Yuan Gao

Yuan Gao is currently a first-year M.S Urban Planning student at GSAPP(Graduate School of Architecture, Planning, and Preservation) Columbia. Prior to this, she studied in architecture in Los Angeles. She is pursuing two concentrations within her program: urban analytics and built environment.

Contact: yg2603@columbia.edu, (213)290-7913

Image Sensors(Camera)

 

CCD Camera with USB Interface

An image sensor or imager is a sensor that detects and conveys information used to make an image. It does so by converting the variable attenuation of light waves (as they pass through or reflect off objects) into signals, small bursts of current that convey the information. The waves can be light or other electromagnetic radiation. As technology changes, digital imaging tends to replace analog imaging.

Below are some applications of the image sensors:

  • Imaging devices such as digital cameras, camera modules, camcorders, smart phones, security cameras, PC cameras, personal digital assistants (PDAs), machine vision, security and surveillance cameras, and videoconferencing
  • Optical mouse, document scanning, barcode readers
  • Toys and games
  • Medical (dental radiography and pill cameras)
  • Scientific imaging

Technical Description

There are two types of image sensors: Charged-Coupled Device (CCD) and Complementary Metal Oxide Semiconductor (CMOS) sensors. Both types of sensors start with converting light into electrons. Each image sensor is built with an array of photodetectors called pixels that gather photons or single particles of light. The photons in the pixels are then converted to electrons. The next step is to read the value (accumulated charge) of each cell in the image, which differentiates two types. In a CCD device, the charge is actually transported across the chip and read at one corner of the array. An analog-to-digital converter turns each pixel’s value into a digital value.In most CMOS devices, there are several transistors at each pixel that amplify and move the charge using more traditional wires. The CMOS approach is more flexible because each pixel can be read individually.

CCD Sample Sensors

Barcode Reader/Scanner Module-CCD Camera-USB Interfacehttps://www.adafruit.com/product/1203

CMOS Sample Sensors

High-quality color CMOS camera module: https://www.sparkfun.com/products/11745

Reference

https://www.azosensors.com/article.aspx?ArticleID=412

https://electronics.howstuffworks.com/cameras-photography/digital/question362.htm

Active Infrared Sensors

RGB and Gesture Sensor

Generally speaking, there are TWO types of infrared sensors: Passive Infrared Sensor (PIR) and Active Infrared Sensors (AIR)

Active Infrared Sensor (AIR)

An active IR sensor gives you any more information on your subject. Setting up an active IR sensor requires both an emitter and receiver, but this sensing method is simpler than its passive counterpart.

Active IR sensing is very common in industrial settings. In these applications, an emitter and receiver pair can accurately note whether an object is, for example, in a certain position on a conveyor. (like IR sensors in garage door to prevent injury or mechanical failure due to obstructions in a door’s path)

Technical Description

These are 3 steps of how an active infrared sensor works:

An IR emitter shoots out a beam of light, facing an in-line receiver.

If nothing is in the way, the receiver sees a signal.

If the receiver fails to see an IR beam, it detects that an object is between the emitter and the receiver, and therefore present in the monitored area.

There are multiple ways of setting up the active infrared sensors. One variation is to use an emitter and receiver facing the same direction. The two sit very close to each other so the receiver can detect an object’s reflection when it enters an area.

Sample Sensors

Proximity, Light, RGB and Gesture Sensor: https://www.adafruit.com/product/3595

Sparkfun RGB and Gesture Sensor: https://www.sparkfun.com/products/12787.

Technical Description

The infrared detector consists of a photodiode. When it is exposed to light, the energy of the photons will be transferred to atoms and thus create more free electrons. The resistance therefore changes as well as the output voltage in proportion to the magnitude of the IR light.

Skill

Competent

Sample Sensors

Proximity, Light, RGB and Gesture Sensor: https://www.adafruit.com/product/3595

Sparkfun RGB and Gesture Sensor: https://www.sparkfun.com/products/12787.

Reference:

https://www.arrow.com/en/research-and-events/articles/understanding-active-and-passive-infrared-sensorshttp://www.glolab.com/pirparts/infrared.html

Passive Infrared Sensors

IR Emitter and Detector

Infrared Thermometer

Generally speaking, there are TWO types of infrared sensors: Passive Infrared Sensor (PIR) and Active Infrared Sensors (AIR)

Passive Infrared Sensor (PIR)

A passive IR sensor’s functionality is to “realize that everything”, such as humans, animals, even inanimate objects that emit a certain amount of IR radiation. How much IR radiation they emit relates to the body or object’s warmth and material makeup.

The PIRs can be found in security alarms and automatic lighting setups. These applications don’t require that the sensor detect an object’s specific location, just that objects or people in a particular area are moving around.

How does it work

Passive IR (PIR) sensors use a pair of pyroelectric sensors to detect heat energy in the surrounding environment. These two sensors sit beside each other, and when the signal differential between the two sensors changes (if a person enters the room, for example), the sensor will engage. That may mean it triggers an alarm, notifies authorities, or maybe turns on a floodlight.

Sample Sensors

Thermometer: Infrared thermometer https://www.sparkfun.com/products/9570.

Thermal Image: FLIR https://www.sparkfun.com/products/15183.

Motion Sensor: PIR Motion Sensor https://www.sparkfun.com/products/13285.

IR (Infrared) Receiver Sensor: https://www.adafruit.com/product/157

Miniature Reflective Infrared Optical Sensors: https://www.adafruit.com/product/3930

Technical Description

The infrared detector consists of a photodiode. When it is exposed to light, the energy of the photons will be transferred to atoms and thus create more free electrons. The resistance therefore changes as well as the output voltage in proportion to the magnitude of the IR light.

Limitation

Infrared sensors are vulnerable to thermal noise and therefore need to be used in thermal equilibrium and isothermal conditions.

Skill

Competent

Sample Exercise:

https://learn.adafruit.com/ir-sensor/overview

Reference:

https://www.arrow.com/en/research-and-events/articles/understanding-active-and-passive-infrared-sensorshttp://www.glolab.com/pirparts/infrared.html