Aiming at being carried on various underwater vehicles for the detection of plankton, a miniaturized in-situ digital inline holographic system named OUC-HoloCam<sup>200</sup> is designed and developed. Although the structure of OUC-HoloCam<sup>200</sup> is simple and compact, the system performance is still excellent. Tests have been carried out and the result shows that the optical resolution of OUC-HoloCam<sup>200</sup> is 8.77 μm, the depth of field is up to 30 cm, the field of view is 8.44×6.75 mm<sup>2</sup> , which means theoretically with each exposure, about 300 mL of seawater can be investigated. OUC-HoloCam<sup>200</sup> have been deployed in the nearshore area of the South China Sea and have worked continuously over 48 hours, after holographic reproduction and image processing the data is able to show the trends of changing in number and species of plankton over time in the same location.
Plankton is an important part of the marine life, which plays a significant role in studying the change of global climate and the marine ecological environment. In order to detect plankton accurately and effectively, we design the Underwater In-situ Dark-field Microscopy Detection System based on the principle of dark-field microscopy. The experiment results show that while the 2× microscope objective is used, the resolution is 90.5lp/mm and the horizontal field of view is 2.6×2.6mm and while the 10× microscope objective is used, the resolution is 181lp/mm and the horizontal field of view is 2.2×2.2mm, when the microscope objective is replaced by 0.9× large format telecentric lens, the detection area will be 11mm with the resolution of 32lp/mm. Double compartment structure is designed, such that the system can work underwater.
This paper proposes a new method for three-dimensional dynamic holographic display that combines computer
generated holography (CGH) and holographic stereogram. Theoretically, three-dimensional (3D) dynamic holographic
display can be achieved by using CGH alone, however the application of CGH is still limited because large amounts of
data processing and complex mathematical calculation of off-axis diffracted light field. A new method combining CGH
and stereogram is proposed, since stereogram uses a set of 2D images instead of a 3D object, both the complexity of the
calculation and the resolution requirements of spatial light modulator (SLM) is reduced. To prove the feasibility of this
method, experiments of making hologram using this method is carried out and the result shows that 3D displaying with a
view angle of 28 is achieved.
Due to the absorption and scattering of water, images acquired in underwater environment have different colors from
those in air, which can cause problem for image processing and object recognition. Addressing the problem of color
correction, this paper presents a method of color restoration based on water absorption spectrum. Considering the
nonlinear attenuate of light in different wavelength at different depths, the changes of tri-stimulus values are calculated.
Experiments are carried out in coastal seawater. The change of tri-stimulus values are used to compensate color loss. The
results demonstrate the feasibility of our method.
This paper presents a novel synthetic generated hologram (SGH) system, in which a digital micromirror device (DMD) is used as space light modulator (SLM). In the system, the object light beam is directed through a sequence of digital images on a space light modulator, digital micromirror device (DMD), rather than the transparent films used in the conventional SGH. A computer controlled distributing device replace manual operation. With this system, threedimensional full color hologram can be generated by synthesizing a series of two-dimension digital images, obtained by digital camera or generated by computer software. The preliminary experimental results have been obtained with this system. The possible future development has also been discussed.