When evaluating an infrared detector, one of the most important specifications to consider is pixel size, also commonly referred to as pixel pitch. Although this parameter is usually expressed as a simple number in micrometers (μm), it has a significant influence on the resolution, optical design, system size, detection performance, and even manufacturing cost of an infrared imaging system.
Pixel pitch has become an increasingly important topic as infrared technology continues to move from traditional 25 μm and 17 μm detectors toward 12 μm, 10 μm, 8 μm, and even smaller pixel sizes.
But does a smaller pixel always mean a better infrared detector? Not necessarily.
To understand why, it is important to look beyond the pixel number itself and consider how the detector, infrared optics, and image-processing algorithms work together.
The pixel size of an infrared detector refers to the physical dimensions of each individual pixel in the focal plane array (FPA). It is generally measured in micrometers (μm).
For example, a detector with a 12μm pixel pitch has a center-to-center distance of approximately 12μm between adjacent pixels. Pixel size is therefore also commonly described as pixel pitch or pixel center-to-center spacing.
This parameter should not be confused with the overall detector resolution.
A detector with 640 × 512 pixels and a 12 μm pixel pitch has the same number of pixels as another 640 × 512 detector with a different pixel pitch, but their physical focal plane dimensions will be different.
The relationship can be expressed simply as:
Focal plane width = Number of pixels × Pixel pitch
Therefore, pixel pitch determines not only how densely pixels are arranged, but also the physical size of the detector's active imaging area.
For infrared thermal imaging systems, this seemingly simple parameter has consequences that extend all the way from the detector chip to the infrared lens and the final image.
Pixel pitch affects several important aspects of thermal imaging performance, including resolution, spatial detail, optical system size, target detection capability, and manufacturing economics.
When the overall focal plane area remains the same, reducing pixel pitch allows more pixels to be placed on the detector.
For example, replacing a 17 μm detector with a smaller-pitch detector while maintaining a similar focal plane size can significantly increase the number of pixels available for imaging.
More pixels mean more spatial sampling points, which can provide higher image resolution and more detailed thermal information.
This is particularly valuable for applications where users need to distinguish small targets, identify fine structures, or observe objects from relatively long distances.
However, it is important to understand that pixel pitch alone does not determine image resolution. Optical resolution, detector performance, signal-to-noise ratio, atmospheric conditions, image processing, and target characteristics all contribute to the final result.
Pixel pitch also has an important influence on infrared optical design.
Suppose two thermal imaging systems need to provide a similar field of view and use detectors with the same pixel count. A smaller pixel pitch means the physical dimensions of the detector are smaller.
This can allow the optical system to be designed with a shorter focal length while maintaining a comparable field of view.
As a result, smaller pixels can contribute to more compact infrared lenses and smaller thermal imaging systems.
This is one reason why pixel miniaturization has become an important development direction for portable thermal cameras, compact infrared modules, UAV payloads, machine vision systems, and other applications where size and weight matter.
Pixel pitch can also affect semiconductor manufacturing economics.
For a wafer with a fixed physical area, smaller pixels allow more detector arrays to potentially be manufactured on the same wafer, depending on the detector architecture and manufacturing process.
This can improve wafer utilization and potentially reduce the manufacturing cost per detector.
However, smaller pixels also introduce greater process and performance challenges. Manufacturing yield, pixel uniformity, optical coupling, readout circuitry, noise performance, and other factors must all be considered.
Therefore, the relationship between smaller pixel pitch and lower final product cost is not simply linear. Advanced small-pixel detector technology often requires more sophisticated manufacturing processes and system design.
Pixel size is one of the core specifications of an infrared focal plane detector. Moving from 25 μm and 17 μm toward 12 μm, 10 μm, 8 μm, and smaller pixel pitches can increase pixel density, improve spatial sampling, support higher-resolution imaging, and enable more compact thermal imaging systems.
But smaller is not always better.
The diffraction limit of the optical system, sampling theory, infrared radiation collected by each pixel, detector sensitivity, and optical-detector matching all place practical limits on how far pixel miniaturization can improve image quality.
For this reason, the most effective infrared imaging solution is not necessarily the detector with the smallest pixel pitch. It is the solution in which the infrared detector and optical system are precisely matched to the application requirements.
With its 8 μm uncooled infrared detector technology and capability to provide 12 μm and larger infrared optical solutions in volume, SensorMicro continues to support the industry's transition toward smaller-pixel, higher-resolution, and more compact thermal imaging systems.
Ultimately, the future of infrared imaging is not simply about making pixels smaller. It is about making every pixel count.
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