April 15, 2006

How important is IR detector resolution?

—Contributed by Jon Chynoweth, VP of Mikron Infrared Inc. (Oakland, N.J.). He can be reached at 888-506-3900 or jon@mikroninfrared.com.

Stretching meager maintenance dollars is a way of life for most maintenance staff. In past years, the cost of an infrared (IR) camera usually came down to a choice between a low-resolution 160 x 120-pixel camera or no camera at all. If the camera was chosen, it usually became clear before long that low resolution can mean missing some details when performing thermography.

If you're fortunate enough to have the budget for an IR camera this year, you'll be pleased to learn that IR cameras' prices have dropped like those of most electronic devices. Now you can choose between high and low resolution. For example, with sticker prices starting at $25,000, professional high-resolution 320 x 240-pixel cameras used to be too costly for anyone but full-time thermographers. That has changed with the introduction of cameras costing less than $15,000 with a high-performance, 320 x 240-pixel microbolometer detector.

With choices come questions. Now inquiring minds want to know: Why is higher resolution important in thermal imaging? Why have professional thermographers been willing to pay the premium for the 320 x 240-pixel detectors used in uncooled, focal-plane-array cameras?

Pixels are the data acquisition points for thermal measurement, and the data are used to create a visual image from the thermal profile. The more pixels and data points, the more accurate the thermal interpretation and the higher the resolution of the thermal image. High resolution is particularly important because it allows identification of smaller image details and therefore more-accurate temperature measurements, for the same field of view.

To make IR cameras affordable to wider range of users, vendors have introduced detectors with pixel counts of 160 x 120, with or without interpolation. However, their resolution is only one-fourth that of 320 x 240 detectors: 19,200 pixels vs. 76,800. The larger detector produces an image twice as wide and twice as high, with four times the data for a given field of view.