Spatial Radiometer
Multi-element infrared detectors capture the thermal distribution across a specific field of view. A thermopile array consists of multiple individual sensing pixels arranged in a grid on a single silicon chip. This allows for the simultaneous measurement of temperatures at different points without moving the sensor.
Detection Grid
Each pixel in the thermopile array operates as an independent thermocouple chain. These elements are typically arranged in formats like 8×8 or 32×32 to provide a low-resolution thermal image. Because each pixel is micromachined on the same substrate, the response characteristics are uniform across the device.
This grid structure is ideal for detecting the presence or movement of heat sources.
Data Acquisition
Serial interfaces like I2C or SPI transfer the temperature data from the pixels to a central processor. The thermopile array produces a frame of data that represents the thermal landscape of the target area. Frame rates are generally slower than those of CMOS cameras, often ranging from 1 to 10 Hertz.
This speed is sufficient for industrial monitoring and occupancy sensing applications.
Lens Requirement
Optical elements focus the infrared radiation onto the pixel grid to define the spatial resolution. The field of view of a thermopile array is determined by the focal length of the integrated lens. Germanium or silicon lenses are common because they are transparent to the long-wave infrared spectrum.
Proper alignment of the optics is necessary to prevent blurring or overlap between adjacent pixels. A fixed-focus lens is often used to maintain a constant field of view in static installations.
