CN110849293B - Four-beam structure laser heterodyne interference roll angle measuring device and method - Google Patents
Four-beam structure laser heterodyne interference roll angle measuring device and method Download PDFInfo
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Abstract
The invention discloses a device and a method for measuring a roll angle by heterodyne interference of laser with a four-beam structure, wherein the device comprises a single-frequency laser, and a depolarization beam splitter prism is arranged on an emergent light path of the single-frequency laser; the reflection optical axis and the transmission optical axis of the depolarization beam splitter prism are respectively connected with the right-angle prism through the acousto-optic modulator and the polarization beam splitter prism to form two groups of diffraction light, the two groups of diffraction light are respectively connected with the beam splitter prism through a quarter wave plate to form two beams of measuring light, and the directions of two emergent surfaces of the beam splitter prism are respectively connected with the phase meter through the photoelectric detector and are connected with the computer through the phase meter. The invention improves the measurement resolution of the single-beam measuring light, greatly improves the measurement resolution, and can provide a more precise and reliable detection method and technology for the roll angle measurement of a precise guide rail kinematic pair, a high-grade numerical control machine tool and the like.
Description
Technical Field
The invention belongs to the technical field of photoelectric roll angle measurement, and particularly relates to a four-beam structure laser heterodyne interference roll angle measurement device and method.
Background
Precision guide rails play an important role in the manufacturing industry, aerospace industry and other industries. There are six geometric errors in the linear guide rail, which are: positioning error, two straightness errors, pitch angle, yaw angle and roll angle. Therefore, the high-precision measurement of the rolling angle error of the guide rail is an important index for measuring the performance of the precision guide rail, and is also a key technology for checking the acceptance of products and compensating the error.
In the six-degree-of-freedom errors, the other five errors except the rolling angle can be measured by an interferometer based on optical path difference change, and for the rolling angle error, because the error direction is vertical to the measuring beam direction, the additional optical path difference cannot be introduced, the measurement of the rolling angle is relatively difficult, and at present, the rolling angle is still in a research and exploration stage at home and abroad.
The current heterodyne interferometer based on polarization state change can measure the roll angle, and the main principle is that the roll of a half wave plate serving as a detection sensitive element introduces the change of the polarization state of a light beam, so that the phase change of the measuring light beam is caused. The rolling angle error of the wave plate can be calculated by detecting the phase variation.
However, the phase change sensitive regions of two frequency components in the measurement light of the current heterodyne interferometer based on polarization state change along with the change of the roll angle are not overlapped, and the sensitive regions of the two components appear alternately, so that the high-resolution measurement of the two light beams cannot be fully utilized, and the measurement resolution of the system cannot be effectively improved.
Disclosure of Invention
The invention aims to solve the technical problem that the defects in the prior art are overcome, and provides a device and a method for measuring the roll angle by using the laser heterodyne interference in the four-beam structure.
The invention adopts the following technical scheme:
a four-beam structure laser heterodyne interference roll angle measuring device comprises a single-frequency laser, wherein a depolarization beam splitter prism is arranged on an emergent light path of the single-frequency laser; the reflection optical axis and the transmission optical axis of the depolarization beam splitter prism are respectively connected with the right-angle prism through the acousto-optic modulator and the polarization beam splitter prism to form two groups of diffraction light, the two groups of diffraction light are respectively connected with the beam splitter prism through a quarter wave plate to form two beams of measuring light, and the directions of two emergent surfaces of the beam splitter prism are respectively connected with the phase meter through the photoelectric detector and are connected with the computer through the phase meter.
