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

光折变晶体作为全息图存储介质非常有前途，因为它不需要像普通照相底片那样的显影过程，并且通过三维存储物镜波的信息而具有大容量。铌酸锂（LiNbO3）等光折变晶体具有长期存储的能力，其写入过程需要较长的时间。一般来说，使用与写入过程相同的波长，通过读取过程逐渐擦除信息。因此，人们期待一种能够实现快速写入和长期读出的新方法，在本研究中，作为一种无损读出的方法，我们提出在写入过程中使用不同波长的激光束，并进行了基础实验。此外，我们将光折变记忆应用于强三维物体的图像识别。采用了钛酸钡（BaTiO3…更多）的光折变晶体，其透射率取决于可见光谱中的波长。在不擦除存储信息的情况下进行读出的实验使用YAG激光器（532 nm）作为写入过程的光源，并使用红外LD（785 nm）作为读取过程的光源。这两个波长对应于高灵敏度和高灵敏度。实验表明，YAG 激光的较短波长快速存储的信息可以通过 LD 的较长波长读出，时间比原始读出的时间长约 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，无法再现所存储信息的整个图像，因此通过使用柱面透镜来扩大读出光的入射角范围。图像识别实验中使用了 LiNbO3 晶体，测量了衍射光束强度，该强度取决于存储图像和输入图像之间的相似性。四个二维图像作为物体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。对于三维物体的识别，使用三个硬币作为物体可以被清楚地识别。由于更接近布拉格条件，仅存在衍射光束，将未破坏的读出与光折变晶体的三维识别相结合，可应用于物体识别、位置传感等。