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Measurements performed using the self‐coupling effect of a semiconductor laser utilize an external resonator by exploiting the reflected light from the surface of an object. The improvement of the measurement accuracy due to the use of self‐coupled signals acquired from terminal voltages has not been thoroughly investigated. The current that flows through a semiconductor laser is adjusted so that its wavelength changes at a specific rate when it is modulated using an arbitrary waveform. As such, the spread of the self‐coupled signal is suppressed, and precision is improved. In addition, the accuracy is improved by considering the influence of lenses on the optical path. [ABSTRACT FROM AUTHOR]

In this paper, signal processing using a statistical algorithm for vibration measurement is reported. The algorithm uses the statistical features of the standard deviation of sinusoidal vibration and is capable of accuracy superior to the peak-to-peak method. Additionally, the algorithm achieves accuracy as good as or better than the FFT method with less hardware. This method gave good results in simulations and actual measurement values. The method is widely applied in self-coupling effect sensors and other vibration sensors. © 2013 Wiley Periodicals, Inc. Electron Comm Jpn, 96(3): 9-16, 2013; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/ecj.11454. [ABSTRACT FROM AUTHOR]

Recently, laser radar has been widely studied as a sensor to measure the distance from a car ahead. Laser radar has the characteristic that the received signal becomes buried in noise with increasing distance. It is difficult to measure long distances at low laser power. Thus, a new type of chaos laser radars has been studied. This laser radar is relatively resistant to noise and can perform processing simply because it uses only addition operations. However, the distance resolution of chaos laser radars is limited by the clock cycle of the FPGA which is used for signal processing of the laser radar. Therefore, a new method of improving distance resolution by means of a phase delay circuit has been developed. As a result, the distance resolution of chaos laser radars has been improved to 1/10 using phase delay circuitry. © 2011 Wiley Periodicals, Inc. Electron Comm Jpn, 94(6): 59-65, 2011; Published online in Wiley Online Library (). DOI 10.1002/ecj.10177 [ABSTRACT FROM AUTHOR]

The demand for noncontact and nondestructive internal defect detection is increasing. Using the photoacoustic effect, internal defects can be detected by a low-power semiconductor laser and an ultrasonic sensor. But the sensitivity of ultrasonic sensors is low in detecting photoacoustic signals. Thus, an internal defect detection using the photoacoustic and self-coupling effect of a semiconductor laser has been studied. To generate photoacoustic signals, a semiconductor laser with an output power of 20 mW is focused by a lens and is directed toward the sample at an angle of 45°. To detect the photoacoustic signal by the self-coupled effect, another laser with an output power of 10 mW is directed against the sample at a right angle. Sample defect can be detected by directing these laser beams at the same point on the sample. The self-coupling sensor can detect internal defects with greater sensitivity than an ultrasonic sensor. The edge effect and the frequency characteristic have also been observed. The device proved able to detect a very small defect of 0.07 mm. © 2010 Wiley Periodicals, Inc. Electron Comm Jpn, 93(7): 17–23, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecj.10307 [ABSTRACT FROM AUTHOR]