Specifically, a first reflector and a first acousto-optic modulator are sequentially arranged on a reflection optical axis of the depolarization beam splitter prism, and a first polarization beam splitter prism is arranged on a first diffraction optical axis emitted by the first acousto-optic modulator; the first emergent surface of the first polarization beam splitter prism is connected with the first right-angle surface of the right-angle prism, and the direction of the second emergent surface of the first polarization beam splitter prism is the same as that of the second right-angle surface of the first right-angle prism; the first diffraction light is divided into a first light beam and a second light beam through a first polarization beam splitter prism and a first right-angle prism; and a first quarter wave plate is arranged in the emergent direction of the second emergent surface of the first polarization beam splitter prism and the second right-angle surface of the first right-angle prism, and the first light beam and the second light beam enter the first incident surface of the beam splitter prism after passing through the first quarter wave plate.
Specifically, a second sound light modulator is arranged on a transmission optical axis of the linear polarization beam splitter prism; a second reflector is arranged on the optical axis of second diffraction light emitted by the second acousto-optic modulator, and a second polarization beam splitter prism is arranged on the optical axis of reflected light of the second reflector; the first emergent surface of the second polarization beam splitter prism is connected with the first right-angle surface of the second right-angle prism, and the direction of the second emergent surface of the second polarization beam splitter prism is the same as that of the second right-angle surface of the second right-angle prism; the second diffracted light is divided into a third light beam and a fourth light beam through a polarization beam splitter prism and a right-angle prism; a second quarter-wave plate is arranged in the emergent direction of a second emergent surface of the second polarization beam splitter prism and a second right-angle surface of the second right-angle prism; and the light beam three and the light beam four enter the second incidence surface of the beam splitter prism after passing through the second quarter wave plate.
Specifically, a half wave plate and a reflector are respectively arranged in the direction of an emergent surface of the beam splitter prism, and two beams of measuring light respectively pass through the half wave plate and are reflected by the reflector in parallel and then pass through the half wave plate again; and polarizing plates and a photoelectric detector are respectively arranged on the optical axes of the two returned measuring light beams, and the light transmission axes of the two polarizing plates are perpendicular to each other.
Furthermore, the reflector is a plane reflector with two mutually vertical reflecting surfaces, the two reflecting surfaces are both plated with dielectric films, and the incident angle of the reflector is 45 degrees.
Specifically, the two groups of diffracted lights are both positive or negative, the driving frequencies of the two acousto-optic modulators are different, and the difference value between the two driving frequencies is within the detection limit range of the photoelectric detector.
Specifically, the polarization direction of the laser emitted by the single-frequency laser and the incidence plane of the depolarization beam splitter prism form 45 degrees.
Specifically, the fast axis directions of the two quarter-wave plates are arranged perpendicular to each other.
The invention also provides a method for measuring the roll angle by heterodyne interference of the four-beam laser, which comprises a single-frequency laser, wherein a depolarization beam splitter prism is arranged on an emergent light path of the single-frequency laser, and a reflection optical axis of the depolarization beam splitter prism is connected with the beam splitter prism after sequentially passing through a first reflector, a first acousto-optic modulator, a first polarization beam splitter prism, a first right-angle prism and a first quarter-wave plate; the transmission optical axis of the linear polarization beam splitter prism is connected with the beam splitter prism after sequentially passing through the second sound optical modulator, the second reflector, the second polarization beam splitter prism, the second right-angle prism and the second quarter wave plate; the half wave plate, the reflector, the two polarizing plates, the two photoelectric detectors, the phase meter and the computer are sequentially arranged in the direction of the emergent surface of the beam splitter prism; the specific measurement steps are as follows:
s1, after passing through a depolarization beam splitter prism, a light beam emitted by the single-frequency laser is split into transmission light and reflection light, and the reflection light is reflected by a first reflector and then passes through a first acousto-optic modulator to generate first diffraction light; the first diffraction light is divided into a first light beam and a second light beam after passing through a first polarization beam splitter prism and a first right-angle prism; the transmitted light is reflected by the second reflector after being generated by the second acousto-optic modulator; the light beam is divided into a third light beam and a fourth light beam through a second polarization beam splitter prism and a second right-angle prism; the light beam I and the light beam II enter the beam splitting prism through the first quarter-wave plate, and the light beam III and the light beam pass through the second quarter-wave plate beam splitting prism;
s2, combining the first light beam and the third light beam into measuring light A through a beam splitter prism, and combining the second light beam and the fourth light beam into measuring light B through the beam splitter prism; the measuring light A and the measuring light B penetrate through a half wave plate fixed on a measured object, then are reflected by a reflector to return in parallel, and after passing through the half wave plate again, the measuring light A and the measuring light B respectively pass through a first polarizer and a second polarizer to form beat light, and then are respectively received by a first photoelectric detector and a second photoelectric detector;
s3, the first photoelectric detector and the second photoelectric detector input the received signals to a phase meter for phase discrimination, and finally data are transmitted to a computer, and the computer calculates the roll angle delta alpha of the object fixed by the half wave plate according to the variation of the phase difference of the two signals and the roll angle.
