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Using Fine Resolution to Improve Thermal Images

Technical Overviews

Keysight Technologies

Using Fine Resolution to Improve Thermal Images

Application Note

Introduction

Digital imaging opened up new possibilities and has been very much part of our lives since social media use became commonplace. With digital imaging, images can be stored, duplicated, and shared digitally almost without any boundary. However, digital imaging is still a discreet system – what you can see really depends on how much resolution your digital imaging system has. However, technology advancement of a digital imaging system has come a long way and is very affordable today. On the contrary, the price of a thermal imaging system increases significantly with the detector’s resolution.

The technology used to enhance the resolution of a digital image is known as super resolution. Over the course of digital imaging system development, many different techniques of super resolution have been developed; each with its advantages and disadvantages. A thermal imaging system assimilates the resolution enhancement technology used in digital imaging system to improve on its resolution. Keysight Technologies’,Inc. TrueIR thermal imager uses a specific multi-frames super resolution technique and algorithms that is known as Fine Resolution (FR), which enhances the resolution of a thermal image by four times. In this paper, we are going to discuss the high level concept of this technology.

Resolution versus cost

Instantaneous Field of View (iFOV), also known as spatial resolution, defines the smallest detail within the Field of View (FOV) that a thermal imager can detect. To measure temperature correctly the target object must be larger than the physical iFOV of the thermal imager. Depending on the distance to the object, each pixel of a thermal imager detector measures the average temperature of the area within the physical iFOV. High resolution is particularly useful when inspecting large objects (building wall, roof), objects at a distance (sub-stations, large machineries) and small objects (electronic printed circuit board assemblies (PCBA)).

A thermal imager with higher resolution provides the ability to see more details of the measured object, and get a clearer infrared (IR) image, hence making measurements more accurate. Since the cost of a thermal imager increases as resolution increases, the available budget often dictates the selection of the thermal imager solution. For example, the price of a 320 x 240 pixels thermal imager could very well be double the price of a thermal imager with 160 x 120 pixels.

Fine resolution solution

There are fundamental limitations of digital imaging systems. Given that thermal imaging systems leverage digital imaging technology, those digital imaging limitations also exist in thermal imaging systems. The discrete nature of detector arrays and finite number of pixels limit the detectable area. Hence there is some missing information on digital images. The optical system (lens) contributes to the fuzziness of digital images. This is more apparent in thermal imaging systems due to their relatively low resolution.

Fine Resolution used in the TrueIR thermal imager offers the capability to improve the effective thermal resolution four-fold and provides 1.5x better instantaneous Field of View (iFOV). This is achieved using complex algorithms on a lower resolution detector. Coupled with a powerful digital image processor, the complex algorithms can be processed without any system lag. Overall, Fine Resolution improves the effective image quality and measurement accuracy without adding much cost to overall thermal imaging system.

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