CN105716526A - Small optical measuring head based on laser self-mixing interference - Google Patents
Small optical measuring head based on laser self-mixing interference Download PDFInfo
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- CN105716526A CN105716526A CN201610204048.3A CN201610204048A CN105716526A CN 105716526 A CN105716526 A CN 105716526A CN 201610204048 A CN201610204048 A CN 201610204048A CN 105716526 A CN105716526 A CN 105716526A
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B11/00—Measuring arrangements characterised by the use of optical techniques
- G01B11/002—Measuring arrangements characterised by the use of optical techniques for measuring two or more coordinates
- G01B11/005—Measuring arrangements characterised by the use of optical techniques for measuring two or more coordinates coordinate measuring machines
- G01B11/007—Measuring arrangements characterised by the use of optical techniques for measuring two or more coordinates coordinate measuring machines feeler heads therefor
Abstract
The invention discloses a small optical measuring head based on laser self-mixing interference. The small optical measuring head comprises a vertical cavity surface emitting laser (VCSEL), a drive circuit and a signal processing circuit, wherein the vertical cavity surface emitting laser (VCSEL) is composed of a collimating lens, a laser body and a photoelectric triode. The laser body is driven by the drive circuit to produce laser beams, the collimating lens converges the laser beams on a measured object, the laser beams reflected by the measured object produce self-mixing interference in the laser body to form a self-mixing interference signal, and the photoelectric triode converts the self-mixing interference signal into a current signal and then transmits the current signal to the signal processing circuit. The small optical measuring head adopts a laser self-mixing interference measuring technique to detect the absolute distance from the measured object to the emergence end face of the laser body, further obtains coordinate values of a detection point in a measuring machine coordinate system and has the advantages of being high in resolution, simple and compact in structure, suitable for centimeter-level narrow spaces, resistant to electromagnetic interference and the like.
Description
Technical field
The present invention relates to sensor technical field, specifically, relate to a kind of compact optical gauge head based on laser self-mixing interference.
Background technology
" basic part and universal component manufacture and design ", " digitized and intelligentized design manufacture " are classified as preferential theme by the medium-term and long-term science and technology development plan of China, " advanced manufacturing technology ", " laser technology " are classified as cutting edge technology, " 12 " planning is it is also proposed that " development advanced equipment manufacturing industry ", " promote that manufacturing industry becomes big and becomes strong ", the patron saint that coordinate measuring machine manufactures as advanced person, must play the important function that can not be substituted wherein.
Gauge head is the senser element of pickoff signals in coordinate measuring machine, directly affects the precision of measuring machine, function and measurement efficiency.Contact gauge head A wide selection of colours and designs traditional in measuring machine, it is widely used, but its volume is relatively big, measures inefficient, also contacts with measured surface, has friction, abrasion and elastic deformation.By contrast, optical measuring head and testee do not have Mechanical Contact, it is possible to measuring soft and yielding object, it is possible to carry out quick scanning survey, hot spot can control to only small, it is possible to is irradiated to traditional mechanical gauge head and cannot stretch into the narrow positions of detection.Therefore, being developed into for a particularly important direction in the development of coordinate measuring machine in recent years of optical measuring head.
Current domestic application optical measuring head on coordinate measuring machine mainly includes trigonometric laser measuirng head, laser out of focus gauge head and these several classes of video gauge head, and all need from Zeiss, Germany, Britain's Reinshaw, Japan's company's import such as Keyemce, U.S. Pu Sai, the domestic optical measuring head product remaining without maturation.Trigonometric laser measuirng head utilizes the scattering light on testee surface image space on CCD or PSD to carry out the detection of measured surface position, make gauge head volume bigger due to the existence of outside imaging lens and photodetector, it is unsuitable for measuring miniature parts, its measurement angle is subject to the restriction of scattering light direction simultaneously, it is unsuitable for measuring irregular surface, when Part Surface Roughness is only small time, scattering light can be very faint compared to specular light, measure signal can be submerged among noise, therefore this gauge head is also unsuitable for measuring smooth surface.Laser out of focus gauge head judges the deviation of measured surface and collecting objective focal plane by the differential signal of two photodiodes, this gauge head measurement resolution is significantly high, submicron order can be reached other, but need the optical accessory such as condenser lens and Amici prism, volume is relatively big, and its dynamic response capability is poor, it is difficult to for the quick measurement of curved surface, and range is only small when quickly measuring, only have tens microns.The illumination by certain way of the video gauge head, the geometric profile of object is become optical profile, re-use digital image processing method to realize measuring, this gauge head can obtain the metrical information in the whole visual field, but influence factor is more, needing the defocus information of image when obtaining object depth information, namely moving the definition getting image with camera lens is judgment criteria, read the distance of measured surface change by grating scale, measure efficiency and be greatly affected.Such as, measuring the shaft hole diameter of a 90mm in automobile engine, the optical measuring head of finished commercial prod is all unable to reach this dimensional requirement.Therefore, a kind of brand-new compact optical gauge head suitable in commercial measurement and the field of manufacture is explored imperative.
