TechNexion Embedded Vision Resources article:
IR-Cut Filter in Embedded Vision: Colour accuracy and Seamless day/night transition
As imaging technology continues to evolve, the nuances of capturing and interpreting visual data become increasingly important.
One such nuance often left unexplored is the use of IR-cut filters, especially in embedded vision systems. IR-cut filters ensure that embedded cameras can capture image data properly during the daytime.
This deep dive into the IR-cut filter will provide insight into its importance, applications, and workings in embedded vision systems.
Whether you’re a tech enthusiast, a professional in the industry, or just curious about modern imaging technology – this exploration promises to offer something for everyone.
Let’s delve deep into this intriguing technology.
Understanding the IR Spectrum
The electromagnetic spectrum is a wide range of wavelengths, encompassing everything from the shortest gamma rays to the longest radio waves.
Within this vast spectrum lies the world of the infrared (IR) spectrum. Positioned between the visible light spectrum and the microwave region, the IR spectrum is useful in imaging techniques and various scientific and medical applications.
The Infrared Spectrum – a few Basic Concepts Related to the IR Spectrum
This post primarily concerns CMOS image sensors, which are inherently sensitive in various degrees to portions of the NIR spectrum, but the IR spectrum is much larger and can be divided into distinct regions, each with its own characteristics and practical applications:
Near-Infrared (NIR, 700-1400 nm): Just beyond the range of human vision, NIR finds valuable use in electronics, particularly in remote controls. By harnessing NIR, you can easily communicate between various electronic devices, making control more
Convenient and efficient.
Short-Wavelength Infrared (SWIR, 1400-3000 nm): With a reflective nature, SWIR plays a vital role in satellite imaging, enabling the detection of moisture and the differentiation between water bodies and dry areas. Using SWIR technology, you can gather accurate and valuable information for various applications.
Mid-wavelength infrared (MWIR, 3000-8000 nm): Sensitive to common terrestrial temperatures, MWIR is extensively employed in night vision devices. By detecting emitted heat, MWIR plays a critical role in enhancing visibility in low-light conditions, ensuring the safety and security of various operations.
Long-Wavelength Infrared (LWIR, 8000-15000 nm): Operating on a thermal basis, LWIR is what is detected by thermal imaging cameras. This technology is widely used in industries such as firefighting, security systems, and various industrial applications. By utilizing LWIR, you gain the ability to detect infrared radiation emitted by objects, providing crucial insights and enabling informed decision-making.
Far Infrared (FIR, 15000 nm-1 mm): FIR is associated with thermal radiation and has found significant application in therapeutic infrared saunas. By leveraging FIR technology, these saunas provide soothing and beneficial heat through absorbed infrared light, promoting relaxation and well-being.
What is an IR-Cut Filter?
Nearly all CMOS image sensors have at least some sensitivity in the near-infrared spectrum.
Because of this, an indispensable component in modern imaging technology, the IR-cut filter, also called an infrared cut-off filter, can block infrared (IR) light while permitting visible light to pass through.
It serves as a notch filter, blocking longer wavelengths such as IR from being transmitted through to the sensor, as well as shorter wavelengths such as UV.
The IR-cut filter serves a vital purpose in embedded cameras by filtering invisible infrared radiation, ensuring only visible light reaches the sensor.
Why is an IR-Cut Filter Important?
IR-cut filters are a game-changer in embedded vision systems primarily because of two reasons:
Unadulterated color accuracy: Digital camera sensors are prone to sensitivity to IR light, which can distort the true colors they perceive. In scenarios where infrared enters the camera lens, it can result in a reddish or washed-out effect, particularly in daylight. Implementing an IR-cut filter ensures that exclusively visible light reaches the camera sensor, thereby preserving the accurate representation of colors in both photos and videos.
Seamless transition between day and night: Numerous security cameras have the day/night mode feature. During daytime operations, an IR-cut filter is placed in the optical path, facilitating clear and precise color capture. This filter disengages as the camera transitions to night mode, allowing IR light to permeate. This enables the camera to excel in capturing images in the dark, often working in conjunction with IR LEDs that emit infrared light.
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