CN111830272A - Object angular velocity measuring device based on rotary Doppler effect - Google Patents
Object angular velocity measuring device based on rotary Doppler effect Download PDFInfo
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- G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
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Abstract
The invention relates to an object angular velocity measuring device based on a rotary Doppler effect, which comprises a laser, a collimation and beam expansion lens, a phase type spatial light modulator, a computer, a beam splitter prism, a secondary reflection right-angle prism, a focusing lens, a CCD (charge coupled device) image sensor and a rotating shaft, wherein the laser emits Gaussian beams, the beams are expanded and collimated by the collimation and beam expansion lens and then irradiate on the phase type spatial light modulator, and a calculation hologram is transmitted to the phase type spatial light modulator through the computer to generate vortex beams and transmit part of the Gaussian beams; after being superposed, the two light beams are transmitted by the beam splitter prism and then are incident on a secondary reflection right-angle prism which rotates synchronously with the rotating shaft along the optical axis; after two reflections in the CCD image sensor, the superposed light beams are reflected by the beam splitter prism and then are converged on the CCD image sensor through the focusing lens to generate interference; and calculating the rotation angle of the dark spot in the interference pattern by a computer to obtain the angular speed of the rotating object. The device of the invention has simple structure and easy operation.
Description
Technical Field
The invention relates to an object angular velocity measuring device based on a rotary Doppler effect.
Background
Poynting provided the concept as early as 1909 for photon carrying angular momentum, and the photon carrying angular momentum is related to the polarization state of light, and the photon spin angular momentum was successfully verified by Beth et al in 1936 by using mechanical experiments, and the spin angular momentum of left-handed and right-handed circularly polarized light was measured.Allen showed by 1992 that photons also carry another form of momentum, called orbital angular momentum. The light carrying the orbital angular momentum is called vortex rotation and can be prepared by a spiral phase plate, a spatial light modulator, a computer generated hologram and the like, the vortex light has a circular intensity distribution and a spiral phase distribution, and the phase of the vortex light can be represented by eilθWhere l is its topological charge number, the characteristic is the number of transitions in phase of the vortex beam from 0 to 2 pi within one wavelength, and theta is the vortex phase angle. The distribution of the optical field of a bundle of vortex rotations can thus be expressed as:
the linear doppler effect is well known, and means that if there is a relative velocity between the wave source and the observer, the frequency of the wave received by the observer will have a certain frequency difference from the wave source. The linear doppler effect has been widely used in the field of measuring the moving speed, acceleration, etc. of an object. The doppler effect is not only present in mechanical waves, but also in the electromagnetic wave field. Unlike linear doppler, when a beam of light with orbital angular momentum is directed along an axis of rotation onto a rough surface of a rotating body, the frequency of the light changes, which results in a change in the frequency of the light due to angular motion between the source and the observer, known as the rotating doppler effect.
The current method for measuring the angular velocity of a rotating object by using the vortex light rotating Doppler effect appears internationally, and the phenomenon of Doppler shift generated by the rotating vortex light beam is observed by J.Courtial et al, St.Andrews university in 1997. British physicist Martin lafree (Martin coverage) and his colleagues in 2013 proposed a method for measuring angular velocity of a rotating metal disc using vortex optical rotating doppler effect and performed experimental verification.
Disclosure of Invention
In order to overcome the defects of the prior art, the invention aims to: aiming at the defects of the existing device for measuring the angular velocity of a rotating object by using an optical gyroscope, a novel device for measuring the angular velocity of the object based on the rotary Doppler effect is provided. The device has simple structure, less used equipment and no complex light path and a plurality of sensing and mechanical equipment; with the development of the technology, the method can be applied to wider environments and conditions, and has considerable application prospect particularly in aircraft engines rotating at high speed, motors rotating at high speed, space non-cooperative target satellites and even astronomy.
The technical scheme adopted by the invention is as follows: an object angular velocity measuring device based on a rotary Doppler effect comprises a laser, a collimation and beam expansion lens, a phase type spatial light modulator, a computer, a beam splitter prism, a secondary reflection right-angle prism, a focusing lens, a CCD image sensor and a rotating shaft. The collimation beam expanding lens, the phase type spatial light modulator, the beam splitter prism, the secondary reflection right-angle prism and the rotating shaft are coaxial and are sequentially placed on an emergent light path of a light beam emitted by the laser, wherein: the secondary reflection right-angle prism is fixed on the rotating shaft, and the fixed position is one half of the lower reflection surface of the secondary reflection right-angle prism; the focusing lens is positioned above the secondary reflection right-angle prism; the CCD image sensor is positioned above the focusing lens; and the computer is respectively connected with the phase type spatial light modulator and the CCD image sensor.
