A part inspection system comprising: a photoacoustic excitation unit comprising at least one pulsed laser source configured to illuminate at least one predetermined position on a part and generate thereby ultrasonic excitation of the part; a coherent illuminator configured to illuminate at least one predetermined location on the part with coherent illumination; a detector; an optical unit in association with the detector, wherein the optical unit is configured to gather an illumination scattered from the at least one predetermined location to the detector, and wherein the detector is configured to generate, based on the scattered illumination, at least one sequence, wherein each of the at least one sequence comprising at least two temporally-sequential de-focused speckle pattern images of one of the at least one predetermined illuminated location; and an image analysis unit configured to: receive the at least one sequence; determine at least one set of speckle pattern image translations, each of the at least one set is determined based on one of the at least one sequence, wherein each speckle pattern image translation in each of the at least one set is determined based on two temporally-sequential speckle pattern images in the respective sequence; determine, based on the at least one set of speckle pattern image translations, an angular distortion "Δφ" of the at least one predetermined location within the part; determine, based on the angular distortion "Δφ" of the at least one predetermined location, an intensity pattern of the ultrasonic excitation propagating through the at least one predetermined location; and identify, based on the intensity pattern of the ultrasonic excitation propagating through the at least one predetermined location, at least one zone comprising at least one of cracks, inhomogeneity, inclusions, defects of the part or any combination thereof, wherein the at least one predetermined position illuminated by the at least one pulsed laser source is at a lateral shift (δx, δz) with respect to the at least one predetermined location illuminated by the coherent illuminator, wherein the lateral shift (δx, δz) is determined and controlled by the inspection system to optimize a detection of the at least one zone. a photoacoustic excitation unit comprising at least one pulsed laser source configured to illuminate at least one predetermined position on a part and generate thereby ultrasonic excitation of the part; a coherent illuminator configured to illuminate at least one predetermined location on the part with coherent illumination; a detector; an optical unit in association with the detector, wherein the optical unit is configured to gather an illumination scattered from the at least one predetermined location to the detector, and wherein the detector is configured to generate, based on the scattered illumination, at least one sequence, wherein each of the at least one sequence comprising at least two temporally-sequential de-focused speckle pattern images of one of the at least one predetermined illuminated location; and an image analysis unit configured to: receive the at least one sequence; determine at least one set of speckle pattern image translations, each of the at least one set is determined based on one of the at least one sequence, wherein each speckle pattern image translation in each of the at least one set is determined based on two temporally-sequential speckle pattern images in the respective sequence; receive the at least one sequence; determine at least one set of speckle pattern image translations, each of the at least one set is determined based on one of the at least one sequence, wherein each speckle pattern image translation in each of the at least one set is determined based on two temporally-sequential speckle pattern images in the respective sequence; determine, based on the at least one set of speckle pattern image translations, an angular distortion "Δφ" of the at least one predetermined location within the part; determine, based on the angular distortion "Δφ" of the at least one predetermined location, an intensity pattern of the ultrasonic excitation propagating through the at least one predetermined location; and identify, based on the intensity pattern of the ultrasonic excitation propagating through the at least one predetermined location, at least one zone comprising at least one of cracks, inhomogeneity, inclusions, defects of the part or any combination thereof, wherein the at least one predetermined position illuminated by the at least one pulsed laser source is at a lateral shift (δx, δz) with respect to the at least one predetermined location illuminated by the coherent illuminator, wherein the lateral shift (δx, δz) is determined and controlled by the inspection system to optimize a detection of the at least one zone.