The three primary broad components of noise in a CCD imaging system are photon noise, dark noise, and read noise, all of which must be considered in a calculation of signal-to-noise ratio.Ī further useful classification distinguishes noise sources on the basis of whether they are temporal or spatial. A detailed engineering consideration of noise contributions in charge-coupled devices includes many sources that are normally handled by combining them into more general categories, or which are not significant except at much lower signal levels than are typically encountered in microscopy. Because a CCD sensor collects charge over an array of discrete physical locations, the signal-to-noise ratio may be thought of as the relative signal magnitude, compared to the measurement uncertainty, on a per-pixel basis. The signal-to-noise ratio for a CCD image sensor specifically represents the ratio of the measured light signal to the combined noise, which consists of undesirable signal components arising in the device, and inherent natural variation of the incident photon flux. In a well designed digital camera, the noise performance is limited by the CCD rather than by associated system electronic components. For any electronic measuring system, the signal-to-noise ratio ( SNR) characterizes the quality of a measurement and determines the ultimate performance of the system.

Noise, arising from a variety of sources, is inherent to all electronic image sensors, and careful control of noise components, both in the design and operation of the CCD system, is necessary to ensure that the signal level relative to noise is adequate to allow capture of accurate image information. In particular, the much greater sensitivity of such sensors compared to film is invaluable in low-light techniques, for which every available signal photon may be significant. By directly producing images in digital format, suitable for immediate computer processing, CCD-based image capture systems are ideally suited to a wide range of current microscopy and image analysis methods. Concepts in Digital Imaging Technology CCD Noise Sources and Signal-to-Noise RatioĬharge-coupled device ( CCD) sensors have numerous advantages over photographic film in scientific imaging applications such as astronomy and optical microscopy.

Dark noise samplers