Enhancing the sensitivity to small phase changes in double-exposure stroboscopic television holography

Area of Science:

• Optical metrology
• Vibration analysis
• Holography

Background:

• Double-exposure stroboscopic television holography (TVH) is a valuable technique for vibration measurement.
• Standard TVH methods have limitations in detecting and measuring very small amplitude vibrations.
• Phase evaluation techniques exist but require further enhancement for sensitivity.

Purpose of the Study:

• To introduce a novel phase modulation technique for enhancing TVH sensitivity.
• To develop and compare two variants of the proposed technique based on different demodulation processes.
• To demonstrate the capability of detecting and measuring small amplitude vibrations with the new method.

Main Methods:

• The technique involves modulating the phase of the reference beam synchronously with the measurand's vibration.
• Two variants are proposed, differing in their secondary correlogram demodulation processes.
• The method was implemented in an electronic speckle-pattern interferometer for experimental validation.

Main Results:

• The new phase modulation technique significantly enhances the sensitivity of stroboscopic TVH.
• Vibrations with amplitudes as small as 8 nanometers were successfully detected and measured.
• The two proposed variants exhibit distinct characteristics regarding sensitivity to vibration sign and ease of detection.

Conclusions:

• The developed phase modulation technique offers superior sensitivity for small amplitude vibration measurement using TVH.
• The proposed variants provide flexibility in vibration analysis, aiding in the detection of vibration presence and shape.
• This advancement in TVH opens new possibilities for precise vibration analysis in various scientific and engineering fields.