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Shiyuan YANG, Teruo SHIMOMURA
1998 Volume 5 Issue 6 Pages
327-330
Published: December 01, 1998
Released on J-STAGE: March 28, 2000
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It is well known that the off-axis reconstruction error is lower than the on-axis one due to the quantization in kinoforms. We show some new results about the on- and off-axis reconstruction of quantized kinoforms which are calculated by the iterative dummy area method. An analysis is made of the dependence of quantized kinoform reconstruction on the position of the desired image. We find that the reconstruction error changes periodically when the image position is changed, and that the off-axis reconstruction can reduce the reconstruction error more than the on-axis one when the multiple number of input image sizes in the horizontal and/or the vertical direction is larger than the quantization levels of kinoforms.
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Koji NONAKA, Hidehiko TAKARA, Atsushi TAKADA, Kentaro UCHIYAMA, Yoshia ...
1998 Volume 5 Issue 6 Pages
331-333
Published: December 01, 1998
Released on J-STAGE: March 28, 2000
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An optical mono-stable multivibrator laser diode (MM-LD) is realized by using a multi-electrode distributed feedback laser diode. All-optical pulse-width conversion of ultra-short pulses to non-return-to-zero (NRZ) is achieved using an MM-LD. The MM-LD is adopted for a wide range of bit-rates between 2-10 Gbit/s by tuning the DC bias. Data format transformation from 10-Gbit/s return-to-zero optical signals to NRZ optical-signals is achieved with error free operation. Converted optical signals, which have a narrower spectral bandwidth and lower peak power than when input, are transmitted using a 1.3-
mm zero dispersion fiber (1.3
l0-SMF).
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Yasuhiro TANAKA, Michihiro YAMAGATA, Tomohiko SASANO
1998 Volume 5 Issue 6 Pages
334-339
Published: December 01, 1998
Released on J-STAGE: March 28, 2000
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An erasable optical disk system requires an objective lens having minimum chromatic aberration. We estimated the chromatic aberration of a conventional refractive singlet. At shorter wavelengths, the focus shift of an objective lens exceeds its depth of focus. A diffractive-refractive hybrid lens can compensate chromatic aberration perfectly. Diffraction efficiency, however, decreases with the degree of compensation. We simulated the relationship between chromatic aberration and diffraction efficiency. Fabrication of designed lenses by glass molding was achieved, and the results showed excellent agreement with the simulation.
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Feng LEI, Hongxin HUANG, Nobukazu YOSHIKAWA, Masahide ITOH, Toyohiko Y ...
1998 Volume 5 Issue 6 Pages
340-347
Published: December 01, 1998
Released on J-STAGE: March 28, 2000
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An entropy network mapped from a binary feature tree is described and compared with the Hamming net. Implementation of the entropy network includes extracting features from an input and making the decision according to these features. The feature extraction in the first layer of the entropy network is implemented by an optical method. Optical implementation with an incoherent shadow casting correlation system is proposed, and experimental demonstrations are given. The processing capability of the proposed optical system is discussed.
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Seiji MURATA, Shigeki HORI, Yoshihisa SUZUKI, Satoshi SUMI
1998 Volume 5 Issue 6 Pages
348-351
Published: December 01, 1998
Released on J-STAGE: March 28, 2000
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We demonstrated characteristics of an optical super-resolution pickup using a liquid crystal (LC) shutter as a shading plate. The problem of laser power loss was solved by an LC shutter which was turned off for writing and turned on for reading. Combining this with CAD-MSR disk, we obtained good signals of high-density recording. This combination increases efficiency of laser power and does not require a slit to eliminate side-lobes. The laser power efficiency for writing is as high as 34% and linear bit density reaches 0.255
mm/bit even with a wavelength of 680 nm and an objective lens NA of 0.60.
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Shin–ichiroh KITOH, Hiroki TOKUOKA, Jun HASEGAWA, Tetsuo NONAMI, ...
1998 Volume 5 Issue 6 Pages
352-357
Published: December 01, 1998
Released on J-STAGE: March 28, 2000
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In endoscopic diagnosis, there has been a strong requirement to measure the internal surface topography of the rectum or esophagus. Accurate measurement, however, is very difficult, because the object is usually observed from an inclined view. In this paper, we propose a method to overcome this difficulty utilizing sequential stereo-pair images; the relative shape is roughly measured from sequential images taken by one of the change coupled device (CCD) cameras, and the size is determined by stereo-pair matching using the measured shape. A coarse-to-fine approach is also used to improve the resolution of topographic measurement. Through a basic experiment using a monocular CCD endoscope and a polyp phantom, the proposed method is confirmed to improve measurement accuracy in comparison with conventional methods.
