Interferometry-free noncontact photoacoustic detection method based on speckle correlation change

Area of Science:

• Optics
• Acoustics
• Biomedical Engineering

Background:

• Optical speckle patterns contain information about the medium through which light propagates.
• Photoacoustic imaging generates ultrasonic waves from light absorption, enabling subsurface imaging.
• Non-contact monitoring methods are crucial in various applications, including biomedical sensing.

Purpose of the Study:

• To develop a simple, non-contact method for monitoring photoacoustic perturbations using optical speckle patterns.
• To investigate the relationship between speckle decorrelation and photoacoustic wave amplitude.
• To assess the feasibility of using speckle patterns for photoacoustic detection.

Main Methods:

• A simple optical setup was designed to capture speckle patterns.
• The medium was perturbed using photoacoustic waves generated by an ultrasonic transducer.
• The decorrelation of speckle patterns was analyzed in relation to the photoacoustic wave amplitude.
• Speckle correlation changes were measured and compared with photoacoustic wave characteristics.

Main Results:

• A linear relationship was experimentally confirmed between the change in speckle correlation and the peak-to-peak amplitude of photoacoustic waves.
• The detection sensitivity of the specklegram-based method was found to be comparable to conventional methods.
• The method demonstrated effective monitoring of photoacoustic perturbations without direct contact.

Conclusions:

• Optical speckle pattern analysis provides a viable and sensitive method for non-contact photoacoustic monitoring.
• The established linear relationship simplifies the interpretation of speckle changes for quantitative measurements.
• This technique holds potential for applications where direct sample-detector contact is not feasible.