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 共查询到20条相似文献,搜索用时 15 毫秒
1.
Liu Q  Ohba R 《Applied optics》1999,38(19):4111-4116
The properties of moiré fringes in Talbot interferometry are analyzed when the angle between the two grating planes is small. The results indicate that the tilt angle of the moiré fringes, observed just behind the test grating, is sensitive to the small angle. Based on this sensitivity, several features of parallelism of the two grating planes are presented, and the influence of the small angle when checking the beam collimation of a lens is also discussed. The validity of the theoretical analysis is illustrated by experiment.  相似文献   

2.
Liu Q  Ohba R 《Applied optics》2001,40(32):5938-5942
The effects of an arbitrary small inclination between the two crossed gratings on moiré fringes in Talbot interferometry are discussed. The small inclination is formed by the rotation by a small angle gamma of the beam splitter's grating about the axis that is on the plane of the grating and has an arbitrary angle delta with respect to the lines of the grating. The results indicate that the small inclination has a great influence on measurements for which Talbot interferometry is applied, such as beam collimation and measurement of the focal length of a lens. The theoretical analyses are proved by experimental results. Some methods for judging the size of a small inclination are also proposed.  相似文献   

3.
Gratings that contain luminance and chromatic components of different spatial frequencies were used to study the segregation of signals in luminance and chromatic pathways. Psychophysical detection and discrimination thresholds to these compound gratings, with luminance and chromatic components of the one either half or double the spatial frequency of the other, were measured in human observers. Spatial frequency tuning curves for detection of compound gratings followed the envelope of those for luminance and chromatic gratings. Different grating types were discriminable at detection threshold. Fourier analysis of physiological responses of macaque retinal ganglion cells to compound waveforms showed chromatic information to be restricted to the parvocellular pathway and luminance information to the magnocellular pathway. Taken together, the human psychophysical and macaque physiological data support the strict segregation of luminance and chromatic information in independent channels, with the magnocellular and parvocellular pathways, respectively, serving as likely the physiological substrates.  相似文献   

4.
A laboratory prototype spectral-spatial interferometer has been constructed to demonstrate the feasibility of the double-Fourier technique at far infrared (FIR) wavelengths (0.15-1 THz). It is planned to use this demonstrator to investigate and validate important design features and data-processing methods for future astronomical FIR interferometer instruments. In building this prototype, we have had to address several key technologies to provide an end-end system demonstration of this double-Fourier interferometer. We report on the first results taken when viewing single-slit and double-slit sources at the focus of a large collimator used to simulate real sources at infinity. The performance of the prototype instrument for these specific field geometries is analyzed to compare with the observed interferometric fringes and to demonstrate image reconstruction capabilities.  相似文献   

5.
The detectability of contrast increments was measured as a function of the contrast of a masking or "pedestal" grating at a number of different spatial frequencies ranging from 2 to 16 cycles per degree of visual angle. The pedestal grating always had the same orientation, spatial frequency, and phase as the signal. The shape of the contrast-increment threshold versus pedestal contrast (TvC) functions depends on the performance level used to define the "threshold," but when both axes are normalized by the contrast corresponding to 75% correct detection at each frequency, the TvC functions at a given performance level are identical. Confidence intervals on the slope of the rising part of the TvC functions are so wide that it is not possible with our data to reject Weber's law.  相似文献   

6.
Bitou Y 《Applied optics》2005,44(9):1577-1581
A two-wavelength moire phase-shifting interferometer that uses a superimposed grating has been developed. The optical phase shifts for the two wavelengths are given by digital phase shifts of a superimposed grating displayed on a liquid-crystal spatial light modulator. A phase shift of the moire fringe is achieved by equal phase shifts with opposite signs in the two gratings. A moire phase-shifting interferometer with no moving parts and no requirement for calibration of the value of the phase shifts was obtained. Our experimental result shows measurements of the profile of a step object with a 2.65-microm synthetic wavelength.  相似文献   

7.
Magnusson A  Hård S 《Applied optics》2000,39(32):5936-5939
With the aim of steering as much incident light power in the +1 diffraction order as possible and suppressing the power in the -1 order, we generated an effective four-level grating by coherently imaging a 180 degrees binary-phase grating onto a 90 degrees phase grating. The periods of the gratings were well matched. The measured overall power fractions in the +1 and -1 orders were 54% and 2%, respectively.  相似文献   