Laser self-mixing interference technology is a kind of precision optics noncontact measurement emerging in recent years, have precision height, electromagnetism interference, to measuring, surface requirements is low, do not rely on the advantages such as laser type, and its measurement system only have one interfere passage, easily collimation, simple and compact for structure.Currently, laser self-mixing interference technology is applied to some extent in conventional geometric measurement fields such as displacement, distance, speed, additionally, the application in the emerging fields such as industrial flaw detection, measuring three-dimensional morphology, measuring blood flow rate, the measurement of cochlea vibration of thin membrane, human body pleura vibration measurement also day by day increases.Laser from application of mixture theory model and measure technology through years development, have been realized in nano level displacement measurement accuracy and ten micron-sized range measurement accuracies at present.Up to now, there is not yet the relevant report that this technology is used for coordinate measuring machine optical measuring head.
Summary of the invention
Patent of the present invention is measured inefficient to solve contact measuring head in coordinate measuring machine, and existing optical measuring head structure is complicated, bulky, it is difficult to suitable in the problem that small space is measured, it is proposed that a kind of compact optical gauge head based on laser self-mixing interference.This optical measuring head adopts laser self-mixing interference to measure the technology for detection testee absolute distance to laser emitting end face, and then obtain sensing point coordinate figure in measuring machine coordinate system, have that resolution is high, simple and compact for structure, can be used for the advantages such as the small space of Centimeter Level, electromagnetism interference.
It is an object of the invention to be achieved through the following technical solutions:
A kind of compact optical gauge head based on laser self-mixing interference, including vertical cavity surface emitting laser (VCSEL), drive circuit and signal processing circuit, described vertical cavity surface emitting laser (VCSEL) is by collimating lens, laser instrument and phototriode are constituted, described laser instrument is driven by described drive circuit and produces laser beam, laser beam is converged at testee by described collimating lens, the laser beam that testee is reflected back occurs self-mixed interference to form self-mixing interference in laser instrument, described phototriode is sent to signal processing circuit after self-mixing interference is converted to current signal.
Described drive circuit includes digital signal processor, digital to analog converter, voltage reference chip, add circuit and current pump, described digital signal processor storage has the sawtooth current data of reconstruct, the outfan of digital signal processor is connected with the input of described digital to analog converter, digital to analog converter is connected with the input of add circuit with the outfan of voltage reference chip, the outfan of add circuit is connected with the input of current pump, and current pump is connected with described laser instrument.
Described current pump is provided with current-limiting protection circuit.
Described signal processing circuit is made up of the current-to-voltage converting circuit being sequentially connected, amplifying circuit, low-pass filter circuit and analog-digital converter.
Compared with prior art, technical scheme is had the benefit that
1, the present invention avoids contact measuring head based on the optical measuring head of laser self-mixing interference and measures inefficient, to be dfficult to apply to small space problem, has that resolution is high, simple and compact for structure, can be used for the advantages such as the small space of Centimeter Level, electromagnetism interference.
2, laser self-mixing interference of the present invention is measured and is only had one and interfere passage, easily collimation, simple and compact for structure, and the size of optical measuring head can be made to reduce further.
3, gauge head adopts vertical cavity surface emitting laser (VCSEL) as light source, and its front end is with collimating lens, and this vertical cavity surface emitting laser enclosed inside has the phototriode for Photoelectric Detection, further reduces gauge head volume.
4, the present invention finally utilizes the frequency of full phase time shift phase difference method calibration of laser self-mixing interference, the method can under the premise not increasing system complexity, improve self-mixing interference frequency solving precision, it is not necessary to synchronized sampling, it is suppressed that spectral leakage ability is strong, algorithm is simple.
5, then regenerate injection current by the relation of Laser Measurement device wavelength (frequency) in advance with injection current, it is possible to make laser frequency linear change, remain stable from mixed signal beat frequency.Electric current reconstructing method can be effectively reduced laser nonlinearity erron in mixing range measurement, improves range measurement resolution.
Accompanying drawing explanation
Fig. 1 is the structure principle chart of patent of the present invention.
Fig. 2 is the driving circuit principle figure of patent of the present invention.
Fig. 3 is the signal processing circuit schematic diagram of patent of the present invention.
Fig. 4 is the full phase time shift phase difference correction principle block diagram of patent of the present invention.
Fig. 5 is the injection current reconfiguration principle block diagram of patent of the present invention.
