Lianhua Jin

Shadow moire´ profilometry using the phase-shifting method

Two-stages are planned to measure the 3-D profile of objects by using the phaseshifting method, based on shadow moiretopography. The stages essentially consist of moving the grating vertically, which produces a change in the moirepattern, and rotating the grating, which results in a constant phase shift regardless of the moirefringe order. In practice, an additional stage of moving the grating horizontally has to be added, which averages the grating period and yields a better moirepat- tern. We aim to improve the shortcomings inherent in the conventional method, such as complicated operation of the optical arrangement, and our emphasis is on describing the novel methodology and justifying it by an error simulation test. The experimental results show that this tech- nique is available for practical applications.

Measurement of characteristics of magnetic fluid by the Mueller matrix imaging polarimeter

Optical characteristics of magnetic fluid are described and measured with the Mueller matrix. Furthermore, the optical activity of the magnetic fluid is discovered. A theory to determine the rotation ratio of two retarders of the Mueller matrix imaging polarimeter is also presented. To measure the entire Mueller matrix elements, due to the sampling theorem, the rate of 5 is chosen as the best and most unique for this polarimeter.

Shadow moire´ profilometry by frequency sweeping

A frequency-sweeping technique is proposed to measure the shape of objects with discontinuous height steps and/or spatially sepa- rated surfaces, which have been impossible to measure with conven- tional shadow moiretopography. By controlling the rotation angle of the grating, spatiotemporal moirepatterns are produced with different con- tour intervals. The Fourier-transform technique has been applied to ana- lyze these patterns and obtain the temporal carrier frequency, to which the height distribution of the object is related. Experimental results show the validity of this method.

Measurement of Dispersion of Effective Electro-Optic Coefficients r13E and r33E of Non-Doped Congruent LiNbO3 Crystal

The effective electro-optic (EO) coefficients r13E and r33E in the wavelength range 409–3390 nm were measured for non-doped congruent LiNbO3 crystal under constant stress by using the multiple reflection interference method, and the wavelength dispersion equation for each coefficient was obtained. Since the effective EO coefficient is related to the change of the refractive index due to the EO effect under constant stress and the change of the crystal length due to the inverse piezoelectric effect, it is a very important parameter for designing low-frequency optical devices.

Image detection system for 157-nm using fluorescent glass

An image detection system for vacuum ultra-violet region used a F2 laser (157nm) as a light source is proposed. A fluorescent glass (LUMILASS-G9) is employed to convert UV light into visible light. Characteristics of fluorescent glass are studied. Some beam profiles of F2 laser are analyzed as a demonstration of the imaging detection. A VUV interferometer is proposed.

Mueller matrix polarimeter in 157nm

A vacuum Mueller matrix polarimeter is developed for measurement of the Mueller matrix of samples, partially, calcium fluoride materials in 157nm wavelength. From the measured Mueller matrix with no sample present, we found the influence of absorption error in the detector and orientation error in quarter-wave plates on measurement results. The birefringence of samples is determined from the Mueller matrix. Experimental results show this Mueller matrix polarimeter is available to be used for characterizing the intrinsic birefringence of materials for processed lens at the 157nm lithography.

Performance of a television camera system for the detection of oil slicks

We performed some laboratory experiments to evaluate a television camera system for sensing oil slicks. This system captures the marked differences in intensity of sunlight reflected from the surface of the sea and from the slick. We also proposed a novel method to compensate for the wavelength dependence of sunlight and the quantum efficiency of the CCD arrays, which has been ignored up to now. During laboratory experiments, a glass plate coated with an Al 2 O 3 film has been employed instead of a real slick. The experimental results showed that detection probability depends on the sample thickness and, greatly, on the angle of incidence.

Development of television camera for detecting oil film floating on the ocean

A television camera system, which automatically picks out exclusive images of the oil at real time, is described. This system essentially consists of two optical band pass filters (BPFs), two CCD cameras and image processing software. Due to the multiple-beam interference resulted from the oil film, there is a marked difference of intensity between light reflected from the surface of the sea and that from oil film. By obtaining these different images, the place with oil can be distinguished. Emphasis of our work is to compensate the effect of dispersion of sunlight intensity and CCDs quantum efficiency on oil film detection probability. Laboratory experiments using static glass coated with Al2O3 film have been conducted. The experimental results showed that sensing probability is dependent on the sample thickness, and greatly on the incident angle. This result is agreed quite well with the simulation done our coauthors in earlier work.

Measurement of characteristics of magnetic fluid by Mueller matrix imaging polarimeter

The optical characteristics of the magnetic fluid are described with the Mueller matrix measured, furthermore, the optical rotary power of the magnetic fluid is discovered. A theory to determine the rotation ratio of two retarders of the Mueller matrix imaging polarimeter is also presented. To measure the entire Mueller matrix elements, due to the sampling theorem, the rate 5 is found as the best and the unique one for this polarimeter.

Two-dimensional birefringence measurement using liquid crystal retarder for plastic disk inspection

A plastic disk for the next generation of an optical disk and/or a hard disk requires high quality surface. Especially its flatness is very important. Moreover surface conditions of disks are very important for covered thin film. A plastic disk inspection system is proposed by using a two-dimensional birefringence distribution using liquid crystal rederders. If there is an internal strain or a residual stress in disk, small birefringence can be observed. It is necessary for the birefringence measurement to determine the relative retardation and the azimuthal angle of the fast axis in plastic disks. In this paper, a measurement system of two-dimensional birefringence distribution is proposed. Several images captured by a CCD camera are sufficient for one birefringence distribution analysis. These experimental procedures and the results of plastic disks are discussed.