8.
Ross IN  Hooker CJ  Dombi P 《Applied optics》2001,40(34):6153-6156
The advantages of a grating interferometer for the generation of large diffraction gratings are demonstrated. In a one- and a two-stage process, high-quality gratings of 120 and 200 mm, respectively, were made with optics no larger than 50 mm together with an argon-ion laser with no line narrowing or beam stabilization and a rotating diffuser for improved beam uniformity.  相似文献   

9.
Abstract

The possibility of observing interference with two modes of different frequencies in a one-photon state by means of parametric up-conversion is studied. This phenomenon could be utilized for discernment between pure and mixed states. There is also a close connection to the question of the extent of indefiniteness of the photon's path.  相似文献   

10.
The phenomenon of luminescence under the action of ultrasound (sonoluminescence, SL) was studied in a liquid exposed to the field of a high-frequency (HF, 880 kHz) focusing radiator with simultaneous or preliminary action of a low-frequency (LF, 19.9 kHz) ultrasound on the sample. It is shown that a nonadditive increase in the SL intensity takes place for simultaneously operating radiators and is observed for a long time (up to several hours) after switching off the LF source. This is evidence of a long-term aftereffect of the LF ultrasound on the magnitude of SL induced by the HF oscillations. The possible mechanisms of the observed effect are discussed.  相似文献   

11.
Q Chen  H Luo  S Wang  F Wang  X Chen 《Applied optics》2012,51(25):6106-6110
A measurement method based on interferometry with two different reference cavity lengths is presented and applied in air refractive index measurement in which the two cavity lengths and a laser wavelength are combined to generate two wavelength equivalents of cavity. Corresponding calculation equations are derived, and the optical path configuration is designed, which is inspired by the traditional synthetic wavelength method. Theoretical analyses indicate that the measurement uncertainty of the determined index of refraction is about 2.3×10-8, which is mainly affected by the length precision of the long vacuum cavity and the ellipticity of polarization components of the dual-frequency laser, and the range of nonambiguity is 3.0×10-5, which is decided by the length difference of the two cavities. Experiment results show that the accuracy of air refractive index measurement is better than 5.0×10-8 when the laboratory conditions changes slowly. The merit of the presented method is that the classical refractometry can be also used without evacuation of the gas cavity during the experiment. Furthermore, the application of the traditional synthetic wavelength method may be extended by using the wavelength equivalents of cavity, any value of which can be easily acquired by changing cavity length rather than using actual wavelengths whose number is limited.  相似文献   

12.
The relative contributions of optical and neural factors to the decrease in visual function with aging were investigated by measurement of contrast detection at three different spatial frequencies, in the presence of external noise, on young and older subjects. Contrast detection in noise functions allows two parameters to be measured: sampling efficiency, which indicates neural changes, and equivalent noise, which demonstrates optical effects. Contrast thresholds were measured in the presence of four levels (including zero) of externally added visual noise. Measurements were obtained from eight young and eight older visually normal observers. Compared with young subjects, older subjects showed significantly (p < 0.05) lower sampling efficiencies at spatial frequencies of 1 and 4 cycles per degree (c/deg) and significantly higher equivalent noise levels for gratings of 10 c/deg. Neural and optical factors affect contrast sensitivity loss with aging differently, depending on the spatial frequency tested, implying the existence of different mechanisms.  相似文献   

13.
Abstract

Speckle interferometry is an important deformation measurement method for an object with a rough surface. In this paper, a novel fringe analysis method is proposed that uses a new optical system, which uses a plane wave as the reference beam of the speckle interferometer. When the optical system is employed in fringe analysis, the deformation information and the bias components of the speckle patterns are clearly separated in the frequency domain. Therefore, the deformation information can be readily extracted using a Fourier transform, which gives a pair of real and imaginary components concerning the information. The specklegram is calculated using such a pair of components, and the phase map is obtained from the specklegram. Experimental results confirmed that the resolution power of this measurement method is higher than 1/261 of the wavelength of the light source of the optical system.  相似文献   

