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Imaging Fibrillar Collagen with Optical Microscopy
Published in Jiro Nagatomi, Eno Essien Ebong, Mechanobiology Handbook, 2018
Tong Ye, Peng Chen, Yang Li, Xun Chen
One of the critical components in fluorescence microscopes is the filter cube, which is placed between the tube lens and the objective, where the illumination and imaging paths meet. As shown in Figure 6.5, a filter cube has three optical components, two of which are mounted on the side ports and one in the middle of the cube with 45° to the light path. The excitation light from the lamp usually passes a glass filter first to block the unwanted infrared (IR) (filter 1 in Figure 6.5) component and then passes the excitation filter to select the excitation lines from the lamp. The excitation filter (filter 2 in Figure 6.5) is usually a band-pass filter whose transmission band covers a good portion of the absorption band of a dye to image. The excitation light is reflected by the dichroic mirror (filter 3 in Figure 6.5) and is incident to the specimen to excite fluorophores. The fluorescence gets out of the specimen and is then collected by the objective. The collected fluorescence is further filtered by the dichroic mirror and the emission filter (filter 4 in Figure 6.5). The coating of the dichroic mirror is carefully chosen to reflect the excitation light and pass the fluorescence. The emission filter is also called the barrier filter, and its passing band matches the fluorescence band of the dye.
Microscopic Tissue Imaging
Published in Vadim Backman, Adam Wax, Hao F. Zhang, A Laboratory Manual in Biophotonics, 2018
Vadim Backman, Adam Wax, Hao F. Zhang
Each fluorescent label requires selection of a filtering scheme to produce high-contrast images. An excitation filter is used to restrict the excitation light to the portion of the spectral region where light is efficiently absorbed by the molecule. A dichroic mirror is used to separate the excitation and emission light to prevent stray excitation light from reducing image contrast. Finally, an emission filter is used to select the range of detected wavelength that corresponds to the emission peak of the molecule. Often, these three filtering elements are incorporated into a filter cube that can be easily exchanged in many fluorescent microscopes. Figure 4.12 shows an example of a filtering scheme installed within such a cube.
Fluorescence Microscopy
Published in Bethe A. Scalettar, James R. Abney, Cyan Cowap, Introductory Biomedical Imaging, 2022
Bethe A. Scalettar, James R. Abney, Cyan Cowap
Filter cubes are used to achieve selective excitation of a specific fluorophore and selective transmission of the fluorophore's emission to a detector. To these ends, filter cubes contain three key components: an excitation filter, a dichromatic mirror, and an emission filter (Fig. 6.11). The excitation filter functions to transmit shorter wavelengths that effectively excite a particular fluorophore while blocking longer wavelengths that might be confused with emission light. Suitable excitation filters include “shortpass” filters, which pass wavelengths below some cutoff, and, more commonly, “bandpass” filters, which filter light both below and above the most suitable excitation wavelengths (Fig. 6.12).
Tracing dam seepage using nuclear logging and tracer techniques – a case study
Published in ISH Journal of Hydraulic Engineering, 2018
G. A. Panvalkar, A. D. Chunade
The tracer studies were carried out using a laboratory fluorometer, TD-700, manufactured by M/s Turner Designs, U.S.A. In this device, the ultraviolet light from a lamp is passed through an excitation filter, which transmits light of a specific wavelength to the sample compound being measured. The light passes through the sample, which emits light proportional to the intensity of the exciting light. The emitted light is then passed through an emission filter, which selects the appropriate wavelength which can be then detected by a photomultiplier tube, as a readout device which indicates the relative intensity of light reaching it.