Yoichi Kitagawa

Image velocity sensing using an optical fiber array

A noncontact velocity sensor with an optical fiber array is described. The end faces of optical fibers which are linearly arrayed at equal intervals act as the spatial filter for velocity sensing. The characteristics of this sensor are investigated in terms of the number of optical fibers, the fiber interval, and the object spectrum. The usefulness of this sensor is confirmed by calculations of the selectivity and experiments. Furthermore, it is shown that an imaging system with a cylindrical lens is effective for measuring the velocity of an object with a large sideway motion.

High-resolution rotation-angle measurement of a cylinder using speckle displacement detection

A new method for measuring the rotation angle of a cylinder is described, based on the speckle displacement detection caused by the cylinder surface rotation. It is shown that this method is effective for measuring the small rotation angle with high resolution. The accuracy, sensitivity, and resolution of this method are determined by the speckle size, detector pitch, and magnification of the speckle displacement. The configuration to obtain an accurate, sensitive, stable measuring system is discussed. The usefulness of this method is confirmed by experiments.

Fiber-optic sensor for distance and velocity measurements using speckle dynamics

A fiber-optic sensor for distance and velocity measurements is described which is based on dynamic properties of speckles formed by two illuminating laser beams. This sensor is composed of two optical-fiber laser guides and an optical-fiber-array spatial filter consisting of linearly arrayed endfaces of optical fibers. The measurable ranges of distance and velocity and their accuracies are expressed in terms of the sensors configuration parameters. The configuration for accurate sensing over a wide range is discussed. The usefulness of this sensor is confirmed by experiments.

SENSITIVITY-VARIABLE MOIRE TOPOGRAPHY WITH A PHASE SHIFT METHOD

We propose a projection moire´ topography with a phase shift method for measuring the fine profile of an object. In this method, a set of interference fringes made using a Mach-Zehnder interferometer and a dove prism is projected on an object surface to generate moire´ fringes. The interval between the moire´ fringes can be easily changed in a range of 160 to 300 µm and we can realize sensitivity-variable moire´ contouring. Also, the phases of the moire´ -fringe pattern are easily changed by shifting one of the interference fringe patterns and the depth at each point on the object are computed with a high accuracy from the several moire´ -fringe patterns with different phases. Although the interferometer is used in the system, the setup is robust against vibrations.

Moire topography for three-dimensional profile measurement using the interference fringes of a laser

Resolution-variable moire topography for measuring the three-dimensional profile of an object is described. With this method, moire fringes are formed by projecting two sets of interference fringes of laser beams on an object. The interference fringes are formed using a Mach-Zehnder interferometer and are divided into two sets by a beamsplitter. The image, including the moire fringes, which are formed in accordance with the object depth, is detected by an image sensor. The effectiveness of this method is demonstrated by practically measuring the profiles of a small object. The intervals between adjacent moire fringes could be experimentally changed from 0.16 to 1.6 mm. The advantage ofthis method is that the interval between moire fringes can be easily changed continuously by a mechanical operation.

Fiber-optic particle size monitor

A fiber-optic particle size monitor for on-line measurement is proposed. This monitor consists of a lightillumination probe and several pickup probes, which are composed of optical fibers and rod lenses. The characteristics of this monitor are discussed in terms of the configuration parameters, and some experimental results for confirming the operation are presented.

Profile measuring method based on reflection characteristics at a critical angle in a right-angle prism

A new method is proposed for profile measurements using a right-angle prism. With this method, the distance to an object surface is measured by using triangulation based on a change of the critical angle of total reflection. An object surface is illuminated by a scanning laser beam and the incident angle of the scattered light into the prism is measured using the change in the critical angle. Three-dimensional profiles of objects with rough surfaces can be measured with high accuracy.

Fiber-optic particle size monitor based on white-light scattering

A new fiber-optic particle size monitor for in situ measurement based on white-light scattering is presented. The particle size is determined from the ratio of two scattered light intensities taken at two wavelength bands. By using white-light scattering, the proper wavelength bands in the broad spectral region can be selected in accordance with the particle size that is to be measured. Then the measurable particle size range can be expanded and the particle size can be measured precisely. The performance of this particle size monitor is theoretically discussed, and experimental data from polystyrene latex suspensions are shown to confirm its operation.

Laser moire topography for 3-D contour measurement

The use of the phase shifting interferometric technique is discussed to make quantitative surface profiling using the Nomarski differential interference microscope. Lateral shift of the Nomarski prism introduces mutual phase shift between interfering two wavefronts with small amount of shear. Since the analyzed phase distribution corresponds to the differential of the surface profile under test, integration of the phase distribution gives the correct surface topography. The procedure for an analysis method and experimental results are presented.

Fabrication of an integrated holographic imaging element for a three-dimensional eye-gaze detection system

We evaluate the imaging characteristics of an integrated optical imaging element that is used to obtain images from opposite directions in one imaging sensor for a three-dimensional eye-gaze detection system. The element consists of a transmission-type holographic imaging element, a reflection-type holographic imaging element, and a noise reduction filter. In the evaluation of the imaging characteristics, modulation transfer functions of both the reflection-type and the transmission-type holographic imaging elements are evaluated. Results indicate that both holographic imaging elements have enough resolution, even under white-light illumination conditions, for eye-gaze detection. We also demonstrate the simultaneous detection of images by an artificial eye and objects by using the integrated element under white light or sunlight.