Page 12 - Sensors and Control Systems in Manufacturing

Contents
2.12 Understanding Laser Sensors . . . . . . . . . . . . 113 xi
2.12.1 Properties of Laser Light . . . . . . . . . 114
2.12.2 Essential Laser Components . . . . . . 114
2.12.3 Semiconductor Displacement
Laser Sensors . . . . . . . . . . . . . . . . . . . 119
2.12.4 Industrial Applications of Laser
Sensors . . . . . . . . . . . . . . . . . . . . . . . . 119
Further Reading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 132

3 Fiber Optics in Sensors and Control Systems . . . . 133
3.0 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . 133
3.1 Photoelectric Sensors—Long-Distance
Detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 133
3.1.1 Light-Emitting Diodes . . . . . . . . . . . 134
3.1.2 Through-Beam Sensors . . . . . . . . . . 136

3.1.3 Reflex Photoelectric Controls . . . . . 137

3.1.4 Polarized Reflex Detection . . . . . . . 138
3.1.5 Proximity (Diffuse-Refl ection)
Detection . . . . . . . . . . . . . . . . . . . . . . 139
3.1.6 Automated Guided Vehicle
System . . . . . . . . . . . . . . . . . . . . . . . . 140
3.2 Fiber Optics . . . . . . . . . . . . . . . . . . . . . . . . . . . 141
3.2.1 Individual Fiber Optics . . . . . . . . . . 143
3.2.2 Bifurcated Fiber Optics . . . . . . . . . . 143
3.3 Optical Fiber Parameters . . . . . . . . . . . . . . . . 145
3.3.1 Excess Gain . . . . . . . . . . . . . . . . . . . . 145
3.3.2 Background Suppression . . . . . . . . 147
3.3.3 Contrast . . . . . . . . . . . . . . . . . . . . . . . 148
3.3.4 Polarization . . . . . . . . . . . . . . . . . . . . 148
3.4 Inductive Proximity Sensors—Noncontact
Metal Detection . . . . . . . . . . . . . . . . . . . . . . . . 148
3.5 Limit Switches—Traditional Reliability . . . . 150
3.6 Factors Affecting the Selection of Position
Sensors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 151
3.7 Wavelengths of Commonly Used
Light-Emitting Diodes . . . . . . . . . . . . . . . . . . . 152
3.8 Sensor Alignment Techniques . . . . . . . . . . . . 152
3.8.1 Opposed Sensing Mode . . . . . . . . . 152

3.8.2 Retroreflective Sensing Mode . . . . . 152
3.8.3 Proximity (Diffuse) Sensing Mode . . . 153
3.8.4 Divergent Sensing Mode . . . . . . . . . 153
3.8.5 Convergent Sensing Mode . . . . . . . 154
3.8.6 Mechanical Convergence . . . . . . . . 154
3.9 Fiber Optics in Industrial Communication
and Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . 155