Specifically, the roll angle Δ α is measured and calculated by the following formula:
G＝16cotθ
and the delta psi is the phase difference variation of the measuring light A and the measuring light B, the G is the amplification factor of the measuring system, and the theta is an included angle between the fast axis direction of the first quarter-wave plate and the three polarization directions of the light beam.
Compared with the prior art, the invention has at least the following beneficial effects:
the layout of four light beams of the measuring device enables the four light beams to be combined into two measuring lights, and the phase change sensitive areas of two frequency components in each measuring light are mutually overlapped by setting the angles of the two quarter-wave plates and the two polaroids, so that the measuring resolution of single measuring light is improved; in addition, the phase shift directions of the two measuring lights generated along with the change of the roll angle are opposite, so that the change of the phase difference of the two signals output by the system is doubled, and the measuring resolution is greatly improved.
Further, the polarization direction of the laser emitted by the single-frequency laser device forms 45 degrees with the incident plane of the depolarization beam splitter prism, and the 45 degrees are arranged so that the depolarization beam splitter prism can divide the first diffracted light into a first light beam and a second light beam with the same light intensity, and divide the second diffracted light into a third light beam and a fourth light beam with the same light intensity.
Further, the transmission axis directions of the first polarizing plate and the second polarizing plate of the present invention are perpendicular to each other, so that the measurement sensitive regions of the measurement light a and the measurement light B coincide.
Further, the driving frequency of the first acousto-optic modulator of the present invention is different from the driving frequency of the second acousto-optic modulator, and the difference between the two driving frequencies is within the detection limit of the detector. The first light beam and the third light beam can be combined into double-frequency laser and can be detected by a detector, and the second light beam and the fourth light beam can also be combined into double-frequency laser and can be detected by the detector.
Furthermore, the reflector of the invention is a plane reflector with two mutually vertical reflecting surfaces, the two reflecting surfaces are both plated with dielectric films, and the incident angle of the reflector is 45 degrees. So that the reflector can reflect the light beam in parallel and keep the polarization unchanged.
Further, the fast axis directions of the first quarter wave plate and the second quarter wave plate of the present invention are perpendicular to each other, so that the phase change sensitive regions of the two frequency components in the measurement light a and the measurement light B can coincide with each other.
Furthermore, the invention also discloses a method for measuring the roll angle by the heterodyne interference of the laser with the four-beam structure, the phase of the measuring light A and the phase of the measuring light B are measured, the roll angle is calculated, and the phase change sensitive areas of the two frequency components of each measuring light are overlapped, so that the measuring resolution of the single measuring light is improved.
In conclusion, the invention improves the measurement resolution of the single beam of measurement light, greatly improves the measurement resolution, and can provide a more precise and reliable detection method and technology for the roll angle measurement of a precise guide rail kinematic pair, a high-grade numerical control machine tool and the like.
The technical solution of the present invention is further described in detail by the accompanying drawings and embodiments.
Drawings
FIG. 1 is a schematic structural diagram of a measuring device according to the present invention.
