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A study on image recognition of three-dimensional objects by undestroyed photorefractive optical memory using two wavelengths

两种波长无损光折变光存储器三维物体图像识别研究

基本信息

批准号：
09650064
负责人：
NIIMI Tomohide
金额：
$ 2.11万
依托单位：
Nagoya University (1998)Tottori University (1997)
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1997
资助国家：
日本
起止时间：
1997 至 1998
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-09650064/
关键词：
Holography Photorefractive effect Undestroyed reading BaTiO_3 LiNbO_3 Optical memory Multi-image memorization Image recognition

项目摘要

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 … More ), 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

光折变晶体是一种很有前途的全息存储介质，因为它不像通常的照相干板那样需要显影过程，并且它通过三维存储物波信息而具有大容量的存储。然而，当使用具有长期存储器存储的光折变晶体如铌酸锂（LiNbO3）时，写入过程需要长时间。通常，使用与写入过程相同的波长通过阅读过程逐渐擦除信息。因此，人们期待一种既能快速写入又能长期读出的新方法。在本研究中，作为一种无损读出的方法，我们提出了使用不同波长的激光束从写入过程中，并进行了基础实验，其有效性。此外，我们还将光折变存储器应用于三维物体的图像识别， ...更多信息），其透射率强烈依赖于可见光谱中的波长，被用于读出而不擦除存储信息的实验。YAG激光器（532 nm）用作写入过程的光源，红外LD（785 nm）用于阅读过程。这两个波长分别对应于BaTiO 3的高灵敏区和不灵敏区。实验表明，通过来自YAG激光器的较短波长快速存储的信息可以通过来自LD的较长波长读出，其时间比通过原始较短波长读出的时间长约10倍。然而，由于较短波长和较长波长之间的布拉格角的差异，不能再现存储信息的整个图像。通过使用柱面透镜扩大读出光的入射角范围，可以有效地改善再现图像。衍射光束强度取决于存储图像和输入图像之间的相似性。使用四个二维图像作为对象的初步实验表明，可以通过比较衍射光束强度来识别其他图像中的特定图像。为了识别三维物体，使用三个硬币作为物体。由于更接近布拉格条件，仅衍射光束的存在就可以清晰地识别三维物体。利用光折变晶体的非破坏性读出和三维识别相结合，可应用于物体识别、位置传感等。Less