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Yukio OKANO
1998 Volume 5 Issue 6 Pages
358-362
Published: December 01, 1998
Released on J-STAGE: March 28, 2000
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The spatial frequency response (SFR) for a digital still camera is affected by non-linear image processing. We analyze the influence of image enhancement processing and gamma correction on SFR characteristics by varying the edge chart contrast. SFR expressions depending on the chart image contrast are proposed, as is a measurement method of resolving power based on the slanted edge.
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Deyuan SHEN, Ken–ichi UEDA
1998 Volume 5 Issue 6 Pages
363-368
Published: December 01, 1998
Released on J-STAGE: March 28, 2000
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We report analytical and experimental studies on the characteristics of a high-brightness laser diode end-pumped Nd:YVO
4/KTP laser. A simple model was developed to optimize the cavity parameters and estimate the green output power of intracavity frequency doubled lasers. Using a 1 W high-brightness laser diode as the pump source, high efficiency operation was realized. The second-harmonic output power at 532 nm was measured to be 286.5 mW at an incident pump power of 881.4 mW, corresponding to an optical to optical efficiency of 32.5%.
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Takuya MATSUMOTO, Tsutomu ICHIMURA, Takashi YATSUI, Motonobu KOUROGI, ...
1998 Volume 5 Issue 6 Pages
369-373
Published: December 01, 1998
Released on J-STAGE: March 28, 2000
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We have developed a novel probe with a nanometric metallized protrusion extending through a subwavelength aperture to increase optical near-field excitation and collection efficiencies. The apex diameter of the fabricated metallized protrusion was 35 nm. The Intensity distribution of the optical near-field at the apex of the probe was measured by scanning another probe across the apex, and it was observed that strong optical near-field was generated at the apex of the metallized protrusion. The width of the intensity distribution was 150 nm including instrumental resolution. Probes with spherical and ellipsoidal metallized protrusion were also fabricated, by which enhancement of the optical near-field is expected due to localized plasmon excitation.
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Takahiro AOKI, Toshihiro SOTOMARU, Takeshi OZAWA, Takashi KOMIYAMA, Yo ...
1998 Volume 5 Issue 6 Pages
374-379
Published: December 01, 1998
Released on J-STAGE: March 28, 2000
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Noting the analogy between electro-magnetic fields and the vector fields of phase gradients obtained by heterodyne techniques, we propose a new algorithm for least-squares phase unwrapping. Instead of solving a Poisson equation for the unwrapped phase map or using Green's formulation, we directly remove singular points or residues from the measured phase map by superposing sign-reversed vortex fields which cancel out the rotational vector fields associated with the phase singular points.
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Mitsuo IKEDA, Hiroyuki SHINODA, Yoko MIZOKAMI
1998 Volume 5 Issue 6 Pages
380-386
Published: December 01, 1998
Released on J-STAGE: March 28, 2000
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Many experimental results have been reported which demonstrated deviation of the apparent lightness from the calculated lightness based on spectral reflectance, and these have caused debate among researchers as to the models to explain them. The judgement of lightness of objects that we see in the outside world is one of the most important tasks in our daily life. We proposed the recognized visual space of illumination, RVSI, as a three dimensional recognition constructed in the brain for the outside world, and showed that the apparent lightness was determined in relation to the size of the RVSI. In the present paper the concept was applied to various results of lightness experiments such as the White effect and simultaneous contrast, and based on the proposition that an observer first builds a three dimensional RVSI from a two dimensional pattern and the lightness of a test patch was judged in relation to the size of this RVSI, the results were then globally and nicely explained. A new demonstration of a pattern was proposed to give different apparent lightness for patches with the same physical lightness to strengthen the proposition. The importance of distinguishing between a test patch and a surrounding field was emphasized when one does a lightness experiment and interprets the results.
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Kouki SHIGA, Tiejun ZHANG, Motoki YONEMURA
1998 Volume 5 Issue 6 Pages
387-388
Published: December 01, 1998
Released on J-STAGE: March 28, 2000
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The effect of self-pumped phase conjugation (SPPC) feedback from a Ce:BaTiO
3 crystal on the lasing spectrum of a commercial laser diode was experimentally investigated, and dependence of the spectrum on the length and reflectivity of the external SPPC cavity was studied. Experimental results showed the optimum reflectivity of the external cavity to be 0.2% for our experimental setup.
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