Development of metrology and calibration devices for ophthalmic OCT equipment based on 3D printing technology

To evaluate the resolution, angular field of view (FOV), coalignment of fundus images and OCT scans, depth scaling and other key parameters of optical coherence tomography (OCT) equipment and ensure the accuracy and validity of the equipment output values. In this paper, a model eye simulating real human eye structure was designed and developed, including the main refractive structures, such as cornea and lens, and its parameters are traceable. A 3D resolution board for lateral and axial resolution detection was designed and fabricated based on 3D printing technology. A stepped concentric ring structure was designed and machined for FOV detection. At the same time, the cross fiber module for image matching detection and the parallel glass module for depth scaling detection were designed and manufactured, which can be adapted to the fundus groove of the model eye. Confocal Raman microscopy was used to trace the size of the 3D resolution board, and the minimum detectable values for lateral and axial resolutions were 9.7 μm and 5.7 μm, respectively. The sizes of the concentric rings and fiber diameter can be traced by a Nikon projector. The maximum detectable FOV is 109.03°, and the image matching minimum accuracy is 62.5 μm. The center thickness of the parallel glass plate was traced by a Nikon digital height gauge, and the measurement uncertainty was less than 5 μm. The test of commercial ophthalmic OCT equipment showed that the model eye metrology and calibration device based on 3D printing technology has the advantages of high accuracy, high integration, wide application range and strong stability, so it is suitable for metrology and calibration of ophthalmic OCT equipment.