Thermal imager with protective grid

摘要

A protective enclosure for a thermal imager having a window and protective grid. The protective grid is designed in relation to the lens of the thermal imaging device such that the grid pattern geometry and size accommodate the thermal imaging device's pupil size.

主权项

1. A protective enclosure for enclosing a thermal imaging device mounted in a predetermined location, the thermal imaging device having a pupil plane and a lens, the thermal imaging device to be used in a hazardous environment comprising:
a housing having a proximal end and a distal end and a sidewall coupling the proximal end to the distal end, such that the sidewall surrounds the thermal imaging device when the thermal imaging device is in the predetermined location; a window assembly located near the distal end of the housing, the window assembly comprising: a window providing passage for infrared radiation to the thermal imaging device within the enclosure; and a protective grid comprising a first plurality of intersecting bars and a second plurality of intersecting bars, the protective grid located on one side of the window at the distal end of the housing wherein the protective grid is exposed on one side to the environment and is exposed on an opposite side to the window, the protective grid having a geometry constructed in relation to the thermal imaging device such that a ratio of blocked beam to adjacent unblocked beam projected on the pupil plane remains constant thereby providing a relatively uniform attenuation in the field of view of the thermal imaging device which may be compensated for with one transmissivity coefficient; wherein each of the first plurality of bars has a cross section with an elongate dimension defining a line extending therethrough, the bars oriented such that the lines extending through the elongate dimensions converge towards a first location within the housing, the first location being substantially coincident with the center of the lens of a thermal imaging camera when the thermal imaging camera is mounted in the predetermined location such that the protective grid provides relatively uniform attenuation from a field of view external to the enclosure to the first location within the housing; and each of the second plurality of bars is located near the periphery of the grid and has an elongate dimension oriented parallel to the elongate dimension of at least one adjacent bar, the at least one adjacent bar being in either the first plurality of bars or the second plurality of bars.