formula:
αp＝arctan(xp/2f)、βp＝arctan(yp/2f)
step 9, according to the two-dimensional angle information of the first reflecting mirror 14 obtained in the step 3, the two-dimensional angle information of the second reflecting mirror 15 obtained in the step 4, the signal drift amount of the first detector 10 obtained in the step 7 and the signal drift amount of the second detector 11 obtained in the step 8, the relative two-dimensional angle change information of the first reflecting mirror 14 and the second reflecting mirror 15, which is used for eliminating the light angle drift, the circuit drift and the mechanical structure stability error, can be obtained through calculation;
the two-dimensional angle change information of the first reflector 14 and the second reflector 15 is calculated by the following two formulas:
△α＝(α2-αp)-(α1-αs)
＝arctan(x2/2f)-arctan(xp/2f)-arctan(x1/2f)+arctan(xs/2f)
△β＝(β2-βp)-(β1-βs)
＝arctan(y2/2f)-arctan(yp/2f)-arctan(y1/2f)+arctan(ys/2f)
and step 10, the first reflector and the second reflector respectively represent two-dimensional angles of two surface types of the polyhedral workpiece, and the two-dimensional angle change information between the first reflector and the second reflector represents the relative two-dimensional angle change of the two surface types of the polyhedral workpiece.
The structure of the apparatus for measuring the change of the included angle of the polyhedral workpiece based on the common-path difference according to the embodiment is shown in fig. 1 and 3, where fig. 1 is a measurement state, and fig. 3 is a zero calibration state. The device comprises a laser emitting unit I, a measuring unit II, a sensitive unit III and a zero calibration optical unit IV. Fig. 2 is a light path diagram of a sensing unit III provided in this embodiment. Fig. 4 is an optical path diagram of a zeroing optical unit provided in this embodiment.
The laser emitting unit I includes: the device comprises a laser 1 and an optical fiber 2, wherein the laser 1 is flexibly connected with a measuring unit through a single optical fiber 2;
the measuring unit II comprises a laser incidence end 3, a collimating mirror 4, an isolator 5, a polarizer 6, a spectroscope 7, a focusing lens 8, a second polarizing spectroscope 9, a first detector 10 and a second detector 11; the laser incident end 3, the collimating mirror 4, the isolator 5, the polarizer 6 and the spectroscope 7 are sequentially placed along the direction of laser emitted from the laser incident end 3, the focusing lens 8 and the second polarizing spectroscope 9 are sequentially placed along the direction of laser reflected back to the measuring unit II by the spectroscope 7, the focusing lens 8 is used for focusing and imaging the reflected measuring light S ' and the measuring light P ', the second polarizing spectroscope 9 is used for splitting the common-path light S ' and P ', and the first detector 10 is arranged at an equivalent focal plane of the focusing lens 8 reflected by the second polarizing spectroscope 9 and used for collecting the light S ' and calculating the light angle drift amount; the second detector 11 is arranged at an equivalent focal plane of the focusing lens 8 after being transmitted by the second polarizing beam splitter 9 and is used for collecting the P' light and calculating two-dimensional angle information of a second reflecting mirror 15 containing the light angle drift amount error; the isolator 5 is used for isolating the S 'light and the P' light reflected by the sensitive unit III and transmitted by the spectroscope 7, and preventing adverse effects on the laser emission unit I;
the sensing unit III comprises a first polarizing beam splitter 13, a first reflecting mirror 14 and a second reflecting mirror 15; the first polarization beam splitter 13 is used for splitting the common-path S light and the common-path P light, the first reflector 14 is used for reflecting the S light and forming a common-path light beam between the measurement unit II and the sensitive unit III with the P light, since the first reflector 14 is fixed in position, the change of the spot position of the S ' light finally measured by the first detector 10 is a measurement error introduced by the drift of the angle of the light, the second reflector 15 is used for reflecting the P light, since the change of the two-dimensional angle of the second reflector 15 causes the change of the light direction of the reflected light P ' light, the change of the spot position of the P ' light finally measured by the second detector 11 includes the change of the two-dimensional angle of the second reflector 15 including the error of the drift of the angle of the light, and according to the change of the spot positions of the S ' light and the P ' light, the two;
