Tsukasa Yamashita

Low-wavefront aberration and high-temperature stability molded micro Fresnel lens

A high-diffraction efficiency (>50%), small lens diameter (0.5 mm phi ), short focal length (1 mm), and thin (0.25 mm) molded micro Fresnel lens suitable for compact optical devices is discussed. The device is fabricated by means of a photopolymerization process using a UV-curable resin. By adopting glass as the substrate, low-wavefront aberration (<0.04 lambda , RMS value) and diffraction-limited focusing characteristics have been obtained at ambient temperatures between 20 degrees C and 100 degrees C. These characteristics are superior to those in a conventional aspherical plastic lens.<<ETX>>

Road surface recognition sensor using an optical spatial filter

A road surface recognition sensor has been realized by using an optical spatial filter. The sensor transforms a road surface image into spatial frequency spectra. Frequency distribution depends on the road surface type. Ground velocity is shown by a filtered moving image. Experimental results show that five road surface types were recognized in cold districts. Both road surface condition and vehicle velocity can be detected by a noncontact sensor; therefore, the sensor is useful for active safety systems.

Grating beam splitting polarizer using multilayer resist method

Recent trends in laser application systems such as optical information systems, optical network systems, and optical measurement systems have increased the need for small size, light weight, low cost, and mass producibility. Advantages of a micro grating device in laser application systems are high integration capability, design flexibility, and mass producibility. In particular, several approaches have been presented for the application of micro grating devices to optical heads for CD players. However, few studies have been made to apply to MO disk heads. This is because it is difficult to realize polarization separation. In this paper, we propose a grating beam splitting polarizer based on form birefringence, which has several applications to MO disk heads including polarization separation, optical path separation, and signal detections. The polarization separation characteristics as a basic operation of the grating beam splitting polarization have been confirmed. The resultant extinction ratios obtained were -7 dB for the ordinary light and -6 dB for extraordinary light.

ZnS micro-Fresnel lens and its uses.

A micro-Fresnel lens replication method by inorganic material deposition has been developed. A ZnS micro-Fresnel lens and a completely flat micro-Fresnel lens have been made by this method. The ZnS microFresnel lens stability characteristics are improved for temperature, humidity, and focusing. Furthermore, higher resolution in electron-beam lithography is made possible by lens thickness reduction. The completely flat micro-Fresnel lens is a new device and improves integration performance. This lens can be applied to stacked planar optics devices for use in the construction of 3-D optical circuits.

Microdisplacement sensor using a polarization-maintaining optical fiber

Abstract A microdisplacement sensor that measures displacement with a 0.1 μm resolution and covers 0 to 100 mm range has been developed using a polarization-maintaining optical fiber. The compact sensor probe, which has a wide operating temperature range, is suitable for applications in the machining industry. This sensor eliminates the influence of the reflected light from the incident end of an optical fiber whose optical path length is larger than the coherence length of the semiconductor laser fight. The incident optical system with a rod lens fixed to the optical fiber provides a high incident efficiency and a large misalignment tolerance.

Optical axle-counting equipment

An axle-counting equipment using a laser-scanning range finder has been proposed and developed for the first time in order to improve the accuracy of vehicle classification in nonstop electronic toll collection systems. Because of laser-scanning at the high frequency the high-speed response of 6 msec for the axle-detection allowed a vehicle traveling at speed over 60 km/h. Although the wheel is black colored, the laser-scanning range finder based on optical triangulation clearly produced range images. The equipment using newly developed model matching algorithm successfully distinguished into three states, that are, road surface, axle on road, and the lower body of vehicle above road. Because of noncontact detection, high durability should be expected.

Compact vehicle sensor using a retroreflective optical scanner

A compact vehicle detection and separation sensor that employs an optical scanner and retroreflective optical system has been proposed and developed for the first time for toll gate systems. The compact size of 150 mm/spl times/130 mm/spl times/200 mm allows easy installation and the tidy appearance of the gate. The sensor that repetitively scans pulse modulated and rectangularly shaped LED light successfully distinguishes between a tailgating vehicle which closes to 300 mm tail to nose at 60 km/h and a vehicle with a trailer jointed with a /spl phi/ 50 mm pole.

Planar microlens arrays using stumping replication method

A planar micro lens array, in which a surface-relief micro lens array is built into the glass substrate using a stamping replication method, has been developed for parallel optical components. The planar micro lens array has completely flat surfaces on both sides, and therefore other parallel optical devices can be monolithically composed in tandem. Furthermore, a high thermal reliability for axial alignment is made possible by the adoption of the same material of the substrate as that of the others. In this paper, we review the fabrication method of this planar microlens array using a stamping replication method and discuss the advantages of its use with liquid crystal displays.

Mass-producible optical guided-wave devices fabricated by photopolymerization

Mass-producible optical waveguide devices and their fabrication method for integrated optics are described. Single-mode polymer rib waveguides and grating couplers in planar polymer waveguides which are a key component for organic integrated optical devices have been successfully developed by using photopolymerization (2P) method. The method is based on an electron-beam lithography technique for writing original patterns and a replicating technique using a molding stamper.

Micro-Fresnel lens fabricated by electron-beam lithography

Novel electron-beam lithography techniques for fabricating micro Fresnel lens are proposed. A high performance blazed-micro Fresnel lens with a diffraction efficiency of 65% and an RMS wavefront aberration ofO.03A was obtained.