Detailed description of the invention
Below in conjunction with accompanying drawing, the invention will be further described:
For describing simplicity, hereinafter vertical cavity surface emitting laser replaces by VCSEL.
Being illustrated in figure 1 the structure principle chart of patent of the present invention, this compact optical gauge head is mainly made up of VCSEL1, drive circuit 3 and signal processing circuit 2, and tested part 4 is used for identifying tested reflector, and is not belonging to the ingredient of gauge head.Wherein VCSEL1 is by collimating lens 10, laser instrument 11 and phototriode 12 form, collimating lens 10 is for converging at testee by laser beam, laser instrument 11 produces laser beam, self-mixed interference also betides among laser instrument 11, and laser power fluctuation is converted to current signal by phototriode 12.VCSEL enclosed inside collimating lens 10 and phototriode 12, further reduce the volume of gauge head.Only stretching in measurement space by VCSEL in work, the size marked from Fig. 1 this measuring head structure visible is small and exquisite, can be used for the measurement in small space.
The principle being carried out distance detection by gauge head of the present invention is as follows:
Adopting band meter measurement to obtain the relation between VCSEL1 injection current and excitation wavelength (frequency), make laser frequency linear change, reverse goes out corresponding current value thus obtaining the injection current of reconstruct；Drive circuit 3 adopts reconstruct sawtooth current to drive the laser instrument 11 in VCSEL1, the laser of laser instrument 11 injection is focused on by collimating lens 10 and produces reflection or scattering on testee surface, the optical feedback of part carry distance information returns the intracavity of laser instrument 11 with intracavity light generation self-mixed interference, causes laser cavity emergent light changed power；Phototriode 12 detects self-mixing interference and is converted into the signal of telecommunication, this signal of telecommunication is through the process of signal processing circuit 2, then adopt the dynamic phase difference method of full phase time shift to extract the frequency of self-mixing interference, and then obtain high-precision distance measurement data.
Fig. 2 represents present invention driver circuit schematic diagram.This partial circuit is mainly made up of digital signal processor 30, digital to analog converter 31, voltage reference chip 32, add circuit 33, current pump 34 and current-limiting protection circuit 35.Digital signal processor 30 stores the sawtooth current data of reconstruct; the sawtooth voltage signal of reconstruct is generated by digital to analog converter 31; voltage reference chip 32 provides stable DC voltage; the sawtooth voltage signal of reference voltage and reconstruct is added by add circuit 33; by providing the current-modulation being offset on certain current value after current pump 34 for VCSEL1, current-limiting protection circuit 35 protects the operating current of VCSEL1 lower than maximum allowed current value.
Fig. 3 represents signal processing circuit schematic diagram of the present invention.This partial circuit is mainly made up of current-to-voltage converting circuit 20, amplifying circuit 21, low-pass filter circuit 22 and analog-digital converter 23.The current signal that phototriode 12 obtains is converted to voltage signal by current-to-voltage converting circuit 20, the amplification to voltage signal implemented by amplifying circuit 21, low-pass filter circuit 22 is to the voltage signal filter away high frequency noise after amplifying, simultaneously working as the effect of anti-aliasing filter before data acquisition, filtered collect from mixed signal is carried out subsequent analysis calculating by analog-digital converter 23 in digital signal processor 30.
Fig. 4 represents the full phase time shift phase difference correction principle block diagram of the present invention.This some algorithm realizes in digital signal processor 30.First take out in a current-modulation cycle from mixed signal, remove the amplitude modulation impact of electric current, choose suitable N value and one modulation period interior is counted as 3N-1 from mixed signal；Then these part data are divided into the data segment of former and later two 2N-1 points, ask for the phase value of intermediate point, k respectively with whole phase FFT*Represent the position at spectrum peak place；Obtain amounts of frequency offset Δ k followed by the frequency offset correction formula shown in Fig. 4, finally obtain with Frequency Estimation formula accurate from mixing frequency signal value, FsRepresenting sample frequency, gained frequency values and testing distance have proportional relation.
Fig. 5 represents the injection current reconfiguration principle block diagram of the present invention.First passing through the relation between band meter or spectrometer measurement VCSEL wavelength and injection current, injection current allows uniform value in current range at VCSEL；The relation then passing through light frequency and wavelength can calculate the relation obtaining light frequency with injection current, uses data fitting method can obtain the equation that light frequency is met with injection current；The scope of injection current in VCSEL work and the light frequency range of correspondence is determined then according to selected sawtooth current peak-to-peak value and bias current value, in light frequency range internal linear value at equal intervals, substituting into optical frequency and current equation, reverse goes out the current waveform data after reconstruct；Finally current waveform data is stored in digital signal processor 30 for generating reconstruct electric current.
