CN112711006B - Optical fiber laser ranging system - Google Patents
Optical fiber laser ranging system Download PDFInfo
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- CN112711006B CN112711006B CN202110019379.0A CN202110019379A CN112711006B CN 112711006 B CN112711006 B CN 112711006B CN 202110019379 A CN202110019379 A CN 202110019379A CN 112711006 B CN112711006 B CN 112711006B
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- collimator
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- circulator
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
- G01S7/48—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S17/00
- G01S7/481—Constructional features, e.g. arrangements of optical elements
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S17/00—Systems using the reflection or reradiation of electromagnetic waves other than radio waves, e.g. lidar systems
- G01S17/02—Systems using the reflection of electromagnetic waves other than radio waves
- G01S17/06—Systems determining position data of a target
- G01S17/08—Systems determining position data of a target for measuring distance only
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- Physics & Mathematics (AREA)
- Engineering & Computer Science (AREA)
- Electromagnetism (AREA)
- Computer Networks & Wireless Communication (AREA)
- General Physics & Mathematics (AREA)
- Radar, Positioning & Navigation (AREA)
- Remote Sensing (AREA)
- Instruments For Measurement Of Length By Optical Means (AREA)
- Optical Radar Systems And Details Thereof (AREA)
Abstract
The invention provides an optical fiber laser ranging system, which comprises an interference ranging module, an absolute ranging module, a wavelength division multiplexing unit, a 1X 2 optical switch, a measuring light path and a compensating light path, wherein the interference ranging module and the absolute ranging module select light sources with different wave bands, the output ends of the interference ranging module and the absolute ranging module are respectively connected with the wavelength division multiplexing unit, the output ends of the interference ranging module and the absolute ranging module are coupled by the wavelength division multiplexing unit and are connected to the 1X 2 optical switch, one output port of the 1X 2 optical switch is connected with the measuring light path, the other output port is connected with the compensating light path, and the 1X 2 optical switch is alternately connected with the measuring light path and the compensating light path at a set time sequence. The beneficial effects of the invention are as follows: the two light beams are combined into the same optical fiber through the wavelength division multiplexing device and then output by the collimator, so that the situation that the two light beams are not subjected to angle mismatch is ensured.
Description
Technical Field
The invention relates to laser measurement, in particular to an optical fiber laser ranging system.
Background
The laser tracker is a high-precision large-size measuring instrument in an industrial measuring system, and can track a space moving target and measure the space three-dimensional coordinates of the target in real time. The host mainly comprises a distance measuring module, an angle measuring module, a tracking control module, a reflecting mirror, a foot rest, a data processing terminal and the like. Compared with the traditional laser interferometer, the core distance measurement module has the function of light interruption and continuous connection, and consists of an interference ranging module (IFM) and an absolute ranging module (ADM), wherein the IFM can only measure the moving distance of a target just like the laser interferometer, the ADM can measure the absolute distance, the reflector is prevented from getting back to a bird nest to acquire the reference distance again, but the distance measurement module is limited by a ranging principle, the ADM measuring speed is low, and dynamic tracking measurement cannot be realized. In the actual ranging operation of the laser tracker, two sub-modules of the IFM and the ADM are matched with each other to complement each other.
The principle and implementation scheme of the IFM and ADM ranging modules are respectively researched and discussed in various papers and patents, and in the ranging application of a laser tracker, the key is the coupling of the two modules.
The come card in the coordinate measuring device (patent number: CN 200780009186) discloses an optical system of a laser tracker, and the implementation scheme and mutual coupling of the IFM and the ADM module are described in more detail.
The prior art has the defects that:
1. IFM and ADM coupling installation are difficult, and the angle mismatch of two modules at the level of angle seconds can lead to the complete separation of light spots of a measurement target outside 80 m;
2. the requirement on structural stability is high, and transportation, ambient temperature and accidental collision can cause the degradation of the coupling effect of the two sub-modules, so that the system fails; stability must be ensured with a high-cost mechanical structure;
3. the optical fiber is easily interfered by environmental factor changes such as temperature, and a simple and effective compensation scheme is lacked.
Disclosure of Invention
In order to solve the problems in the prior art, the invention provides an optical fiber laser ranging system.
