Compact and fast depth sensor based on a liquid lens using chromatic aberration to improve accuracy

Area of Science:

• Optics and Photonics
• Computer Vision
• Metrology

Background:

• Depth from defocus (DFD) provides high-resolution depth maps but faces limitations in real-time applications due to mechanical focus limitations and a narrow depth range.
• Conventional DFD systems struggle with rapid focus adjustments and achieving both high accuracy and an extended depth range simultaneously.

Purpose of the Study:

• To develop a compact and real-time capable DFD system that enhances depth accuracy and extends the measurable depth range.
• To utilize a liquid lens and chromatic aberration for improved DFD performance.

Main Methods:

• A novel DFD system was designed incorporating a liquid lens for rapid, electronically controlled focus changes.
• Chromatic aberration was employed to divide the depth range into multiple channels, enhancing depth accuracy.
• System performance was validated through theoretical analysis, simulations, and experimental measurements on 3D objects.

Main Results:

• The liquid lens enabled image acquisition within a single frame period (10 ms response time), suitable for real-time applications.
• The proposed system achieved a significantly lower root mean square error (RMSE) ranging from 0.7 mm to 4.98 mm compared to conventional methods (2.275 mm to 12.3 mm) over a 30 cm to 70 cm depth range.
• The optical system was simplified to only three lenses.

Conclusions:

• The liquid lens-based DFD system offers a practical solution for real-time, high-accuracy depth measurement.
• Leveraging chromatic aberration effectively improves depth accuracy and extends the measurement range in DFD systems.
• This compact DFD system demonstrates superior performance over conventional approaches for 3D object depth measurement.