The popularity of miniaturized CMOS image sensors in embedded platforms, such as mobile telephones, is driving the
move to increasingly small pixel pitches. The resulting pixels suffer from increased sensitivity to microlens
misalignment and degradation in crosstalk performance, as a direct result of their reduced pixel size. This paper presents
a novel application of pixel scan techniques to characterize microlens misalignment, the effect of microlens
misalignment on crosstalk, and crosstalk performance in general. Pixel scans are performed on 2.2μm pitch sensors,
under monochromatic light. A series of scans are taken for each device under test, sweeping the incident light across and
beyond the visible spectrum. The captured data is remapped from the image space into a pixel space. Analysis of how
the scans develop over the course of the spectral sweep provides insight into the primary directional sources of crosstalk.
Further processing derives approximations of pixel spectral responses at various microlens misalignments. It is likely
that the device under test has its microlens layer misaligned by an unknown amount, which must be corrected for. This
misalignment is characterized by identifying common positional offsets between the peaks of in-band channels in the
recorded scans. The spectral responses can be then used to estimate the effects of microlens misalignment on colour and
crosstalk performance across the imaging array. The techniques detailed in the paper are designed to be run on
unmodified product dice and do not require expensive test devices.
This paper gives an outline of the coverage of the Standard Mobile Imaging Architecture (SMIA) standard and its adoption by the mobile phone industry for camera phone applications. The different elements of the standard, including functionality, interface, package options, and characterization will be described in brief. The paper then moves on to describe in detail image sensor characterization using the SMIA standard. The overall test method, and coverage will be reviewed along with the detail of the individual tests, highlighting the depth of detail of the SMIA characterization documentation. Both electrical and optical tests are reviewed with some emphasis on the colour accuracy test. Throughout this paper where required, the example of a typical CMOS camera module will be used to illustrate the method of parameter extraction. Finally, the paper examines some of the exceptions to and possible weaknesses of the current SMIA characterization standard and considers future possible revisions of the standard. This includes both refinements of and improvements in the existing test coverage and extension of the standard into areas it does not cover today, for example the definition of test requirements for auto-focus and optical zoom modules.
This paper presents the development of an electrical SPICE model of a Ferroelectric Liquid Crystal (FLC) on silicon microdisplay. Previous work has investigated the use of an electro-optical SPICE model to simulate the optical response of an FLC cell to a given electrical signal. However, the design of the backplane drive scheme for the display also requires an accurate model of the electrical load represented by an FLC cell. The model presented here provides a good fit to electrical measurement results and, in addition, can be combined with elements of the electro-optical model to allow the optical response of the cell to be modelled at the same time. This paper also presents results of charge collection current measurements which highlight the differences in the behavior of the cell when it is switched between positive and negative voltages and then in the other direction.