Night Imaging Technologies

In daily life, our eyes can see an object by reflected light. Daylight cameras can detect the reflected visible light energy and convert it to an image. Our eyes and daylight cameras both must receive enough visible light source to be able to see something. In limited light provided by starlight or moonlight, night vision technologies can help us. Night imaging technologies can be broadly divided into four main categories – image intensifier, low light CCD camera, IR illuminator, and thermal imaging camera.

Figure 1: Electromagnetic Spectrum

Image Intensifier

An image intensifier is an optoelectronic device that amplifies low levels of visible light (400-900 nm band) for nighttime viewing under moonlight or starlight. The image intensifier is capable of detecting images in low light (weak emission/ reflected light). When photons are detected in an image intensifier, they are converted into electrons and amplified, then converted back into photons for viewing.

Its image is said to become "intensified" because the output visible light is brighter than the incoming light.

Low-Light CCD Camera

Figure 2: (a) The Image In Phosphor Screen From Image Intensifiers (b) IR Illuminator

A low-light CCD camera uses a conventional silicon CCD (Charge-Coupled Device) sensor. Its low light performance enhances by amplifying its CCD signal and increasing its gain. However, it makes the camera more noise sensitive, and it may decrease the image quality.

IR Illuminator

This technology combines infrared illumination of spectral range 700–1,000 nm (just below the visible spectrum of our human eye) with CCD cameras sensitive to this light. An IR illuminator is like a sneaky flashlight because its infrared illuminated source is invisible to the human eye. The camera shows reflected IR rather than emitted IR. This type of night-vision device using active near-infrared illumination allows people or animals to be observed without the observer being detected.

Thermal Imaging Camera

A thermal imaging camera requires no active illumination, and it is capable of longer range detection since no reflected light is needed. Thermal imaging “cameras” are actually sensors. Thermal imaging usually detects radiation in the long-infrared (LWIR) range of the electromagnetic spectrum (roughly 8–15 µm) and outputs a uniform image, called a thermogram.

Thermal imaging is a technique to produce an electronic image by detecting IR energy emitted by objects in difficult conditions such as night, smoke, and fog. Thermal cameras can detect temperature differences in IR range and convert it into an electronic image in the form of a color palette. Nowadays, thermal imaging cameras are used across various ranges of industries like defense, automotive, aerospace, industrial, and medical. Firefighters can use thermography to see through smoke to find people and to locate the base of a fire. Building construction technicians can use a thermal signature to detect heating and cooling loss problems.

Figure 4: Thermal Imaging Applications – Building Diagnostics, Liquid Storage Tank, Freezer

FLIR thermal imaging solution

FLIR's thermal camera cores are designed for easy and efficient integration into higher level assemblies and platforms.

The FLIR Lepton^® is a radiometric-capable LWIR camera solution that is smaller than a dime. It can fit inside a smartphone, and it is ten times less expensive than a traditional IR camera. Using a focal plane array (FPA) of 80 × 60 active pixels, Lepton easily integrates into many mobile devices and other electronics as an IR sensor or thermal imager. The radiometric Lepton provides accurate, calibrated, non-contact temperature data in every pixel of each image for even greater utility in commercial applications. Non-radiometric versions are also available.

Figure 5: (a) FLIR Lepton Miniature IR Camera Modules (b) Block Diagram For The Lepton Camera Module

Figure 6: Molex Camera Socket

Molex camera socket for FLIR Lepton camera module

The FLIR Lepton module is compatible with a commercially-available socket, the Molex 1050281001. Molex unveiled a class of space-saving and highly reliable SMIA-compliant camera sockets to support ultra-slim mobile phone, tablet, PC, and vision system applications. Molex’s SMIA-compliant sockets come with an anti-short housing wall design which prevents electrical shorting between socket terminals and its base metal shell when mated with a camera module. This feature ensures the application investments are protected.

Development Tool for Thermal Imaging

The FLIR Lepton® Thermal Camera Breakout, 250-0587-00 is an easy interface evaluation board which can quickly evaluate the FLIR Lepton® Camera module. It is compatible with a number of low-cost ARM based evaluation boards such as STM32 NUCLEO-F401RE from STMicroelectronics.

Figure 7: (a) FLIR Lepton Thermal Camera Breakout Molex Camera Socket (b) STM32 NUCLEO-F401RE ARM Based Evaluation Board

The STM32NUCLEO-F401RE provides an affordable and flexible way for users to try out new concepts and build prototypes with the STM32 microcontroller, choosing from the various combinations of performance, power consumption and features. This evaluation board does not require any separate probe as it integrates the ST-LINK/V2-1 debugger and programmer.

Reference:

1. FLIR Lepton LWIR Camera Module Video

2. STM32 Nucleo Ecosystem Training Module

3. Camera Sockets for Serial and Parallel Data Applications