5/30/2023 0 Comments Dark noise current charge![]() The upper limit of the input/output linearity is determined by the maximum current that the detector can produce without becoming saturated. Noise will determine the lowest level of incident light that is detectable. If the output of the detector is plotted versus the input power, there should be no change in the slope of the curve. The response may be linear over a broad range, perhaps many orders of magnitude. Detectors are characterized by a response in which the output is linear with incident intensity. Linearity - another important characteristic of optical detectors is their linearity. The lightest signal would correspond to the brightest highlights in an image, the darkest signal to the deepest shadows. It is the ratio of the highest (lightest) signal, which a detector can record to the lowest (darkest) signal. Later, in the discussion of noise, we will describe the effect of modulation frequency and bandwidth on the noise characteristics.ĭynamic Range - measures the range of signals, which can be recorded by a detector. A high value of D*(l,f,Df ) means that the detector is suitable for detecting weak signals in the presence of noise. The units of D*(l,f,Df ) are cm-Hz1/2/watt. The reference bandwidth is often 1 Hertz. The dependence of D* on the wavelength l, the frequency f at which the measurement is made, and the bandwidth Df are expressed by the notation D*(l,f,Df). When a value of D* for an optical detector is measured, it is usually measured in a system in which the incident light is modulated or chopped at a frequency f so as to produce an AC signal, which is then amplified with an amplification bandwidth Df. The detectivity thus gives a measure of the intrinsic quality of the detector material itself. Since many detectors have NEP proportional to the square root of their areas, D* is independent of the area of the detector. It is defined as the square root of the detector area per unit value of NEP. Detectivity is represented by the symbol D*, which is pronounced as D-star. To provide a figure of merit that is dependent on the intrinsic properties of the detector, not on how large it happens to be, a term called detectivity is defined. Glossary for Optical Detectors Detector Characteristicsĭetectivity - The NEP of a detector is dependent on the area of the detector.
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