Ultrasonic thickness measuring and imaging system and method

Abstract

An ultrasonic thickness measuring and imaging system uses an ultrasonic fsed beam probe for measuring thickness of an object, such as a wall of a tube, a computer for controlling movement of the probe in a scanning pattern within the tube and processing an analog signal produced by the probe which is proportional to the tube wall thickness in the scanning pattern, and a line scan recorder for producing a record of the tube wall thicknesses measured by the probe in the scanning pattern. The probe is moved in the scanning pattern to sequentially scan circumferentially the interior tube wall at spaced apart adjacent axial locations. The computer processes the analog signal by converting it to a digital signal and then quantifies the digital signal into a multiplicity of thickness points with each falling in one of a plurality of thickness ranges corresponding to one of a plurality of shades of grey. From the multiplicity of quantified thickness points, a line scan recorder connected to the computer generates a pictorial map of tube wall thicknesses with each quantified thickness point thus being obtained from a minute area, e.g. 0.010 inch by 0.010 inch, of tube wall and representing one pixel of the pictorial map. In the pictorial map of tube wall thicknesses, the pixels represent different wall thicknesses having different shades of grey.

We claim: 
     
       1. An ultrasonic thickness measuring and imaging system, comprising: (a) means for ultrasonically inspecting an object with a focused beam probe and generating an analog signal proportional to the thickness of the object;   (b) means coupled to said inspecting means for driving said inspecting means to scan the object in a predetermined pattern;   (c) means coupled to said driving means for generating and outputting to said driving means a driving signal to control said driving means in driving said inspecting means to scan the object in the predetermined pattern;   (d) means coupled to said inspecting means for receiving the analog signal therefrom representing thicknesses of the object scanned in the predetermined pattern and for converting the analog signal into a digital signal and quantifying the digital signal into a multiplicity of thickness points in the scanned pattern with each point falling in one of a plurality of different thickness ranges; and   (e) means coupled to said converting and quantifying means for receiving the quantified digital signal and generating a pictorial map of wall thicknesses of the object in the predetermined pattern from the multiplicity of quantified thickness points, each quantified thickness point on the pictorial map being obtained from a minute area of the object and representing one pixel of the pictorial map.   
     
     
       2. The system as recited in claim 1, wherein said inspecting means is driven by said driving means to scan the object at spaced apart locations in order to measure the thicknesses of the object. 
     
     
       3. The system as recited in claim 1, wherein said inspecting means includes: an ultrasonic focused beam probe; and   a probe drive assembly having first and second mechanisms for driving said probe and respectively producing movement of said probe to position said probe at successive spaced apart locations to scan the object in the predetermined pattern.   
     
     
       4. The system as recited in claim 3, wherein said inspecting means also includes an ultrasonic thickness gage coupled to said ultrasonic probe for generating the analog signal. 
     
     
       5. The system as recited in claim 3, wherein said first and second driving mechanisms are stepping motors. 
     
     
       6. The system as recited in claim 1, wherein said pictorial map generating means is a line scan recorder. 
     
     
       7. The system as recited in claim 1, wherein the pixels composing the pictorial map have one of a plurality of different shades of grey, each different shade of grey corresponding to one of the different thickness ranges containing each thickness point. 
     
     
       8. The system as recited in claim 7, wherein the pixels in the blackest shade of grey represent object areas of minimum thickness, whereas the pixels in the whitest shade of grey represent object areas of maximum thickness, and wherein each pixel represents an area of the object no greater than approximately 0.010 inch by 0.010 inch. 
     
     
       9. The system as recited in claim 8, wherein the pixels in shades of grey ranging from blackest to whitest represent object areas which incrementally increase from the minimum to maximum thickness. 
     
     
       10. An ultrasonic thickness measuring and imaging system, comprising: (a) means for ultrasonically inspecting a tube and generating an analog signal proportional to the wall thickness of the tube, said inspecting means including an ultrasonic focused beam probe and a probe drive assembly having first and second mechanisms for driving said probe and respectively producing axial movement of said probe to position said probe at successive spaced apart axial locations and rotational movement of said probe to scan the interior tube wall at each of the axial locations;   (b) means coupled to said inspecting means for driving said inspecting means to scan the interior of the tube along the axis and about the circumference of the tube in a predetermined pattern;   (c) a computer coupled to said driving means for generating and outputting to said driving means a predetermined sequence of signals to control said driving means in driving said inspecting means to scan the tube interior in the predetermined pattern;   (d) said computer also coupled to said inspecting means for receiving the analog signal therefrom representing thicknesses of the tube wall scanned in the predetermined pattern and for processing the analog signal by converting the analog signal into a digital signal and quantifying the digital signal into a multiplicity of thickness points in the predetermined pattern with each point falling in one of a plurality of different thickness ranges; and   (e) a line scan recorder coupled to said computer for receiving the quantified digital signal and generating a pictorial map of tube wall thicknesses in the predetermined pattern from the multiplicity of quantified thickness points, each quantified thickness point on the pictorial map being obtained from a minute area of tube wall no greater than (0.010 in.) 2 and representing one pixel of the pictorial map.   
     