the zeroing optical unit IV is composed of a third polarizing beam splitter 16, a third reflecting mirror 17, a fourth reflecting mirror 18, and a guide rail 19. When the time zero calibration is carried out, a parallel light beam containing two orthogonal polarized lights S and P is emitted by the measuring unit, and the S light is changed into S after being reflected by the third polarizing beam splitter 16, the surface of the third reflector 17 and the third polarizing beam splitter 16 in sequence0Light, S0The light returns to the measuring unit II and is reflected by the spectroscope 7, focused by the focusing lens 8 and reflected by the second polarizing spectroscope 9 in sequence, and then is collected and imaged by the first detector 10; the P light is transmitted by the third PBS 16, reflected by the surface of the fourth reflector 17 and transmitted by the third PBS 16 in sequence, and then becomes P0Light, P0The light returns to the measuring unit II and is reflected by the spectroscope 7, focused by the focusing lens 8 and transmitted by the second polarizing spectroscope 9 in sequence, and then is collected and imaged by the second detector 11; the measurement unit II simultaneously acquires S reflected by the zeroing optical unit IV0Light and P0The light is processed to obtain the measurement error caused by the mechanical structure of the measurement unit II and the circuit noise.
Example two
Fig. 5 is an optical path diagram of a sensing unit according to a second embodiment of the present invention, in which the reflecting mirror 14 of the first embodiment is changed to a reflecting film 14' plated on the surface of the first polarizing beam splitter 13.
EXAMPLE III
Fig. 6 is a light path diagram of a sensing unit according to a third embodiment of the present invention, in which the measured surfaces are two surfaces of a cube VI, the first pbs 13 is attached to one of the measured surfaces, and the second reflecting mirror 15 is attached to the other measured surface. The parts 13, 14 and 15 in this embodiment are the same as those in the embodiment, except that the object to be measured in the embodiment one is in an L shape, and the part 15 is adhered to the back of the L-shaped polyhedron. The object to be measured in this example is cube-shaped, so 15 is larger in size than in the first example, and is attached to the cube on the front side.
Example four
Fig. 7 is a light path diagram of a sensing unit according to a fourth embodiment of the present invention; the structure of the sensitive unit is adjusted according to the position of the measured surface. And because the two measured surfaces are not perpendicular to each other, an auxiliary module 20 is added to make the reflector 14 and the reflector 15 perpendicular to each other.
EXAMPLE five
Fig. 8 is an optical path diagram of a zeroing optical unit according to a fifth embodiment of the present invention, in which the third reflector 17 and the fourth reflector 18 of the zeroing optical unit according to the first embodiment are replaced with reflective films 17 'and 18' plated on the surface of the third polarization beam splitter 16.
EXAMPLE six
Fig. 9 is a structural view of a measurement state of the two-dimensional small-angle variation laser measurement device based on common-path difference according to the embodiment, fig. 10 is a structural view of a zeroing state of the two-dimensional small-angle variation laser measurement device based on common-path difference according to the embodiment, and fig. 11 is an optical path diagram of a zeroing optical unit according to the embodiment. The first zero calibration optical unit of the first embodiment is additionally provided with a pentagonal prism, the guide rail drives the pentagonal prism to move, and the third polarization beam splitter and the two reflectors are fixed.