The invention provides an optical fiber laser ranging system, which comprises an interference ranging module, an absolute ranging module, a wavelength division multiplexing unit, a 1X 2 optical switch, a measuring light path and a compensating light path, wherein the interference ranging module and the absolute ranging module select light sources with different wave bands, the output ends of the interference ranging module and the absolute ranging module are respectively connected with the wavelength division multiplexing unit, the output ends of the interference ranging module and the absolute ranging module are coupled by the wavelength division multiplexing unit and are connected to the 1X 2 optical switch, one output port of the 1X 2 optical switch is connected with the measuring light path, the other output port is connected with the compensating light path, and the 1X 2 optical switch is alternately connected with the measuring light path and the compensating light path at a set time sequence.
As a further improvement of the present invention, the interference ranging module includes a first light source, a first collimator, a first circulator, a 1×2 beam splitter, an interference module and a reference module, where the first light source is connected to an input end of the first circulator through the first collimator, a forward output end of the first circulator is connected to the 1×2 beam splitter, a reverse output end of the first circulator is connected to the interference module, one output port of the 1×2 beam splitter outputs reference light to the reference module, another output port outputs measurement light to the wavelength division multiplexing unit, and completes beam combination with the absolute ranging module, a returned light signal enters the interference module through the first circulator, and measurement of a target relative movement distance is completed by detecting an interference signal intensity between the measurement light and the reference light.
As a further improvement of the invention, the first light source, the first collimator, the first circulator, the 1×2 beam splitter, the interference module and the reference module are respectively connected by polarization maintaining fibers, and the fast axis or the slow axis of the polarization maintaining fibers are aligned with the polarization direction of the light.
As a further improvement of the invention, the first collimator and the first circulator are integrally processed, and the collimator lens is arranged at the input end of the first circulator.
As a further improvement of the invention, the absolute distance measuring module comprises a second light source, a second collimator, a second circulator, a modulator and a measuring module, wherein the second light source is connected with the input end of the second circulator through the second collimator, the positive output end of the second circulator is connected with the modulator, and the negative output end of the second circulator is connected with the measuring module.
As a further improvement of the invention, the absolute ranging module further comprises a third collimator and a fourth collimator, wherein the forward output end of the second circulator is connected with the third collimator to output parallel light, the parallel light passes through the modulator and is then coupled into the fourth collimator, and the tail fiber of the fourth collimator is connected with the wavelength division multiplexing unit to complete beam combination with the interference ranging module.
As a further development of the invention, the modulator is an electro-optical body modulator or a fibre-optic waveguide modulator.
As a further improvement of the invention, the second collimator and the second circulator are integrally processed, and the collimator lens is arranged at the input end of the second circulator.
As a further improvement of the invention, the measuring light path comprises a fifth collimator, a 1/4 wave plate and a reflector, wherein the input end of the fifth collimator is connected with the 1×2 optical switch, and the optical signal output by the fifth collimator is transmitted to the reflector through the 1/4 wave plate.
As a further improvement of the invention, the fifth collimator is designed for achromatism of the wave bands of the two light sources of the interference ranging module and the absolute ranging module.
The beneficial effects of the invention are as follows:
1. the two light beams are combined into the same optical fiber through the wavelength division multiplexing device and then output by the collimator, so that the situation that the two light beams are not subjected to angle mismatch is ensured.
2. By the optical system design of the optical fiber, the stability only slightly influences the coupling efficiency, and the system failure is not caused.
3. A new environment compensation scheme with a simple structure is provided.
Drawings
FIG. 1 is a schematic diagram of a fiberized laser ranging system of the present invention.
Detailed Description
The invention is further described with reference to the following description of the drawings and detailed description.
As shown in FIG. 1, the optical fiber laser ranging system mainly comprises two modules, namely an IFM and an ADM.
The IFM module 1 mainly comprises a light source 11, a collimator 12, a circulator 13, a 1×2 beam splitter 15, an interference module 14, a reference module 16, and an optical fiber.
The ADM module 2 mainly comprises a light source 21, a collimator 22, a circulator 23, a modulator 26, a measuring module 24 and an optical fiber.
The whole optical path system also comprises WDM (wavelength division multiplexing) 3, a 1×2 optical switch 4, a compensation optical path and a measurement optical path.
The optical fiber, circulator 13, circulator 23, 1×2 beam splitter 15, WDM3, and 1×2 optical switch 4 are all polarization maintaining optical devices.
The light source 11 of the IFM module 1 is coupled into the optical fiber by a collimator 12, the fast or slow axis direction of the polarization maintaining optical fiber must be aligned with the polarization direction of the light, by rotating the collimator 12 to match the polarization direction, a 1/2 wave plate may be added, by rotating the wave plate to match the polarization direction. The optical fiber is then connected to the circulator 13, and the matching of the fast axis or the slow axis is ensured, or the circulator 13 and the collimator 12 are integrally processed, and a collimator lens is arranged at the input optical fiber of the circulator 12, so that the step of aligning and welding the collimator tail optical fiber and the fast axis and the slow axis of the input optical fiber of the circulator can be omitted.
