CMOS APS MTF Modeling

Abstract

Abstract:The modulation transfer function (MTF) of an optical or electro-optical device is one of the most significant factors determining the image quality. Unfortunately, characterization of the MTF of the semiconductor-based focal plane arrays (FPA) has typically been one of the more difficult and error-prone performance testing procedures. Based on a thorough analysis of experimental data, a unified model has been developed for estimation of the overall CMOS active pixel sensor (APS) MTF for scalable CMOS technologies. The model covers the physical diffusion effect together with the influence of the pixel active area geometrical shape. Agreement is excellent between the results predicted by the model and the MTF calculated from the point spread function (PSF) measurements of an actual pixel. This fit confirms the hypothesis that the active area shape and the photocarrier diffusion effect are the determining factors of the overall CMOS APS MTF behavior, thus allowing the extraction of the minority-carrier diffusion length. Section 2.2 presents the details of the experimental measurements and the data acquisition method. Section 2.3 describes the physical analysis performed on the acquired data, including the fitting of the data and the relevant parameter derivation methods. Section 2.4 presents a computer model that empirically produces the PSF of the pixel. The comparisons between the modeled data and the actual scanned results are discussed in Section 2.5. Section 2.6 summarizes the chapter.

Characterization and deblurring of lateral crosstalk in CMOS image sensors

“…It may be useful to note that a raster spot-scanning technique utilizing a relatively small spot ( m) has been effectively used in the investigation of subpixel photoresponse and lateral crosstalk [23]- [25]. With the spot-scanning technique, only the scanning field needs to be adjusted to accommodate different pixel sizes and shapes.…”

Filtration of optical signal in machine vision systems based on solid-state image sensor

“…Nowadays different analytical models for MTF evaluation have been described. They can be divided into two categories: the first are based on topological parameters of image sensors and physical diffusion effects [1,2,3], the second on implementation Fourier transformation to approximated impulse response function of a pixel [4,5,6]. In the case of the first, the models are distinguishable by their complexity and they are almost entirely based on topological parameters and parameters of diffusion, and they are almost always sharpened for certain image sensor structures.…”

Does resolution really increase image quality?

“…photocarrier diffusion effect) and optical crosstalk are the main determining factors of the overall detector MTF. 10 For sake of simplicity, a first-order approximation of sensor MTF is obtained by considering only the ideal geometrical PRF (i.e. uniform pixel sensitivity within the active area) convolved with an anisotropic (Gaussian or exponential-type) blur filter.…”