Based on the spectral combination function of grating and the bi-grating diffraction imaging effect, ZWP Grating Diffraction Imaging Instrument has been designed and developed, and some new experiment courses about grating diffraction have been set up for college students using the instrument. The new grating experiments are aimed to help students understand the comprehensive knowledge of grating diffraction. Also, it is a good training to improve student’s hands-on abilities. The instrument has been used by more and more universities.
Varied line spacing plane gratings have the features of self-focusing , aberration-reduced and easy manufacturing ,which are widely applied in synchrotron radiation, plasma physics and space astronomy, and other fields. In the study of diffracting imaging , the optical path function is expanded into maclaurin series, aberrations are expressed by the coefficient of series, most of the aberration coefficients are similar and the category is more, can't directly reflects image quality in whole. The paper will study on diffraction imaging of the varied line spacing plane gratings by using computer simulation technology, for a method judging the image quality visibly. In this paper, light beam from some object points on the same object plane are analyzed and simulated by ray trace method , the evaluation function is set up, which can fully scale the image quality. In addition, based on the evaluation function, the best image plane is found by search algorithm .
Recently, ZWP grating diffraction imaging instrument has been applied in the research and teaching of bi-grating imaging effects by some universities. However, there are problems exposed in the use. The main problem is position location of bi-grating operation which hardly achieves the “Z” shape that is fit for imaging path, especially the diagonal direction deviation of the second grating when it is moving in the platform, which leads to measurement errors for the bi-grating diffraction imaging, and the experiment results are inaccurate. To the grating imaging instrument, the electronic control method has been studied, which is to control moving and rotation of gratings more easily and with high measurement accuracy. The new reform plan of the grating imaging instrument is done and tested, and the experiment results are compared with before reform undone.
The bi-grating diffraction imaging effect is the effect that a clear object image can be seen after the polychromatic beam coming from object is diffracted twice by two gratings. And the bi-grating diffraction imaging equation reflects the relationship between the spatial frequencies, diffraction orders, and positions of the two gratings, it plays an important role during the use of the bi-grating imaging. This paper reported on factors of influencing the value of w in the bi-grating diffraction imaging equation. The coefficient W is approximately equal to 1 when the bi-grating system under the ideal conditions, but in fact, it is not strictly equal to 1. This paper researched factors of influencing the value of W and studied the law of these values deviate from 1 for the bi-grating system when the two gratings are parallel to each other by experiments. The experiment results show that: when the center of the second one grating G2 is set in the side of wavelength shorter than centre wavelength of the diffraction beam of the first grating G1, the value of W decreases, otherwise, it increases.
The VLS grating has the ability of self-focusing and eliminating aberration, and it has been widely used in many fields. The plane VLS grating has two types, one is the one-dimensional VLS grating and another is two-dimensional VLS grating. In some practical applications, we need to know the focusing property of the two-dimensional VLS grating, so it is important to research the focusing property of the two-dimensional VLS grating illuminated by different types of light beams. In this paper, we mainly studied the focusing property of the two-dimensional VLS grating whose grating lines are arc. Light beams diffracted by this kind of the VLS grating can form a focal point in one position or form a horizontal focal line and a vertical focal line respectively in two different positions. We experimentally studied the change of the focusing position under different incident angles using the monochromatic plane wave or spherical wave as incident light, and studied the influence of different wavelengths of the monochromatic plane wave on the focusing position. The difference between the positions of two focal lines which relates with the focusing property of the two-dimensional VLS grating is also discussed in our work.
With 3-D finite difference time domain (FDTD) method, we investigate the effect of the geometry parameters and near
field distribution on sensitivity of the bowtie type nanoresonator biosensor in terms of refractive index. The calculation
results show that the geometry parameters including gap (G), radius of curvature (R) and tip angle (A) have different
effects on bulk sensitivity of bowtie metallic nanostructure. The sensitivity linear decreases as G increases while
exponential decreases as R increases. Moreover, with A taking 15° to 135°, the sensitivity descends initially and then rises. As for the influence of near field on sensitivity, we can conclude that sensitivity is proportional to maximal local field and
the scale factor of fitted curve for R is larger than the one for G.
