Correcting Misleading Image Quality Measurements

We discuss several common image quality measurements that are often misinterpreted, so that bad images are falsely interpreted as good, and we describe how to obtain valid measurements.

Sharpness, which is measured by MTF (Modulation Transfer Function) curves, is frequently summarized by MTF50 (the spatial frequency where MTF falls to half its low frequency value).

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Describing and Sampling the LED Flicker Signal

High-frequency flickering light sources such as pulse-width modulated LEDs can cause image sensors to record incorrect levels. We describe a model with a loose set of assumptions (encompassing multi-exposure HDR schemes) which can be used to define the Flicker Signal, a continuous function of time based on the phase relationship between the light source and exposure window. (more…)

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Validation Methods for Geometric Camera Calibration

Camera-based advanced driver-assistance systems (ADAS) require the mapping from image coordinates into world coordinates to be known. The process of computing that mapping is geometric calibration. This paper provides a series of tests that may be used to assess the goodness of the geometric calibration

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Measuring camera Shannon information capacity with a Siemens star image

Shannon information capacity, which can be expressed as bits per pixel or megabits per image, is an excellent figure of merit for predicting camera performance for a variety of machine vision applications, including medical and automotive imaging systems.

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Verification of Long-Range MTF Testing Through Intermediary Optics

Measuring the MTF of an imaging system at its operational working distance is useful for understanding the system’s use case performance. (more…)

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Reducing the cross-lab variation of image quality metrics

Abstract

As imaging test labs seek to obtain objective performance scores of camera systems, many factors can skew the results. (more…)
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