We present a new device, the diffractive optics calibrator, for measuring duty cycle and etching depth for computer-generated holograms (CGHs). The system scans the CGH with a collimated laser beam and collects the far-field diffraction pattern with a CCD array. The relative intensities of the various orders of diffraction are used to fit the phase shift from etching and the duty cycle of the binary pattern. The system is capable of measuring variations that cause 1-nm peak-to-valley (PV) phase errors in the wavefront created by the CGH. The measurements will be used primarily for quality control CGHs, but the data can also be used to provide a lookup table for corrections that allow calibration of the lithography errors. Such calibrations may be necessary for us to achieve our goal of measuring freeform aspheric surfaces with 1-nm RMS accuracy.
We present a new device, the Diffractive Optics Calibrator (DOC), for measuring duty-cycle and etching depth for
computer generated holograms (CGH). The system scans the CGH with a collimated laser beam, and collects the far
field diffraction pattern with a CCD array. The relative intensities of the various orders of diffraction are used to fit
the phase shift from etching and the duty cycle of the binary pattern. The system is capable of measuring variations
that cause 1 nm PV phase errors in the wavefront created by the CGH. The measurements will be used primarily for
quality control CGHs, but the data can also be used to provide a lookup table for corrections that allow calibration of
the lithography errors. Such calibration may be necessary for us to achieve our goal of measuring freeform aspheric
surfaces with 1 nm RMS accuracy.
Computer-generated holograms are often used to test aspheric surfaces. This paper provides a parametric model for
the CGH phase function using the exact geometric model. The phase function is then used to derive the sensitivity
functions to alignment errors in testing. When using the CGH to test aspheric surface, it is important to separate the
diffraction orders and only allow the desired order to pass the system. This paper also provides a recipe for
determining the amount of carriers needed to eliminate the ghost images.
In optical lens assembly, metal retaining rings are often used to hold the lens in place. If we mount a lens to a sharp metal
edge using normal retention force, high compressive stress is loaded to the interface and the calculated tensile stress near
the contact area from Hertzian contact appears higher than allowable. Therefore, conservative designs are used to ensure that glass will not fracture during assembly and operation. We demonstrate glass survival with very high levels of stress. This paper analyzes the high contact stress between glass lenses and metal mounts using finite element model and to predict its effect on the glass strength with experimental data. We show that even though contact damage may occur under high surface tensile stress, the stress region is shallow compared to the existing flaw depth. So that glass strength will not be degraded and the component can survive subsequent applied stresses.
Conference Committee Involvement (1)
Novel Optical Systems Design and Optimization XVIII
12 August 2015 | San Diego, California, United States
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