The optical fibers referred to above must be polarization maintaining fibers, and the connection between the polarization maintaining fibers must ensure alignment of the fast and slow axes, which is also referred to below and will not be described in detail.
The output end of the circulator 13 is connected to a 1×2 fiber optic splitter 15, one of which is used as a reference module, and the other of which is used as a measuring light path to be connected to the WDM3, and the beam combination with the ADM module 2 is completed. The returned optical signal enters the interference module 14 through the circulator 13, and the measurement of the relative movement distance of the target is completed by detecting the interference signal intensity between the measuring light and the reference light.
The above-mentioned interference module 14 is based on a michelson interferometer, and basic implementation schemes and various modifications are disclosed in the prior art, and will not be described in detail here.
The above-mentioned 1×2 optical fiber beam splitter 4 is designed according to the light splitting ratio to ensure that the reference light and the measured light intensity are substantially equal, and it is considered that the measured light path further has a plurality of subsequent devices to introduce insertion loss.
The reference module 16 may be composed of a collimator, a 1/4 wave plate, and a pyramid mirror, where the crystal optical axis direction of the 1/4 wave plate forms 45 ° with the fast axis or the slow axis direction of the polarization maintaining fiber.
The reference module 16 may be a fiber 1/4 wave plate, and a high reflection film is coated on the end face.
The light source 21 of the ADM module 2 is coupled into an optical fiber by a collimator 22, the optical fiber is connected into a circulator 23, the forward output end of the circulator 23 is connected into a collimator 25 to output parallel light, the parallel light passes through a modulator 26 and is then coupled into the next collimator 27, and the tail fiber of the collimator 27 is connected into a WDM, so that the combination with the IFM module 1 is completed.
The circulator 23 has its reverse output connected to the measurement module 24.
The measuring module 24 is composed of a collimator, a PBS and a photodetector, and is used for measuring the optical signal intensity in the designated polarization direction, and many documents have been described in detail about the principle of ADM and its implementation scheme, which are not repeated here.
The modulator 26 may be an electro-optical modulator; the optical fiber waveguide modulator can be used, front and back collimators are omitted, and the optical fiber degree of the system is improved.
The collimators 22, 25 and 27 can be integrally processed with the connected devices, and the collimator lens is arranged at the tail fiber of the device, so that the step of aligning and welding the tail fiber of the collimator and the tail fiber of the device in a speed axis is omitted.
The IFM and ADM modules select light sources with different wave bands, WDM3 with corresponding wave bands is coupled to the same optical fiber, and the optical fiber is connected to a 1X 2 optical switch 4, wherein one output port is connected with a measuring light path, and the other output port is connected with a compensating light path.
The 1×2 optical switch 4 alternately connects the measuring optical path and the compensating optical path at a certain time sequence, and the time duty ratio of each channel can be adjusted.
The measuring light path includes a collimator 51, a 1/4 wave plate 52, and a reflector 53.
The collimator 51 performs achromatic design for the wave bands of the two light sources of the IFM and the ADM, and ensures the consistency of the collimation effect.
The 1/4 wave plate has a crystal optical axis direction forming 45 degrees with the fast axis or slow axis direction of the polarization maintaining fiber, and adopts a broadband wave plate containing the wave bands of the two light sources of the IFM and the ADM or wave plates designed for the two wave bands.
According to the measuring light path, the beam expander can be added after the 1/4 wave plate to adjust the collimation distance, and the beam expander is designed for achromatism aiming at wave bands of the IFM light source and the ADM light source. The beam expander is not limited to the 1/4 wave plate.
The above-described reflector 53 is mounted on the object to be measured as a measurement partner.
The compensation light path can be composed of a collimator, a 1/4 wave plate and a reflector, and is the measuring light path.
The compensation light path can also be an optical fiber 1/4 wave plate, and a high reflection film is plated on the end face.
The length of the optical fiber of the measuring optical path and the compensating optical path is as short as possible.
The optical fiber is easily interfered by environmental factors such as temperature, and in the working process of the ranging module, the ranging data obtained by the signal light returned by the compensation light path comprises drift of the whole light path due to the environmental influence, and the influence of the environmental factors on the optical system can be eliminated by making a difference between the data and the ranging data obtained by the signal light returned by the measurement light path.