Optic imaging system is information transmission system. The quality of imaging depends on the
transmission characteristics of optical system completely. The bi-grating diffraction imaging is the formation of
the image of an object with two gratings. First,gather object information and transform them into object beams
by irradiatiion of incandescent lamp. Then the first grating disperses the muti-color object beams with object
information and second combines the dispersed light beams to form the image.This paper describes the
characteristics of information about object color and size transmission. The characteristic is studied by
theoretical analysis. The relationship between the two gratings' spatial frequencies and diffraction orders that
reflecting the information of object color and size transmission quality on certain condition is given. To
recognize the transmission characteristics of bi-grating diffraction imaging deeply is very helpful for its
application.
Lengthways and transverse offset of the position of the virtual image relative to the object are analyzed theoretically in
different situations of bi-grating imaging, and an experiment on the verification of the offset is carried out. The result
shows that the position of the virtual image is just behind the object relative to the positive direction of Z axis, the
distance between virtual image and object increases with the increasing of the distance between object and grating G2;
Therefore, the position of virtual image deviates from objects in the X-axis if looking it through grating G2. Thus the
grating G2 and the virtual image are "located on" the same side of the Z-axis.
This paper researches the phenomenon of bi-grating imaging by the computer simulation. The process that white lights
are diffracted by two gratings with different space frequencies is simulated and the imaging characteristics are studied. A
bi-grating imaging relationship is given based on the simulation results. It agrees basically with the experiments.
of grating. First, we studied the reversibility of optical path of grating illuminated by monochromatic light, and then
illuminated by polychromatic light. We found that the optical path of diffraction of grating has partial reversibility.
Using the partial reversibility of optical path of diffraction of grating, we analyzed the spectral combination
characteristic of grating and the bi-grating diffraction imaging effect.
Two gratings consist of an imaging system in which a clear virtual image of an object is formed. The diffraction
properties of gratings have important influence on the information of images. In this paper, the imaging characteristics
of bi-reflection, bi-transmission gratings system and the transmission-reflection grating system are studied. The imaging
process and the quality of images of three systems are compared and some characters are summarized. It is useful for
the deep understanding of bi-grating imaging effect and its new applications.
The comparison of bi-grating diffraction imaging and the displaying of ordinary transmission hologram with white light
source, shows two different imaging methods have same essence, but different characteristic. In these two processes of
imaging, the light-wave of the object has been diffracted twice, both methods have to combine the dispersed image of
different wave length, so both of them have to employ the spectral combination characteristic of grating. The bi-grating
imaging equation not only is fit for the bi-grating imaging process, but also has guidance meaning in ordinary
transmission hologram displaying with white light source and the aid of grating.
A novel experimental instrument of diffraction imaging and its applications are introduced in this paper. This apparatus is composed of movable mechanical parts, optical elements and computer image acquisition system. It can be readily used in the confirmation of bi-grating imaging phenomena and observation of the ordinary transmission hologram displaying with white light source.
Diffraction astigmation formed by the grating diffraction light was investigated. The grating diffraction astigmation varies with the incidence angle and the characteristics of the variation were discussed. The angles of incidence light and other conclusions corresponding to the minimum diffraction astigmation were obtained based on a systematic analysis.
A method for displaying ordinary transmission holograms with white light and grating was investigated further. Based on the basic principle of this method, factors coming from the case of application and having influence on the image color and quality were analyzed systematically.
We reported the previous research of spectrum imaging with a double-grating imaging system in 2001. In this paper, we will investigate the energy of the image obtained using the same imaging method. A mercury-vapor lamp was used as the light source to measure the light energy of the image at different positions for four grating combinations. The experimental results were analyzed systematically. The factors affecting the brightness of the image were also discussed in this paper.
A method to obtain the image information from spectrum and reconstruct the image is presented in this paper. The theoretical explanation, experimental results and application to the imaging method are also introduced.
A new device for displaying ordinary transmission holograms with a white light source is described, based on compensating the dispersion in a broad band of the visible spectrum. Using the device, the clear image from the ordinary transmission hologram plane have been reconstructed.
A new high-resolution-silver-halide (HRSH-II) material was produced, which has proper initial hardness for fabricating silver halide sensitized gelatin (SHSG) holograms. That would avoid high noise by seeking the gelatin in hot water. With different alkali halide component in B solution and its concentration (the ratio B/A), experiments were presented about bleaching effect with R-10 on processing for SHSG derived from this new material. High diffraction efficiency, as high as 81%, was achieved. Some of the observations are discussed.
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