Improving quality of high-frame-rate imaging with coherent and incoherent processing

High-frame-rate (HFR) imaging methods using delay-and-sum (D&S), steered plane waves (SPW), and limited-diffraction beams (LDB) have been studied in 1990s. In the HFR imaging methods, multiple transmissions can be used to obtain sub-images that can be combined coherently or incoherently to form a final frame of image. Coherent superposition of sub-images can obtain images of a high image contrast and resolution but has a low signal-to-noise (SNR) ratio on speckle. In opposite, incoherently-superposed images have low image contrast and resolution but have a high SNR. To maintain high image contrast and resolution of the coherently-superposed images while also having the high SNR of the incoherently-superposed images, a new imaging method using coherent and incoherent processing is developed. In this method, a ratio image is first obtained by dividing the incoherently-superposed image with the coherently-superposed image. Then, the ratio image is used in a nonlinear process to obtain the final image that is a combination of the coherently- and incoherently-superposed images. To verify the method, an experiment was performed with a home-made HFR imaging system and the results show that the new method can obtain high image contrast and resolution while having a high SNR. Due to its simplicity, the method has a potential to be incorporated into existing commercial imaging systems to obtain high contrast, high resolution, and low speckle images. The high SNR may also improve the accuracy of image segmentations for various applications.