A high accurate figure measurement system without a reference optic has been required. Nikon has developed a new deflectometry measurement system "PSM (Precision Slope Master)". Our goal is to achieve single nm accuracy with the PSM for a wide variety of sphere and asphere figures. In deflectometry field, a high accurate auto collimator is commonly used as an angle sensor. This is the reason why measurement targets for deflectometry have been confined to flat and large curvature radius mirrors. To expand deflectometry's targets, we have developed a new angle sensor for the PSM. Due to the new sensor, the PSM makes measurements of small curvature radius lenses and mirrors possible. There is one more issue for measuring small curvature radius optics with the PSM. The issue is a precise measurement of distance and angle between the sensor and a sample. To overcome the issue, the PSM adopts a metrology loop system designed specially. The metrology loop system was constructed from several sensors and a special metrology frame. The metrology frame was designed to avoid any deformation from environmental temperature change and stage positions change. We have evaluated the repeatability by using sphere and asphere samples. The results of repeatability indicated their variation within single nm in RMS. From these evaluations, we concluded that the PSM has the possibility to achieve single nm accurate measurements. The PSM has a potential of being a useful tool for measuring high accurate optics.
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