TOP > Sensor

Sensors used in OSV


Light Emitting Deformation Sensor(Manufactured by Hokuto Electronics,Inc.)

Japanese Patent No. 5320651In-Situ Device for Displaying Deformation of Natural and Artificial StructureswithColored Light This device is comprised of a wire and spring connected in series.
A measurement is taken of the relative displacement between two points,
in this case as elongation of the spring, and represented by the color of the LED light source.

Installation of light emitting deformation sensorson significantly deformed cross-sectional surfaces facilitates the confirmation of reinforced support structure integrity.
(Cooperation: East Nippon Expressway Co., Ltd, Konoike Construction Co., Ltd.)

Once the open-cut tunnel’s main body was complete, light emitting deformation sensors were installed during the strut removal process. In this example, loosening one of the jacks resulted in a yellow light from a nearby deformation sensor clearly displaying a small amount of deformation.
(Cooperation: Hanshin Expressway Co., Ltd, Nishimatsu Construction Co., Ltd.)

Using multiple light emitting deformation sensors produces a Christmas tree-like effect.


Light Emitting Inclination Sensor(Manufactured by Akebono Brake Industry Co., Ltd.)

Outfitted with two internal acceleration sensors maintained at 50℃, the LEIS precisely measures the inclination of a structure and displays the resultant data as colored light.
Angular measurements with accuracy within 1/100 degree are achievable.

The LEIS made its debut at OSV Consortium’s first international project in New Delhi, India.

Girders become heavier and longer as construction progresses.

During this process the girder is supported by the main bridge piers and temporary trusses, with each support point only capable of supporting a span length of around 4.5m. As a result, pouring concrete on either side of the lengthening girder causes the girder to lean in that direction. High-precision inclination sensors were introduced to measure the extent of this inclination. The sensor box was placed in a sunshade device and interior of the sensor box were kept at 50℃ to minimize the effects of ambient temperature on measurements. The maximum outside temperature during measurements was around 48℃. The system displayed final measurement data with tri-color rotating PATLITE LED signal lights. (New Delhi, India)

An easy-to-follow response to each light color was displayedon a board and shown to workers every day in both English and Hindi. (New Delhi, India)

Light emitting sensors used for an OSV project appear most vividly at nighttime. Only a glance at the color of each sensor’s light is required to establish the condition of the work site. Some of these lights are visible to the public, also enabling the surrounding residents to establish the site’s condition. The appearance of the rooftop laser as a red line is due to the existence of dust in the atmosphere around New Delhi, one of the region’s pressing environmental issues.
(New Delhi, India)

LEDS / rock bolt and anchor

Light Emitting Deformation Sensor(Manufactured by Hokuto Electronics,Inc.)

Japanese Patent No. 5181213 Wire Rod Deformation Detection Device
This device applies the LED concept to rock bolts and ground anchors. A thin cable experiencing the same deformation as the main anchor tendon is installed in a frictionless state and the expansion of a spring attached to that cable is displayed as colored light.

Example of a light emitting anchor functional test. The anchor’s axial tension can be visually identified at a glance. (Cooperation: SE Corporation)



Light Emitting Converter is a compact data logger that is capable of 1) converting analog signal from an arbitrary sensor into digital one, and 2) showing it by the color of LED light based on a pre-defined color scheme. A sensor to be connected to LEC can be chosen from a family of available sensors for measurement of deformation, strain, inclination, pressure, temperature, etc. The color scheme can be defined and changed later, if necessary, for each LEC-sensor unit by the control software installed on a PC. Up to 100 units of LEC and an arbitrary sensor can be connected to one personal computer. Each unit is given its own ID number and the data can be recorded on the hard disk or SD card with specified time interval. Five colors of choice can be used to visualize the measured data of arbitrary type.