Claims (5)
1. the compact optical gauge head based on laser self-mixing interference, it is characterized in that, including vertical cavity surface emitting laser (VCSEL), drive circuit and signal processing circuit, described vertical cavity surface emitting laser (VCSEL) is by collimating lens, laser instrument and phototriode are constituted, described laser instrument is driven by described drive circuit and produces laser beam, laser beam is converged at testee by described collimating lens, the laser beam that testee is reflected back occurs self-mixed interference to form self-mixing interference in laser instrument, described phototriode is sent to signal processing circuit after self-mixing interference is converted to current signal.
2. a kind of compact optical gauge head based on laser self-mixing interference according to claim 1, it is characterized in that, described drive circuit includes digital signal processor, digital to analog converter, voltage reference chip, add circuit and current pump, described digital signal processor storage has the sawtooth current data of reconstruct, the outfan of digital signal processor is connected with the input of described digital to analog converter, digital to analog converter is connected with the input of add circuit with the outfan of voltage reference chip, the outfan of add circuit is connected with the input of current pump, current pump is connected with described laser instrument.
3. a kind of compact optical gauge head based on laser self-mixing interference according to claim 2, it is characterised in that be provided with current-limiting protection circuit on described current pump.
4. a kind of compact optical gauge head based on laser self-mixing interference according to claim 1, it is characterised in that described signal processing circuit is made up of the current-to-voltage converting circuit being sequentially connected, amplifying circuit, low-pass filter circuit and analog-digital converter.
5. a kind of compact optical gauge head based on laser self-mixing interference according to claim 1, it is characterised in that the diameter of described vertical cavity surface emitting laser (VCSEL) is 6mm, long for 8mm.
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Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN106643543A (en) * | 2016-12-30 | 2017-05-10 | 东北石油大学 | Method for detecting deformation of surface of magnetic disk storage |
| CN107816940A (en) * | 2016-09-14 | 2018-03-20 | 西安航通测控技术有限责任公司 | A kind of gamut photoelectric sensor for Laser Light Plane Scanning cyberspace alignment system |
| CN108303705A (en) * | 2017-12-27 | 2018-07-20 | 西安理工大学 | Nd:YAG solid state lasers are from mixing velocity sensor and its speed-measuring method |
| CN108827448A (en) * | 2018-07-28 | 2018-11-16 | 天津大学 | Vibration and inclination measuring system and method based on plane mirror and photovoltaic array |
| US11201669B2 (en) | 2018-05-30 | 2021-12-14 | Apple Inc. | Systems and methods for adjusting movable lenses in directional free-space optical communication systems for portable electronic devices |
| US11303355B2 (en) | 2018-05-30 | 2022-04-12 | Apple Inc. | Optical structures in directional free-space optical communication systems for portable electronic devices |
| US11549799B2 (en) | 2019-07-01 | 2023-01-10 | Apple Inc. | Self-mixing interference device for sensing applications |
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Cited By (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN107816940A (en) * | 2016-09-14 | 2018-03-20 | 西安航通测控技术有限责任公司 | A kind of gamut photoelectric sensor for Laser Light Plane Scanning cyberspace alignment system |
| CN107816940B (en) * | 2016-09-14 | 2020-01-21 | 西安航通测控技术有限责任公司 | Full-range photoelectric sensor for laser plane scanning network space positioning system |
| CN106643543A (en) * | 2016-12-30 | 2017-05-10 | 东北石油大学 | Method for detecting deformation of surface of magnetic disk storage |
| CN108303705A (en) * | 2017-12-27 | 2018-07-20 | 西安理工大学 | Nd:YAG solid state lasers are from mixing velocity sensor and its speed-measuring method |
| US11201669B2 (en) | 2018-05-30 | 2021-12-14 | Apple Inc. | Systems and methods for adjusting movable lenses in directional free-space optical communication systems for portable electronic devices |
| US11303355B2 (en) | 2018-05-30 | 2022-04-12 | Apple Inc. | Optical structures in directional free-space optical communication systems for portable electronic devices |
| US11870492B2 (en) | 2018-05-30 | 2024-01-09 | Apple Inc. | Optical structures in directional free-space optical communication systems for portable electronic devices |
| CN108827448A (en) * | 2018-07-28 | 2018-11-16 | 天津大学 | Vibration and inclination measuring system and method based on plane mirror and photovoltaic array |
| CN108827448B (en) * | 2018-07-28 | 2023-09-26 | 天津大学 | Vibration and inclination angle measurement system and method based on plane reflector and photoelectric array |
| US11549799B2 (en) | 2019-07-01 | 2023-01-10 | Apple Inc. | Self-mixing interference device for sensing applications |
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Application publication date: 20160629 |