社会情報学部　社会情報学科
榎並　直子　准教授
専門分野：知覚情報処理、パターン認識

風化の実態を読み解く新視点

　石造建築や着物（織物）など、時代を越えて受け継がれてきた文化財は、私たちの歴史や技術を伝える貴重な指標である。しかし、長い年月の中で、屋外の石材は風雨や紫外線、大気汚染に、繊維製品は退色や変質にさらされ、劣化は着実に進行する。こうした劣化は一度始まると後戻りできず、適切なタイミングで「今、どんな状態か」を正確に把握できるかが、保存の成否を左右する。

光学情報から立ち上がる素材の素性解析

　榎並研究室では現在、東京電機大学、本学建築学部との共同研究体制のもと、石材および織物などの劣化を光の反射（スペクトル）解析する手法を探求している。研究対象の一つが、国の登録有形文化財である甲子園会館（本学建築学部学舎）の石材である。同施設は屋外石材の風化が確認され、科学的根拠に基づく状態把握が課題である。

　研究では、複数の光学センサーを用いて表面のスペクトル情報（光の指紋）を取得し、それを画像として位置に対応させることで、石材内部で起きている組成を詳細に（画素レベル）で「見える化」する環境を構築している。この計測を通じて、高解像度な反射特性データを取得し、劣化状況を科学的に特定することを目指す。初期の解析では、異なる石材間でスペクトルに明確な違いがあることが確認され、非破壊で素材を分類できるという実証的な見通しを得た。

　さらに榎並准教授は、計測で得られた超精密な色や素材のデータを、次にどのように使うかに力を注いでいる。

　このデータを、CG（コンピュータグラフィックス）で立体物を作る際の色の設定や質感として利用している。これにより劣化前の色彩や素材感を忠実に再現した「デジタル上のタイムカプセル」を完成させることができる。CG上で素材の劣化分布を可視化することで、専門家は現物に触れずに修復計画を立てるためのシミュレーションを行うことが可能になる。また、当時の人が見ていたであろう状態を体験できる展示手法も実現し、「人の営みのレガシー」を次世代へ確実につなぐことができる。

非破壊計測が導く保存活用の新基盤

　この研究の社会的価値は、文化財保護分野にとどまらない。日本が誇るカメラ・センサー技術を基盤とする非破壊計測と高解像度データ解析の技術は、汎用性が非常に高い。文化財保護分野だけでなく、社会インフラ（道路や橋の劣化診断）、スマート農業（作物の健康診断）、車載センサーなど、幅広い分野での応用も期待されており、研究の社会実装に向けた価値は非常に大きいといえる。

　また、持ち運び可能な光学センサーは、海外の遺跡や発展途上国の文化遺産にも応用でき、世界規模での文化財保護に寄与する。現地に大型機器を搬入できない環境でも非破壊計測を実施できる意義は大きく、国際協力の新たな選択肢を拓く技術である。

　今後は博物館や修復機関と連携強化することで、研究領域はさらなる広がりを見せるだろう。榎並准教授が目指すのは、失われていく文化遺産の姿や情報をデジタル上に正確に遺し、これまで把握できなかった状態や変化を可視化しながら、未来の保存と活用に資する新たなデータを蓄積していく社会である。光を読み解く技術を軸に、文化財の価値と人の営みの記録を次世代へ確かにつなぐ取り組みは、これからも深化していく。

School of Social Informatics, Department of Social Informatics
Associate Professor Naoko Enami
Areas of specialization: Perceptual information processing, pattern recognition

Optical Technology Pioneering the Future of Cultural Heritage: Passing Down the “Legacy of Human Endeavors” with Non-destructive Measurement

A new perspective to understand the reality of material deterioration

Cultural properties, such as stone architecture and traditional textiles such as kimonos that have been passed down through the ages are valuable indicators that convey our history and technology. However, over the course of many years, outdoor stone materials are exposed to wind, rain and ultraviolet rays as well as air pollution, while textile products are subject to fading and degradation. In both cases, deterioration steadily progresses. Once this type of deterioration starts, it cannot be reversed. The success or failure of preservation depends on whether “the current state” is accurately assessed at the right time.

With conventional measurement methods, there is the risk of damaging the cultural property materials from contact as well as the limitations of on-site use due to large equipment such as X-ray equipment. What is needed is “optical measurement technology” that can safely obtain material information non-destructively, without damaging the cultural properties. Associate Professor Naoko Enami stresses the importance of this field of research stating that “Technology that measures the progress of weathering in a high-resolution, non-destructive manner will become the basis for the long-term protection of cultural properties.”

Analysis of material properties based on optical information

Currently, at the Enami Laboratory, under a joint research system with Tokyo Denki University and our university’s Department of Architecture, they are researching methods for analyzing the deterioration of stones and textiles using light reflection (spectrum). One of the properties targeted for this research is the stone material of Koshien Hall, the registered tangible cultural property which is also the school building for our Department of Architecture. Weathering of the outdoor stone for this facility has been confirmed, and the challenge is how to make a scientific assessment of the current state.

In this research, spectral signature is obtained using multiple optical sensors and by making that information correspond to the position as an image, they are building an environment where the composition occurring inside the stone can be “visualized” in detail (pixel level). They are aiming to scientifically identify the state of deterioration by obtaining high-resolution reflection characteristic data through this method of measurement. In the initial analysis, it was confirmed that there are clear differences in the spectra between different stone materials and they obtained the empirical evidence that materials can be classified non-destructively.

Furthermore, Associate Professor Enami is now focusing on how this ultra-precise color and material data obtained from the measurements can be used next.

This data is being used in computer graphics (CG) for color settings and textures when creating three-dimensional objects. In this way, a “digital time capsule” that faithfully reproduces the color and texture of the material before deterioration can be completed. By visualizing the deterioration distribution of the materials in computer graphics, it becomes possible for experts to perform simulations for developing a restoration plan without having to touch the actual item. Additionally, realizing an exhibition method that allows audiences to experience the conditions as the people at that time would have seen them would ensure passing the “legacy of human endeavors” on to the next generation.

New foundation for preservation and utilization led by non-destructive measurement

The social value of this research is not limited to the field of cultural property protection. Non-destructive measurement and high-resolution data analysis technology, which is based on the camera and sensor technology that Japan prides itself on, is highly versatile.

It can be said that the value of this research in terms of real-world application is extremely large, as it is also expected to be applied not only in the field of cultural property protection, but in a wide range of fields including social infrastructure (road and bridge deterioration diagnosis), smart agriculture (crop health assessment), and car sensors.

In addition, as optical sensors are portable, they can also be used at ruins overseas and cultural heritage sites in developing countries, contributing to the protection of cultural properties on a global scale. Being able to perform non-destructive measurements even in environments where large equipment cannot be brought to the site is highly significant. It’s a technology that will open up new options for international cooperation.

In the future, by strengthening collaboration with museums and restoration organizations, the scope of research will likely expand even further. Associate Professor Enami aims to create a society that accumulates new data that will contribute to future preservation and utilization by accurately preserving the images and information of cultural heritages that are being lost digitally while visualizing conditions and changes that could not be grasped until now. Efforts to ensure passing the value of cultural properties and records of human endeavors on to the next generation will continue to deepen, centered on the technology to decipher light.