Wherein: 1. a single-frequency laser; 2. a depolarization beam splitter prism; 3. a first reflector; 4. a first acousto-optic modulator; 5. a second acousto-optic modulator; 6. a second reflector; 7. a first polarization splitting prism; 8. a first right-angle prism; 9. a second polarization beam splitter prism; 10. a second right-angle prism; 11. a first quarter wave plate; 12. a second quarter wave plate; 13. a beam splitter prism; 14. a half wave plate; 15. a reflector; 16. a first polarizing plate; 17. a second polarizing plate; 18. a photodetector; 18a. a first photodetector; 18b. a second photodetector; 19. a phase meter; 20. and (4) a computer.
Detailed Description
In the description of the present invention, it is to be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "one side", "one end", "one side", and the like indicate orientations or positional relationships based on those shown in the drawings, and are only for convenience of description and simplicity of description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed in a particular orientation, and be operated, and thus, are not to be construed as limiting the present invention. Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of the present invention, "a plurality" means two or more unless otherwise specified.
In the description of the present invention, it should be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "connected," and "connected" are to be construed broadly, e.g., as meaning either a fixed connection, a removable connection, or an integral connection; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present invention can be understood in specific cases to those skilled in the art.
Referring to fig. 1, the high-precision measuring device for roll angle by four-beam laser heterodyne interference of the present invention includes a single-frequency laser 1, a depolarizing beam splitter 2, a first reflector 3, a first acousto-optic modulator 4, a second acousto-optic modulator 5, a second reflector 6, a polarization beam splitter 7, a first right-angle prism 8, a polarization beam splitter 9, a second right-angle prism 10, a first quarter-wave plate 11, a second quarter-wave plate 12, a beam splitter 13, a half-wave plate 14, a reflector 15, a first polarizer 16, a second polarizer 17, a photodetector 18, a phase meter 19, and a computer 20.
The depolarization beam splitter prism 2 is arranged on an emergent light path of the single-frequency laser 1; a first reflector 3 and a first acousto-optic modulator 4 are sequentially arranged on a reflection optical axis of the depolarization beam splitter prism 2; a first polarization beam splitter prism 7 is arranged on the optical axis of a first diffraction light emitted by the first acousto-optic modulator 4; a first emergent surface of the first polarization beam splitter prism 7 is connected with a first right-angle surface of the first right-angle prism 8, and the direction of a second emergent surface of the first polarization beam splitter prism 7 is the same as that of a second right-angle surface of the first right-angle prism 8; the first diffracted light is divided into a first light beam and a second light beam through a first polarization beam splitter prism 7 and a first right-angle prism 8; a first quarter-wave plate 11 and a beam splitter prism 13 are sequentially arranged in the emergent direction of the second emergent surface of the first polarization beam splitter prism 7 and the second right-angle surface of the first right-angle prism 8; the first light beam and the second light beam enter at the first incident surface of the beam splitter prism 13.
A second sound light modulator 5 is arranged on the transmission optical axis of the linear polarization beam splitter prism 2; a second reflector 6 is arranged on the optical axis of second diffraction light emitted by the second acousto-optic modulator 5, and a second polarization beam splitter prism 9 is arranged on the optical axis of reflected light of the second reflector 6; a first emergent surface of the second polarization beam splitter prism 9 is connected with a first right-angle surface of the second right-angle prism 10, and the direction of a second emergent surface of the second polarization beam splitter prism 9 is the same as that of a second right-angle surface of the second right-angle prism 10; the second diffracted light is divided into a third light beam and a fourth light beam through a polarization beam splitter prism 9 and a right-angle prism 10; a second quarter-wave plate 12 and a beam splitter prism 13 are sequentially arranged in the emergent direction of a second emergent surface of the second polarization beam splitter prism 9 and a second right-angle surface of the second right-angle prism 10; the third light beam and the fourth light beam enter at the second incident surface of the beam splitter prism 13.
