Measure current at each sensor photodetector
signalCurrentImage = spatialIntegration(scdi,OI,ISA,[gridSpacing = 1/5])
The signal current density image (scdi) specifies the current (A/m2)
across the sensor surface at a set of sample values specified by the
optical image (OI). This routine converts the scdi to a set of currents at
each photodetector.
The routine can operate in two modes. In the first (lower resolution,
fast, default) mode, the routine assumes that each photodetector is
centered in the pixel. In the second (high resolution, slow) mode, the
routine accounts for the position and size of the photodetectors within
each pixel.
Algorithms:
The sensor pixels define a coordinate frame that can be measured (in
units of meters). The optical image also has a size that can be
measured in meters. In both modes, we represent the OI and the ISA
sample positions in meters in a spatial coordinate frame with a common
center. Then we interpolate the values of the OI onto sample points
within the ISA grid (regridOI2ISA).
The first mode (default). In this mode the current is computed with
one sample per pixel. Specifically, the irradiance at each wavelength
is linearly interpolated to obtain a value at the center of the pixel.
The second mode (high-resolution). This high-resolution mode requires
a great deal more memory than the first mode. In this method a grid is
placed over the sensor and the irradiance field is interpolated to
every point in that grid (e.g., a 5x5 grid). The pixel is computed by
summing across those grid points (weighted appropriately).
The high-reoslution mode used to be the default mode (before 2004).
But over time we came to believe that it is better to understand the
effects of photodetector placement and pixel optics using the
microlenswindow module. For certain applications, though, such as
illustrating the effects of wavelength-dependent point spread
functions, this mode is valuable.
INPUT: scdi [nRows x nCols] [A/m^2]
OI: optical image [structure]
ISA: image sensor array
gridSpacing specifies how finely to interpolate within each
pixel. This value must be of the form 1/N where N is an odd integer.
Copyright ImagEval Consultants, LLC, 2003.