A generalized reference-plane-based calibration method in optical triangular profilometry

Calibration of an illuminance meter is indispensable for accurate measurement of the illuminance of indoor lighting and daylight. In recent years, because of the phasing-out of incandescent lamps and their replacement with LED lamps, it has become difficult to obtain an incandescent type standard lamp to calibrate an illuminance meter. To replace the standard lamp method, we constructed an illuminance meter calibration system based on an LED-based spectrally tunable light source. The approximate CIE Illuminant A spectrum realized by the LED-based spectrally tunable light source was controlled at various illuminance values (800–10,000 lx). A test illuminance meter was calibrated by comparison against a reference photometer with the realized approximate Illuminant A spectrum. The illuminance values measured using the reference photometer and using the test illuminance meter in the calibration system agreed within 2.5% without reference plane correction of the test illuminance meter, and within 1% with reference plane correction. Reference plane correction depends strongly on the measurement distance and the illuminance meter structure. This study demonstrated that it can be improved. Therefore, we infer that an illuminance meter calibration method using an LED-based spectrally tunable light source is a promising means of overcoming difficulties posed by the phasing-out of incandescent standard lamps.

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Calibration Method for a Structured Light Rangefinder Using a Reference Plane

IEEJ Transactions on Electronics Information and Systems ◽

10.1541/ieejeiss.129.1162 ◽

2009 ◽

Vol 129 (6) ◽

pp. 1162-1168

Author(s):

Koichiro Yamauchi ◽

Hideo Saito ◽

Yukio Sato

Keyword(s):

Structured Light ◽

Calibration Method ◽

Reference Plane

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MMIC on-Wafer Test Method Based on Hybrid Balanced and Unbalanced RF Pad Structures

Electronics ◽

10.3390/electronics7090208 ◽

2018 ◽

Vol 7 (9) ◽

pp. 208

Author(s):

Yue Bian ◽

Yifan Gu ◽

Xu Ding ◽

Zhiyu Wang ◽

Jiongjiong Mo ◽

...

Keyword(s):

Integrated Circuit ◽

Impedance Matching ◽

Calibration Method ◽

Test System ◽

Test Method ◽

Reference Plane ◽

Calibration Error ◽

Test Accuracy ◽

Monolithic Integrated Circuit ◽

Wafer Test

Nowadays, more and more MMICs (Microwave Monolithic Integrated Circuit), such as limiters and switches, are designed to have balanced and unbalanced test pad structures to solve the challenging size restrictions and integration requirements for MMICs. Hybrid balanced and unbalanced RF (Radio Frequency) probes are adopted for an on-wafer test of the heteromorphy structures. The thru standard based on single balanced or unbalanced structures cannot meet the impedance matching requirements of the hybrid RF probes at the same time, which leads to a dramatic decreasing of the calibration accuracy and cannot satisfy the requirement of MMIC test. Therefore, in this paper, the calibration error estimating of hybrid RF probes based on traditional SOLR (Short Open Load Reciprocal) calibration method is performed, and an on-wafer test approach of MMIC based on hybrid balanced and unbalanced RF probes is proposed which combines the OSL (Open Short Load) second-order de-embedding technique with vector error correction and the matrix transformation technique. The calibration reference plane can be accurately shifted to the probe tip with this method, which greatly improves the test accuracy, and an automatic test system is built for this method based on the object-oriented C# language.

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In-line stereo-camera assisted robotic spot welding quality control system

Industrial Robot the international journal of robotics research and application ◽

10.1108/ir-06-2017-0117 ◽

2018 ◽

Vol 45 (1) ◽

pp. 54-63 ◽

Cited By ~ 1

Author(s):

Cengiz Deniz ◽

Mustafa Cakir

Keyword(s):

Quality Control ◽

Spot Welding ◽

Calibration Method ◽

The Body ◽

Reference Plane ◽

Welding Quality ◽

Content Type ◽

Stereo Camera ◽

Center Position ◽

Inline Measurement

Purpose The purpose of this study is to design a robotic inline measurement system for spot welding quality control to achieve process requirement without any operator during the manufacturing flow. Design/methodology/approach A robot manipulator carries a stereo-camera and an ultrasonic control probe. The center position of the spot welding point is determined by evaluating the results of the edge, gradient and symmetry approaches from the methods proposed up to now in the literature to increase reliability. The center position of the spot welding point, determined in the camera reference plane, is transferred to the robot base plane coordinates with the hand–eye calibration proposed in this manuscript. Weld quality is checked by the ultrasonic test probe located at the spot welding point. Findings While operators can only control welding quality, the developed station can also evaluate the quality based on geometric accuracy by processing the deviation of the position of the spot welding points. The proposed calibration method and the results of other methods in the literature are presented in this study by comparing it with synthetic data in simulations and in practical application. Research limitations/implications The quality control is performed not only for the spot welding made with robots but also for the manual welds as well. Because of vision configuration, and reliability issues, maximum allowable offset by the correct spot position is limited to 20 mm to position the manipulator for testing. The installation and pretest works of the developed robotic welding quality control station are completed in the Body Shop Area of Ford Otosan factory in Kocaeli/Turkey. The results of the robotic control process are monitored by the quality assurance team. Integration of automation with the production line will be completed and an inline measurement will be done. Originality value In this paper, a new hand–eye calibration method based on simple and closed-form analytical solutions has been presented. The objective function is defined as reducing the deviation in the point projection, rather than reducing the error in the calibration equation. To increase reliability, combining the results of existing centering algorithms for the detection of the strongly deformed spot welding spot center, although it is normally in a circular form, has been suggested.

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Time Domain Reflectometry Technique for Failure Analysis

ISTFA 2004: Conference Proceedings from the 30th International Symposium for Testing and Failure Analysis ◽

10.31399/asm.cp.istfa2004p0616 ◽

2004 ◽

Author(s):

Teoh King Long ◽

Ko Yin Fern

Keyword(s):

Failure Analysis ◽

Time Domain ◽

Time Domain Reflectometry ◽

Fault Isolation ◽

Reference Plane ◽

First Case ◽

Main Emphasis ◽

Plastic Ball ◽

Solder Balls ◽

Non Destructive

Abstract In time domain reflectometry (TDR), the main emphasis lies on the reflected waveform. Poor probing contact is one of the common problems in getting an accurate waveform. TDR probe normalization is essential before measuring any TDR waveforms. The advantages of normalization include removal of test setup errors in the original test pulse and the establishment of a measurement reference plane. This article presents two case histories. The first case is about a Plastic Ball Grid Array package consisting of 352 solder balls where the open failure mode was encountered at various terminals after reliability assessment. In the second, a three-digit display LED suspected of an electrical short failure was analyzed using TDR as a fault isolation tool. TDR has been successfully used to perform non-destructive fault isolation in assisting the routine failure analysis of open and short failure. It is shown to be accurate and reduces the time needed to identify fault locations.

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