ISET image sensors are modeled as an array of pixels. Each pixel includes a microlens , color filters, a tunnel of some depth corresponding to the sensor metal layers , and a photodetector. A large number of optical and electrical properties can be modeled, including the spectral characteristics of the filters , indices of refraction of the metal layers, electrical noise in the detectors, array inhomogeneities, and so forth.
The image sensor model includes the effects of the spatial sampling of the optical image by the image sensor with finite-size pixels with a given fill-factor. Both pixel size and fill-factor are user-defined parameters. Furthermore, the optical signal collected by each pixel (photons/nm/m2) is converted into an electrical signal on a wavelength-basis using a spectral QE. The resulting current (electrons/s) is converted into a voltage (V) using a conversion gain (mV/electron). Both QE and conversion gain are user-defined parameters. To complete the physical signal pipeline, the analog voltage (V) is converted into a digital signal (DN) according to the specifications of the user (analog-to-digital step size in V/DN).
In addition to the signal, we also model noise. First, there is the noise intrinsic to the optical signal, i.e., the photon shot-noise, and second there is the noise introduced by the image sensor (read noise and fixed-pattern noise). The latter can be changed by the user depending on pixel properties described in the manufacturer’s specification sheet of the image sensor.
The GUI will allow the user to input parameters specifying pixel geometry, color filter array layout, spectral response, conversion gain, sensor noise properties, exposure, ADC bit counts, dynamic range, and many more