Owing to the capability of noncontact measurement, optical profilometry is required for measurement of cylindrical openings for thin transparent objects, which are easily deformed and damaged by the contact of mechanical probes. In our previous work, we have developed optical profilometry for opaque and translucent objects. During measurement, disk shaped beam illuminates across the objects, and the intersection of beam with the objects is collected by an image sensor. When the surface of objects is rough enough to scatter light, the cross-sectional profile images are detectable by the sensor. The transparent objects have smooth surface so that reflection from the surface is much stronger than scattering. Consequently, the capture of intersection image becomes very difficult. In this work, we introduce the method to measure dimension of cylindrical openings for transparent objects. To generate the cross-sectional profile, the disk shaped beam illuminates the objects obliquely. The dynamic range of the oblique/ tilted angle was investigated for transparent objects measurement. Several transparent objects with cylindrical openings were employed for practical measurement. Measurement results showed the wall thickness strongly affects the measurement accuracy.
Using a see-through optical viewer with a prism combiner is an affordable solution for head mounted devices. Free-form surfaces are a general way to correct off-axis aberrations generated by combiners. A glass high index wedge prism is used as a combiner to keep the wedge angle small while maintaining total internal reflection and the combiner becomes thinner. Free-form surfaces, on the other hand, are used in relay lenses to correct off-axis aberrations. The diagonal FOV is 44° and the exit pupil diameter is 4.8 mm. After two optical design using XY and Zernike polynomial, we confirm which free-form expression is superior in aberration correction for the viewer.
Imaging ellipsometry (IE) possesses characteristics of both single-point measurement ellipsometry and optical microscopy. To obtain quantitative measurement, it is very important for design of the spectroscopic imaging ellipsometer to employ a correct imaging system, solve non-uniformities of optical components. Here, we introduce a reflection imaging system, measurement noises due to non-ideal optical components, and describe solutions of problems.
Dimensional measurement of internal profile is conventionally performed mechanically with instruments like vernier calipers. Here, we cope with the measurement by using an optical caliper. The caliper consists of a semiconductor laser, a right conical mirror, a lens system, and an image sensor. The concept of the measurement approach is intersecting the object with a disk light sheet, collecting the cross-sectional profile image with an image sensor, and extracting dimensions of the profile. Example of practical measurement is presented.
A method for extracting properties of individual components of a retader-linear diattenuator- retarder system is proposed. Since the evaluation performs in noncontact and nondestructive way, this method is applicable to inspect as-produced devices and optics. Example for its application to inspection of the polarizing beamsplitter is presented.
The Stokes parameters of scattering from diffuse glass plates were measured and analyzed as a function a virtual
scattering angle and a longitude scattering angle. Both of these scattering angles are defined for the facet model. The
facet model for scattering from a diffuse surface predicts the polarization states of scattering quite well. The method and
results of this analysis have a significant impact on the application of light scattering to the inspection and processevaluation
industry, material science, etc.
A new approach of Fabry-Perot (F-P) filter, where the optical length of cavity is tuned by using linear electro-optic (EO)
effect of crystals, is demonstrated with the numerical analysis. For achievement of polarization-independent tunability of
this filter, directions of light propagation and the external field applied are illustrated by means of the index ellipsoid. An
example of the F-P filter using LiNbO3 crystal is discussed and its tunability is analyzed.
Analyzing the state of polarization of these reflected beams by using Stokes parameters is used to characterize the natural
properties of the surface. We show the angle-resolved Stokes parameters of several objects with rough surface, and
derive depolarized components caused by scattering. The preliminary results offer our further investigation of the
relation between the optical performance and the structure of the rough surface.
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 Al2O3 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.
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 CCD's 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.
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.
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.
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.
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.
The frequency sweeping technique is proposed to measure the shape of objects with discontinuous height steps and/or spatially separated surfaces, which have been impossible to measure with conventional shadow moire topography. By controlling the amount of the rotation angle of the grating, the spatiotemporal moire patterns are produced with different contour intervals. The Fourier transform technique has been applied to analyze these patterns and obtain the temporal carrier frequency in which the height distribution of the object is involved. Experimental results show the validity of this method.
In order to measure 3-D surface of objects by using phase- shifting method, based on shadow moire topography, two stages are planned. The stages are moving the grating vertically, which produces a change in moire pattern; rotating the grating, which results in the constant phase-shift regardless of the moire fringe order. The paper emphasis is on describing the novel method, and justifying it by error simulation test. The experimental results show that this technique is available for some industrial fields.