2nd lesson 3rd quarter

• Infrared sensors


  • Consist of an emitter (often an IR LED) and a detector (typically an IR photodiode)
  • Provide information about the temperature, presence, or movement of objects in their vicinity
• An infrared sensor is an electronic device that emits to sense some aspects of the surroundings
• Receiver Sensor Circuit

  1. The emitter (IR LED) generates and emits infrared light, serving as the source of radiation for sensing

  2. The detector (IR photodiode) captures or senses the emitted infrared radiation, recognizing variations in intensity or wavelength to provide information about the surroundings
• The emitter in an infrared sensor circuit is an IR LED, and the detector is an IR photodiode sensitive to IR light of the same wavelength as that emitted by the IR LED
• Infrared Sensor


  An electronic device designed to detect and measure infrared radiation in its surroundings, operating on the principle that objects emit infrared radiation based on their temperature
• Signals interacting with objects

  • Reflection
  • Transmission
  • etc.
• Technology


  • Works based on Specific Object Detection Technology
• Photo-coupler


  Utilizes light as the medium of communication
• Technology


  • Wide range of application depending on the Technology used
• How Infrared Receivers Detect Radiation

  Infrared receivers detect radiation by utilizing an infrared transmitter. The infrared receiver captures and detects variations in the infrared radiation, providing information about the presence, absence, or characteristics of objects in the sensor's field
• Photo-coupler


  Optical coupling ensures electrical isolation between the two circuits, preventing unwanted interference. Crucial in scenarios where isolation is necessary
• Technology


  • Depends on the Application and Environment
• Technology


  • Range varies depending on the technology and Sensors
• Active Infrared Sensors

  Includes both the transmitter and receiver. LED is used as a non-imaging infrared sensor, while the laser diode is used as an imaging infrared sensor
• Use of LED and Laser Diode


  LED serves as the non-imaging infrared sensor, emitting infrared light for detection purposes. Laser diodes provide a more precise and directional infrared beam, enhancing the sensor's capabilities in certain applications
• Technology

  • Suitable for various applications (Security, Automation, etc.)
• Photo-coupler


  Electronic component that transfers electrical signals between two isolated circuits by using light
• Technology

  • Works based on Infrared Radiation Principles
• Technology

  • Limited Range in some applications
• Commonly used in

  • Photodiodes as Detector
• Comparison of LED to Laser Diodes


  LED emits incoherent light, while laser diodes emit coherent and directional light. LED is less directional, spreading light in multiple directions, whereas laser diodes are highly directional, focusing light on a specific area
• Photo-coupler


  When an electrical signal is applied to the light emitter, it emits light. The light is detected by the receiver in the isolated circuit, generating a corresponding electrical signal
• Infrared Sensors


  Infrared receivers detect radiation using an infrared transmitter. Infrared receivers are available in photodiode form
• Active Infrared Sensors


  The transmitter emits infrared signals into the surroundings, and the receiver captures the reflected or transmitted signals. Interaction between the emitted and received signals enables the sensor to detect objects, changes in the environment, or movement within its field
• Availability in Photodiode Form

  Photodiodes are semiconductor devices that generate electrical current in response to incident light. Specifically designed for infrared applications, they convert infrared light into an electrical signal for further analysis and use in various applications
• Passive infrared sensor includes detectors only, but they don't include a transmitter
• Passive Infrared Sensors do not include a transmitter component and solely rely on detecting naturally occurring infrared radiation from objects within their detection range. The absence of a transmitter simplifies the sensor design, making it cost-effective and energy-efficient for applications where continuous infrared emission is not necessary
• Passive Infrared Sensors operate based on the temperature differences between the objects and their background, capturing variations in heat. When an object moves within the sensor's range, it alters the infrared radiation pattern, triggering the sensor to detect motion or presence
• Examples of Passive IR Sensor

  • Pyroelectric Detector: Utilizes changes in temperature to generate electric charge
  • Bolometer: Measures the change in resistance or electrical conductivity of a material in response to incident infrared radiation
• Passive Infrared (PIR) Sensor is designed to detect infrared radiation emitted or reflected by objects in its field of view
• PIR sensors are commonly used in applications where the detection of human or animal presence is required, such as automatic lighting systems or security systems
• Long-Wavelength Infrared Detection

  • Less effective in detecting long-wavelength infrared radiation
  • Particularly effective in detecting long-wavelength infrared radiation
• Quantum IR Sensors

  1. Specialized detectors that capture infrared light and convert it into electrical signals

  2. Operate based on the direct interaction of IR photons with the sensor's material
• Thermal IR Sensor

  1. Converts infrared radiation into an electrical signal, which is then processed to generate temperature readings or thermal images

  2. Used in various applications including temperature measurement, night vision, security systems, and industrial monitoring

  3. Can operate in a wide range of temperatures and environmental conditions

  4. Provide non-contact and non-invasive measurement capabilities
• Disadvantages of IR Sensors

  1. Line of sight requirement

  2. Limited range

  3. Vulnerability to fog, rain, and dust

  4. Lower data transmission rate
• Application of Quantum IR Sensors

  1. Spectroscopy: Used to analyze the IR absorption and emission patterns of materials

  2. Astronomy: Detect infrared emissions from distant celestial objects

  3. Night vision and surveillance: Detection of heat signatures in low-light environments

  4. Advanced Medical Imaging: Specialized applications for studying biological processes and diagnosing conditions
• Characteristics of Quantum IR Sensors

  1. Wavelength Dependence: Quantum IR sensors respond to specific wavelengths within the infrared spectrum

  2. High Sensitivity: Quantum IR sensors are remarkably sensitive and can detect even faint IR signals

  3. Fast Response Time: Quantum IR sensors often have rapid response times

  4. Need for Cooling: Quantum IR sensors usually require significant cooling to reduce thermal noise
• Independence from Wavelength

  1. Thermal IR sensors don't require specific wavelengths to detect objects, they detect heat emitted by objects regardless of the source's specific wavelength within the infrared spectrum

  2. This makes them more versatile as they can detect a wide range of objects regardless of their material composition or emissivity
• Advantages of IR Sensors

  1. Less power usage

  2. Motion detection in various light conditions

  3. No need for contact with objects

  4. No data leakage

  5. Resistance to oxidation & corrosion

  6. Strong noise immunity
• Thermal Imaging Cameras


  • Not typically used in thermal imaging cameras
  • Commonly used in thermal imaging cameras for high-precision temperature measurements