Chinese Version Light学术出版中心
Latest Issue
Issue 6 ， 2004
-
Aspheric surface testing with CGH on curved surface
Abstract：A research on aspheric surface testing by using a computer-generated hologram(CGH)on curved surface is presented. The diffractive property of CGH on curved surface is briefly analyzed, and the principle, property and design examples are given for testing concave and convex aspheric surface, respectively. Compared with the traditional testing methods, this method not only simplifies the optical system, but also decreases the fabrication accuracy of the computer-generated hologram. A CGH on a concave surface with diameter of 110 mm and radius curvature of 504 mm was fabricated by using a laser direct writer, and used to test a convex aspheric surface produced by diamond-turning successfully. Two methods were developed, one that utilizes the strategy in measuring twice can overcome the difficulty in measuring the center areas of the aspheric surface under test, the other that utilizes the strategy of rotating and subtracting can eliminate adjustment errors. We have successfully measured a 110 mm diameter convex surface with the error of 234 nm P-V, which well agree with the fabrication accuracy of the surface produced by diamond-turning.Keywords：laser direct writer;aspheric surface testing;computer-generated hologram- 65
- |
- 8
- |
- 15
Published：2020-08-12 -
Computerized white light scanning interferometer and the application
Abstract：The instrumentation principles and designing of two kinds of white light scanning interferometer systems are studied. One, based on the two-beam Mirau phase-shifting interferometer and the PZT used as a phase shifter, is developed to measure the micro-profile with nanometer accuracy. The other, employing Michelson interferometer for light path compensation, with the polarization states adjusted and controlled by rotating a Glan prism, and by varying reference arm to compensate the difference of light path induced by polarization coupling point, is developed to measure the position of polarization coupling pointing optical fiber. The results are that the spatial resolution of autoecious Polarization coupling measuring apparatus is 50mm, the measure range is 1km, and the detection sensitivity is better than -80 dB.Keywords：white light interferometer;canning fashion;Micro profile testing;position of polarization coupling point measurement- 60
- |
- 7
- |
- 11
Published：2020-08-12 -
Single-point diamond mirror turning of infrared aspheric lens
Abstract：According to the ductile-mode machining principle of hard-brittle material and error compensation turning method, the ductile-mode turning method of aspheric surface of infrared lens is mainly discussed, which is concerning arc diamond tool and straight diamond tool, in order to directly obtain mirror cutting surface. The error compensation turning method is introduced to eliminate the influence of tool wear, machine librations and thermal distortion, etc. on the surface roughness and form accuracy. An experiment for a single-point diamond turning of germanium lens of φ70 mm was carried out by the use of error compensation turning method. The result shows that it may improve aspheric form accuracy PV from 1.23 mm to 0.36 mm, and surface roughness Ra from 0.27 mm to 0.04 mm.Keywords：aspheric surface;hard-brittle material;form accuracy;error compensation- 37
- |
- 5
- |
- 5
Published：2020-08-12 -
Mechanism research on lapping of optical fiber end-face
Abstract：The material removal mechanism in optical fiber lapping is presented. With diamond lapping-film whose abrasive grain size is from micron to sub-micron, when the nominal lapping pressure was 0.48 MPa, the optical fiber end-face lapping experiment was conducted on optical fiber connector lapping machine of KE-OFP-12. The experiment results show that there are three material removal modes during lapping optical fiber,i.e. brittle fracture mode, semi-brittle and semi-ductile mode, and ductile mode. These modes are mainly controlled by abrasive grain size; there appears brittle-ductile transition's critical point when the lapping-films whose abrasive grain size is 3 μm is used to lap optical fiber. And these material modes are analyzed theoretically. The surface roughness can reach nanometer grade and there are not any scratches and cracks on the fiber end-face when fiber material is removed by ductile mode; and only sub-micron grade surface roughness can be gotten when fiber material is removed by brittle fracture mode. It proves that the ductile lapping mode is an effective method that improves surface quality of fiber end-face.Keywords：optical fiber lapping;brittle ductile transition;ductile removal;surface roughness- 62
