Exposure Time Control Method for Higher Intermediate Frequency in Optical Heterodyne Imaging and Its Application to...

Area of Science:

• Optics and Photonics
• Signal Processing
• Scientific Imaging

Background:

• Equivalent time sampling (ETS) with image sensors enables detection of frequencies beyond the sensor's frame rate.
• Previous ETS methods using image sensors were susceptible to interference from lower frequencies (e.g., 1/4 frame rate).
• High noise conditions, particularly in the low-frequency band, challenge conventional imaging techniques.

Purpose of the Study:

• To develop a selective frequency detection method using image sensors.
• To improve the signal-to-noise ratio (SNR) in equivalent time sampling.
• To enable precise electric field imaging under challenging noisy conditions.

Main Methods:

• Implementing equivalent time sampling by shortening image sensor exposure times.
• Introducing a novel phase control mechanism by inserting an interval every four frames.
• Applying the technique to electric field imaging utilizing the electro-optic effect.

Main Results:

• The proposed method selectively detects the target frequency, suppressing unwanted lower frequencies.
• Demonstrated improved signal-to-noise ratio compared to conventional methods.
• Successfully performed electric field imaging in a high-noise, low-frequency environment.

Conclusions:

• The developed phase-controlled ETS method offers selective and robust frequency detection.
• This advancement significantly enhances SNR for image sensor-based frequency analysis.
• The technique is effective for precise electric field imaging, even under adverse noise conditions.