A CMOS-based Hartmann-Shack Sensor for Real-Time Adaptive Optical Applications

Adaptive optical systems have a growing field of applications in opthalmology. In every adaptive system there is the need for a sensor and an actuator. The Hartmann-Shack wavefront sensor uses the displacement of spots in the focal plane of a lenslet array for subsequent calculation of the wavefront. The bandwidth of current sensors is mostly limited by software processing of the focal plane image to some tens of Hz, which makes it unsuitable for real-time adaptive optical systems. To overcome the current bandwidth limitations a fast Hartmann-Shack sensor based on an application specific integrated circuit has been developed and tested, that reaches a bandwidth of up to 6 kHz. The sensor includes photodetectors with 40% quantum efficiency at 680 nm wavelength and an image processing, that is especially suitable to reduce the effects of the common mismatching of process parameters in CMOS-based sensors (Complementary Metal Oxide Semiconductor). A special problem in ophthalmic applications is the low available spot power below 1 nW.Adaptive optical systems have a growing field of applications in opthalmology. In every adaptive system there is the need for a sensor and an actuator. The Hartmann-Shack wavefront sensor uses the displacement of spots in the focal plane of a lenslet array for subsequent calculation of the wavefront. The bandwidth of current sensors is mostly limited by software processing of the focal plane image to some tens of Hz, which makes it unsuitable for real-time adaptive optical systems. To overcome the current bandwidth limitations a fast Hartmann-Shack sensor based on an application specific integrated circuit has been developed and tested, that reaches a bandwidth of up to 6 kHz. The sensor includes photodetectors with 40% quantum efficiency at 680 nm wavelength and an image processing, that is especially suitable to reduce the effects of the common mismatching of process parameters in CMOS-based sensors (Complementary Metal Oxide Semiconductor). A special problem in ophthalmic applications is the low available spot power below 1 nW. The developed Hartmann-Shack sensor allowed wavefront measurements with an accuracy of 0.16 dpt defocus at 160 pW spot power. It has been possible for the first time, to measure wavefront aberrations at the living humane eye with 300 Hz repetition rate and to calculate the power spectral density of these aberrations