The standard imaging lens for a high resolution sensor was modified to achieve the extended depth of field (EDoF) from
300 mm to infinity. In the module the raw sensor outputs are digitally processed to obtain high contrast images. The
overall module is considered as an integrated computational imaging system (ICIS). The simulation results for
illustrative designs with different amount of spherical aberrations are provided and compared. Based on the results of
simulations we introduced the limiting value of the PSF Strehl ratio as the integral threshold criteria to be used during
EDoF lens optimization. A four-element standard lens was modified within the design constraints to achieve the EDoF
performance. Two EDoF designs created with different design methods are presented. The imaging modules were
compared in terms of Strehl ratios, limiting resolution, modulation frequencies at 50% contrast, and SNR. The output
images were simulated for EDoF modules, passed through the image processing pipeline, and compared against the
images obtained with the standard lens module.
The integration of novel optics designs, miniature CMOS sensors, and powerful digital processing into a single
imaging module package is driving progress in handset camera systems in terms of performance, size (thinness) and
cost. The miniature cameras incorporating high resolution sensors and fixed-focus Extended Depth of Field (EDOF)
optics allow close-range reading of printed material (barcode patterns, business cards), while providing high quality
imaging in more traditional applications. These cameras incorporate modified optics and digital processing to
recover the soft-focus images and restore sharpness over a wide range of object distances. The effects a variety of
parameters of the imaging module on the EDOF range were analyzed for a family of high resolution CMOS
modules. The parameters include various optical properties of the imaging lens, and the characteristics of the sensor.
The extension factors for the EDOF imaging module were defined in terms of an improved absolute resolution in
object space while maintaining focus at infinity. This definition was applied for the purpose of identifying the
minimally resolvable object details in mobile cameras with bar-code reading feature.
KEYWORDS: Semiconducting wafers, Chemical mechanical planarization, Sensors, Polishing, Signal processing, Silicon, Fiber optics, Fiber optics sensors, Surface finishing, Control systems
A method of Chemical-Mechanical Planarization (CMP) endpoint detection of shallow trench isolation wafer is discussed in this paper. The detection algorithm was developed based on the interferometric intensity modulation of the light reflected from the wafer being polished. The physical model of the process proved to reliably predict behavior of the reflected signal during successive removal of a silicon oxide film and transition into patterned silicon nitride layer. The model calculates film thickness removed from STI wafers with known layer structure, from the reflected signal recorded during CMP process. The in-situ miniature system incorporating fiber-optic coupled diode laser and InGaAs photodetector was successfully implemented for the purpose of Endpoint Detection. On a patterned wafer the system can control nitride thickness removal with a better than 200 angstrom accuracy. The wireless modular design permits real- time simultaneous multiple points operation in a fully automated mode.
Conference Committee Involvement (2)
Novel Optical Systems Design and Optimization XII
3 August 2009 | San Diego, California, United States
Novel Optical Systems Design and Optimization XI
13 August 2008 | San Diego, California, United States
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