14.
进给速度对不同纤维方向CFRP铣削表面形貌的影响   总被引:1,自引:0,他引:1       下载免费PDF全文
采用金刚石涂层硬质合金铣刀对0°、45°、90°、135°4种纤维方向的碳纤维增强复合材料(CFRP)进行了顺铣加工试验。通过对铣削力和加工表面形貌的对比,分析了纤维方向和每转进给量对加工表面质量的影响。结果表明:主切削力随着每转进给量的增大而增大,0°方向纤维受到的主切削力最大,90°方向纤维受到的主切削力最小;0°方向纤维表面破碎树脂与纤维的残留随着每转进给量的增大而增多,135°方向纤维表面树脂粘附逐渐减小;90°方向纤维表面会有大小不同的微坑,同时在样件上、下表面易产生分层缺陷,45°方向纤维表面多呈现沟槽或波浪形形貌。  相似文献   

15.
A new type of translation-rotation encoder that makes use of two identical transparent dielectric gratings lighted in a -1-order Littrow mount is proposed. The correct choice of the wavelength-to-groove-spacing ratio produces only two transmitted beams, which interfere with the highest possible visibility in a large range of experimental conditions. Thus this mounting permits high-accuracy encoders to be produced by the use of cheap photoresist or plastic gratings and opens the way to industrial applications in high-precision mechanics, information processing, etc.  相似文献   

16.
对两种莫尔条纹(光闸条纹和横向条纹)信号的谐波含量以及它们对光栅系统测量精度的影响进行了分析,并用实测数据加以比较,指出在光栅系统中,取横向莫尔条纹信号的谐波量小,正弦性好,细分误差小,在其它参数相同的情况下,可提高系统的测量精度2倍左右。  相似文献   

17.
赵霞 《光电工程》2003,30(4):34-38
提出了一种利用空域采样实现相移干涉计量的新方法和实验演示装置。演示装置使用倾斜镜或阶梯镜作为相移器件,线阵CCD做为光学传感器。实验表明:此方法非常适用于测量快速变化的目标或动态过程,其测量精度与传统时域采样相移技术相当但具有更好的稳定性和更高的测量速度,而测量范围是离焦量的2倍。  相似文献   

18.
The recording of holographic volume and surface-relief gratings in a photorefractive crystal using a photo-thermoplastic (PTP) holographic camera with an image-bearing signal beam leads to the appearance of two Bragg and two or more non-Bragg diffracted beams that show the transformed images in each beam (rotation and angular amplification of images). Using this real-time mode of interferometry, the hologram is retrieved with a deformed object beam, resulting in the appearance of fringes with a proper phase shift in each of four diffracted beams. This one-shot (one-exposure) phase-shifting interferometry results in clarification of the object wave-front information (for example, from surface deformation) and solution of the sign ambiguity problem. This procedure demonstrates that high-resolution holographic imaging of the PTP holographic camera static deformations in the order of ~0.1?mm can be revealed on the diffusion reflection surface. In addition, it was demonstrated that using the PTP materials could achieve holographic recording and imaging through phase aberration, with the image appearing in the non-Bragg diffraction order.  相似文献   

19.
The Talbot effect of a grating with different kinds of flaws is analyzed with the finite-difference time-domain (FDTD) method. The FDTD method can show the exact near-field distribution of different flaws in a high-density grating, which is impossible to obtain with the conventional Fourier transform method. The numerical results indicate that if a grating is perfect, its Talbot imaging should also be perfect; if the grating is distorted, its Talbot imaging will also be distorted. Furthermore, we evaluate high-density gratings by detecting the near-field distribution with the scanning near-field optical microscopy technique. Experimental results are also given.  相似文献   

20.
The properties of two-dimensional rod systems are examined, use being made of the complex potential in conjunction with the conformal-transformation technique. The concept of prescribed trajectories whereby stronger, effective, levitational forces can be obtained is introduced. It is shown that the high-gradient magnetogravimetric-separation system is amenable to scale-up since sufficient levitational force, in terms of the equivalent specific gravity, is generated. Examples of gratings with circular and different oval cross sections, which are subject to the magnetizing field in two alternative directions, are discussed.  相似文献   

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