Minoru Toyama

Unevenness of illuminance caused by gradient-index fiber arrays

A theoretical study of unevenness of illuminance on the image plane of a gradient-index fiber array is discussed under the first-order approximation.

Gradient-index objective lens for the compact disk system

A radial gradient-index aplanatic singlet pickup objective lens for the compact disk (CD) system has been designed, manufactured, and evaluated. A plano-convex aplanatic singlet was designed by optimizing the refractive-index coefficients of the gradient-index medium, lens thickness, and one curvature. The necessary ion exchange technology and surface fabrication technology have been developed to successfully fabricate the objective lens. The gradient-index singlet was mounted in a CD player, and tests confirmed that the lens meets the system requirements.

Spherical aberration of gradient-index rod lenses

Spherical aberration was measured and, by carrying out the computer simulation for ray tracing with the approximate solution of ray equation, the refractive-index distribution parameters of a gradient-index rod lens were determined to most fit the observed data.

Gradient-index lens for low-loss coupling of a laser diode to single-mode fiber

Plano–convex gradient-index lens coupling a laser diode to single-mode fiber was designed and fabricated by the ion exchange technique. A low coupling loss (2 dB) was achieved.

Luminous intensity of a gradient-index lens array.

The illuminance of a gradient-index lens array is analyzed theoretically, and some examples of the design of a line scanning optical system are discussed.

Complementary two-dimensional laser Doppler velocimeter with an optical fiber probe

Optical probing and interferometric sensing techniques have great advantages of non-loading, high resolution and wide dynamic range for motion measurement of a solid object. For this purpose, laser Doppler velocimeter (LDV) is widely utilized. However, optical measurement of two dimensional (2D) motion is a hard problem for a conventional LDV, because the instrument has a big frame size and heavy wight, and requires stable measurement environment such as an optical bench or a rigid base. In this paper, we discuss a newly proposed 2D LDV with a compact remote sensing probe. Laser light is bidirectionally transmitted via two optical fibers from a base unit to the probe head. The system is designed to measure a specific solid object that moves in 2D plane such as an optical pickup head equipped in an optical data storage system. As testing of the system, 1D displacement, velocity and acceleration of a moving membrane of a loudspeaker and 2D motion of a moving optical pickup actuator were successfully measured.

Axial Gradient Index Singlet Collimator Lens For The Compact Disk System

An axial gradient index singlet collimator lens for use in the compact disk system has been designed and successfully fabricated. Cost and manufacturing constraints have led to a plano-convex design with the axial gradient index profile symmetric about the plane, perpendicular to the optical axis, passing through the center of the lens. Diffraction limited performance has been obtained in the collimator singlet.

Design Of An Aplanatic GRIN Singlet For The Compact Disk System

A radial gradient index aplanatic singlet pickup objective lens for the compact disk (CD) system has been designed, manufactured, and evaluated. We have realized a piano-convex aplanatic singlet by optimizing the refractive index coefficients of the GRIN medium,lens thickness and one curvature. The GRIN singlet was mounted in a CD player and tests confirmed that the lens meets the system requirements.