Pressure of fresh concrete


Temperature and moisture in tunnel


Water quality (pH level)


Deformation in underground cavern


Bridge tower inclination


Deformation of a slope


Inclination of a building and retaining walls (New Delhi, India, 2011)


Inclination of retaining wall (Jakarta, Indonesia, 2015)


Stress in concrete


Inclination of a building and forces in strut beams (Bangalore, India, 2011)




Single Observation Point

Mirror is used to measure and visualize inclination. To execute this unique method, a mirror is first installed in a mobilized zone so that an observer can identify a light source, prepared in a stable and secured zone, in the mirror. If then the mirror starts to rotate, the observer would first find the reflected image of the light source moving in the mirror, then would lose its sight once the rotation exceeds a limit value determined by mirror size, distance between the observer and the mirror, and the distance between the mirror and the light source. An integrated system of measuring and visualizing inclination using this method allows a low cost monitoring system of arbitrary structures only from a unique point called a “Single Observation Point”.

sop sop
sop sop sop sop sop sop sop sop sop sop

LS³ / RR Sensor

Easy Water Detection ARMA 17-313

Experimental characterization of
in granular material by using optic fiber sensor
with an emphasis on Refractive Index of Light

A drop of water dryingslowly01 A drop of water dryingslowly02 A drop of water dryingslowly03

A drop of water drying slowly

Air,foam and water01 Air,foam and water02 Air,foam and water03

Air, foam and water

Box of sand wetted and dried01 Box of sand wetted and dried02 Box of sand wetted and dried03 Box of sand wetted and dried04

Box of sand wetted and dried

Specially designed data logger is used to record light collected by plastic optic fibers

Rock salt absorbing water01 Rock salt absorbing water02 Rock salt absorbing water03 Rock salt absorbing water04

Rock salt absorbing water

Akutagawa, S., Kobe University, Kobe, Japan

Machijima, Y., LAZOC, Tokyo, Japan
Sato, T., Asano Taiseikiso Engineering Co., Ltd., Tokyo, Japan
Takahashi, A., The General Environmental Technos Co., Ltd., Osaka, Japan

LS³ / RR Sensor water to ice

Experimental Observation of Hardening Process of Engineering Materials by Optic Fiber Sensor

ls3rrsw ls3rrsw

How RR sensor works:

This paper introduces RR sensor as its measurement concept was derived from the physics of Reflection and Refraction of light. In this sensor, light is first sent into Fiber 1 as indicated as L1, part of which is refracted as L2 leaving Fiber 1 and the rest is reflected as L3. Then, the light with the flux L3, reaches the side face of Fiber 1; part of it gets reflected, and the rest goes out of Fiber 1. The light that has just left Fiber 1 immediately reaches the side face of Fiber 2, where some of it gets reflected, and the rest finally goes into Fiber 2 as L3’. L3’, again, reaches the inclined face of Fiber 2 and what has happened before on the inclined face of Fiber 1 occurs again in the same manner; the paths of light in Fiber 2 are defined with the fluxes of L4 and L5. The important fact over this sequence of how light travels across two inclined faces is that the magnitude of flux L5 depends primarily on Δn, which is the difference between refractive index of POF, 1.49, and that of the surrounding material.

Future potentials of RR sensor:

As the sensing principle lies in the detection of change in Δn (difference between refractive index of plastic optic fiber and that of surrounding material) with time, RR sensors could be used to detect presence of water, phase change of water and ice, mortar hardening process and all other phenomena in which Δn changes with time, which would help rock mechanics engineers in many important projects.

■ Freezing and thawing of water/ice monitored by RR sensor

ls3rrsw ls3rrsw ls3rrsw

A plastic cup was half-filled with water at room temperature and placed in a freezer. The change in light intensity of L5 was then monitored as the water cup was kept in the freezer, where the temperature gradually went down to approximately -30 °C for about 2 hours. The frozen water sample was then taken out of the freezer as shown and the change of L5 was monitored for another 1 hour after that. The measurement results in the freezing process and the melting process are shown in the figure on the left. It can be seen that the freezing front of ice in the water cup reached the position of the RR sensor at around 96th minute as L5 sharply rose from the initial level of approximately 50 up to values over 800. It is supposed that this jump occurred when water around the RR sensor was frozen, and the refractive index there changed from 1.33 (water) to 1.31 (ice). In contrast, the light intensity of L5 dropped sharply at around the 19th minute in the figure on the right, as the ice around the RR sensor melted back to water.

