Infrared bandpass lens: What is it? What does it do？

While choosing the right camera module is important for embedded vision applications, choosing the right IR bandpass filters and lenses is equally important. The right IR bandpass filters and lenses ensure image quality and system performance. For example, in a particular embedded vision application, where we need to block out specific wavelengths of light while allowing the desired wavelengths to fall on the sensor, an IR bandpass filter is required.
 
So what exactly is an IR bandpass filter? What does it do? Let's go through this article to briefly understand.
 

What are IR bandpass filters and lenses?

IR bandpass lenses are specifically designed to allow specific wavelengths of infrared light to pass through while blocking the rest of the light spectrum, and are necessary for embedded vision applications that need to operate at specific infrared wavelengths. For example, infrared light (typically referred to as near infrared ranging from 780-1500nm) needs to be accurately captured for processing by system algorithms, while visible light (380nm to 700nm) needs to be effectively blocked.Does the infrared block the lens? We have an understanding before.

 
IR bandpass filters accomplish this by means of a special optical glass coating that allows specific IR wavelengths to pass through while reflecting or absorbing visible light. The two main types of IR filters that are more common are:

1. reflective IR filters.
2. absorbing IR filters.

The following is a detailed understanding of these two types of ir pass filter.

 
Reflective IR filters

This type of filter is also called an optical cooled mirror and is manufactured by vacuum coating on optical white glass. The main function is to reflect visible light while allowing infrared wavelengths to pass through. It has a mirror-like appearance, hence the name. Reflective IR filters perform well in applications that require low infrared transmittance, such as in certain surveillance systems or industrial inspections, where they are effective in minimizing visible light interference while maintaining a certain level of infrared light transmission.Learn about ir camera module.
 

Absorptive IR Filters

Unlike reflective types, absorptive IR filters are typically black coated or made of black glass, and they absorb visible light and allow infrared wavelengths to reach the image sensor. This type of ir pass filter is more common in applications that require high IR transmission, such as medical imaging and biometrics. Absorptive IR filters have a higher IR sensitivity than reflective types, which makes them more effective in scenarios where accurate IR image capture is required.
 
Of course, when choosing an IR bandpass filter, the percentage of transmission and spectral selection of the filter should also be considered.

 
Comparison of Transmission Percentage for Reflective and Absorptive Filters

Transmission percentage, the ratio of transmitted light intensity to incident light intensity, directly affects the quality of the image and the amount of ir lens light received by the sensor.
 
Reflective IR filters are less efficient at transmitting infrared light, but they are able to reflect most visible light, which is useful in certain applications where there is a need to minimize the interference of infrared light on visible images. However, their low transmission of IR light can limit their use in applications requiring high IR transmission.
 
In contrast, absorption IR filters exhibit higher efficiency in transmitting IR light, especially in the near IR range (780-1500nm). They are able to absorb most of the visible light, thus allowing more IR light to reach the sensor. This property makes absorptive IR filters ideal for applications that require high IR sensitivity, such as night vision surveillance or medical imaging.

 
Key features of IR bandpass filters for embedded vision applications

Superior Blocking Capability: IR bandpass filters excel at blocking unwanted light waves. Light from other spectral regions is effectively blocked, thus enhancing the contrast and overall quality of the transmitted IR light. This ensures that the image sensor receives only the desired wavelengths of infrared light.
 
Higher Transmission Efficiency: These filters achieve high transmission in the specified wavelength range, ensuring smooth passage of the desired infrared light. This improves image quality and sensor performance in applications where infrared light is the primary or only light source.
 
Wavelength selectivity: ir pass filter allow only a narrow range of wavelengths to pass through, effectively isolating specific IR wavelengths to meet the needs of the target application. This selectivity allows them to precisely control the wavelength.
 
Thermal Stability: IR bandpass filters maintain their performance characteristics even in environments with temperature variations. This means they can be used in environments with fluctuating temperatures, such as outdoor surveillance or industrial process control, without their filtration being affected by temperature changes.
 
Enhanced image quality: By reducing stray light and increasing the purity of infrared light, IR bandpass filters help to improve image clarity and detail, which is important for high-precision visual inspection and analysis.

Wide range of application adaptability: Whether in surveillance systems, medical imaging devices, smart agricultural systems or biometric systems, infrared pass filter provide the necessary infrared light transmission to support the effective operation of these technologies.

 
Areas of application for IR bandpass filters

Surveillance Systems: In the field of security surveillance, IR bandpass filters enhance nighttime surveillance capabilities by isolating specific infrared wavelengths to improve image clarity and detail, which is useful for 24-hour surveillance systems that can capture clear images in low-light or no-light environments, thereby improving security.
 
Medical Imaging Devices: In medical imaging applications such as thermal imaging cameras, infrared pass filter are used to isolate specific infrared wavelengths for accurate temperature measurement and tissue analysis. Beneficial for early disease detection, patient monitoring and treatment evaluation.
 
Smart Farming Systems: In precision agriculture, IR bandpass filters help drones and remote sensing equipment analyze crop health by isolating wavelengths indicative of plant stress, water levels and chlorophyll content. This enables farmers to make smarter irrigation, fertilization, and pest control decisions, leading to improved crop yields and health.

 
Sinoseen has the right embedded vision solution for you

Sinoseen has 14+ years of experience designing, developing and manufacturing OEM camera modules. We have customized camera modules for a wide range of lens types, including but not limited to IR bandpass lenses.
 
We offer diverse and differentiated camera module solutions to ensure you can find the right camera module with the right lens here. If you have any needs, please feel free to contact us.