Infrared Thermometers: No Lens Thermometers

No-lens thermometers, like the IR Pocket infrared thermometer, use a reflective funnel design to focus infrared energy against the thermopile rather than a lens. Not having a lens at all offers its own distinct advantages:

1. typically they cost less
2. more durable and survive drops even better than fresnel lens thermometers
3. usually smaller and easier to handle than other types of infrared thermometers
4. are the most accurate in cold spaces

Since there is no lens between the electromagnetic waves being emitted by a surface and the thermometer's thermopile, there are no significant contraction or expansion effects on no-lens thermometers. In most units, an internal sensor compensates for the ambient temperature effect on the electronics themselves, so you can literally walk from a warm room directly into a sub-zero freezer and begin taking measurements without waiting.

The important caveat with no-lens thermometers is that their distance to target ratio or DTR is always 1:1 or lower. That means that you should hold no-lens thermometers as close to the target surface as possible when taking measurements. No-lens thermometers are not as well suited for taking measurements at a distance.