巧用PPT多层模板制作华丽的字幕效果

每年我都帮老师制作课件,参加教育部组织的课件大赛并获奖,有很多心得。我们先来看题图,一首歌颂教师的诗句逐一从左下方向右上方飞出。用动画实现的吧?对!但是PPT自带的动画(如飞入、切入、渐变、上升等效果)在起点时就能看到所有字幕,这个例子中的诗句为什么能先藏起来呢?这就是"遮罩板"的妙用。在PPT中使用多层模板,利用层次关系就可以精确定位字幕出现和消失的位置,获得很不错的视觉效果,与Flash媲美,方法很简单!     

为什么显示器也需要通过Vista认证

最近有些读者朋友问：现在微软为什么这么霸道,连显示器都要通过它的认证,没有通过Windows Vista认证的液晶显示器会有什么不同吗？液晶显示器和Windows Vista操作系统之间到底有什么必要的联系呢？通过Windows Vista认证的显示器又有什么好处呢？针对上述种种疑问,今天我们将为大家一一解答。     

Derivation and implementation of a cone-beam reconstruction algorithm for nonplanar orbits

B.D. Smith (ibid., vol.MI-4, p.15-25, 1985; Opt. Eng., vol.29, p.524-34, 1990) and P. Grangeat (These de doctorat, 1987; Lecture Notes in Mathematics 1497, p.66-97, 1991) derived a cone-beam inversion formula that can be applied when a nonplanar orbit satisfying the completeness condition is used. Although Grangeat's inversion formula is mathematically different from Smith's one, they have similar overall structures to each other. The contribution of the present paper is two-fold. First, based on the derivation of Smith, the authors point out that Grangeat's inversion formula and Smith's one can be conveniently described using a single formula (the Smith-Grangeat inversion formula) that is in the form of space-variant filtering followed by cone-beam back projection. Furthermore, the resulting formula is reformulated for data acquisition systems with a planar detector to obtain a new reconstruction algorithm. Second, the authors make two significant modifications to the new algorithm to reduce artifacts and numerical errors encountered in direct implementation of the new algorithm. As for exactness of the new algorithm, the following fact can be stated. The algorithm based on Grangeat's intermediate function is exact for any complete orbit, whereas that based on Smith's intermediate function should be considered as an approximate inverse excepting the special case where almost every plane in 3D space meets the orbit. The validity of the new algorithm is demonstrated by simulation studies.     

Index-distributed planar microlenses for three-dimensional micro-optics fabricated by silver-sodium ion exchange in BGG35 substrates

Fabrication of planar microlens arrays by silver-sodium ion exchange is possible by using a new glass type, optimized for this technology. Because of its nonlinear diffusion response it is well suited to the fabrication of microlens arrays. We show that the diffusion coefficient can be described theoretically by an exponential concentration dependence. The parameters of the planar microlenses are measured interferometrically and by imaging experiments. Because of the specific index distribution, new evaluation techniques for the determination of lens parameters from interferometric measurements have been applied. We also present a simple model that relates the achievable lens parameters to the diffusion conditions.     

Reflection-grating self-pumped phase conjugation with optical feedback free of input conditions

A reflection-grating self-pumped phase-conjugate mirror is demonstrated with a photorefractive KNbO(3) crystal in a novel ring configuration. The feedback beam in the ring configuration is made to track the input probe beam automatically so that the phase conjugation is sustained without readjustment of the optical feedback loop when the angle or the position of the input probe beam is changed. The tracking feedback is realized by means of a simple three-lens erect imaging system. The angular and the positional acceptances for a tightly focused input beam of 50-μm diameter are Δθ(x). = 55 mrad, Δθ(y), = 67 mrad, and Δ(x) = 2.1 mm, Δ(y) = 4.2 mm, respectively.     

Scattering mechanism and reduction of insertion losses in a laminated polarization splitter

We experimentally found the unexpected phenomena of scattering in laminated polarization splitters (LPS's) composed of a-Si:H-SiO(2) multilayer and studied its mechanism. The scattering phenomena strongly depend on the incident angle and polarization of the incident light. To reduce the scattering loss in LPS's, a multilayer with flat layer boundaries is fabricated with rf bias sputtering. As a result, the insertion loss of the LPS is reduced to ~ 1 × 10(-3) dB/ μm, which is acceptable for practical uses.     

Use of the fast Fourier transform method for analyzing linear and equispaced Fizeau fringes

The Fourier transform method is applied to analyze the initial phase of linear and equispaced Fizeau fringes. We develop an algorithm for high-precision phase measurement by using the Fourier coefficient that corresponds to the spatial frequency of the Fizeau fringes, and we describe methods for determining the fringe carrier frequency. Errors caused by carrier frequency fluctuation and data truncation are studied theoretically and by computer simulation. To demonstrate the method we apply it to the real-time calibration of a piezoelectric transducer mirror in a Twyman-Green interferometer.     

Detection of low levels of trichloroethylene vapor with Raman spectrometry

The response of a novel fiber-optic Raman probe to low levels of trichloroethylene (TCE) vapors is characterized. The detection limit of the current probe for TCE vapor is 34 mg/L, and the probe exhibits a fully reversible response. The probe uses an organic-polymer, low-density polyethylene to concentrate TCE vapors in the optical path of the fiber-optic Raman spectrometer. The relative standard deviation for measurement of 677 mg/L of TCE in the vapor is 0.3%.     

Graded-index polymer optical fiber for high-speed data communication

We successfully obtained a high-bandwidth (1 GHz km) and low-loss (90 dB/km at 0.572 μm of wavelength) graded-index polymer optical fiber by using the interfacial-gel polymerization technique, in which we used an unreactive component to obtain the quadratic refractive-index distribution. This high-bandwidth graded-index polymer optical fiber makes it possible to transmit a high-speed optical signal in a short-range network, which is not possible when we use the step-index type of polymer optical fiber commercially available.