Acoustic imaging system and method

In an acoustic imaging system for generating a visual image representative of the acoustic properties of an object, of the kind including:

• insonification means for insonifying the object with acoustic waves having a frequency above ten megahertz to develop a pattern of perturbations on an at least partially light-reflective interface surface, coupled to the object, which pattern is representative of acoustic properties of the object;
• scanning means for scanning a high-energy small diameter light beam across the interface surface;
• photodetection means for detecting a portion of the light beam reflected from the interface surface to develop an initial electrical signal;
• signal processor means, coupled to the photodetection means, for processing the initial electrical signal to develop an acoustic image signal;
• and display means, coupled to the signal processor means, for utilizing the image signal to develop a visual image representative of acoustic properties of the object;
• the improvement comprising:
• low pass filter means, coupled to the photodetection means, for developing an optical content signal from the initial electrical signal;
• comparator means for comparing the optical content signal with a given reference signal level to develop a gain control signal;
• and
• gain control means, interposed between the photodetection means and the signal processor means, responsive to the gain control signal, for varying the amplitude of the initial signal supplied to the signal processor means to minimize the effects of non-uniformity in operation of the scanning means and photodetection means.

In a method of acoustic imaging comprising the basic steps of:

• A. scanning a high-energy small-diameter light beam across an at least partially light-reflective interface surface coupled to an object to be examined;
• B. insonifying the object, concurrently with scanning step A with acoustic waves having a frequency above ten megahertz to develop a pattern of perturbations at the interface surface, which pattern is representative of acoustic properties of the object;
• C. detecting a portion of the light beam reflected from the interface surface to develop an initial electrical signal;
• D. processing the initial electrical signal to develop an acoustic image signal;
• E. and utilizing the image signal to develop a visual image representative of acoustic properties of the object;
• the improvement comprising:
• F. detecting the amplitude level of the image signal;
• G. adjusting the intensity of the acoustic waves insonifying the object to afford an image signal level corresponding to a given reference level;
• and
• H. recording the adjustment of acoustic wave intensity as a quantitative measure of variation of acoustic properties of the object, relative to the reference, that minimizes the effects of inadequate dynamic range and nonlinearities in the imaging system.

In a method of acoustic imaging comprising the basic steps of:

• A. scanning a high-energy small-diameter light beam across and at least partially light-reflective interface surface coupled to an object to be examined;
• B. insonifying the object, concurrently with scanning step A with acoustic waves having a frequency above ten megahertz to develop a pattern of perturbations at the interface surface, which pattern is representative of acoustic properties of the object;
• C. detecting a portion of the light beam reflected from the interface surface to develop an initial electrical signal;
• D. processing the initial electrical signal to develop an acoustic image signal;
• E. and utilizing the image signal to develop a visual image representative of the acoustic properties of the object;
• the improvement comprising:
• J. developing an optical content signal from the initial electrical signal of step C, using low pass filter means;
• and
• K. using the optical content signal to control the amplitude of the acoustic image signal to compensate for non-uniformities occurring in the scanning and detecting operations of steps A and C.