The embodiment provides a two-dimensional small-angle change laser measurement method based on common-path difference, which comprises the following steps:
(1) same as in the example step (1);
(2) same as in the example step (2);
(3) same as in the example, step (3);
(4) same as in the example, step (4);
(5) same as in the example, step (5);
(6) as shown in fig. 10, the light emitted from the pentagonal prism 20 to the middle of the beam splitter 7 and the first polarization beam splitter 13 in the same track obtained in step (1) passes through the pentagonal prism 20, changes direction, and enters the third polarization beam splitter 16, and the S light is reflected by the third polarization beam splitter 16, reflected by the surface of the third reflector 17, and reflected by the third polarization beam splitter 16 in sequence to become S light0The light P is transmitted by the third PBS 16, reflected by the surface of the fourth reflector 18 and transmitted by the third PBS 16 in sequence, and then becomes P0Light, S0Light and P0The light changes direction after passing through the pentagonal prism 20 along the same track and returns to the spectroscope 7;
(7) same as in example step (7);
(8) same as in example step (8);
(9) same as in example step (9);
(10) same as in example step (10).
The difference between the measurement device provided by the embodiment and the first embodiment, which is based on the common-path difference polyhedral workpiece included angle change laser measurement method, is that the zeroing optical unit IV has a different structure.
The zeroing optical unit IV is composed of a third polarizing beam splitter 16, a third reflecting mirror 17, a fourth reflecting mirror 18, a guide rail 19, and a pentagonal prism 20. When the time alignment is finished, the pentagonal prism 20 moves to the middle of the beam splitter 7 and the first polarizing beam splitter 13 along the guide rail 19, a parallel light beam containing two orthogonal polarized lights S light and P light is emitted from the measuring unit, the direction of the parallel light beam is changed after passing through the pentagonal prism 20, the parallel light beam is incident to the third polarizing beam splitter 16, and the S light is changed into S light after being reflected by the third polarizing beam splitter 16, the surface of the third reflector 17 and the third polarizing beam splitter 16 in sequence0Light, S0The light changes direction after passing through the pentagonal prism 20, returns to the measuring unit II, is reflected by the spectroscope 7, focused by the focusing lens 8 and reflected by the second polarizing spectroscope 9 in sequence, and is collected and imaged by the first detector 10; the P light is transmitted by the third PBS 16, reflected by the surface of the fourth reflector 17 and transmitted by the third PBS 16 in sequence, and then becomes P0Light, P0Light passes throughThe direction of the light beam is changed after passing through a pentagonal prism 20, the light beam returns to the measuring unit II, and the light beam is reflected by a spectroscope 7, focused by a focusing lens 8 and transmitted by a second polarizing spectroscope 9 in sequence and then is collected and imaged by a second detector 11; the measurement unit II simultaneously acquires S reflected by the zeroing optical unit IV0Light and P0The light is processed to obtain the measurement error caused by the mechanical structure of the measurement unit II and the circuit noise.
In summary, in the embodiment of the present invention, the two signals of the S light and the P light are common signals from the measurement unit to the sensing unit, so that the measurement error is reduced. The zero calibration optical unit can reduce circuit noise and measurement errors caused by a mechanical structure of the measurement unit during long-term measurement, and can realize measurement of the change of an included angle of a precision workpiece in different states.
The two signals of the S light and the P light are common signals from the measuring unit to the sensitive unit, so that the measuring error is reduced.
The zero calibration unit in the invention can reduce the measurement error caused by circuit noise and the mechanical structure of the measurement unit during long-term measurement.
Those of ordinary skill in the art will understand that: the figures are merely schematic representations of one embodiment, and the blocks or flow diagrams in the figures are not necessarily required to practice the present invention.
The embodiments in the present specification are described in a progressive manner, and the same and similar parts among the embodiments are referred to each other, and each embodiment focuses on the differences from the other embodiments. In particular, for apparatus or system embodiments, since they are substantially similar to method embodiments, they are described in relative terms, as long as they are described in partial descriptions of method embodiments. The above-described embodiments of the apparatus and system are merely illustrative, and the units described as separate parts may or may not be physically separate, and the parts displayed as units may or may not be physical units, may be located in one place, or may be distributed on a plurality of network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the solution of the present embodiment. One of ordinary skill in the art can understand and implement it without inventive effort.
The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.
