An Optical Topographic Technique to Map the 3-D Deformed Profile of a Convex Lens under External Loading
- 193 Downloads
A novel laser-aided topographic apparatus has been designed and constructed to capture the deformed profile of a hydrogel convex shell (contact lens) under an external load. A laser sheet illuminates a thin cross section of the deformed shell and scans the entire lens from one side. Two side cameras fixed on opposite sides of the sample contact lens and perpendicular to the laser sheet record the 3-dimensional geometry. The contact lens rests on the circular shoulder, while the loading shaft is lowered to a desirable depth, w 0, along the optical axis. The applied load, F, and vertical displacement of the shaft, w 0, are measured simultaneously with the video recording showing the progressive changes in indentation dimple radius, a, and the shell profile, w(r). The mechanical behavior is consistent with a previously developed solid mechanics model, and material parameters such as elastic modulus can be deduced.
KeywordsTopography Hydrogel Shell Large deformation
The authors acknowledge support from the Senior Capstone Design program at the Department of Mechanical and Industrial engineering at Northeastern University. We are grateful to Professor Andrew Gouldstone for his expertise and help with OCT.
- 1.French K (2005) Contact lens material properties: part II, mechanical behavior and modulus. Optician 230(6026):29–34Google Scholar
- 5.Enns JB (1996) Dynamic mechanical properties of hydrogels. 54th Annual Technical Conference, 3Google Scholar
- 6.Tranoudis NEI (2004) Tensile properties of soft contact lens materials. Contact Lens & Anterior Eye 27Google Scholar