Multi-exposure laser speckle contrast imaging using a video-rate multi-tap charge modulation image sensor.

Area of Science:

• Biomedical Optics
• Medical Imaging Technology
• Blood Flow Measurement

Background:

• High frame rate cameras enable wide-field quantitative blood flow measurement using multi-exposure laser speckle contrast imaging (MELSCI).
• Existing high-speed camera MELSCI systems are limited by high power consumption, large memory, and processing demands, resulting in bulky and expensive hardware.
• There is a need for compact and cost-efficient MELSCI systems for broader applications.

Purpose of the Study:

• To develop a compact and cost-efficient MELSCI system.
• To explore the application of a multi-tap CMOS image sensor for MELSCI.
• To achieve quantitative blood flow measurement at moderate frame rates.

Main Methods:

• Utilized a multi-tap CMOS image sensor, originally designed for time-of-flight range imaging, operated in global shutter mode.
• Programmed exposure patterns for each tap to acquire multiple images with different exposures simultaneously.
• Simulated feasibility with high-speed camera speckle images and conducted experiments using a four-tap CMOS sensor.

Main Results:

• Demonstrated simultaneous acquisition of multiple images with varying exposures using the multi-tap CMOS sensor.
• Achieved moderate frame rates (35-45 fps) for blood flow speed mapping.
• Successfully obtained flow speed maps for moving ground glass and flowing Intralipose.

Conclusions:

• A multi-tap CMOS image sensor can be effectively repurposed for compact and cost-efficient MELSCI.
• This approach overcomes the hardware limitations of traditional high-speed camera-based MELSCI systems.
• Enables quantitative blood flow measurement at practical video frame rates.