Calibration Object for Three-Dimensional Refractive Index Distribution

Essence of the Solution (What It Concerns):

The invention involves a calibration standard (physical sample and its digital twin) with geometry and optical properties (especially refractive index) mimicking biological specimens, as imaged under the microscope. The calibration object enables qualitative and quantitative metrological analysis of 3D phase microscopes by providing a reference for system performance.

PROBLEM:

Three-dimensional phase microscopy systems struggle with accuracy and reliability of the results. Existing calibration methods  lack the ability to represent the intricate refractive index variations found in real-world samples. This creates challenges in validating algorithms, optimizing systems, and achieving reliable, reproducible measurements for both technical and biomedical applications.

SOLUTION:

The invention provides a 3D calibration object designed for precise metrological assessments of systems sensitive to refractive index variations. Key features of the invention include:

• Three-Dimensional Calibration Standards: External dimensions ranging from 10 to 300 µm; Internal structures with minimum sizes of 100 nm; Refractive index contrast (at any point and in 3D) of up to 0.04

1. Advanced Manufacturing Process:
   • Fabricated using two-photon polymerization technology, allowing arbitrary 3D geometries and localized refractive index control.
   • The process is scalable and adaptable, enabling calibration objects tailored to different 3D microscopy needs.

APPLICATION:

The calibration standard supports a wide range of applications in technical and biomedical domains:

1. Validation and Control of Measurement Systems:
   • Periodic functional parameter checks of phase imaging systems.
   • Comparative studies (e.g., round-robin testing) for performance benchmarking across different setups.
2. Optimization of Systems and Data Processing:
   • Supports system optimization by providing detailed feedback on performance.
   • Enables algorithm validation by accompanied digital twin for end-to-end comparison.
3. Integration with Various Technologies:
   • Designed for use with cover slips, Petri dishes and microfluidic channels
   • Can be placed on optical fiber tips for alternative perspectives or tomographic systems with rotating samples.

TECHNOLOGY:

The calibration standard is available in both digital and physical forms, ensuring flexibility and adaptability to user needs:

1. Digital Model:
   • Enables strict virtual testing of 3D microscopy setups and reconstruction methods.
   • Developed to represent key features of measured class of objects
2. Physical Standard:
   • Provides an objective experimental assessment of metrological parameters.
   • Allows real-world end-to-end validation of the entire measurement protocol.

SOLUTION ADVANTAGES:

• Unique and Representative Design: The 3D refractive index distribution closely mimics mammalian adherent cells.
• Versatile Manufacturing Process: Fabricated sample accommodates any measurement system
• Biomedical Relevance: Calibration and uncertainty evaluation enable confidence and reliability in medical setting.
• Comprehensive Validation: Combines digital and physical models to validate both hardware and software of new imaging solutions.