■ Freezing of half-saturated ground monitored by RR sensor

ls3rrsw ls3rrsw ls3rrsw

A sample of fine ?sand was prepared in a glass cup. The bottom-half of this sample was saturated with water and two RR sensors were installed in the upper dry zone and the lower wet zone. The light intensity obtained from the RR sensor in the wet zone showed multiple steps, indicating that the light intensity around the RR sensor increased as the water was turned into ice, as shown in the figure on the left. The exact cause for this steps formation is yet to be investigated; however, it is suggested that sand particles near the RR sensor were moved as the freezing process around caused expansion of the frozen zone. In contrast, the results obtained by the RR sensor in the dry zone revealed no sharp increase in the light intensity, as shown in the figure on the right. This is believed to be linked to the fact that there was basically no water around this RR sensor and the only cause for small variation of data is the small deformation of sand particles in the dry zone due to the expansion of the frozen zone on the bottom of the specimen.

■ Freezing of saturated ground monitored by RR sensor

ls3rrsw ls3rrsw ls3rrsw

A slightly larger sand specimen with a height of 100 mm was prepared in a cubic container (150 mm×150 mm×150 mm) and was fully saturated. Then, four RR sensors were installed at different positions; hence, the freezing front would reach them at different times. The three dimensional x-y-z coordinates of these 4 monitoring points were: Point 1 (75 mm, 75 mm, 75 mm), Point 2 (75 mm, 75 mm, 50 mm), Point 3 (100 mm, 75 mm, 50 mm), and Point 4 (125 mm, 75 mm, 50 mm). The results shown on the left reveal that the freezing front reached Point 4 first, Point 3 second, Point 2 third, and finally Point 1. This order may not agree with the order anticipated from the distances between each RR sensor and specimen boundary faces, but the results simply show how the specimen was frozen with respect to time. This result suggests that multiple RR sensors installed in ground can be used to identify progress of ground freezing operation in-situ, which is sometimes difficult if the only information source to judge whether water is actually frozen is temperature.

■Cement hardening process monitored by RR sensor

ls3rrsw ls3rrsw ls3rrsw

A couple of mortar samples were prepared using so-called “quick dry cement,” so that hardening process of mortar in plastic cups could be monitored by RR sensors. The RR sensors were installed immediately after water was added to and mixed with the quick dry cement. The results are shown on the left indicating how the light intensity changed as both specimens hardened over time. Because of a special chemical additive used for the quick dry cement, the light intensities rose quickly in the first few minutes and then they kept increasing gradually as time elapsed and hydration process progressed.

■ Freezing and subsequent cement hardening process monitored by RR sensor

ls3rrsw ls3rrsw

First, the sample was created in a plastic cup by mixing the quick dry cement with water with an RR sensor already installed. The sample was then immediately put in the freezer and was kept there for about 44 hours. The light intensity measured in this process is shown on the left. The rise of the light intensity at the beginning is believed to be partly due to the hardening effect caused by the special chemical additive for the quick dry cement and also due to freezing that occurred to the specimen. A gradual rise of the light intensity after the initial rise is due to the fact that light intensity reading is affected slightly by low temperature (approximately -30 °C).


The sample was then taken out of the freezer and the monitoring continued for the next 48 hours, as shown in the figure on the immediate left. The first flat part that lasted for about 350 minutes seems to be corresponding to the melting process of the sample. The following rising part of the measured light intensity is believed to represent the hardening process that resumed after the sample was completely melted and hydration process continued at relatively low temperature.

Akutagawa, S. (
Tanaka, Y. (
Kobe University, Japan


g-flash enzan

G-Flash is a generalized scheme for re-distributing measured information wirelessly to data receivers equipped with LED, so that values of measured displacements, for example, can be shown as flashing color of LED light determined from pre-defined threshold values used for safety management. The system is applicable for pseudo real time visual presentation of measured information in tunnels, slopes, embankments, bridges, and so on to improve safety management practices.


Measured data are compared with pre-determined threshold values for safety management on a control PC to define a current level of data for each measurement location. Lighting instructions are then sent wirelessly to receivers that show management levels at each location by flashing LED with designated color.