- |
- 6
- |
- 5
Published：2020-08-12 -
Soft X-ray reflectometer based on laser-produced plasma source with a gas-jet target
Abstract：A soft X-ray reflectometer using a laser produced-plasma(LPP)light source with gas-jet target is built, and the method to measure the reflectance of soft X-ray multilayer coatings employing the reflectometer is presented. In comparison with metal target LPP source, due to usage of gas-jet target LPP source, the reflectometer is debris-free and can continuously operate for a long time. At the same time, a new method to delete the effect of 2nd spectrum from monochromator on measurement results of soft X-ray multilayer coatings reflectance is put forward. A curve of reflectance Vs. wavelength of soft X-ray multilayer coating with center wavelength 17.1 nm is modified to utilize the method.Keywords：soft X-ray reflectometer;multilayer coating;laser-produced plasma;gas-jet traget- 47
- |
- 6
- |
- 5
Published：2020-08-12 -
Counting LDA signal processor and its application
Abstract：A practical LDA signal processor based on the burst counting technique is presented, focusing on its working principle, hardware system and detailed construction. The processor is constructed by the common integrated circuits functioning as counter, memory, comparator and logic. The Doppler frequency related to the velocity being measured is extracted out all by hardware, so fast response can be achieved with high accuracy. Optimized design of three main parts for constructing the instrument, the burst generator which detects particles passing through the measurement volume, the counter core which obtains the period of Doppler signal and the counting validation analyzer, increase the capability of noise rejection as well. An application of the processor in the measurement of tangential and axial velocity distributions inside a hydraulic cyclone is given. The results show that the locus of zero vertical velocity, which divides the flow field into outer eddy area and inner eddy area, of the double-cone hydrocyclone is a compound surface of a cylinder and a cone, which is related to the construction parameter of the cyclone.Keywords：laser doppler anemometry;LDA signal processor;counter;hydraulic cyclone- 38
- |
- 7
- |
- 1
Published：2020-08-12 -
Numerical control laser pipe cutting machine for industrial use
Abstract：Laser processing equipment for metal tube-cutting is introduced. the cutting track is formed by the laser head moving along axis combined with the workpiece turning droven by an electric chuck circumvolve, thus the subsection cutting for the workpiece with different radius could be easily realized without changing the chuck. Low oxygen pressure cutting by air cooling can reduce the consumed oxygen by 2/3 oxygen compared with traditional ones. Its maximum single cutting length is 1 000 mm, the cutted surface roughness Ra≤6.3 μm, position accuracy ±0.1 mm/m, and oxygen pressure ≤0.15 MPa.Keywords：laser cutting;pipe;electric chuck;air cooling- 28
- |
- 5
- |
- 2
Published：2020-08-12 -
High precision friction drive of large telescope
Abstract：A kind of optical detecting mechanism is proposed to detect the skew angle between the axes of contact roller and wheel in high precision friction drive system adopted in large astronomical telescopes. The mechanism to adjust the skew angle is also given. With the help of these mechanisms, the skew angle between roller and wheel axes is controlled below 30″. The results of experiments show that there is no skip during the movement and the friction drive can achieve high precision at ultra slow speed. The lowest long-steady velocity of the experiment drive system is 0.2″/s with corresponding precision 0.01″(RMS), and during 30′ the lowest steady velocity is 0.05″/s with corresponding precision 0.009″(RMS). The precision of the variable velocity motion is(0.1)″(RMS)with the corresponding amplitude 30′, maximum velocity 36″/s, maximum acceleration 0.18″/s2. All these experiment results meet the LAMOST's specifications. The problem of object image tracked by telescope stirring in the field of view, what is more, drifting off the field of view caused by skew angle between axes of contact roller and wheel is solved by these mechanisms. The axes of roller and wheel can be kept in the ideal position in friction drive system.Keywords：astronomical telescope;friction drive;drive precision;precision analysis- 41
