Purpose
Comparison of four different Swept-Source interferometers for detection of the biometric data of the eye. The main difference between the developed Swept-Source systems is the way of tuning the wavelength at the broadband gain medium. Characteristics, conveniences and accessibilities of these developed systems are presented.
Methods
Four Swept-Sources systems based on Semiconductor Optical Amplifiers (SOA) with different central wavelengths (800nm, 1060nm and 1300nm) and tunable optical filters were designed to measure the axial length inside the eye. The first system consists of a tunable optical filter, a reflective diffraction grating with 1800 lines/mm, two Littrow prisms and a rotating polygon mirror. A SOA (type: SOA-382-SM-DBUT-800, central wavelength 800 nm, Superlum Co. Cork, Ireland) is used as a broadband gain medium. In the second system the rotating polygon mirror is replaced by a rotating polygon grating. An additional mirror is not necessary. A tunable optical filter in the third system consisting of a reflective diffraction grating with 1800 lines/mm, two Littrow prisms and a scanner (dynAXIS SCANLAB AG) was used. The SOA of the type SOA-1060-100-PM-24dB (central wavelength1060 nm, Innolume, Germany) was used as a broadband gain medium. The fourth system is based on the concept of a Fourier Domain Mode Locking (FDML). It includes a long fiber-ring with a broadband SOA (S9FC1132P, central wavelength1300 nm, Thorlabs, Germany) as a gain medium and a fiber Fabry-Perot filter (Lambda Quest LLC). as a tunable, narrowband optical band-pass filter [Huber et al].
Results
The results for the measuring depth and time, the signal to noise ratio (SNR), accuracy, conveniences and accessibilities are listed in the table. The laser power is adjusted following the laser safety regulations for human eyes.
Conclusions
The four systems demonstrate excellent results for biometric measurements inside the eye. However, the systems differ significantly in their conveniences and accessibilities.