Abstract
Multi-spectral quantitative phase imaging (QPI) is an emerging imaging modality for wavelength dependent studies of several biological and industrial specimens. Simultaneous multi-spectral QPI is generally performed with color CCD cameras. Here, we present a new approach for accurately measuring the color crosstalk of 2D area detectors, without needing prior information about camera specifications. Color crosstalk is systematically studied and compared using compact interference microscopy on two different cameras commonly used in QPI, single chip CCD (1-CCD) and three chip CCD (3-CCD). The influence of color crosstalk on the fringe width and the visibility of the monochromatic constituents corresponding to three color channels of white light interferogram are studied both through simulations and experiments. It is observed that presence of color crosstalk changes the fringe width and visibility over the imaging field of view. This leads to an unwanted non-uniform background error in the multi-spectral phase imaging of the specimens. The color crosstalk of the detector is observed to be the limiting factor for phase measurement accuracy of simultaneous multi-spectral QPI systems.
Highlights
Color charge coupled devices (CCD) have the capability to record the response of specimens as a function of red, green and blue (RGB) wavelengths in a single shot [1]
Two different methods are presented for the characterization of color crosstalk of CCD cameras: (1) direct measurement of signal intensities at RGB color channels of bright field images and (2) interferometric measurement of signal intensities at RGB color channels of recorded interferograms corresponding to 620, 532, and 460 nm bandpass filters. 3.1.1
Direct measurement First, the color crosstalk of two different CCD cameras is measured through the direct quantification of signal intensities at RGB color channels/bands of bright field images
Summary
Color charge coupled devices (CCD) have the capability to record the response of specimens as a function of red, green and blue (RGB) wavelengths in a single shot [1]. 1-CCD camera utilizes a pattern of Bayer color filters (25% red, 25% blue and 50% green filters) onto the image sensor to acquire RGB information of the specimen [2,3]. Produce 50% sparse images for green wavelength, whereas, 75% sparsity is observed for red and blue wavelengths. This overall reduces the spatial resolution of the captured images [4]. The color filters and electronic noise lead to generation of color crosstalk between RGB channels of 1CCD camera and causes noise in the color images, reducing the overall sensitivity of the camera [4]. The problem of color crosstalk can be overcome by using 3-CCD camera as it utilizes three separate monochrome sensors with dichroic prism optics, which has steeper spectral response, i.e., minimal spectral overlap, to split the input beam into three distinct
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