- |
- 5
- |
- 7
Published：2020-08-12 -
Design and thermal analysis of gas pressure sensor with micro-hotplate
Abstract：Fabrication process and working principle of thermal gas pressure sensors based on a surface-machining micro-hotplate(MHP)are presented. The effects of dimensions of MHP, gas gap, and supporting beams on fabrication and working performance of the sensor are analyzed, and a new sensor structure with unequal beams is designed. Three heat transfer approaches of MHP including conduction through the supporting beams, thermal radiation, and gas conduction, and their variation with gas pressure under constant temperature operation are investigated in theory. Temperature distribution and its amplitude of the sensor under constant current excitation are simulated with finite element method. The results show that heat loss of MHP is mainly determined by gas conduction in high pressure range, while conduction through the supporting beams dominates in low pressure range. Temperature distribution of MHP is uniform and its amplitude depends on pressure. The designed device can be operated from 10 Pa to 10~5 Pa and its power consumption is at the level of milliwatts. It also has other advantages,such as being small in size, fast thermal response, and ease of integration with circuits, etc.Keywords：micro-hotplate;gas pressure sensor;thermal analysis;finite element method- 51
- |
- 8
- |
- 7
Published：2020-08-12 -
Vacuum microelectronic pressure sensor
Abstract：A vacuum micro-electronics pressure sensor with the function of overloading protection is brought forward. The analysis and calculation on some structure parameters of the sensor have been done, such as the dimension of pressure sensitive film, the space length between anode and cathode and so on. As to overloading protection, there is a protection ring. Combining of silicon dry corrosion, wet corrosion, oxidizing sharpening and vacuum bonding techniques, a novel vacuum microelectronic pressure senor was developed. Then, a series of parameters of this sensor has been analized and tested. As a result, the density of field emission tip array reaches 24 000 units per mm2, the start emission voltage is between 0.5 V to 1 V , the reverse voltage is over 25 V.When the positive voltage is 5 V, the unicuspid emission current is 0.2 nA,pressure sensitivity is 0.1 μA/KPa.Keywords：pressure sensor;overloading protection;field emission cathode array;anisotropy erosion- 90
- |
- 6
- |
- 4
Published：2020-08-12 -
Monochromator cooling bender in synchrotron radiation
Abstract：The cooling bender with a flexural hinge-based framework is researched to reduce the crystal thermal distortion. The types and their principles of the crystal thermal distortion are introduced, and the mechanical forces and cooling bender structure are analyzed with the finite element method. The results show that the bender can greatly cut down the thermal distortion of the first crystal, the crystal surface error is only 0.04 μrad3 μrad at the peak power density of 5 N/mm2, which is much lower than the design requirement to the beam line in synchrotron radiation. Such kind of bender especially fits in high-heat load, and it is one of the key techniques to solve the problems in developing the third generation of synchrotron radiation light source.Keywords：synchrotron radiation;flexural hinges;bender;double-crystal monochromator- 34
- |
- 8
- |
- 2
Published：2020-08-12 -
Tensioning digital control system for aerial negative film tester
Abstract：The accuracy of displacement and location of the negative is greatly affected by the change of its tension in the aerial negative film tester. Based on the kinematics and dynamics of the transmission mechanism, a control model was built by means of DSP(digital signal processing)to carry out the real time control of the tension when the negative is in motion. The fixed tension guarantees the stability of the system and the requirement to the accuracy standard, which makes possible for the tester to get the real image data. It lays a good foundation for the accurate testing of aerial negative film. The highest moving speed of the negative is 23 m/min, the range of tension is from Fmin=0 N to Fmax=30 N, the variety of controlled tension is ΔF=±0.05 N and the repeating orientation precision of the tester is ±10 μm,which meet the design requirements.Keywords：aerial negative film;tension;veal time control;DSP- 53
- |
- 7
- |
- 0
Published：2020-08-12 -
Digital image processing technology for spur gear measurement