Claims (11)
1. A common-path difference-based laser measurement method for angle change of a polyhedral workpiece is characterized by comprising the following steps:
step 1, a beam of laser emitted by a laser is expanded and collimated into a parallel beam by a collimating lens, the parallel beam passes through a polarizer to obtain two orthogonal polarized lights S and P, and the S and P are emitted along the same track after being transmitted by a spectroscope;
step 2, after the S light and the P light emitted from the same track are incident to the first polarization beam splitter, the S light is reflected by the first polarization beam splitter, and the P light is transmitted by the first polarization beam splitter;
step 3, the reflected light of the first polarizing beam splitter is reflected by the first reflector and then changed into S ' light, the S ' light is reflected by the first polarizing beam splitter and then returns along the original light path, the S ' light is imaged on the sensitive surface of the first detector after being reflected by the beam splitter, focused by the focusing lens and reflected by the second polarizing beam splitter, and two-dimensional angle information of the first reflector containing the light angle drift amount error is calculated according to the imaging coordinate;
step 4, the transmitted light of the first polarizing beam splitter is reflected by a second reflecting mirror and carries two-dimensional angle information of the second reflecting mirror to be changed into P ' light, the P ' light is transmitted by the first polarizing beam splitter and returns along an original light path, the P ' light is reflected by the beam splitter, focused by a focusing lens and transmitted by the second polarizing beam splitter and is imaged on a sensitive surface of a second detector, and the two-dimensional angle information of the second reflecting mirror containing the light angle drift amount error is calculated according to imaging coordinates; the first reflector and the second reflector are respectively adhered to two surfaces of the polyhedral workpiece, and two-dimensional angles of two surface types of the polyhedral workpiece are respectively represented;
and 5, calculating to obtain the relative two-dimensional angle change information of the first reflector and the second reflector according to the two-dimensional angle information of the first reflector and the two-dimensional angle information of the second reflector containing the light angle drift amount error, wherein the relative two-dimensional angle change information represents the relative two-dimensional angle change of two surface types of the polyhedral workpiece.
2. The method of claim 1, wherein calculating two-dimensional angular information of the first mirror including the error in the angular shift of the light from the imaging coordinates comprises:
let the imaging coordinate be (x)1,y1) When the components of the light angle drift amount in the x-axis and the y-axis are α 'and β', respectively, and the focal length of the focusing lens is f, the two-dimensional angle information of the first reflecting mirror including the error of the light angle drift amount is α1+α′＝arctan(x1/2f)、β1+β′＝arctan(y2/2f)。
3. The method of claim 2, wherein said calculating two-dimensional angular information of the second mirror including the error in the angular shift of the light from the imaging coordinates comprises:
let the imaging coordinate be (x)2,y2) The focal length of the focusing lens is f, and since the P 'light and the S' light are basically in the same path, the components of the ray angle drift in the two directions of the x axis and the y axis are respectively alpha 'and beta', and the two-dimensional angle change of the second reflector including the ray angle drift error is respectively alpha2+α′＝arctan(x2/2f)、β2+β′＝arctan(y2/2f)。
4. The method of claim 3, wherein said calculating two-dimensional angular change information of the first mirror relative to the second mirror comprises:
the relative two-dimensional angle variation of the first reflector is calculated by the following formula:
△α＝α2-α1＝arctan(x2/2f)-arctan(x1/2f)
the relative two-dimensional angle variation of the second reflector is calculated by the following formula:
△β＝β2-β1＝arctan(y2/2f)-arctan(y1/2f)。
5. the method of any one of claims 1 to 4, further comprising:
step 6, moving a zero calibration optical unit composed of a third polarizing beam splitter, a third reflector and a fourth reflector to the middle of the beam splitter and the first polarizing beam splitter, so that S light and P light emitted along the same track are incident to the third polarizing beam splitter, and the S light is changed into S light after being reflected by the third polarizing beam splitter, the surface of the third reflector and the third polarizing beam splitter in sequence0The light P is transmitted by the third polarization beam splitter, the surface of the fourth reflector and the third polarization beam splitter in sequence and then becomes P0Light, S0Light and P0The light returns to the spectroscope along the same trajectory;