The first light beam and the third light beam are synthesized into measuring light A through the beam splitter prism 13, and the second light beam and the fourth light beam are synthesized into measuring light B through the beam splitter prism; a half wave plate 14 and a reflector 15 are respectively arranged in the direction of the emergent surface of the beam splitter prism 13; the measuring light A and the measuring light B respectively pass through the half-wave plate 14, are reflected by the reflector 15 in parallel and then pass through the half-wave plate 14 again; a first polaroid 16 and a first photoelectric detector 18a are sequentially arranged on the optical axis of the returned measuring light A, and a second polaroid 17 and a second photoelectric detector 18B are sequentially arranged on the optical axis of the returned measuring light B; the first photodetector 18a and the first photodetector 18b are each connected to a phase meter 19, and the phase meter 19 is connected to a computer 20 for deriving the roll angle from the phase difference.
The first diffraction light and the second diffraction light are both positive first order or negative first order.
The polarization direction of the laser emitted by the single-frequency laser 1 and the incident plane of the depolarization beam splitter prism 2 form an angle of 45 degrees.
The driving frequency of the first acousto-optic modulator 4 is different from the driving frequency of the second acousto-optic modulator 5, and the difference between the two driving frequencies is within the detection limit of the detector 18.
The fast axis directions of the first quarter-wave plate 11 and the second quarter-wave plate 12 are perpendicular to each other.
The reflector 15 is a plane reflector with two reflecting surfaces perpendicular to each other, the two reflecting surfaces are both plated with dielectric films, and the incident angle of the reflector is 45 degrees.
The transmission axis directions of the first polarizer 16 and the second polarizer 17 are perpendicular to each other.
The invention provides a beam-splitting modulation type heterodyne interference method roll angle measurement method, which comprises the following steps of:
s1, after passing through a depolarization beam splitter 2, a light beam emitted by the single-frequency laser 1 is split into transmitted light and reflected light, and the reflected light is reflected by a first reflector 3 and then passes through a first acousto-optic modulator 4 to generate first diffracted light; the first diffraction light is divided into a first light beam and a second light beam through a first polarization beam splitter prism 7 and a first right-angle prism 8; the transmitted light is reflected by a second reflecting mirror 6 through a second sound light modulator 5 to generate second diffraction light; the second diffraction light is divided into a third light beam and a fourth light beam through a second polarization beam splitter prism 9 and a second right-angle prism 10; the first light beam and the second light beam enter the beam splitter prism 13 through the first quarter-wave plate 11, and the third light beam and the second light beam enter the beam splitter prism 13 through the second quarter-wave plate 14;
s2, the first light beam and the third light beam are combined into measuring light A through the beam splitter prism 13, and the second light beam and the fourth light beam are combined into measuring light B through the beam splitter prism 13; the measuring light A and the measuring light B penetrate through a half wave plate 14 fixed on a measured object, then are reflected by a reflector 15 to return in parallel, and after passing through the half wave plate 14 again, the measuring light A and the measuring light B respectively pass through a first polarizing plate 16 and a second polarizing plate 17 to form beat frequency light, and then are respectively received by a first photoelectric detector 18a and a second photoelectric detector 18B;
s3, the first photoelectric detector 18a and the second photoelectric detector 18b input the received signals to the phase meter 19 for phase discrimination, and finally transmit the data to the computer 20, and the computer 20 calculates the roll angle Delta alpha of the object fixed by the half-wave plate 14 according to the relation between the variation of the phase difference of the two signals and the roll angle.
The roll angle Δ α is measured and calculated by the formula:
G＝16cotθ
wherein, Δ ψ is the phase difference variation of the measuring light a and the measuring light B, G is the amplification factor of the measuring system, and θ is the angle between the fast axis direction of the first quarter-wave plate 11 and the polarization direction of the light beam.
