Direct reading pyrometer employing pyroelectric crystal detector

Claim 2

The pyrometer of claim 2 further including a movable focusing control mechanically connected to adjust said lens along its optical axis; and an electrical control connected to said readout circuit for varying the sensitivity of said circuit in accordance with the position of said lens.

Claim 3

The radiometer defined in claim 1 wherein said readout circuit includes a phase detector circuit synchronized with the periodic movement of said movable means interrupting the radiation to said crystal to allow only those signals having a frequency in the range of the frequency of oscillation of said movable means to pass therethrough to render the output of said circuit essentially independent of piezoelectric voltages generated by said crystal due to mechanical forces.

Claim 4

The radiometer defined in claim 1 wherein said readout circuit includes a filter circuit having a band pass frequency centered about the frequency of the periodic movements of said movable means interrupting the radiation to said crystal further to permit amplification of only those signals having a frequency in the range of frequencies of oscillations of said movable means to render the output of said circuit independent of piezoelectric voltages generated by said crystal due to mechanical forces.

Claim 5

A radiometer defined in claim 1 further including electrostatic shielding means disposed across the opening in said housing means to isolate the pyroelectric crystal contained therein from ambient electrostatic fields.

Claim 6

The radiometer defined in claim 1 wherein said pyroelectric crystal is formed from lead zirconium titanate.

Claim 7

A pyrometer comprising a housing means effective to shield the pyrometer from electrostatic fields, mechanical forces and instantaneous changes in ambient temperature, said housing having an opening in one portion thereof to admit incident radiation from an object, the temperature of which is to be measured; a pyroelectric crystal capable of undergoing changes in electrical polarization as a result of changes in the temperature sensed thereby for producing a voltage indicating the intensity of the incident radiation applied thereto, and an electrically conducting coating on opposite surfaces of said crystal; means on the surface of said crystal facing the opening in said housing means for converting the incident radiation into heat; means transparent to infrared radiation mounted on said housing to isolate said crystal from instantaneous changes in ambient temperature while pErmitting radiation at least in the infrared range to pass therethrough; means shock mounting said pyroelectric crystal within said housing means to render said crystal substantially insensitive to mechanical forces and to minimize piezoelectric voltages produced thereby; means for optically focusing the incident radiation onto said pyroelectric crystal including a forward looking objective lens mounted on said housing and being adjustable along its optical axis for focusing an eyepiece mounted on said housing positioned to direct a small portion of the radiation received from said objective lens to said eyepiece and to direct the remaining radiation onto said crystal; a movable focusing control mechanically connected to adjust said lens along its optical axis; means movable between a first position clear of the path between said crystal and the source of the incident radiation and a second position in the path of the radiation, said movable means having an area sufficient to shield the crystal from the radiation when in said second position; means to move said movable means at regular intervals between said first position and said second position and into the path of the radiation to cause periodic changes in the temperature of said crystal thus casing the crystal to produce a voltage, the magnitude of which is an indication of the temperature of the object; a readout circuit connected to said electrically conducting coatings on said pyroelectric crystal and responsive to the variations in voltage produced thereby to provide an output which is a direct function of the temperature of the object being observed; and an electrical control connected to said readout circuit for varying the sensitivity of said circuit in accordance with the position of said lens, said electrical control being connected for simultaneous movement with said focusing control.