Method and system for non-contact temperature measurement of spot on target object
A method, which is applied for non-contact temperature measurement of a spot on a target object, includes the following steps: image a thermal image of a target area on the target object and projecting the thermal image to an image plane; select an image spot in the image plane corresponding to the spot to allow corresponding light rays to pass through, while blocking all the rest of the light rays; measure a thermal radiation strength of the corresponding to light rays; and determine a temperature from the measured thermal radiation strength according to a calibration relation. A system of performing the above method is also provided.
1 . A method for non-contact temperature measurement of a spot on a target object comprising:
a step of imaging a thermal image of a target area on the target object and projecting the thermal image to an image plane, the target area including the spot;
a step of selecting an image spot in the image plane corresponding to the spot to allow light rays of the thermal image corresponding to the image spot to pass through while blocking passages of light rays corresponding to other parts of the thermal image;
a step of measuring a thermal radiation strength of the light rays corresponding to the image spot; and
a step of determining a temperature of the spot from the measured thermal radiation strength of the light rays corresponding to the image spot according to a calibration relation.
2 . The method of claim 1 , wherein the calibration relation is established from a calibration method comprising:
applying the step of imaging a thermal image of a target area on the target object to image a reference thermal image of a reference area of a known uniform temperature on a reference object with same properties as the target object and projecting the reference thermal image to the image plane;
applying the step of selecting an image spot in the image plane to select a reference spot in the reference thermal image on the image plane and applying the step of measuring a thermal radiation strength to measure a thermal radiation strength of light rays corresponding to the reference spot; and
establishing the calibration relation between the thermal radiation strength of the light rays corresponding to the reference spot and the known uniform temperature on the reference object.
3 . The method of claim 1 , wherein
the thermal radiation strength of the light rays corresponding to the image spot is a first thermal radiation strength measured at a first wavelength;
the calibration relation is established based on the dual-wavelength method for IR temperature measurement comprising an additional step of:
measuring a second thermal radiation strength of the light rays corresponding to the image spot at a second wavelength.
4 . The method of claim 1 , further comprising a step of changing a location of the image spot relative to the thermal image projected in the image plane such that the image spot scans over a certain area to obtain a temperature map of the target area on the target object.
5 . A system for non-contact temperature measurement of a spot on a target object comprising:
a set of imaging optics for imaging a thermal image of a target area on the target object and projecting the thermal image to an image plane, the target area including the spot;
a pinhole mask at the image plane for selecting an image spot in the image plane corresponding to the spot to allow light rays of the thermal image corresponding to the image spot to pass through while blocking passages of light rays corresponding to other parts of the thermal image;
a set of collecting optics collecting the light rays passing the pinhole mask;
a thermal radiation detector for measuring a thermal radiation strength of the light rays collected by the set of collecting optics.
6 . The system of claim 5 , wherein the pinhole mask comprises a movable pinhole mechanism that enables the pinhole mask to select multiple image spots in the image plane in order to measure temperatures of multiple spots in the target area.
7 . The system of claim 6 , wherein the movable pinhole mechanism comprises a small system of stages to translate the pinhole mask in two degrees of freedom.
8 . The system of claim 6 , wherein the movable pinhole mechanism comprises a reflective type Nipkow disk.
9 . The system of claim 6 , wherein the movable pinhole mechanism comprises a Digital Micromirror Device (DMD).