When the laser works, a laser emits a fundamental mode Gaussian beam to enter the collimation beam expanding lens; the basic mode Gaussian beam is collimated and expanded and then passes through a phase type spatial light modulator; transmitting the computed hologram to a phase type spatial light modulator through a computer to generate a fundamental mode Laguerre Gaussian beam with vortex and transmit part of the fundamental mode Gaussian beam; the generated superimposed beam after the coaxial superposition of the fundamental mode Laguerre Gaussian beam with the vortex and the transmitted fundamental mode Gaussian beam is partially transmitted after passing through the beam splitter prism; the transmitted superposed beams enter a secondary reflection right-angle prism which rotates synchronously with the rotating shaft to induce a rotating Doppler effect, so that the superposed beams carry the motion information of a rotating object; the superposed light beams are subjected to two internal reflections in the rotating secondary reflection right-angle prism, leave the secondary reflection right-angle prism in opposite directions and are incident into the beam splitting prism; the superposed light beams are reflected in the beam splitter prism, converged by the focusing lens, interfered and recorded by the CCD image sensor, and the rotating Doppler effect appears as the rotation of dark spots in the interference pattern; recording the time from rest to rotation of the dark spots in the interference pattern on a computer and calculating the rotation angle of the dark spots in the interference pattern; thereby extracting the motion information of the rotating object carried by the superposed light beams; and finally, obtaining the angular velocity information of the rotating object by using a vortex light rotating Doppler effect conclusion.
The phase type spatial light modulator is arranged in a rear light path of the collimation and beam expansion lens, is connected with a computer and is used for loading a calculation hologram to generate a fundamental mode Laguerre Gaussian beam with vortex and a partial transmission fundamental mode Gaussian beam;
the beam splitter prism is arranged in an optical path behind the phase type spatial light modulator and used for partially transmitting an incident superposed beam and reflecting an emergent beam emergent from the secondary reflection right-angle prism;
the secondary reflection right-angle prism is fixed on the rotating shaft and synchronously rotates along with the rotating shaft, the included angle between the upper reflecting surface and the lower reflecting surface of the prism is 90 degrees, and the included angle between the incident light beam and the emergent light beam is 180 degrees;
the rotating shaft is coaxial with the optical axis of the incident beam and is connected with the incident beam at one half of the lower reflecting surface of the secondary reflection right-angle prism to drive the secondary reflection right-angle prism to synchronously rotate;
and the computer is respectively connected with the phase type spatial light modulator and the CCD image sensor and is respectively used for preparing a calculation hologram, loading the calculation hologram to the spatial light modulator, recording the rotation time of the dark spots in the interference pattern and calculating the rotation angle of the dark spots in the interference pattern.
Due to the adoption of the technical scheme, the invention has the beneficial effects that:
the device has high detection precision, larger lifting space, intuition and convenience; on the other hand, the structure is simple, and no complex optical path and a plurality of sensing and mechanical devices are provided, so that the error sources are greatly reduced, and the method has great advantages compared with the conventional scheme.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate an embodiment of the invention and, together with the description, serve to explain the invention and not to limit the invention.
FIG. 1 is a schematic structural view of the present invention;
FIG. 2 is a schematic view of the rotation angle of dark spots in an interference pattern;
description of reference numerals: 1-a laser; 2-collimating and beam expanding lens; 3-a phase-type spatial light modulator; 4-a computer; 5-a beam splitting prism; 6-secondary reflection right-angle prism; 7-a rotating shaft; 8-a focusing lens; 9-CCD image sensor.
Detailed Description
It should be noted that the embodiments and features of the embodiments may be combined with each other without conflict. Embodiments of the present invention will be described below with reference to the accompanying drawings, which are simplified schematic drawings and illustrate only the basic structure of the present invention in a schematic manner, and therefore, only show the structures related to the present invention.
The invention provides an object angular velocity measuring device based on a rotary doppler effect, for example, fig. 1 is a schematic structural diagram of an object angular velocity measuring device based on a rotary doppler effect, which includes a laser 1; a collimating and beam expanding lens 2; a phase-type spatial light modulator 3; a computer 4; a beam splitter prism 5; a secondary reflection right-angle prism 6; a rotating shaft 7; a focusing lens 8; a CCD image sensor 9.
