We present a multicolor fluorescence imaging modality to visualize in real-time tissue structures emitting multispectral fluorescent light from different focal depths. Each designated spectrum of fluorescent emission from a specific depth within a volumetric tissue is probed by a depth-spectrum selective holographic grating. The grating for each fluorescent color are multiplexed within a volume hologram, which enables simultaneously obtaining multicolored fluorescent information at different depths within a biological tissue sample. We demonstrate the imaging modality's ability to obtain laser-induced multicolored fluorescence images of a biological sample from different depths without scanning. We also experimentally demonstrate that the imaging modality can be simultaneously operated at both fluorescent and bright field modes to provide complementary information of volumetric tissue structures at different depths in real-time.
A real-time three dimensional (3D) fluorescence imaging system incorporating wavelength-coded and multiplexed
holographic gratings is presented. Holographic gratings formed in thick Phenanthrenquinone- (PQ-) Doped Poly (methyl
methacrylate) (PMMA) have narrowband spectral-spatial transmittance filtering properties to generate wavelengthspectrum
selective multi-focal planes within a biological object. We demonstrate the imaging modality to obtain laserinduced
fluorescent tissue structures from different depths at the excitation wavelength of 355nm.
We present a theoretical formulation to quantify the imaging properties of volume holographic microscopy (VHM).
Volume holograms are formed by exposure of a photosensitive recording material to the interference of two mutually
coherent optical fields. Recently, it has been shown that a volume holographic pupil has spatial and spectral sectioning
capability for fluorescent samples. Here, we analyze the point spread function (PSF) to assess the imaging behavior of
the VHM with a point source and detector. The coherent PSF of the VHM is derived, and the results are compared with
those from conventional microscopy, and confocal microscopy with point and slit apertures. According to our analysis,
the PSF of the VHM can be controlled in the lateral direction by adjusting the parameters of the VH. Compared with confocal microscopes, the performance of the VHM is comparable or even potentially better, and the VHM is also able to achieve real-time and three-dimensional (3D) imaging due to its multiplexing ability.
We overview a class of optical imaging systems utilizing volume holograms as imaging elements. The three-dimensional
(3D) nature of volume holograms as optical elements enables the realization of very general shift-invariant impulse
responses and dispersion relationships. We present experimental results and computational approaches towards the
analysis and optimization of 3D optical systems. The results indicate promising applications in profilometry of reflective
objects and slice-wise hyper-spectral imaging of fluorescent objects without or with minimal scanning.
As the mapping of the human genome has been completed, increasing emphasis is being placed on large-scale protein separation and identification methods to define the function of proteins and their associated genes. Within the last decade the sensing technique using the surface plasmon resonance(SPR) has received a great deal of attention and has become a leading technology for affinity-based biosensing. In this paper I report a novel design of SPR fiber optic sensing elements which allows developing highly miniaturized SPR probes. A fiber-optic chemical sensor is presented which utilizes surface plasmon resonance excitation. The sensing element of the fiber has been made by removing a section of the fiber cladding and symmetrically depositing a thin layer of highly reflecting metal onto the fiber core. A white light source is used to introduce a range of wavelengths into the fiber optic. Changes in the sensed parameters are determined by measuring the transmitted spectral intensity distribution. Therefore, when a protein layer is adsorbed on the metal surface, an increase in the refractive index occurs and can be detected. Based on theoretical analysis, the sensor structure is optimized to achieve the maximum sensitivity.
Optical triangulation displacement sensors are widely used for their non-contact measurement characteristics, sub-micron order resolution, simple structure, and long operation range. However, errors originating from surface inclination, speckle effect, light source fluctuation, and detector noise limit the wider use. In order to minimize these errors, the structure for optical triangulation displacement sensors, which is composed of an incoherent source and a linear CCD, has been proposed. But using a linear CCD causes several problems in signal processing. In this paper, we propose an adequate signal processing system for the proposed structure. With the help of the proposed algorithm, the limited resolution problem of CCD can be solved.
Optical triangulation displacement sensors detect linear displacements of objects without mechanical contact. They have simple structure, good resolution, and long operating range. However, there are several errors generated from speckle effects, environmental effects, and electronic noises, etc. To reduce errors from the electronic noises, the easiest way is to average the measurement outputs. Because the electronic noises are random in nature, their variance can be reduced with the averaging operation. However, this method is inherently time consuming process. To decrease the averaging time, several sensors or better signal processing hardwares are needed. So it increases the size of the measurement system and is not costeffective. In this paper, we propose a simple and cost-effective system structure for optical triangulation displacement sensors, which simplifies the averaging by inserting a transmission-type diffraction grating. When an incident ray enters to the diffraction grating, the grating separates the incident ray into several rays by the diffraction effect. The diffraction grating helps us to attain several signals simultaneously. Theoretical analysis is given and the feasibility of the proposed system is verified through experiments.
Point triangulation probes (PTBs) fall into a general category of noncontact height or displacement measurement devices. PTBs are widely used for their simple structure, high resolution, and long operating range. However, there are several factors that must be taken into account in order to obtain high accuracy and reliability; measurement errors from inclinations of an object surface, probe signal fluctuations generated by speckle effects, power variation of a light source, electronic noises, and so on. In this paper, we propose a novel signal processing algorithm, named as EASDF (expanded average square difference function), for a newly designed PTB which is composed of an incoherent source (LED), a line scan array detector, a specially selected diffuse reflecting surface, and several optical components. The EASDF, which is a modified correlation function, is able to calculate displacement between the probe and the object surface effectively even if there are inclinations, power fluctuations, and noises.