IR-CUT: A Filter That Ensures Optimal Camera Image Quality
An IR-CUT dual-filter system refers to a set of filters built into a camera lens assembly. When the infrared light sensor outside the lens detects changes in ambient light intensity, the built-in IR-CUT automatically switches between filters according to lighting conditions, allowing the camera to achieve optimal image quality.
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In other words, whether it is daytime or nighttime, the dual-filter system automatically switches filters to ensure the best possible imaging performance under all lighting conditions.
What Does IR-CUT Mean?
- IR = Infrared
- CUT = Cut / Reduce
The imaging sensors used in cameras—CCD or CMOS—are capable of detecting light across a very wide wavelength range. Because multiple wavelengths participate in image formation, the colors reproduced by the camera often differ from what the human eye perceives.
To minimize color distortion, the conventional solution is to place a single-layer or multi-layer dual-bandpass filter (allowing both visible light and infrared light to pass) in front of the CCD.
During daytime, infrared light and other stray light entering the CCD interfere with color reproduction. For example, green plants may appear grayish-white, and red clothing may look faded—especially noticeable in outdoor sunlight.
At night, the filtering effect of the dual-bandpass filter prevents the CCD from fully utilizing available light, resulting in poor low-light performance and increased image noise.
With an IR-CUT dual-filter switching system:
In daylight, when sufficient light is available, the infrared-cut filter is engaged, blocking infrared light and allowing the CCD/CMOS to reproduce accurate, true-to-life colors.
At night, when light levels are low, the infrared-cut (or infrared-absorbing) filter is automatically removed, and a full-spectrum transparent filter is activated. This allows the sensor to utilize all available light, significantly improving low-light sensitivity and image brightness.
Key Factors That Determine IR-CUT Quality
The performance and reliability of an IR-CUT system depend on three main components:
- Optical filters
- Drive mechanism
- Control circuitry
Working Principle of the IR-CUT Dual-Filter Switch
A full-spectrum optical filter film is installed in front of the camera lens and driven by a micro electronic motor.
When the CMOS/CCD image sensor receives light of various wavelengths from the environment, the dual-filter system automatically blocks or allows specific wavelengths to pass based on detected ambient lighting conditions. This ensures that the sensor receives the most appropriate light for imaging.
As a result, the processed image achieves optimal brightness, color accuracy, and overall visual quality—all without any manual intervention.
In the field of surveillance cameras, this process of blocking or allowing infrared light is commonly referred to as a dual-filter switcher.
The Role of IR-CUT in Cameras
The IR-CUT dual-filter switching system plays a critical role by:
- Correcting color distortion during daytime
- Enhancing brightness and clarity at night
Structure of the IR-CUT Dual-Filter Switching System
An IR-CUT dual-filter switcher consists of:
Optical filters:
- One infrared-cut or infrared-absorbing filter
- One full-spectrum transparent filter
Drive mechanism:
- Electromagnetic actuator, motor-driven system, or other power sources
Visible and Invisible Light
In nature, light exists across a wide range of wavelengths. The human eye can perceive wavelengths approximately between 320 nm and 760 nm. Light outside this range—such as infrared and ultraviolet radiation—is invisible to the human eye but can still be detected by imaging sensors.
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