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U.S. Food and Drug Administration

Digital Image Correlation (DIC) Target Speckle Size Calculator and Pattern Lookup Tool

Catalog of Regulatory Science Tools to Help Assess New Medical Devices

This regulatory science tool (RST) is a browser-based resource for identifying a target speckle size and suitable patterning approach when planning digital image correlation (DIC) measurement studies of implantable medical devices.

Technical Description

Digital image correlation (DIC) uses digital images of solid surfaces undergoing deformation to measure full-field displacements and strains. These measurements have several potential uses in medical device performance evaluation including characterization of implant mechanics, micromotion measurement, informing durability analyses, investigating the influence of design changes, and generating data to support validation of computational solid mechanics models.

The subject tool calculates the spatial resolution and target speckle size associated with a particular imaging setup considering characteristics of the imaging sensor and the spatial field of view. The tool additionally suggests patterning techniques suitable for the identified target speckle size, provides representative pattern images, and references relevant literature studies including prior DIC-based investigations of medical devices.

User inputs: 

  • Camera resolution
  • Spatial dimensions of field of view

Tool outputs:

  • Calculated target speckle size
  • Speckle pattern spatial scale visualizations
  • Suggested patterning techniques and relevant medical device literature studies

Intended Purpose

This tool is intended for use in planning digital image correlation (DIC) experiments for mechanical assessment of medical devices, including but not limited to cardiovascular or orthopedic implants with smooth, dry surfaces. Target users are durability and solid mechanics specialists working with implantable medical devices.

Testing

The tool is based on 1) foundational optics and digital image correlation principles and 2) laboratory experiments documented in Rothermel et al. 2025.

Limitations

The tool targets fields of view relevant to medical device mechanics applications. Relatively large (>2mm) and very small (<500nm) speckle sizes are not specifically addressed. The tool is also specific to surface measurements and is not relevant to volumetric DIC and other non-surface techniques.

The suitability of speckling media varies with surface-specific factors (e.g., roughness, surface energy, moisture content, and porosity), as documented in Rothermel et al. (2025).

Supporting Documentation

The tool is based on content in the peer-reviewed manuscript: 

Rothermel, T.M., Mirmohammad, H., Weaver, J.D., Porter, D.A., Nguyen, M., He, Z., Cannon, A.H., Hochhalter, J.D., & Aycock, K.I. (2025). Full-Field Strain Measurements on Medical Devices Using Digital Image Correlation: Considerations and Practical Examples. Journal of the Mechanical Behavior of Biomedical Materials. doi: 10.1016/j.jmbbm.2025.107020

Additional resources include:

Aycock, K. I., Weaver, J. D., Paranjape, H. M., Senthilnathan, K., Bonsignore, C., & Craven, B. A. (2021). Full-field microscale strain measurements of a nitinol medical device using digital image correlation. Journal of the Mechanical Behavior of Biomedical Materials, 114, 104221. doi: 10.1016/j.jmbbm.2020.104221

Palanca, M., Tozzi, G., & Cristofolini, L. (2016). The use of digital image correlation in the biomechanical area: a review. International Biomechanics, 3(1), 1-21. doi: 10.1080/23335432.2015.1117395

Dong, Y. L., & Pan, B. (2017). A review of speckle pattern fabrication and assessment for digital image correlation. Experimental Mechanics, 57, 1161-1181. doi: 10.1007/s11340-017-0283-1

Jones, E. M., & Iadicola, M. A. (2018). A good practices guide for digital image correlation. International Digital Image Correlation Society, 10, 1-110. doi: 10.32720/idics/gpg.ed1

Sutton, M. A., Orteu, J. J., & Schreier, H. (2009). Image correlation for shape, motion and deformation measurements: basic concepts, theory and applications. Springer Science & Business Media. doi: 10.1007/978-0-387-78747-3

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