초록 ▼

An IR transient thermography imaging system includes high-power flash lamps fitted with spectrally tuned optical filters and a focal-plane array camera for IR image data acquisition. The image data processing control computer analyzes acquired IR image data frames and provides a color-keyed display

An IR transient thermography imaging system includes high-power flash lamps fitted with spectrally tuned optical filters and a focal-plane array camera for IR image data acquisition. The image data processing control computer analyzes acquired IR image data frames and provides a color-keyed display of an imaged object that correlates to object thickness over the imaged surface area. Acquisition of IR data is initiated at a firing of flash lamps used to heat a surface of the object along with a reference standard. A predetermined number of IR image frames are acquired and recorded over a predetermined period of time after firing of the lamps to develop a temperature-time (T-t) history of the object surface and the reference standard. A contrast curve is calculated for each pixel in the image frame, each pixel corresponding to an elemental region on the object surface. Gaussian temporal smoothing of contrast curve data is performed to improve signal-to-noise characteristics and a derivative of the contrast curve is determined using data points mathematically related to image frame number. All local peaks in the derivative of the contrast curve are identified and given significance according to a predetermined weighting function. The frame number of the most significant peak is used to determine time of occurrence of an "inflection point" in the contrast curve which is then used in determining object thickness. Gain correction of pixel intensity data is employed to offset IR emissivity variations caused by surface curvatures and varying surface conditions on an object.

대표청구항 ▼

1. A high speed infrared (IR) transient thermography method for determining the thickness of an object, comprising the steps of: a) storing pixel intensity data from a predetermined sequence of image frames acquired from an IR sensitive focal-plane array camera, wherein each sequentially acquired im

1. A high speed infrared (IR) transient thermography method for determining the thickness of an object, comprising the steps of: a) storing pixel intensity data from a predetermined sequence of image frames acquired from an IR sensitive focal-plane array camera, wherein each sequentially acquired image frame is assigned a frame number of increasing value that linearly corresponds to elapsed time; b) determining a pixel contrast curve from the pixel intensity data for a pixel from said sequence of image frames; c) performing Gaussian temporal smoothing of pixel contrast curve data developed in step (b); d) determining a time derivative of the pixel contrast curve data from separate data points in time along the contrast curve after Gaussian temporal smoothing; e) identifying localized peak derivative values in the time derivative of the pixel contrast curve data; f) applying a predetermined weighting function to said localized peak values identified in step (e) to determine a significance value for each derivative peak value identified; g) selecting one contrast curve derivative peak value based on a most significant value determined in step (f); and h) determining an object thickness, L, based on a frame number of an image frame in which the contrast curve derivative peak selected in step (g) occurs.