Compared with the prior laser tracker ranging technology, the optical fiber laser ranging system provided by the invention has the following advantages:
(1) The IFM and the ADM are coupled to the same optical fiber, so that the problem that two light beams are separated in angle possibly, and light spots are not overlapped at a measuring position during remote measurement is avoided;
(2) The processing difficulty of the optical element and the mechanical structural part is reduced; the difficulty of assembly and adjustment is reduced, and the efficiency is improved;
(3) Even if deformed, the coupling efficiency of the collimator is only slightly reduced, the light efficiency of the system is affected, the ranging performance is not directly affected, the phenomenon that the IFM and ADM beam separation systems fail is avoided, and the reliability of the system is improved;
(4) And a compensating light path is newly added, so that the environment adaptability of the system is improved.
The foregoing is a further detailed description of the invention in connection with the preferred embodiments, and it is not intended that the invention be limited to the specific embodiments described. It will be apparent to those skilled in the art that several simple deductions or substitutions may be made without departing from the spirit of the invention, and these should be considered to be within the scope of the invention.
Claims (7)
1. An optical fiber laser ranging system, which is characterized in that: comprises an interference ranging module, an absolute ranging module, a wavelength division multiplexing unit, a 1X 2 optical switch, a measuring light path and a compensating light path, wherein the interference ranging module and the absolute ranging module select light sources with different wave bands, the output ends of the interference ranging module and the absolute ranging module are respectively connected with the wavelength division multiplexing unit, the output ends of the interference ranging module and the absolute ranging module are coupled by the wavelength division multiplexing unit and are connected to the 1X 2 optical switch, one output port of the 1X 2 optical switch is connected with the measuring light path, the other output port is connected with the compensating light path, the 1X 2 optical switch is alternately connected with the measuring light path and the compensating light path at a set time sequence, the interference ranging module comprises a first light source, a first collimator, a 1X 2 beam splitter, an interference module and a reference module, wherein the first light source is connected with the input end of the first circulator through the first collimator, the forward output end of the first circulator is connected with the 1 x 2 beam splitter, the reverse output end of the first circulator is connected with the interference module, one output port of the 1 x 2 beam splitter outputs reference light to the reference module, the other output port outputs measurement light to the wavelength division multiplexing unit and completes beam combination with the absolute ranging module, a returned optical signal enters the interference module through the first circulator, the measurement of the target relative movement distance is completed by detecting the interference signal intensity between the measurement light and the reference light, the first light source, the first collimator, the first circulator, the 1 x 2 beam splitter, the interference module and the reference module are respectively connected through polarization maintaining optical fibers, the fast axis or the slow axis of the polarization maintaining optical fibers is aligned with the polarization direction of the light, the first collimator, the first circulator is integrally processed, and a collimator lens is arranged at the input end of the first circulator.
2. The fiberized laser ranging system of claim 1, wherein: the absolute distance measurement module comprises a second light source, a second collimator, a second circulator, a modulator and a measurement module, wherein the second light source is connected with the input end of the second circulator through the second collimator, the forward output end of the second circulator is connected with the modulator, and the reverse output end of the second circulator is connected with the measurement module.
3. The fiberized laser ranging system of claim 2, wherein: the absolute ranging module further comprises a third collimator and a fourth collimator, wherein the forward output end of the second circulator is connected into the third collimator to output parallel light, the parallel light passes through the modulator and is then coupled into the fourth collimator, and the tail fiber of the fourth collimator is connected into the wavelength division multiplexing unit to complete beam combination with the interference ranging module.
4. A fiberized laser ranging system according to claim 3, wherein: the modulator is an electro-optical body modulator or an optical fiber waveguide modulator.
5. A fiberized laser ranging system according to claim 3, wherein: the second collimator and the second circulator are integrally processed, and a collimator lens is arranged at the input end of the second circulator.
6. The fiberized laser ranging system of claim 1, wherein: the measuring light path comprises a fifth collimator, a 1/4 wave plate and a reflector, wherein the input end of the fifth collimator is connected with the 1X 2 optical switch, and an optical signal output by the fifth collimator is transmitted to the reflector through the 1/4 wave plate.
7. The fiberized laser ranging system of claim 6, wherein: the fifth collimator is designed for achromatism aiming at wave bands of two light sources of the interference ranging module and the absolute ranging module.
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| CN202110019379.0A CN112711006B (en) | 2021-01-07 | 2021-01-07 | Optical fiber laser ranging system |
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| CN202110019379.0A CN112711006B (en) | 2021-01-07 | 2021-01-07 | Optical fiber laser ranging system |
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| CN112711006B true CN112711006B (en) | 2023-08-22 |
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