The modulation transfer function (MTF) is widely used to describe the spatial resolution of x-ray imaging systems. The MTF is defined to have a zero-frequency value of unity, and it is common practice to ensure this by normalizing a measured MTF curve by the zero-frequency value. However, truncation of the line spread function (LSF) within a finite region of interest (ROI) results in spectral l...

An imaging sensor’s spatial quality can be expressed by the system’s point spread function (PSF). The PSF of a pushbroom Charge-Coupled Device (CCD) satellite sensor was numerically modeled including contributions from optic, detector, sensor motion, and electronic components. Synthetic edge and pulse targets with various intensity levels were developed and then convolved with the generic senso...

A method for conditioning data used in the measurement of the modulation transfer function (MTF) is discussed. This method is based upon imposing the constraint that the edge spread function (ESF) is monotonic. The advantages of this technique, when applicable, are demonstrated with simulated examples for which the true MTF is known. The application of this technique in the measurement of the M...

This letter presents a new cascade ΣΔ modulator architecture with unity signal transfer function that avoids the need of digital filtering in the error cancellation logic. The combination of these two aspects make it highly tolerant to noise leakages, very robust to non-linearities of the circuitry and especially suited for low-voltage implementations at low oversampling. Behavioral simulations...

Two-dimensional optical transfer functions (OTF's) of individual human eyes are computed from the retinal images of a point test object, using a phase-retrieval method. The retinal reflection directionality effect is included in the computations by means of an apodization pupil, and subsequently the Stiles-Crawford effect is also considered. The modulation transfer functions obtained when the r...

Modulation transfer functions (MTFs) were measured with three different psychoacoustical paradigms in the same normal-hearing subjects. In the temporal-probe method, the threshold of a 4-ms probe tone (frequencies of 1000 and 4000 Hz) was measured at various envelope phases within a 100% sinusoidally amplitude-modulated (SAM) noise at modulation frequencies from 2 to 256 Hz. For the derived-MTF...

An efficient means for constructing a narrow bandpass filter for an analogto-digital converter based on a bandpass sigma-delta modulator is presented. It is shown that the filter can be made with very simple hardware, comparable to that required by an analog-to-digital converter using standard lowpass sigma-delta modulation. Introduction Bandpass sigma-delta modulation [1] is a variant of the m...