Laser Doppler blood flow complementary metal oxide semiconductor imaging sensor with analog on-chip processing.

Area of Science:

• Biomedical Engineering
• Optical Imaging
• Sensor Technology

Background:

• Laser Doppler flowmetry is crucial for non-invasive blood flow assessment.
• On-chip processing offers miniaturization and efficiency for blood flow imaging systems.
• Implementing complex signal processing at the pixel level presents significant challenges.

Purpose of the Study:

• To develop and characterize a prototype 4x4 pixel array sensor for laser Doppler blood flow imaging.
• To integrate analog on-chip processing, including necessary filters, within a complementary metal oxide semiconductor (CMOS) process.
• To evaluate the sensor's performance and potential for scalability in blood flow imaging applications.

Main Methods:

• Fabrication of a 4x4 pixel array sensor using a 0.35 µm CMOS process.
• Design and integration of bandpass and frequency-weighted filters for laser Doppler signal processing at each pixel.
• Approximation of the omega(0.5) filter using a high-pass filter with a 10 kHz cutoff frequency.
• Characterization of the sensor using a modulated laser source and preliminary blood flow measurements.

Main Results:

• Successful fabrication of a prototype 4x4 pixel array sensor with integrated analog processing.
• Identification of repeatable fixed-pattern noise across the array, which is amenable to calibration.
• Demonstration of preliminary blood flow imaging results on a human finger before and after occlusion.

Conclusions:

• The prototype sensor array demonstrates feasibility for laser Doppler blood flow imaging.
• On-chip filter approximation is a viable strategy for pixel-level processing.
• The sensor design holds potential for scaling to larger arrays for advanced blood flow imaging systems.