CCD image sensor induced error in PIV applications

Abstract

The readout procedure of charge-coupled device (CCD) cameras is known to generate some image degradation in different scientific imaging fields, especially in astrophysics. In the particular field of particle image velocimetry (PIV), widely extended in the scientific community, the readout procedure of the interline CCD sensor induces a bias in the registered position of particle images. This work proposes simple procedures to predict the magnitude of the associated measurement error. Generally, there are differences in the position bias for the different images of a certain particle at each PIV frame. This leads to a substantial bias error in the PIV velocity measurement (∼0.1 pixels). This is the order of magnitude that other typical PIV errors such as peak-locking may reach. Based on modern CCD technology and architecture, this work offers a description of the readout phenomenon and proposes a modeling for the CCD readout bias error magnitude. This bias, in turn, generates a velocity measurement bias error when there is an illumination difference between two successive PIV exposures. The model predictions match the experiments performed with two 12-bit-depth interline CCD cameras (MegaPlus ES 4.0/E incorporating the Kodak KAI-4000M CCD sensor with 4 megapixels). For different cameras, only two constant values are needed to fit the proposed calibration model and predict the error from the readout procedure. Tests by different researchers using different cameras would allow verification of the model, that can be used to optimize acquisition setups. Simple procedures to obtain these two calibration values are also described.

UmUTracker: A versatile MATLAB program for automated particle tracking of 2D light microscopy or 3D digital holography data

“…Furthermore, the CCD sensor can induce measurement bias [31] and noise generated from thermal electrons within the exposure time can produce diffusive diffraction patterns. This effect becomes only prominent if short shutter times are used to acquire images.…”

“…To improve the reconstruction accuracy in these two extreme cases, the illumination can be optimized by using low coherent laser illumination [30]. Furthermore, the CCD sensor can induce measurement bias [31] and noise generated from thermal electrons within the exposure time can produce diffusive diffraction patterns. This effect becomes only prominent if short shutter times are used to acquire images.…”

Star smear removal for full-frame charge-coupled device images based on Gaussian fitting

“…In response to the smear problem, related works have been developed focusing on three topics: removing fake targets in the smeared image after detection, 6 employing special hardware 7 or modifying the design of CCD image sensors, 8 , 9 and numeric algorithms for postfacto correction of image smear 10 – 19 Generally, the latter is considered the most economical and efficient solution.…”

Smear correction of highly variable, frame-transfer CCD images with application to polarimetry

“…If the CCD is continuously illuminated during frame transfer, the resulting image will be smeared reducing its contrast and spatial resolution [1]. This artifact can be a draw back in many applications [2][3][4][5] becoming particularly relevant when high frame rate and duty cycle are required. Given its general applicability, low cost and null effect on duty cycle among others, numeric algorithms for post-facto correction of image smear are an attractive alternative to the classic mechanical or optoelectronic shutter systems.…”