The invention is suitable for the field of high-precision industrial measurement, in particular to a precision guide rail kinematic pair and equipment based on the precision guide rail kinematic pair, such as: the wide application of the roll angle error measurement of the high-grade numerical control machine tool can greatly promote the development of industries such as machine tool manufacturing and the like.
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. The components of the embodiments of the present invention generally described and illustrated in the figures herein may be arranged and designed in a wide variety of different configurations. Thus, the following detailed description of the embodiments of the present invention, presented in the figures, is not intended to limit the scope of the invention, as claimed, but is merely representative of selected embodiments of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Referring to fig. 1, the derivation of the phase difference variation and the roll angle specifically includes:
and establishing a unified laboratory coordinate system, wherein the polarization direction of the light beam three is taken as an x axis, the polarization direction of the light beam four is taken as a y axis, and the forward propagation direction of the light beam is taken as a z axis.
Wherein the quarter-wave plate QWPAThe included angle theta between the fast axis direction and the polarization direction of the measuring lighta，QWPBThe included angle between the fast axis direction and the three polarization directions of the measuring light is thetabAnd has a value of thetab-θaPi/2, polarizing plate PAThe transmission axis of (A) and the x axis form gammaaCorner, PBThe transmission axis of (A) and the x axis form gammabAngle and having a value of gammab-γa＝π/2。
Expressing the process in terms of a jones matrix, the four initial beams can be represented as:
the two quarter-wave plates are respectively represented as:
the jones matrix for the half-wave plate and polarizer is expressed as:
PA＝[cosγasinγa]
PB＝[cosγbsinγb]
the measurement signal a and the measurement signal B are specifically:
EA＝PAH(-α)H(α)[QaB1+QbB3](1)
EB＝PBH(-α)H(α)[QaB2+QbB4](2)
substituting the matrix into a formula to obtain the expression of two measuring lights as follows:
the alternating current signal in the measurement signal is:
the last term of the phase terms in the two formulas is the phase variation of the two measurement signals introduced by the roll, the two parts are subtracted and simplified to obtain the variation of the phase difference of the two measurement signals along with the roll, and the method specifically comprises the following steps:
the slope of the phase difference change curve can be obtained by performing derivation calculation on the formula 7), that is, the system responsivity is:
when 4 alpha-theta1-γaAt 0 or 180 deg., the responsivity of the system is at a maximum, i.e., the phase change is most pronounced with roll angle at the location which becomes the sensitive region of the system.
The responsivity at the sensitive spot is:
G＝16cotθa(9)
in the sensitive area, the relation between the phase difference of the measurement signals and the roll angle is
Δψ＝GΔα (10)
Wherein Δ α, i.e., the slight variation of the roll angle, caused by the roll of the half-wave plate 14 of the sensing element, is measured; Δ ψ is the amount of change in the phase difference between the measurement light and the reference light.
From equation 10), the roll angle Δ α is measured and calculated as:
when the included angle theta between the first quarter-wave plate and the x axis is 2 degrees, G is 456; at this point, if the resolution of the phase score is 0.01 °, the resolution of the measured roll angle is 0.07 ", and the sign is determined by system calibration.
The light path of the invention makes the phase change sensitive areas of the two frequency components coincide by splitting and modulating the two frequency components in the measuring light, thereby further improving the measurement magnification and the resolution by two times.
In summary, the measuring device of the invention sets four initial beams and four beams, so that the four beams are combined into two measuring lights, and the phase change sensitive regions of two frequency components in each measuring light are overlapped by setting the angles of the two quarter-wave plates and the two polarizing plates, thereby improving the measuring resolution of the single measuring light; in addition, the phase shift directions of the two measuring lights generated along with the change of the roll angle are opposite, so that the change of the phase difference of the two signals output by the system is doubled, and the measuring resolution is greatly improved. The method and the technology can provide a more precise and reliable detection method and technology for measuring the roll angle of a precision guide rail kinematic pair, a high-grade numerical control machine tool and the like.
