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Displacement Sensor

Profiling has become a crucial practice for transportation departments throughout the world. Road builders, contractors and even US State DOT's (Departments of Transportation) are responsible for gathering statistical information on road surfaces including the longitudinal profile, mactrotextures, microtextures and roughness to determine coefficients of friction. The measuring tasks are especially challenging for most lasers because road surfaces present many dynamically-changing targets including tarmac, concrete, yellow striping, white striping, etc. Acuity developed special lasers to maintain a consistent sampling rate over varying targets.

Road surface profiling is an important part of highway and pavement engineering. Systems have been developed to collect real-time continuous highway-speed measurements of longitudinal profiles of road surfaces. From this data, engineers calculate International Roughness Index (IRI) or Ride Number (RN). Both of these numbers are expressions for the roughness (and therefore ride comfort) of a road surface.

Road profiling systems incorporate non-contact laser sensors to measure to the road surface and accelerometers to compensate for the effects of the vehicles movement. There are specialized road profiling systems for transverse profile, rut depth, macro texture and other shape characteristics.

The steel industry demands accurate measuring equipment to be used under difficult circumstances.

The environment is harsh, with high dust content and hot temperatures. The targets, hot metal, can be especially difficult because they radiate glowing light at elevated temperatures.

Acuity’s AR700 series is especially designed to measure to glowing targets. Most sensors used within this industry are equipped with the optional filter and high power laser option. The 20 mW diode generates a stronger signal for a stronger return signal back to the detector. The bandpass filter emits radiation except for a band of wavelengths close to the wavelength of the laser diode.

Dimensions are captured with either single or multiple sensors. Thickness measurements are achieved with the use of two opposing sensors and a standard, PC computer to perform the mathematics and to display the result, even at high speeds.

The sensors are often protected behind insulating glass or within a protective enclosure. Acuity offers customized enclosures for the AR600 sensors through Sequence Technologies, a measurement and controls company serving the steel industry. These enclosures can be either air or water cooled so that the sensor can be placed close to hot surface targets.

The AR1000 is a time-of-flight sensor that measures distance by a repidly-modulated and collimated laser beam that creates a spot on a target surface. Components of the reflected light signal are collected by a lens and focused onto a photodiode within the sensor unit. The reflected light returns with a shift in phase compared with the reference signal. From the amount of phase shift, a required distance is calculated with millimeter accuracy. The distance is transmitted through serial communications or analog outputs. Maximum ranges exceed 100 feet ( 30 m ) with the optional usage of reflectors.

Monitoring the position of trollies and hoists on bridge cranes in busy seaports requires accurate distance measurements afforded by the AR1000 laser distance sensor. Laser distance meters often replace damaged encoders. The position is continually monitored for crash-avoidance and for automated retrieval systems.

The AR3000 sensor is a time-of-flight sensor that measures distance by a rapidly-modulated and collimated laser beam that creates a spot on a target surface. Components of the reflected light signal are collected by a lens and focused onto a photodiode within the sensor unit. The reflected light returns with a shift in phase compared with the reference signal. From the amount of phase shift, a required distance is calculated with good accuracy. The distance is transmitted through serial communications or analog outputs. The device monitors the distance to ( and speed of ) objects in motion. The sensor has a range of 1000 feet ( 300 m ) to natural surfaces with 90% reflectance and to 1.8 mi. ( 3 km ) to special reflectors. A visible laser beam is used to aim the sensor.

Helicopter altitude measurement is an application that demands high performance for non-contact distance sensors. The AR3000 is well-suited as a laser altimeter, aiding pilots in gauging the distance to the landing pad. The AR3000 can measure 300 meters to natural surfaces and is perfectly capable of functioning outdoors. The high sampling rate means near-real-time updates to the pilot.

This sensor has also been adopted by developers of UAV's (Un-manned Autonomous Vehicles) for automatically measuring the distance to the ground.

Customers who use the AR3000 for this purpose and similar altitude measurements include NASA and other developers of unmanned aerial vehicle technology for research, defense and homeland security organizations.

One particular aerospace company used a pair of AR3000 sensors for measuring low and high altitudes. They selected the AR3000 with 10mRad divergence to measure 0-50 m and the AR3000 with 2mrad divergence to measure up to 50-300 m altitude. The 2mrad version was not successful at measuring to dark tarmac at close ranges so they added the second sensor for the altitude measurements on tarmac landings.

The AccuProfile™620 Laser Profile Sensor measures surface heights by projecting a beam of visible laser light that creates a line on a target surface. Reflected light from the surface is viewed from an angle by a two-dimensional CMOS detector array inside the AP620 sensor. The 2D contour profile is calculated by the scanner’s microprocessor from the pixel data from the diffusely - reflected laser line. The height distance profile is transmitted through ethernet communications to a PC computer. Real-time 3D profiling is created by synchronizing the position of the scanner with encoder inputs from conveyors, linear stages or robotic movements. A variety of models are specified, each to to allow a different measurement range and field of view.

This measuring instrument emits a laser line from a semiconductor laser diode. The laser class of the system may vary, depending the model's measurement range and standoff distance. Additionally, users control the laser power through configuration parameters set through the Ethernet interface. This control of laser power allow users to customize the sensor for particular target reflectivity, turning up the laser power for black surfaces and down for bright surfaces.

There are three different case designs for the AP620 series of laser profile sensors. Each has its own industrial design attributes and mechanical dimensions. The shortest-range units use the most compact case which has the minimal footprint. Mounting to this model is on the side and along the center axis, allowing fits into round tubes and other tight spaces. The longer-range scanners are in a larger case. All enclosures are robust in design and are rated IP67 for ingress of water and dust.

The AccuRange™ CCS Prima white light confocal displacement sensor is the most precise measurement system from Acuity. Using a novel optical principle of measuring the reflected light’s component wavelengths, these confocal sensors measure distance and position to within tens of nanometers. These compact probes can measure to opaque, shiny or even transparent surfaces.

Unlike the other Acuity distance sensors, the Prima Confocal systems are comprised of an optical measurement "pen" and a separate controller. This controller houses all of the electronics, light source, etc. Only emitted white light and reflected signals are passed between the pen and the controller via a thin fiber-optic transmission cable.

The Confocal-Chromatic Sensors (CCS) are offered in a variety of measurement ranges and standoff distances, each with corresponding resolutions. The shortest-range models resolve to 5 nanometers of height change!

AP620 2D Profile

CCS Prima White

Displacement

Displacement

Displacement

Displacement