Kanami Ikeda

High-speed holographic correlation system by a time-division recording method for copyright content management on the internet

Using a holographic disc memory on which a huge amount of data can be stored, we constructed an ultra-high-speed, all-optical correlation system. In this method, multiplex recording is, however, restricted to “one page” on “one spot.” In addition, signal information must be normalized as data of the same size, even if the object data size is smaller. Therefore, this system is difficult to apply to part of the object data scene (i.e., partial scene searching and template matching), while maintaining high accessibility and programmability. In this paper, we develop a holographic correlation system by a time division recording method that increases the number of multiplex recordings on the same spot. Assuming that a four-channel detector is utilized, 15 parallel correlations are achieved by a time-division recording method. Preliminary correlation experiments with the holographic optical disc setup are carried out by high correlation peaks at a rotational speed of 300 rpm. We also describe the combination of an optical correlation system for copyright content management that searches the Internet and detects illegal contents on video sharing websites.

Optical correlation-based cross-domain image retrieval system

A novel cross-domain image retrieval system that is based on a high-speed optical correlator with a coaxial holographic system is presented. Our newly designed conversion module for the optical correlator allows various kinds of data to be converted to pagedata with a uniform optical intensity by using an autoencoder, which is difficult with other conventional methods. By using our conversion module, an existing model for deep learning could be utilized as a feature extractor. A sketch-based cross-domain image retrieval system with the goal of discovering similar photos by querying freehand human sketches was experimentally demonstrated using our optical correlator. We believe that this proposed optical correlation-based system helps expand the applications of the optical correlator.

High-speed holographic correlation system for video identification on the internet

Automatic video identification is important for indexing, search purposes, and removing illegal material on the Internet. By combining a high-speed correlation engine and web-scanning technology, we developed the Fast Recognition Correlation system (FReCs), a video identification system for the Internet. FReCs is an application thatsearches through a number of websites with user-generated content (UGC) and detects video content that violates copyright law. In this paper, we describe the FReCs configuration and an approach to investigating UGC websites using FReCs. The paper also illustrates the combination of FReCs with an optical correlation system, which is capable of easily replacing a digital authorization sever in FReCs with optical correlation.

Microscopic optical path length difference and polarization measurement system for cell analysis

In recent years, noninvasive, nonstaining, and nondestructive quantitative cell measurement techniques have become increasingly important in the medical field. These cell measurement techniques enable the quantitative analysis of living cells, and are therefore applied to various cell identification processes, such as those determining the passage number limit during cell culturing in regenerative medicine. To enable cell measurement, we developed a quantitative microscopic phase imaging system based on a Mach–Zehnder interferometer that measures the optical path length difference distribution without phase unwrapping using optical phase locking. The applicability of our phase imaging system was demonstrated by successful identification of breast cancer cells amongst normal cells. However, the cell identification method using this phase imaging system exhibited a false identification rate of approximately 7%. In this study, we implemented a polarimetric imaging system by introducing a polarimetric module to one arm of the Mach–Zehnder interferometer of our conventional phase imaging system. This module was comprised of a quarter wave plate and a rotational polarizer on the illumination side of the sample, and a linear polarizer on the optical detector side. In addition, we developed correction methods for the measurement errors of the optical path length and birefringence phase differences that arose through the influence of elements other than cells, such as the Petri dish. As the Petri dish holding the fluid specimens was transparent, it did not affect the amplitude information; however, the optical path length and birefringence phase differences were affected. Therefore, we proposed correction of the optical path length and birefringence phase for the influence of elements other than cells, as a prerequisite for obtaining highly precise phase and polarimetric images.

Bio-imaging using planar lightwave circuit digital holographic microscope

We have proposed a digital holographic microscope using a planar lightwave circuit. Using the system, we report the evaluation of the spatial resolution and measurement of Closterium.

Optical–digital hybrid image search system in cloud environment

To improve the versatility and usability of optical correlators, we developed an optical–digital hybrid image search system consisting of digital servers and an optical correlator that can be used to perform image searches in the cloud environment via a web browser. This hybrid system employs a simple method to obtain correlation signals and has a distributed network design. The correlation signals are acquired by using an encoder timing signal generated by a rotating disk, and the distributed network design facilitates the replacement and combination of the digital correlation server and the optical correlator.

High-speed image matching with coaxial holographic optical correlator

A computation speed of more than 100 Gbps is experimentally demonstrated using our developed ultrahigh-speed optical correlator. To verify this high computation speed practically, the computation speeds of our optical correlator and conventional digital image matching are quantitatively compared. We use a population count function that achieves the fastest calculation speed when calculating binary matching by a central processing unit (CPU). The calculation speed of the optical correlator is dramatically faster than that using a CPU (2.40 GHz × 4) and 16 GB of random access memory, especially when the calculation data are large-scale.

High-speed optical correlator with coaxial holographic system

A high-speed volume holographic optical correlator is developed, which takes advantage of a coaxial holographic system. We have realized this high-speed correlator using an optimal design of the signal pattern, which improves the shift multiplex recording shift pitch. The speed of this correlator was further improved by increasing the number of pixels in the spatial light modulator and using a high speed rotating actuator. This correlation system successfully achieved an equal error rate of 0% by performing optical correlation over 900 times. It also achieved optical correlation experiment, at a shift pitch of 2.45 µm and a disk rotation speed of 900 rpm. In terms of optical correlation calculation speed, it yielded a peak interval of 542 ns, which corresponds to 1.846 × 106 frames per second.

Improvement of the correlation speed in an optical correlation system using a holographic disc

We developed an optical correlation system that has a potential to achieve data transfer speed higher than 110 Gbps. An equal error rate of 0% with a 2-µm recording pitch and a disc rotation speed of 900 rpm were obtained.