A study on image recognition of three-dimensional objects by undestroyed photorefractive optical memory using two wavelengths
| Project/Area Number |
09650064
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Applied physics, general
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| Research Institution | Nagoya University (1998)
Tottori University (1997) |
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Principal Investigator |
NIIMI Tomohide (1998) Nagoya Univ., Faculty of Engg., Assocate Professor, 工学部, 助教授 (70164522)
原 豊 (1997) 鳥取大学, 工学部, 助教授 (60242822)
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| Co-Investigator(Kenkyū-buntansha) |
HARA Yutaka Tottori, Univ., Faculty of Engg., Assocate Professor, 工学部, 助教授 (60242822)
新美 智秀 名古屋大学, 工学部, 助教授 (70164522)
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| Project Period (FY) |
1997 – 1998
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| Project Status |
Completed (Fiscal Year 1998)
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| Budget Amount *help |
¥3,300,000 (Direct Cost: ¥3,300,000)
Fiscal Year 1998: ¥900,000 (Direct Cost: ¥900,000)
Fiscal Year 1997: ¥2,400,000 (Direct Cost: ¥2,400,000)
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| Keywords | Holography / Photorefractive effect / Undestroyed reading / BaTiO_3 / LiNbO_3 / Optical memory / Multi-image memorization / Image recognition |
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| Research Abstract |
Photorefractive crystal is very promising as a medium of hologram memory because it does not require a process of development unlike an usual photographic plate and it has a large capacity of memory by three-dimensional storage of the information of an objective wave. However, when using a photorefractive crystal like a lithium niobate (LiNbO3) with a long-term storage of memory, it needs long time for writing process. In general, the use of the same wavelength as the writing process gradually erases the information through the reading process. Therefore, a new method that enables both quick writing and long-term readout has been expected. In this study, as a method for undestroyed readout, we propose the use of laser beam with different wavelength from the writing process and carry out fundamental experiments for its effectiveness. In addition, we apply the photorefractive memory to the image recognition of three-dimensional objects.
A photorefractive crystal of barium titanate (BaTiO3
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), which has a transmissibility strongly dependent on the wavelength in the visible spectrum, was employed for the experiments of readout without erasing the stored information. A YAG laser (532 nm) was used as a light source for the writing process and an infrared LD (785 nm) for the reading process. The two wavelengths correspond to the high sensitive and insensitive regions of BaTiO3, respectively. The experiments made clear that the information stored quickly by the shorter wavelength from the YAG laser can be read out by the longer wavelength from the LD for about 10 times longer-term than readout by the original shorter wavelength. However, a whole image of the stored information could not be reproduced because of discrepancy of the Bragg angles between the shorter and longer wavelengths. Broadening the range of incident angle of the readout light by use of a cylindrical lens turned out to be effective for improvement of the reproduced image.
A LiNbO3 crystal was used in the experiments for image recognition. The diffractive beam intensity, which depends on the similarity between the memorized image and the input image, was measured. A preliminary experiment using four two-dimensional images as the objects made clear that it was possible to recognize a specific image among other images by comparison of diffractive beam intensities. For recognition of three-dimensional objects, three coins were used as the objects. The three-dimensional objects could be distinctly recognized by the existence of the diffractive beam alone owing to the closer Bragg condition. The combination of the undestroyed readout and the three-dimensional recognition using a photorefractive crystal can be applied to identification of an object, position sensing, and so on. Less
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Report
(3 results)
Research Products
(5 results)
