Convex aspheric surface is tested by a circular amplitude computer-generated hologram (CGH) fabricated with our equipment and techniques, and much research work has been done simultaneously. However, the analysis of the detailed characters of the CGH used in the test system has not been systematically given in detail, including the correct phase, amplitude, and filter condition of the CGH. The calculation equation of the proper duty circle and the phase of the CGH are deduced, the frequency filter condition of the different diffracted orders of the CGH is demonstrated, and the deduction results are validated by the related experiment. The conclusion can help us to determine the radius ratio of the uncontrolled area over the full aperture of the aspheric surface during the process of optical system design, and it also points out that the radius ratio can be reduced by adjusting the radius of curvature of the reference surface and the distance between the reference surface and the convex aspheric surface. The work can assist us in designing the test system efficiently and correctly with CGH.
To suppress the stray light caused by the diffraction and scattered light of a digital micromirror device (DMD) in a DMD-based spectrometer, a new concentrator system with a compound parabolic concentrator (CPC) is presented, which has the advantage that all stray light beyond the acceptance angle can be rejected with the most compact device available. The diffraction of DMD is explored to determine the acceptance angle, and the parameters of the concentrator system are analyzed to determine the geometric concentration ratio. The simulation results show that the spectrum concentration efficiency of the CPC is 98.7%, that the stray light concentration efficiency from the DMD is 36.3%, and that the stray light concentration efficiency beyond the acceptance angle is 0.00%. Finally, according to the discussion about tolerance on the CPC, a conclusion can be drawn that the new DMD-based spectrometer with CPC is feasible and significant in suppressing the stray light.
A digital micromirror device (DMD) acts as a spatial light modulator in a maskless photolithography system. Illuminated by coherent light, DMD performs as a two-dimensional diffraction grating because of its periodical internal structure. Diffraction efficiency is an important factor for evaluating the exposure doses. A diffraction model of DMD based on Fourier analysis demonstrates that errors of the DMD’s manufacture and the precision of the machining of the optical mechanical structure affect the diffraction efficiency. Additionally, analysis of exposure results by the diffraction model of DMD in Tracepro explains the degradation of the exposure quality and is helpful for calibrating the direction of optical focusing.
A new design of compound Fresnel-R concentrator is presented which is composed of two lenses:
a primary lens (Fresnel lens) that works by total internal reflection at outer facets but refraction
at inner facets, and a secondary lens that works by refraction. In contrast to previous Fresnel lens
concentrator, this design increases the acceptance angle, improves the irradiance uniformity on
the solar cell, and reduces the aspect ratio significantly. Another outstanding advantage of this
concentrator is the fact that it mainly works by performing total internal reflection, reducing
chromatic dependence as well as Fresnel losses. An optical efficiency more than 80% can be
achieved. Moreover, in order to reduce the influence of manufacture accuracy and to increase the
optical efficiency further, the central part of the bottom of the secondary lens which directly
adhered to the solar cell is designed as a cone-shaped prism to collect the sunlight that doesn't
reach the solar cell.
The finite-difference time-domain (FDTD) method is used as rigorous electromagnetic analysis model to calculate the field for a diffractive microlens (DML). The FDTD is used for the entire solution rather than using a near- to far-field propagation method to obtain the far-field energy distribution; thus, all the results are vector based. We derived a formula to calculate the magnitude of electric field, which is time dependent and can be used to graphically show the light wave propagation and focusing process through a DML. Both the comparison and the integral methods are presented to obtain wave amplitude in full solution space, and the distribution of light energy behind a DML is illustrated based on the wave amplitude. The formula of diffractive efficiency of the DML is derived from a time-averaged Ponyting vector, which can indicate the propagation direction of light energy. Application of these formulations in the analysis of a DML example demonstrates the high accuracy and efficiency of our method.
The main feature of the compound diffractive telescope is the combination of diffractive optics with compound structure
arranged eyepieces. In this paper, a design of the compound diffractive telescope is firstly introduced, and a 4.2° FOV
is obtained with one primary lens and twenty-one eyepieces. Secondly, image characteristic of different channels is
analyzed with the design wavelength in ASAP, and one modified phase function model of diffractive optical element is
introduced to analyze the MTF curves for 0° FOV, which provides a more accurate prediction of the performance of the
system. Then the system is tested by the star image test, and the diffraction limit images are got within ± 2° FOV. And
finally, two pictures taken from the adjacent FOV proved to be able to be spliced together. All the results above
demonstrate that a good performance of the compound diffractive telescope.
In the solar tower thermal power generation system, the precision of the slope angle of the heliostat is the major factor,
which influences the efficiency of the system, consequently, this angle should be tested accurately. In this paper, the
methods based on laser deflectometry are proposed to measure the shape error of the mirror facet and the connected error
of the facets; such apparatus and corresponding software packages are developed. With the help of these two apparatus,
the heliostat of 1002, consisting of 55 mirror facets of 1.8182 m2; (hexagon), for the 1MWe solar tower power plant in Beijing are measured and connected successfully.
The diffractive optical element (DOE) is always modeled as an ideal pure diffractive element which neglects the
refractive dispersion of the element's material. In this paper, a new model of the diffractive optical element is proposed,
in which the effect of the refractive dispersion of the DOE's material is considered. The new model is explained and
compared with standard diffraction-order expansion with the help of a hybrid system example. The analytical results
show that the new model has an important meaning for the exact analysis of the hybrid refractive-diffractive optical
By using a CGH test plate fabricated with our equipment and techniques, we measured a
perfect sphere surface. The measurement result is quantified into four parts: the figure error from the
spherical surface under test; the figure error from the spherical reference surface; the error from
hologram and the adjustment error from misalignment. The measurement result removed from the later
three errors, shown excellent agreement with Zygo test of the same sphere surface. This verified that
the measurement accuracy by using this kind of CGH could be very high.
Compound telescope is a new type of space optical system. It uses the concept of compound eyes and the property of diffractive lens. With the help of diffractive lens, the diffractive optical system could become lighter weight, lower cost, and looser tolerance. And with the help of compound-eye configuration, the field of view is expanded. A design example of compound diffractive optical system is given. It is composed of many diffractive telescope of F/4, 200mm aperture, 0.1 degrees field of view. It is shown that the whole system can approximately attain the diffraction limit over wide field of view.
This paper will introduce the principle and techniques to realize laser color video display. The characteristics of techniques and bottleneck of restricting the development are analyzed .A novel technical approach to eliminating the laser interference, improving the uniformity of optical field, transforming the chromaticity and extending the virtual color is proposed. The principle device of laser display system has been produced on the basis of the blue, green and red diode-pumped solid state lasers. The wavelengths of the blue, green and red are respectively 473nm, 532nm and 671nm. The output powers of the lasers are 1.3W, 0.32W and 3.5W respectively.