Applicable to other various measurement systems with this real-time controlling system.

No cable wiring is required and battery for LED-equipped data receiver lasts for a month.

LS³ / Twin fiber and Gap sensors

A new optical fiber sensor for reading RGB intensities of light returning from an observation point in geo-materials

ARMA 15-784

Twin fiber

Light once out of the 1st fiber, hits surfaces of nearby particles and gets scattered. Part of the scattered light gets into the 2nd fiber which is digitally recorded. The properties of the returning light (intensity and color) are affected by many factors telling the story of what is happening at the tip of the fibers.

Twin fiber


By aligning the 2nd fiber in the line of the 1st fiber, a slightly different type of fiber sensor is formed. The Gap sensor is conveniently used to identify existence and properties of arbitrary materials between the two fibers.


Gap/arbitrary angle

Gap/arbitrary angle

By aligning the 2nd fiber at an arbitrary angle to the 1st fiber, a slightly different type of fiber sensor is formed. This type might be needed where geometrical constraint is present in installation of fiber sensors.

Using plastic optic as 1-pixel-camera

Akutagawa, S., Kobe University, Kobe, Japan
Machijima, Y., LAZOC Corporation, Tokyo, Japan

LS³ / digital

Light State Sensor System

PCT/JP2012/000971 Device for Detecting Deformation in Natural and Artificial Structures Capable of representing a wide range of state changes and phenomena using colored light, this device uses precision light sensors to both read and record visual information such as variations in brightness and color in areas experiencing a variety of natural phenomenon. Collectively referred to as LS³ (Light State Sensor System), this technique of sensing the state of light is divided into analogue and digital methods. The digital method (Lazoc Inc.) involves installing optical fiber in areas experiencing various phenomenon and using the tip of the optical fiber to record light-based information (light intensity, color, etc.) originating from changes in various natural states of arbitrary materials nearby. A set of optical fiber for lighting and another set for sensing is ideal considering the dark nature of most areas being monitored. This method is expected to be applied as a new method for unraveling a wide range of phenomenon consisting of solids, liquids, gases and mixed mediums.

Composition of LS³/digital system. A variety of useful information can be read by the tip of the optical fiber. This method has an extremely wide range of applications. (Lazoc Inc.)

LS³ / analogue

Areas experiencing deformation and inclination are fitted with a color filter and a white light source behind it. The movement of the area being monitored is directly connected to the filter’s movement, causing the white light to appear colored. A low-cost technique for representing deformation with colored light, this method offers a wide spectrum of applications through alternate filter settings and lighting arrangements.

Example of visualizing displacement ahead of a tunnel face using a color filter and optical fiber. (student experiment)

Example of visualizing displacement withmillimeterprecision using a colored filter. (student experiment)

LEIS / pocket

Light Emitting Inclination Sensor(Manufactured by Akebono Brake Industry Co., Ltd.)

An easily installable portable inclinometer for visuallyrepresenting the inclination of a structure ascolored light. The sensor can be setup in an extremely short time and is capable of high mobility on-site visualization-based monitoring.


Electrical Paper(Manufactured by Dai Nippon Printing Co., Ltd.)

A power saving display device for use with a wide variety of sensors that features extremely low running costs and can be freely customized. Even in the case of a power loss, the final image displayed can be maintained for a long period of time.

Electrical paper with a 5*5 grid. A power saving display device capable of displaying a variety of colors and patterns. Can also be flexibly connected to other sensors.


Mechanical tools

A simple, non-powered method of representing deformation and inclination using only mechanical movement. Development aims to produce a “must-have tool” for disaster prone areas implementing a thorough cost-cutting, smart design.


Chemical tools

Materials themselves can be effectively utilized if they feature built-in sensor capabilities. Our research focuses on new and unique functional materials in ongoing efforts to formulate a human network aimed at developing securitysurveillance systems for social infrastructure.


A temperature indicating label that changes color at the set temperature.
A variety of possible applications are anticipated both independently and in combination with other methods.
(Manufactured by Assey Co., Ltd.)

Page Top