Abstract: An apparatus for use in determining the temperature of or at a specific area by measuring the infrared radiation from that area through the use of a reflector structure to direct the radiation from the area to an infrared detector can be improved by using a laser to provide two light beams which are directed so as to intersect at a distance from the apparatus corresponding to the principal focus of the reflector structure.

Abstract: A temperature indicating device for use in indicating when the temperature of the device has been changed to a predetermined temperature can be constructed so as to utilize a snap spring such as a bimetal bowed washer capable of rapidly changing from a first configuration to a second configuration when the temperature of the spring is changed to a predetermined temperature. In a device of the invention the spring is located within an internal cavity of a housing in such a manner as to hold an indicator member within the housing so that it is visible from the exterior of the housing when the spring is in the first configuration. When the temperature of the spring is changed so as to cause the spring to go to the second configuration the indicator member is released so as to be free to fall within the cavity to a position in which it is no longer visible. If desired the indicator member may be coated with a coating indicating a specific temperature other than the predetermined temperature.