The above-mentioned contents are only for illustrating the technical idea of the present invention, and the protection scope of the present invention is not limited thereby, and any modification made on the basis of the technical idea of the present invention falls within the protection scope of the claims of the present invention.
Claims (10)
1. A method for measuring a roll angle by four-beam structure laser heterodyne interference is characterized by comprising a single-frequency laser (1), wherein a depolarization beam splitter prism (2) is arranged on an emergent light path of the single-frequency laser (1), and a reflection optical axis of the depolarization beam splitter prism (2) is connected with a beam splitter prism (13) after sequentially passing through a first reflector (3), a first acousto-optic modulator (4), a first polarization beam splitter prism (7), a first right-angle prism (8) and a first quarter-wave plate (11); the transmission optical axis of the depolarization beam splitter prism (2) sequentially passes through the second sound optical modulator (5), the second reflecting mirror (6), the second polarization beam splitter prism (9), the second right-angle prism (10) and the second quarter wave plate (12) and then is connected with the beam splitter prism (13); a half wave plate (14), a reflector (15), two polarizing plates, a first photoelectric detector (18a), a second photoelectric detector (18b), a phase meter (19) and a computer (20) are sequentially arranged in the direction of an emergent surface of the beam splitter prism (13); the specific measurement steps are as follows:
s1, after passing through a depolarization beam splitter prism (2), light beams emitted by the single-frequency laser (1) are split into transmitted light and reflected light, and the reflected light is reflected by a first reflector (3) and then passes through a first acousto-optic modulator (4) to generate first diffracted light; the first diffraction light is divided into a first light beam and a second light beam after passing through a first polarization beam splitter prism (7) and a first right-angle prism (8); the transmitted light generates second diffraction light through a second sound light modulator (5), and the second diffraction light is reflected by a second reflecting mirror (6); the light beam is divided into a third light beam and a fourth light beam through a second polarization beam splitter prism (9) and a second right-angle prism (10); the light beam I and the light beam II enter the beam splitter prism (13) through the first quarter-wave plate (11), and the light beam III and the light beam IV pass through the beam splitter prism (13) of the second quarter-wave plate (12);
s2, the first light beam and the third light beam are combined into measuring light A through the beam splitter prism (13), and the second light beam and the fourth light beam are combined into measuring light B through the beam splitter prism (13); the measuring light A and the measuring light B penetrate through a half wave plate (14) fixed on a measured object, then are reflected by a reflector (15) to return in parallel, and after passing through the half wave plate (14) again, the measuring light A and the measuring light B respectively pass through a first polaroid (16) and a second polaroid (17) to form beat frequency light, and then are respectively received by a first photoelectric detector (18a) and a second photoelectric detector (18B);
s3, the first photoelectric detector (18a) and the second photoelectric detector (18b) input the received signals into the phase meter (19) for phase discrimination, and finally transmit the data to the computer (20), and the computer (20) calculates the roll angle delta alpha of the object fixed by the half wave plate (14) according to the variation of the phase difference of the two signals and the roll angle.
2. The method of claim 1 wherein the roll angle Δ α is measured and calculated as:
G＝16cotθ
and the delta psi is the phase difference variation of the measuring light A and the measuring light B, the G is the amplification factor of the measuring system, and the theta is an included angle between the fast axis direction of the first quarter-wave plate and the three polarization directions of the light beam.
3. A four-beam structure laser heterodyne interference roll angle measuring device using the method of claim 1, wherein a depolarizing beam splitter (2) is arranged on an outgoing light path of the single-frequency laser (1); the reflection optical axis and the transmission optical axis of the depolarization beam splitter prism (2) are respectively connected with the right-angle prism through the acousto-optic modulator and the polarization beam splitter prism to form two groups of diffraction light, the two groups of diffraction light are respectively connected with the beam splitter prism (13) after passing through a quarter-wave plate to form two beams of measuring light, the directions of two emergent surfaces of the beam splitter prism (13) are respectively connected with the phase meter (19) after passing through the photoelectric detector, and are connected with the computer (20) through the phase meter (19).
