A color transparent screen was designed in this paper, utilizing a planar glass combined with lens array holographic optical elements (HOEs). The lens array HOEs were exposed using two coherent beams, one of which was the reference wave directly illuminating on the holographic material and the other was modulated by the micro lens array. The lens array HOEs can display the images with see-through abilities. Unlike the conventional ones that used the lens array HOEs as the screen solely, planar glass was adopted here as the waveguide. The projecting light was totally internalreflected in the planar glass to eliminate undesired zero-order diffracted light and realize high system compactness. Colorful display can be realized in our system as the holographic materials were capable for multi-wavelength display. To verify the effectiveness of this method, a color transparent screen incorporating the lens array HOEs and waveguide was designed. Results showed the circular display area with 20mm in diameter and the pixel resolution of 100μm were achieved in the system. This simple and effective method could be an alternative in the augment reality (AR) applications, such as transparent phone and television.
In this paper, an overlapped sub-block gray-level average method for contrast enhancement is presented. The digital
image correction of uneven illumination under microscope transmittance is a problem in image processing, also sometimes
the image in the dark place need to correct the uneven problem. A new correction method was proposed based on the mask
method and sub-blocks gray-level average method because Traditional mask method and background fitting method are
restricted due to application scenarios, and the corrected image brightness is low by using background fitting method, so
it has some limitations of the application.
In this paper, we introduce a new method called AOSCE for image contrast enhancement. The image is divided into
many sub-blocks which are overlapped, calculate the average gray-level of the whole image as M and the calculate the
average gray-level of each one as mi, next for each block it can get d = mi - m, each block minus d to get a new image,
and then get the minimum gray-level of each block into a matrix DD to get the background, and use bilinearity to get the
same scale of the image. over fitting the image in matlab in order to get smoother image, then minus the background to
get the contrast enhancement image.
Ultrashort laser pulse has been widely used in various applications. Its parameters, such as the pulse duration and the
spectral bandwidth, should be controlled accurately in order to achieve high spatial and temporal resolution, as well as
high local field intensity. In this paper, we have proposed a method to trace the propagation of ultrashort pulses through
optical systems, especially the complex optics. The approach, in which both the material’s dispersion and optical
aberrations are taken into consideration, is developed based on the geometrical ray-tracing combined with wave theories.
This method is validated by simulating the propagation of a femtosecond pulse through a specific practical imaging system.
As the numerical result shows that the spatial-temporal performances of pulses are influenced greatly by optical elements,
the calibration arrangement is employed to compensate for those undesired distortions. The negative dispersion of the
optical grisms (the combination of gratings and prisms) is utilized in the calibration process to offset the positive dispersion
introduced by lenses. The final result shows effectiveness of the correction.