Optical sensors are those sensors that detect electromagnetic radiation in what is generally understood as the broad optical range - from far IR to UV. The sensing methods may rely on direct methods of transduction from light to electrical quantities such as in photovoltaic or photoconducting sensors or indirect methods such as conversion first into temperature variation and then into electrical quantities such as in passive IR (PIR) sensors and bolometers. The third method of sensing related to optics - sensors based on light propagation and its effects (reflection, transmission refraction), which will not be discussed here because the optical aspect is usually not the sensing mechanism, but rather an intermediate transduction mechanism. Nevertheless, the physics will be mentioned briefly for completeness.

Chapter Contents:

• 4.1 Introduction
• 4.2 Optical Units
• 4.3 Materials
• 4.4 Effects of Optical Radiation
• 4.4.1 Thermal Effects
• 4.4.2 Quantum Effects
• 4.4.2.1 The Photoelectric Effect
• 4.4.2.2 Quantum Effects: The Photoconducting Effect
• 4.4.2.3 Spectral Sensitivity
• 4.4.2.4 Tunneling Effect
• 4.5 Quantum-Based Optical Sensors
• 4.5.1 Photoconducting Sensors
• 4.5.2 Photodiodes
• 4.5.3 Photovoltaic Diodes
• 4.5.4 Phototransistors
• 4.6 Photoelectric Sensors
• 4.6.1 The Photoelectric Sensor
• 4.6.2 Photomultipliers
• 4.7 Coupled Charge (CCD) Sensors and Detectors
• 4.8 Thermal-Based Optical Sensors
• 4.8.1 Passive IR Sensors
• 4.8.1.1 Thermopile PIR
• 4.8.1.2 Pyroelectric Sensors
• 4.8.1.3 Bolometers
• 4.9 Active Far Infrared (AFIR) Sensors
• 4.10 Optical Actuators
• 4.11 Problems

Inspec keywords: optical sensors; photoconducting devices; photodetectors; infrared detectors; actuators; ultraviolet detectors; bolometers

Other keywords: photoconducting sensors; far IR detection; bolometers; UV detection; transduction mechanism; temperature variation; optical sensors; passive IR sensors; actuators; photovoltaic sensors

Subjects: Optical instruments and techniques; Photoelectric devices; Photodetectors; Sensing and detecting devices; Detection of radiation (bolometers, photoelectric cells, i.r. and submillimetre waves detection)