**1. Introduction**

[5] Fontaine, N. K., Yang, J., Pan, Z., Chu, S., Chen, W., Little, B. E., & Yoo, S. J. B. (2008, Dec). Continuously tunable optical buffering at 40Gb/s for optical packet switching

[6] Yang, H., & Yoo, S. J. B. (2005, June). Combined input and output all-optical variable buffered switch architecture for future optical routers. *IEEE Photonics Technol. Lett.*,

[7] Ogashiwa, N., Harai, H., Wada, N., Kubota, F., & Shinoda, Y. (2005, Jan). Multistage fiber delay line buffer in photonic packet switch for asynchronously arriving varia‐

[8] Harai, H., & Murata, M. (2006, Aug). Optical fiber-delay-line buffer management in optical-buffered photonic packet switch to support service differentiation. *IEEE J. on*

[9] Wang, Z., Chi, C., & Yu, S. (2006, Aug). Time-slot assignment using optical buffer with a large variable delay range based on AVC crosspoint switch. *J. Lightwave Tech‐*

[10] Liew, S. Y., Hu, G., & Chao, H. J. (2005, Apr). Scheduling algorithms for shared fiberdelay-line optical packet switches- part I: The single-stage case. *J. Lightwave Technol.*,

[11] Shinada, S., Furukawa, H., & Wada, N. (2011, Dec). Huge capacity optical packet

[12] Kurumida, J., & Yoo, S. J. Ben. (2012, Mar/Apr). Nonlinear optical signal processing in optical packet switching systems. *IEEE J. Selected Topics in Quantum. Electron.*,

[13] Shiramizu, Y., Oda, J., & Goto, N. (2008, Aug). All-optical autonomous first-in-firstout buffer managed with carrier sensing of output packet. *Optical Engineering*, 47(8),

networks. *J. Lightwave Technol.* [23], 3776-3783.

*Sel. Areas in Commun.*, 24(8), 108-116.

ble-length packets. *IEICE Trans. Commun.*, E88-B(1), 258-265.

switching and buffering. *Optics Express*, 19(26), B406-B414.

17(6), 1292-1294.

388 Optoelectronics - Advanced Materials and Devices

*nol.*, 24(8), 2994-3001.

23(4), 1586-1600.

18(2), 978-987.

085006-1-8.

In optoelectronic scanning, it has been found that in order to find the position of a light source, the signal obtained looks like a Gaussian signal shape. This is mainly observed when the light source searched by the optoelectronic scanning is punctual, due to the fact that when the punctual light source expands its radius a cone-like or an even more complex shape is formed depending on the properties of the medium through which the light is trav‐ elling. To reduce errors in position measurements, the best solution is taking the measure‐ ment in the energy centre of the signal generated by the scanner, see [1].

The Energy Centre of the signal concept considers the points listed below, see [2], in order to search which one of them represents the most precise measurement results:


The Energy Centre of the signal could be found by means of the optoelectronic scanner sen‐ sor output processing, through a computer programming algorithm, taking into account the points mentioned above, in a high level technical computing software for engineering and science like MATLAB. However, our contribution is a method and an electronic hardware to produce an output signal related to the Energy Centre in the optoelectronic scanning sensor, for applications in position measurements.

This method is based on the assumption that the signal generated by optical scanners for position measurements is a Gaussian-like shape signal. However, during experimentation it has been seen that the optoelectronic scanning sensor output is a Gaussian-like shape signal with some noise and deformation. This is due to some internal and external error sources like the motor eccentricity at low speed scanning, noise and deformation that could interfere with the wavelength of the light sources. Other phenomena could also affect such as of re‐ flection, diffraction, absorption and refraction, producing a trouble that can be minimized by taking measurement in the energy centre of the signal.

The main interest of this chapter is to describe and explain a method to find the energy cen‐ tre of the signal generated by optical scanners based on a dynamic triangulation, see [3], to reduce errors in position measurements.

**Figure 1.** Principle of Triangulation.

**2.2. Scanners with rotating mirrors and remote sensing**

focused via finite-conjugate optics from a local fixed source, see [6].

the object to be moved in order to create the second dimension of the image.

In the previous section, we described the operational principle of scanners for monitoring the distance of small objects, now we will describe the operational principle of scanners with rotating mirrors for large distances measurement or in structural health monitoring tasks.

A Method and Electronic Device to Detect the Optoelectronic Scanning Signal Energy Centre

http://dx.doi.org/10.5772/51993

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There are two main classification of optical scanning: remote sensing and input/output scan‐ ning. Remote sensing detects objects from a distance, as by a space-borne observation plat‐ form. For example an infrared imaging of terrain. Sensing is usually passive and the radiation incoherent and often multispectral. Input / output scanning, on the other hand, is local. A familiar example is the document reading (input) or writing (output).The intensive use of the laser makes the scanning active and the radiation coherent. The scanned point is

In remote sensing there is a variety of scanning methods for capturing the data needed for image formation. These methods may be classified into framing, push broom, and mechani‐ cal. In the first one, there is no need for physical scan motion since it uses electronic scan‐ ning and implies that the sensor has a two-dimensional array of detectors. At present the most used sensor is the CCD and such array requires an optical system with 2-D wide-angle capability. In push broom methods a linear array of detectors are moved along the area to be imaged, e. g. airborne and satellite scanners. A mechanical method includes one and two di‐ mensional scanning techniques incorporating one or multiple detectors and the image for‐ mation by one dimensional mechanical scanning requires the platform with the sensor or

In these days there is a technique that is being used in many research fields named Hyper‐ spectral imaging (also known as imaging spectroscopy). It is used in remotely sensed satel‐ lite imaging and aerial reconnaissance like the NASA's premier instruments for Earth exploration, the Jet Propulsion Laboratory's Airborne Visible-Infrared Imaging Spectrome‐ ter (AVIRIS) system. With this technique the instruments are capable of collecting high-di‐ mensional image data, using hundreds of contiguous spectral channels, over the same area