step 7, S0Light is reflected by the beam splitter, focused by the focusing lens and reflected by the second polarizing beam splitter in sequence, then is collected by the first detector for imaging, the signal drift amount of the first detector is calculated according to imaging coordinates, and the signal drift amount of the first detector comprises the circuit drift amount of the first detector and S0Errors introduced by mechanical structural stability of the optics through which the light passes;
the first detector signal drift amount is calculated by the following formula:
αs＝arctan(xs/2f)、βs＝arctan(ys/2f)
step 8, P0The light is reflected by the spectroscope, focused by the focusing lens and transmitted by the second polarizing spectroscope in sequence, then is collected by the second detector for imaging, and the signal drift amount of the second detector is calculated according to the imaging coordinateThe second detector signal drift amount comprises second detector circuit drift amount and P0Errors introduced by mechanical structural stability of the optics through which the light passes;
the second detector signal drift amount is calculated by the following formula:
αp＝arctan(xp/2f)、βp＝arctan(yp/2f)
step 9, calculating to obtain relative two-dimensional angle change information of the first reflector and the second reflector for eliminating light angle drift, circuit drift and mechanical structure stability errors according to the two-dimensional angle information of the first reflector, the two-dimensional angle information of the second reflector, the signal drift amount of the first detector and the signal drift amount of the second detector;
the relative two-dimensional angle change information of the first reflector is calculated by the following formula:
△α＝(α2-αp)-(α1-αs)
＝arctan(x2/2f)-arctan(xp/2f)-arctan(x1/2f)+arctan(xs/2f)
the relative two-dimensional angle change information of the second reflector is calculated by the following formula:
△β＝(β2-βp)-(β1-βs)
＝arctan(y2/2f)-arctan(yp/2f)-arctan(y1/2f)+arctan(ys/2f)。
6. the method of claim 5, further comprising:
adding a pentagonal prism to the zero calibration optical unit, and driving the pentagonal prism to move by the guide rail;
in the step 6, the light emitted from the pentagonal prism 20 is moved to the middle of the beam splitter 7 and the first polarization beam splitter 13, so that the S light and the P light emitted along the same track change directions after passing through the pentagonal prism 20 and enter the third polarization beam splitter 16, the S light is reflected by the third polarization beam splitter 16, reflected by the surface of the third reflector 17, and split by the third polarization beam splitter in sequenceAfter reflection by the mirror 16, it becomes S0The light P is transmitted by the third PBS 16, reflected by the surface of the fourth reflector 18 and transmitted by the third PBS 16 in sequence, and then becomes P0Light, S0Light and P0The light follows the same trajectory, changes direction after passing through the penta prism 20, and returns to the beam splitter 7.
7. A laser measuring device of a method for measuring the change of an included angle of a polyhedral workpiece based on common path difference is characterized by comprising the following steps: the device comprises a laser emitting unit, a measuring unit and a sensitive unit;
the laser emitting unit comprises a laser; or the device comprises a laser and an optical fiber, wherein the laser is flexibly connected with the measuring unit through a single optical fiber;
the measurement unit includes: the device comprises a laser incident end, a collimating mirror, an isolator, a polarizer, a spectroscope, a focusing lens, a second polarizing spectroscope, a first detector and a second detector; the laser beam splitter comprises a laser incidence end, a collimating mirror, an isolator, a polarizer and a beam splitter, wherein the laser incidence end, the collimating mirror, the isolator, the polarizer and the beam splitter are sequentially arranged along the direction of laser emitted from the laser incidence end, a focusing lens and a second polarizing beam splitter are sequentially arranged along the direction of laser reflected by the beam splitter and reflected by the beam splitter, the focusing lens is used for focusing and imaging the reflected measuring light S ' and the measuring light P ', the second polarizing beam splitter is used for splitting the common-path S ' and P ' light, and a first detector is arranged at an equivalent focal plane of the focusing lens reflected by the second polarizing beam splitter and used for collecting the S ' and calculating the light angle drift amount; the second detector is arranged at the equivalent focal plane of the focusing lens after being transmitted by the second polarizing beam splitter and is used for collecting the P' light and calculating the two-dimensional angle information of the second reflecting mirror containing the light angle drift amount error; the isolator is used for isolating the S 'light and the P' light reflected by the sensitive unit and transmitted by the spectroscope, and preventing the laser emission unit from being adversely affected.