4. The device according to claim 3, characterized in that the first reflector (3) and the first acousto-optic modulator (4) are arranged on the reflection optical axis of the depolarizing beam splitter prism (2) in sequence, and the first polarizing beam splitter prism (7) is arranged on the optical axis of the first diffraction light emitted from the first acousto-optic modulator (4); a first emergent surface of the first polarization beam splitter prism (7) is connected with a first right-angle surface of the first right-angle prism (8), and the direction of a second emergent surface of the first polarization beam splitter prism (7) is the same as that of a second right-angle surface of the first right-angle prism (8); the first diffracted light is divided into a first light beam and a second light beam through a first polarization beam splitter prism (7) and a first right-angle prism (8); a first quarter wave plate (11) is arranged in the emergent direction of a second emergent surface of the first polarization beam splitter prism (7) and a second right-angle surface of the first right-angle prism (8), and the first light beam and the second light beam enter a first incident surface of the beam splitter prism (13) after passing through the first quarter wave plate (11).
5. A device according to claim 3, characterized in that a second acousto-optic modulator (5) is arranged on the transmission optical axis of the depolarizing beam-splitting prism (2); a second reflector (6) is arranged on the optical axis of second diffraction light emitted by the second acousto-optic modulator (5), and a second polarization beam splitter prism (9) is arranged on the optical axis of reflected light of the second reflector (6); a first emergent surface of the second polarization beam splitter prism (9) is connected with a first right-angle surface of the second right-angle prism (10), and the direction of a second emergent surface of the second polarization beam splitter prism (9) is the same as that of a second right-angle surface of the second right-angle prism (10); the second diffracted light is divided into a third light beam and a fourth light beam through a second polarization beam splitter prism (9) and a second right-angle prism (10); a second quarter-wave plate (12) is arranged in the emergent direction of a second emergent surface of the second polarization beam splitter prism (9) and a second right-angle surface of the second right-angle prism (10); and the light beam three and the light beam four enter the second incidence surface of the beam splitter prism (13) after passing through the second quarter wave plate (12).
6. The device according to claim 3, characterized in that the half wave plate (14) and the reflector (15) are respectively arranged in the direction of the exit surface of the beam splitter prism (13), and the two measuring lights respectively pass through the half wave plate (14) again after being reflected by the reflector (15) in parallel through the half wave plate (14); and polarizing plates and a photoelectric detector are respectively arranged on the optical axes of the two returned measuring light beams, and the light transmission axes of the two polarizing plates are perpendicular to each other.
7. A device according to claim 6, characterized in that the reflector (15) is a plane mirror with two reflecting surfaces perpendicular to each other, both reflecting surfaces being coated with a dielectric film, the reflector (15) having an angle of incidence of 45 °.
8. The apparatus of claim 3, wherein the two sets of diffracted lights are both positive orders or both negative orders, and the two acousto-optic modulators have different driving frequencies, the difference between the two driving frequencies being within the detection limit of the photodetector.
9. A device according to claim 3, characterized in that the polarization direction of the laser light emitted by the single-frequency laser (1) is 45 ° to the entrance face of the depolarizing beam-splitting prism (2).
10. A device according to claim 4 or 5, characterized in that the fast axis directions of the first quarter wave plate (11) and the second quarter wave plate (12) are arranged perpendicular to each other.
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| CN101581576A (en) * | 2009-06-22 | 2009-11-18 | 浙江理工大学 | Method for measuring straightness accuracy and position thereof based on double frequency interference principle |
| CN104180776A (en) * | 2014-08-21 | 2014-12-03 | 西安交通大学 | High-resolution roll angle measuring method and device based on heterodyne interferometric phase method |
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