Infrared Detectors Principles Applications and Selection Guide

Imagine sensing an object's temperature without touching it, or detecting hidden gas components without visible light. Infrared detectors make these seemingly superhuman abilities possible. These unassuming devices act as silent investigators, capturing infrared radiation invisible to the naked eye and revealing hidden aspects of our material world.

Commonly referred to as infrared sensors or pyroelectric detectors, these photoelectric devices specialize in detecting and measuring infrared radiation. According to the DIN 1319-1 standard, they are classified as transducers, while European terminology typically labels them as sensors. Technical literature often uses these three terms—infrared detector, infrared transducer, and infrared sensor—interchangeably.

These components serve as critical elements in various equipment including gas analyzers, flame sensors, spectroscopic instruments, and non-contact temperature measurement devices.

Infrared radiation constitutes a form of electromagnetic radiation generated by thermal motion within objects. All matter above absolute zero (-273.15°C) emits electromagnetic waves, with infrared representing a portion of this spectrum. Surface characteristics and temperature directly influence both radiation intensity and spectral composition, enabling non-contact temperature measurement through precise infrared energy detection.

Occupying a unique position in the electromagnetic spectrum, infrared radiation borders visible red light (approximately 760 nanometers) and extends into the microwave region, covering wavelengths from about 760 nanometers to 1 millimeter.

As a category of thermal detectors, pyroelectric infrared detectors distinguish themselves through their specialized black absorption layer. This feature provides exceptionally broad spectral response and uniform sensitivity across wavelengths. While semiconductor detectors (such as InGaAs, PbS, or PbSe) typically offer superior detection rates below 3 microns at room temperature, pyroelectric detectors demonstrate clear advantages across wider spectral ranges.

Compared to thermopile detectors—another technology capable of long-wave infrared detection—pyroelectric detectors from manufacturers like InfraTec deliver faster response times and higher signal voltages. These devices typically operate optimally between 2.5 to 25 microns with modulation frequencies ranging from 0.5 to 400 Hz.

Notably, specialized black absorption layers enable certain pyroelectric detectors to function as stable receivers for ultraviolet radiation (down to 193 nm) and even terahertz radiation (100 microns to 1 mm).

• Versatility: Suitable for diverse measurement applications including multicomponent analysis
• Advanced Analysis: Capable of examining complex mixtures with overlapping spectral bands using chemometric methods
• Material Identification: Effective for unknown substance recognition
• Practical Advantages: Cost-effective, durable, and easily miniaturized

The most widespread use involves motion detection, whether for security systems identifying intruders or automated lighting controls. These applications typically employ economical pyroelectric ceramic sensors.

Higher-performance applications including nondispersive infrared (NDIR) gas analysis and flame monitoring generally utilize premium single-crystal lithium tantalate (LiTaO ₃ ) detectors to ensure long-term stability and superior signal-to-noise ratios. Additional applications span spectroscopy and radiometry, supporting scientific research and industrial measurements.

Pyroelectric detectors serve critical roles in environmental monitoring (measuring CO ₂ , methane, etc.), industrial safety (flammable gas leak detection), and medical applications (anesthetic gas monitoring).

Specialized detectors can reliably identify spectral signatures from organic material combustion, making them ideal for fire alarm systems requiring rapid response to prevent catastrophic damage.

Detectors designed for spectroscopy feature uniformly absorbing layers across broad wavelength ranges, ensuring consistent sensitivity for accurate spectral measurements.

Manufacturers like InfraTec employ polished lithium tantalate single crystals to produce high-sensitivity, low-noise detectors. Advanced techniques allow mass production of ultra-thin 25-micron chips offering exceptional response speed and sensitivity.

Infrared filters represent another critical component, selectively transmitting specific wavelengths to enhance detector selectivity. Key filter parameters include transmission percentage, center wavelength, bandwidth, and blocking depth.

Modern production facilities incorporate physical vapor deposition (PVD), automated chip bonding, and precision measurement systems to ensure consistent quality and reliability.

Manufacturers typically offer various single-channel detectors in TO18 or TO39 packages, featuring temperature compensation and integrated JFET/CMOS amplifiers. Material options include LiTaO ₃ or deuterated L-alanine doped triglycine sulfate (DLaTGS), with specialized versions available for analytical instruments requiring flat spectral response.

Complete product lines may include approximately 50 standard detectors, with options featuring reduced microphone noise, integrated operational amplifiers, or digital outputs.