The sensitive unit comprises a first polarizing beam splitter, a first reflecting mirror and a second reflecting mirror; the first polarizing beam splitter is used for splitting the S light and the P light which share the same path, the first reflector is used for reflecting the S light and forming a light beam which shares the path with the P light between the measuring unit and the sensitive unit, the change of the spot position of the S ' light measured by the first detector is changed into a measuring error introduced by the angle drift of the light, the second reflector is used for reflecting the P light, the change of the spot position of the P ' light measured by the second detector is changed into a two-dimensional angle of the second reflector which contains the error of the angle drift of the light, and the two-dimensional angle information of the second reflector is obtained by calculation according to the change of the spot position of the S ' light and the P.
8. The apparatus of claim 7, further comprising:
the zero calibration optical unit consists of a third polarizing beam splitter, a third reflector, a fourth reflector and a guide rail, wherein when zero calibration is performed, a parallel light beam containing two orthogonal polarized lights S light and P light is emitted by the measuring unit, and the S light is changed into S light after being reflected by the third polarizing beam splitter, the surface of the third reflector and the third polarizing beam splitter in sequence0Light, S0The light returns to the measuring unit, is reflected by the beam splitter, focused by the focusing lens and reflected by the second polarizing beam splitter, and is collected and imaged by the first detector; the P light is transmitted by the third polarization spectroscope, the surface of the fourth reflector and the third polarization spectroscope in sequence and then becomes P0Light, P0The light returns to the measuring unit, is reflected by the spectroscope, is focused by the focusing lens and is transmitted by the second polarization spectroscope, and then is collected by the second detector for imaging; the measuring unit simultaneously collects the S light and the P light reflected by the zero calibration optical unit, and the measurement error caused by the mechanical structure of the measuring unit and the circuit noise is obtained after processing.
9. The apparatus of claim 7, further comprising:
the zero calibration optical unit consists of a third polarizing spectroscope, a third reflector, a fourth reflector, a guide rail and a pentagonal prism, wherein the pentagonal prism moves to the middle of the spectroscope and the first polarizing spectroscope along the guide rail during zero calibration, a parallel light beam containing two orthogonal polarized lights S light and P light is emitted from the measuring unit, and the direction of the parallel light beam is changed after passing through the pentagonal prism and then the parallel light beam is incident to the third polarizing spectroscopeThe S light is reflected by the third polarizing beam splitter, the surface of the third reflector and the third polarizing beam splitter in sequence and then becomes S0Light, S0The direction of the light is changed after passing through the pentagonal prism, the light returns to the measuring unit and is collected and imaged by the first detector after being reflected by the beam splitter, focused by the focusing lens and reflected by the second polarizing beam splitter in sequence; the P light is transmitted by the third polarization spectroscope, the surface of the fourth reflector and the third polarization spectroscope in sequence and then becomes P0Light, P0The light changes direction after passing through the pentagonal prism, returns to the measuring unit, is reflected by the beam splitter, focused by the focusing lens and transmitted by the second polarizing beam splitter in sequence, and is collected and imaged by the second detector; the measuring unit simultaneously collects S reflected by the zero calibration optical unit0Light and P0The light is processed to obtain the measurement error caused by the mechanical structure of the measurement unit and the circuit noise.
10. The apparatus according to claim 7, 8 or 9, wherein the structure of the sensing unit is adjusted according to the position of the measured surface, and when the two measured surfaces are not perpendicular to each other, an auxiliary module is added to make the first reflecting mirror and the second reflecting mirror perpendicular to each other.
11. The apparatus of claim 7 wherein the first mirror is modified to be a reflective film plated on a surface of the first polarizing beamsplitter.
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