Collimation beam expanding lens 2, phase type spatial light modulator 3, beam splitter prism 5, secondary reflection right angle prism 6, rotation axis 7 are coaxial and place in order on the outgoing light path of the light beam that laser instrument 1 sent, wherein: the collimation and beam expansion lens 2 is used for collimating and expanding beams; the phase type spatial light modulator 3 is used for generating a fundamental mode Laguerre Gaussian beam with vortex and partially transmitting the fundamental mode Gaussian beam; the beam splitter prism 5 is used for partially transmitting and reflecting the incident superimposed beam to an outgoing beam emitted from a secondary reflection right-angle prism 6; the secondary reflection right-angle prism 6 is fixed on the rotating shaft 7, the included angle between the two reflection surfaces is 90 degrees, the included angle between the incident light beam and the emergent light beam is 180 degrees, the fixed position is one half of the lower reflection surface of the secondary reflection right-angle prism 6, and the secondary reflection right-angle prism 6 synchronously rotates along with the rotating shaft 7; the focusing lens 8 is positioned above the secondary reflection right-angle prism 6; the CCD image sensor 9 is positioned above the focusing lens 8; the computer 4 is connected with the phase type spatial light modulator 3 and the CCD image sensor 9 respectively.
When the system works, a fundamental mode Gaussian beam emitted by a laser 1 firstly enters a collimation beam expanding lens 2; the incident beam after the collimation and the beam expansion passes through a phase type spatial light modulator 3, and the computer 4 loads the prepared calculation hologram into the spatial light modulator 3 to generate a fundamental mode Laguerre Gaussian beam with vortex and partially transmits the fundamental mode Gaussian beam; the superposed light beam generated by coaxially superposing the fundamental mode Laguerre Gaussian beam and the fundamental mode Gaussian beam passes through the beam splitter prism 5, and the superposed light beam is partially transmitted in the beam splitter prism 5; the transmitted superposed beams are incident into a secondary reflection right-angle prism 6 fixed on a rotating shaft 7 to induce a rotary Doppler effect, and the secondary reflection right-angle prism 6 synchronously rotates along with the rotating shaft 7 to enable the superposed beams to carry motion information of a rotating object; the superimposed beam carrying the motion information of the rotating object undergoes two internal reflections in the rotating secondary reflection right-angle prism 6, and the sign of the topological charge of the superimposed beam is reversed by each reflection, so that the reflected superimposed beam and the incident superimposed beam have the same sign; the superposed light beams leave the secondary reflection right-angle prism 6 in the opposite direction and then enter the beam splitter prism 5; the superposed light beams are reflected to a focusing lens 8 in a beam splitter prism 5, the superposed light beams are converged by the focusing lens 8 to generate interference, a CCD image sensor 9 records an interference pattern, and the rotary Doppler effect is expressed as rotation of dark spots in the interference pattern; recording the rotation time of the dark spots on the computer 4 and calculating the rotation angle of the dark spots in the interference pattern, thereby extracting the motion information of the rotating object carried by the superposed light beams; and finally, obtaining the angular velocity information of the rotating object by using a vortex light rotating Doppler effect conclusion.
For the convenience of understanding, the invention carries out supplementary explanation on the theoretical part:
the Laguerre-Gaussian beam is called LG beam for short, and the fundamental mode Gaussian beam is coaxially phasedThe number of topological charges of the axial charge being superimposed by interference
In the mode, after the secondary reflection right-angle prism rotates, the rotating Doppler effect is induced to generate frequency shift, and then the frequency shift is generated
The phase shift achieved by the mode, so that the total field reaches the following equation:
in the formula (1), w is a waist circumference parameter, EGAmplitude of a fundamental mode Gaussian beam, ELGIs composed of
The amplitude of the mode. Thus, the off-axis optical vortex rotates counterclockwise by one
And (4) an angle. For opposite optical vortex signs, the same phase shift will cause the optical vortex to move in the opposite direction. Thus, in
Any phase shift between the mode and the fundamental mode gaussian beam can be considered a break-over of the dark spot.
When the coaxially superimposed beams begin to rotate, the angular frequency of the optical vortex will shift by ω → ω + Δ ω. This will cause the dark spot within the beam to rotate at an angular velocity- Δ ω. The light intensity distribution on the section of the rotating beam is as follows:
equation (2) shows that the local value of the light intensity will vary with frequency,
gaussian of mode and fundamental modeThe resultant phase difference between the beams is a two-fold relationship; thus beat indicates that the rotating doppler effect is similar to the rotating doppler shift in a two-beam measurement scheme.
Off-axis optical vortex rotation can be explained from a purely geometric perspective, with complex amplitude distribution
Can be expressed as:
let now each component of equation (3) get a phase shift l θ. The whole formula is converted into
It is clear that the beam rotation through angle theta, i.e. the rotation angle theta of the beam, causes a phase shift l theta of formula (3) with an index l. At an angular velocity omega0Continuous rotation means that the frequency offset of these components is l Ω0To do so
If the beam is rotated relative to a fixed double-reflection rectangular prism, the signal will contain the angular frequency Δ ω when in the fundamental mode, i.e., l is 0 and l' is 0l,l′＝(l-l′)Ω0＝Ω0. Under the condition of simple superposition of a fundamental mode Gaussian beam and a fundamental mode Laguerre Gaussian beam, the frequency spectrum is not complicated, and the rotary Doppler displacement of a single optical vortex is directly displayed. Since the apparatus of the present invention provides a two-fold phase relationship, ω is1，0＝2Ω，
The angular velocity of the rotating object can be found to be:
those skilled in the art will appreciate that the details of the present invention not described in detail herein are well within the skill of those in the art.
