A method of a digital holography based on the use of a self-imaging of the phase element is presented and assessed in
terms of image quality and resolution. The experimental results of digital hologram acquisition and reconstructions are
given for a standard USAF test pattern. The self imaging effect is used in the reference beam of the Mach-Zehnder
interferometer in order to project a structured phase modulated beam directly onto the photosensitive matrix of a digital
camera. The main advantage of this method is a simple optical setup and the possibility of performing phase-shifting
with a single camera exposure. The numerical reconstruction takes advantage of the Talbot effect and does not involve
any approximation or interpolation techniques. In order to evaluate the applicative potential of the method, in this work
the image quality is checked for various parameters of the optical setup, especially the period of the self-imaging
structure and imaging distances.
A method of color projection of 2D images utilizing red, green and blue laser sources and Fourier holograms addressed
on a single phase modulator has been reported. High quality rich-colored images were achieved, although the main
difficulty in reaching the TV-quality is the presence of a 0th diffractive order. It is inevitably created due to a limited fill
factor and phase modulation nonlinearity of the used Spatial Light Modulator (SLM) device. However, in certain
conFigureurations the light energy contributing to the spurious diffractive order can be focused in a single point in space
and absorbed with an amplitude filter. In this work we present the experimental results of a color projection with the
non-diffracted peak shifted outside the viewing range in both transverse directions and along the optical axis.
There is a continuous demand for the computer generated holograms to give an almost perfect reconstruction with a
reasonable cost of manufacturing. One method of improving the image quality is to illuminate a Fourier hologram with a
quasi-random, but well known, light field phase distribution. It can be achieved with a lithographically produced phase
mask. Up to date, the implementation of the lithographic technique is relatively complex and time and money
consuming, which is why we have decided to use two Spatial Light Modulators (SLM). For the correctly adjusted light
polarization a SLM acts as a pure phase modulator with 256 adjustable phase levels between 0 and 2π. The two
modulators give us an opportunity to use the whole surface of the device and to reduce the size of the experimental
system. The optical system with one SLM can also be used but it requires dividing the active surface into halves (one for
the Fourier hologram and the second for the quasi-random diffuser), which implies a more complicated optical setup. A
larger surface allows to display three Fourier holograms, each for one primary colour: red, green and blue. This allows to
reconstruct almost noiseless colourful dynamic images. In this work we present the results of numerical simulations of
image reconstructions with the use of two SLM displays.
A study of imaging in an isoplanatic optical setup with a spatially incoherent illumination is presented. In such optical
setups a light intensity distribution in an image plane can be calculated by a convolution of an input field with a Point
Spread Function (PSF). Additionally a numerical simulation of incoherent monochromatic illumination is done by an
integration of intensity images obtained with different random initial phase distributions (equivalent to a long exposure
with a rotating diffuser in an optical setup). When an optical system is non space-invariant the point source image
changes in various regions of the image plane and imaging simulation becomes complicated. Method with a simple
convolution with PSF distribution cannot be applied because there is no one well defined PSF for the whole optical
setup. This second method needs a bigger computational effort but can provide imaging modelling for both isoplanatic
and non space invariant situations. In this contribution we compare the two mentioned methods in terms of imaging
quality and its agreement with theoretical expectations. We give some statistical analysis of a contrast and noise level of
the obtained pictures. We discuss the advantages and limitations of both modelling techniques for typical greyscale test
patterns.
The experimental demonstration of a blind deconvolution method on an imaging system with a Light Sword optical
element (LSOE) used instead of a lens. Try-and-error deconvolution of known Point Spread Functions (PSF) from an
input image captured on a single CCD camera is done. By establishing the optimal PSF providing the optimal contrast of
optotypes seen in a frame, one can know the defocus parameter and hence the object distance. Therefore with a single
exposure on a standard CCD camera we gain information on the depth of a 3-D scene. Exemplary results for a simple
scene containing three optotypes at three distances from the imaging element are presented.
This work presents the observation, measurement and utilization of phase modulation in-time flickering, on a high-end
Liquid Crystal on Silicon (LCoS) Spatial Light Modulator (SLM). The flicker due to binary driving electronics is a
negative effect. However, this drawback can be minimized by appropriate adjustment of phase modulation depth, which
results in a time-synchronization of peak efficiencies for selected wavelengths. In this paper optimal parameters for three
wavelengths of primary RGB colors are investigated. The result is optimal performance of the SLM for full-color
dynamic holography.
A diffractive optical element with self-imaging capabilities is used to make a phase-shifting digital holography optical system simpler and cheaper. Sequential phase-shifting requires multiple exposures, and parallel phase-shifting demands a more complicated optical system. As opposed to typical phase-shifting methods, using the self-imaging diffractive optical element requires only one exposure on a low-cost CMOS matrix, and due to the small number of needed elements, the optical system is very compact. Instead of the approximation and interpolation methods, the properties of the self-imaging effect are utilized in the recording process and in the numerical reconstruction process.
The possibility of encoding multiple asymmetric symbols into a single thin binary Fourier hologram would have a practical application in the design of simple translucent holographic head-up displays. A Fourier hologram displays the encoded images at the infinity so this enables an observation without a time-consuming eye accommodation. Presenting a set of the most crucial signs for a driver in this way is desired, especially by older people with various eyesight disabilities. In this paper a method of holographic design is presented that assumes a combination of a spatial segmentation and carrier frequencies. It allows to achieve multiple reconstructed images selectable by the angle of the incident laser beam. In order to encode several binary symbols into a single Fourier hologram, the chessboard shaped segmentation function is used. An optimized sequence of phase encoding steps and a final direct phase binarization enables recording of asymmetric symbols into a binary hologram. The theoretical analysis is presented, verified numerically and confirmed in the optical experiment. We suggest and describe a practical and highly useful application of such holograms in an inexpensive HUD device for the use of the automotive industry. We present two alternative propositions of car viewing setups.
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