Abstract：Non-contact measuring for spur gears using digital image processing technology is studied. At first, distortion correction and filter in the original image captured by CCD camera. Were taken account of edge image of single pixel was achieved after treatments such as threshold segmentation and four-neighborhood erosion based on mathematical morphology. As to the shape character istic of gear, some basic principles such as gravity model, least squares fit, Hough transform, and Bresenham drawing circle were applied synthetically, and the algorithm of measuring numbers of teeth, module, radius of center hole, radius of addendum circle, radius of dedendum circle, modification coefficient, etc. was established. A gear whose diameter of indexing circle is 50 mm was tested using 1280×1024 CCD camera and acquisition block, and the results indicated that absolute error of measuring value is less than a pixel compared with manual measurement; the absolute error of radius of addendum circle-the largest size in all the measuring parameters is 13 μm. The research indicates that by high resolution CCD camera and optical amplifying system, minute gear and high precision gear can be measured,because the higher the resolution of CCD camera is and the smaller the objects are, the higher the measuring precision is, what's more, they are of linear relation. When spur gears whose diameters of indexing circle are less than 5 mm are measured by CCD camera with the resolution of over 1280×1024, the precision of measurement is below than 2 μm.Keywords：digital image processing;spur gear measurement;least squares fit;subpixel- 32
- |
- 5
- |
- 21
Published：2020-08-12 -
Stereo vision sensor field calibration method based on volume template
Abstract：A volume template-based method is proposed for the field calibration of the intrinsic and extrinsic parameters of stereo vision sensor, which adopts an ideal pin-hole model that ignores the nonlinear distortion of the cameras. Taking the transform matrix elements as unknown, when the group of 3-D target points coordinates and their image coordinates are known, they can be used in a linear algorithm to work out the unknown elements and the parameters needed. In the end, a volume calibration template is used to calibrate a stereo vision sensor, which measures a known length. The relative precision is up to 0.02%. Experimental results show that method needs no iteration and has a high operation speed, which needs to put the template only once for the field calibration, cameras' intrinsic and extrinsic parameters could be calibrated with high precision.Keywords：stereo vision;camera calibration;volume template;coordinates measurement- 41
- |
- 6
- |
- 20
Published：2020-08-12 -
Computed X radiography image compression
Abstract：According to the characteristics of computed radiography(CR)imaging and the close relation ship between CR imaging procedure and image plate(IP), the compression algorithm is presented to segment image by threshold value, and different compressing methods are used for different segmented area. First, the segmentation process identifies the black surrounding and utilizes run-length coding. Then according therelation ship between imaging plate(IP)and dose of X radiography, the region of interest(ROI)CR images are transformed from 12 bit into 9.3 bit images and followed by Embedded image coding using embedded zerotree of wavelet(EZW)loss compression. This coding algorithm can ensure the image quality of the region of interest and PSNR, and give better visual effects.Keywords：CR image;image compress;region of interest- 59
- |
- 5
- |
- 4
Published：2020-08-12 -
New probe positioning method
Abstract：A probe positioning method is proposed, which sets up a probe coordinate system using markers caught by camera and makes out the transformation between probe coordinate system and reference coordinate according coordinate transformation theory in computer vision. Then, the coordinate of the probe tips on operation place out of sight can be worked out. This method can avoid the dependence on techniques in improving operation precision and decrease absolute error to 1 mm. Experiment data and results are also attached to show the excellent efficiency of the method. It solves the bottleneck in improving operation precision because of technical reason. The method can be used not only in operation field, but also in other many industrial occasions.Keywords：probe positioning;machine vision- 52
- |
- 11
- |
- 2
Published：2020-08-12
Loading...
0