Claims (4)
1. An object angular velocity measuring device based on a rotary Doppler effect comprises a laser, a collimation and beam expansion lens, a phase type spatial light modulator, a computer, a beam splitter prism, a secondary reflection right-angle prism, a focusing lens, a CCD image sensor and a rotating shaft, and is characterized in that the laser, the collimation and beam expansion lens, the phase type spatial light modulator, the beam splitter prism, the secondary reflection right-angle prism and the rotating shaft are sequentially arranged on an optical axis of laser beam propagation; the computer is respectively connected with the phase type spatial light modulator and the CCD image sensor; the focusing lens is positioned right above the beam splitter prism and is parallel to the beam splitter prism; the CCD image sensor is positioned right above the focusing lens.
2. The device for measuring the angular velocity of an object based on the rotary doppler effect according to claim 1, wherein the light emitted from the laser sequentially enters the collimating beam expanding lens, the phase type spatial light modulator, and the beam splitting prism; the phase type spatial light modulator is arranged in front of a light splitting prism, and a computer loads a computer hologram for generating a fundamental mode Laguerre Gaussian beam with vortex and partially transmitting the fundamental mode Gaussian beam.
3. The device of claim 1, wherein the angle between the two reflective surfaces of the secondary reflection right-angle prism is 90 °, the angle between the incident beam and the emergent beam is 180 °, and one half of the lower reflective surface of the secondary reflection right-angle prism is connected to the rotation axis.
4. The device of claim 1, wherein the rotation axis is coaxial with the optical axis of the incident beam and is connected to the secondary reflection right-angle prism at a position half of the lower reflection surface.
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Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112924397A (en) * | 2021-01-22 | 2021-06-08 | 中国人民解放军战略支援部队航天工程大学 | Target rotating speed and steering measurement method based on dual-frequency superposition state vortex optical rotation |
| CN114322851A (en) * | 2021-12-01 | 2022-04-12 | 东莞理工学院 | Micro rotation angle measuring system based on orbital angular momentum light beam |
| CN114383538A (en) * | 2021-12-03 | 2022-04-22 | 山东师范大学 | Device and method for accurately measuring angular quantity through linear quantity modulation |
| CN114441793A (en) * | 2022-01-07 | 2022-05-06 | 山西大学 | Rotating object angular velocity measuring device and method based on heterotopological charge vortex optical rotation |
| CN116298373A (en) * | 2023-05-24 | 2023-06-23 | 之江实验室 | Device and method for measuring angular velocity of object based on rotary Doppler effect |
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2020
- 2020-08-14 CN CN202010816672.5A patent/CN111830272A/en active Pending
Cited By (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112924397A (en) * | 2021-01-22 | 2021-06-08 | 中国人民解放军战略支援部队航天工程大学 | Target rotating speed and steering measurement method based on dual-frequency superposition state vortex optical rotation |
| CN112924397B (en) * | 2021-01-22 | 2022-10-14 | 中国人民解放军战略支援部队航天工程大学 | Target rotating speed and steering measurement method based on dual-frequency superposition state vortex optical rotation |
| CN114322851A (en) * | 2021-12-01 | 2022-04-12 | 东莞理工学院 | Micro rotation angle measuring system based on orbital angular momentum light beam |
| CN114322851B (en) * | 2021-12-01 | 2023-12-08 | 东莞理工学院 | Micro rotation angle measuring system based on orbital angular momentum light beam |
| CN114383538A (en) * | 2021-12-03 | 2022-04-22 | 山东师范大学 | Device and method for accurately measuring angular quantity through linear quantity modulation |
| CN114383538B (en) * | 2021-12-03 | 2023-12-26 | 山东师范大学 | Device and method for accurately measuring angle through line quantity modulation |
| CN114441793A (en) * | 2022-01-07 | 2022-05-06 | 山西大学 | Rotating object angular velocity measuring device and method based on heterotopological charge vortex optical rotation |
| CN114441793B (en) * | 2022-01-07 | 2022-11-11 | 山西大学 | Rotating object angular velocity measuring device and method based on heterotopological charge vortex optical rotation |
| CN116298373A (en) * | 2023-05-24 | 2023-06-23 | 之江实验室 | Device and method for measuring angular velocity of object based on rotary Doppler effect |
| CN116298373B (en) * | 2023-05-24 | 2023-10-20 | 之江实验室 | Device and method for measuring angular velocity of object based on rotary Doppler effect |
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