Thermal Imaging

Introduction:

Thermal imaging is the technique of using the heat given off by an object to produce an image of it or to locate it.First developed for military purposes in the late 1950s and 1960s by Texas Instruments, Hughes Aircraft and Honeywell. In recent times it is being used in firefighting, law enforcement, industrial applications, security, transportation, medical and many other industries.

It is the technique of using the heat given off by an object to producean image of it. Works in environments without any ambient light and can penetrate obscurants such as smoke, fog and haze. Normally grey scale in nature: black objects are cold, white objects are hot and the depth of grey indicates variations between the two. Some thermal cameras, however, add color to images to help users identify objects at different temperatures. An image generated from a Thermal Imaging Camera. The persons skin (as a heat source) is shown as ‘white hot’ whilst the background (which is cold) is shown as black.

Thermal Imaging Camera: A thermal imaging camera records the intensity of radiation in the infrared part of the electromagnetic spectrum and converts it to a visible image.

Thermal Imaging Camera, Thermal Image, Spectrum

Working of Thermal Imaging Camera:

A thermal imaging camera consists of five components: an optic system, detector, amplifier, signal processing and display.

All objects emit infrared energy, known as a heat signature. An infrared camera (also known as a thermal imager) detects and measures the infrared energy of objects. The camera converts that infrared data into an electronic image that shows the apparent surface temperature of the object being measured.

Image processing is any form of signal processing for which the input is an image, such as a photograph or video frame and the output may be either an image or a set of characteristics or parameters related to the image.

An infrared camera contains an optical system that focuses infrared energy onto a special detector chip (sensor array) that contains thousands of detector pixels arranged in a grid.

Each pixel in the sensor array reacts to the infrared energy focused on it and produces an electronic signal. The camera processor takes the signal from each pixel and applies a mathematical calculation to it to create a color map of the apparent temperature of the object. Each temperature value is assigned a different color. The resulting matrix of colors is sent to memory and to the camera’s display as a temperature picture (thermal image) of that object.

Many infrared cameras also include a visible light camera that automatically captures a standard digital image with each pull of the trigger. By blending these images it is easier to correlate problem areas in your infrared image with the actual equipment or area you are inspecting.

Types of Thermal Imaging Cameras:

COOLED THERMAL IMAGER: Cooled detectors are typically contained in a vacuum-sealed case and cryogenically cooled. Cooling is necessary for the operation of the semiconductor materials used else they would be blinded by their own radiation. Cooled infrared cameras provide superior image quality. Bulky and expensive to produce and run. Cooling is power-hungry and time consuming hence the camera needs time to cool down before it can begin working again.

UNCOOLED THERMAL IMAGER: Un-cooled detectors use a sensor operating at ambient temperature or a sensor stabilized at room temperature using control elements. Resolution and image quality tend to be lower than cooled detectors. Smaller and less costly to produce and run. Fast operation and consumes less power.

Components of Thermal Imaging Camera:

  1. An optic system
    • Lens
  2. Detector
    • Cooled Detector
    • Uncooled Detector
  3. Amplifier
  4. Signal processor
  5. Display
    • Standard Video Monitor

Thermal Imaging Applications:

  1. Industrial Applications
  2. Medicine Applications
  3. Security Applications
  4. Building Constructions
  5. Night Vision