     
       11. The system as recited in claim 10, wherein said inspecting means also includes an ultrasonic thickness gage coupled to said ultrasonic probe for generating the analog signal. 
     
     
       12. The system as recited in claim 10, further comprising: a X-Y recorder coupled to said computer for generating a plot of thickness versus axial distance when said probe is moved axially at a given circumferential location.   
     
     
       13. The system as recited in claim 10, wherein the pixels composing the pictorial map have one of a plurality of different shades of grey, each different shade of grey corresponding to one of the different thickness ranges containing each thickness point. 
     
     
       14. The system as recited in claim 13, wherein the pixels in the blackest shade of grey represent tube wall areas of minimum thickness, whereas the pixels in the whitest shade of grey represent tube wall areas of maximum thickness. 
     
     
       15. The system as recited in claim 14, wherein the pixels in shades of grey ranging from blackest to whitest represent tube wall areas which incrementally increase from the minimum to maximum thickness. 
     
     
       16. An ultrasonic thickness measuring and imaging method, comprising the steps of: (a) scanning an object in a predetermined pattern;   (b) ultrasonically inspecting the object with a focused beam probe in the predetermined pattern and generating an analog signal proportional to the thicknesses of the object in the predetermined pattern;   (c) receiving the analog signal representing thicknesses of the object scanned in the predetermined pattern and converting the analog signal into a digital signal;   (d) quantifying the digital signal into a multiplicity of thickness points in the predetermined pattern with each point falling in one of a plurality of different thickness ranges; and   (e) receiving the quantified digital signal and generating a pictorial map of thicknesses of the object in the predetermined pattern from the multiplicity of quantified thickness points, each quantified thickness point on the pictorial map being obtained from a minute area no greater than (0.010 in.) 2 of the object and representing one pixel of the pictorial map.   
     
     
       17. The method as recited in claim 16, wherein said map generating includes generating the pixels which compose the pictorial map such that each has one of a plurality of different shades of grey, each different shade of grey corresponding to one of the different thickness ranges containing each thickness point. 
     
     
       18. The method as recited in claim 17, wherein said map generating includes generating the pixels which represent object areas of minimum thickness in the blackest shade of grey and generating the pixels which represent object areas of maximum thickness in the whitest shade of grey. 
     
     
       19. The method as recited in claim 18, wherein said map generating includes generating the pixels which represent object areas which incrementally increase from the minimum to maximum thickness in shades of grey ranging from blackest to whitest. 
     
     
       20. An ultrasonic thickness measuring and imaging method, comprising the steps of: (a) scanning the interior of a tube along its axis and about its circumference in a predetermined pattern;   (b) ultrasonically inspecting the tube with a focused beam probe in the predetermined pattern and generating an analog signal proportional to the wall thicknesses of the tube in the predetermined pattern;   (c) receiving the analog signal representing thicknesses of the tube wall scanned in the predetermined pattern and converting the analog signal into a digital signal;   (d) quantifying the digital signal into a multiplicity of thickness points in the predetermined pattern with each point falling in one of a plurality of different thickness ranges; and   (e) receiving the quantified digital signal and generating a pictorial map of wall thicknesses of the tube in the predetermined pattern from the multiplicity of quantified thickness points, each quantified thickness point on the pictorial map being obtained from a minute area of tube wall and representing one pixel of the pictorial map.   
     
     
       21. The method as recited in claim 20, wherein said map generating includes generating the pixels which compose the pictorial map such that each has one of a plurality of different shades of grey, each different shade of grey corresponding to one of the different thickness ranges containing each thickness point. 
     
     
       22. The method as recited in claim 21, wherein said map generating includes generating the pixels which represent tube wall areas of minimum thickness in the blackest shade of grey and generating the pixels which represent tube wall areas of maximum thickness in the whitest shade of grey. 
     
     
       23. The method as recited in claim 22, wherein said map generating includes generating the pixels which represent tube wall areas no greater than (0.010 in.) 2 which incrementally increase from the minimum to maximum thickness in shades of grey ranging from blackest to whitest.