AR4000 Laser Range Finder

Acuity's AR4000 series of laser rangefinders are discontinued due to obsolescence issues with major components. Acuity will continue to service deployed AR4000 rangefinders.


The AR4000 laser rangefinder is Acuity's fastest sensor for measuring long distances. Employing time-of-flight measuring principles, the rangefinder can accurately gauge distances up to 54 feet (16.45 m).

Non-contact measurement is made simple with the three models within the AR4000 rangefinder series that have different laser diodes. All models are compact and durable, residing in a NEMA-4 enclosure for challenging industrial environments.

The AR4000-LIR laser rangefinder has a working range to 54 feet (16.5m) on light surfaces (85% diffuse reflectance, such as paper or light paint) or 35 feet on a 30% reflectance target with an accuracy of 0.1 inches (2.5 mm). It uses an infrared 780 nm 8 milliwatt laser. This is the sensor of choice for best accuracy in most applications. An optional 20 mW laser upgrades is also available for the AR4000-LIR sensor for extended range to darker surfaces (54 feet on 30% reflectance) and in sunlight.

The AR4000-LV rangefinder has a working range of zero to 40 feet (12.2 m) on light target surfaces or 30 feet on a 30% reflectance target with an accuracy of 0.3 inches (7.5 mm). It uses a visible 670 nm 5 milliwatt laser. This is the sensor of choice where a visible beam spot is required or your application must remain under and FDA Class 3B (EN 60825-1 Class 3B) laser category.

The AR4000-RET rangefinders are used with reflective tape supplied with the sensor. It is a low-power, Class I eye-safe device, with an accuracy of 0.1 inches with a range of 2 to 54 feet. This is the sensor of choice where it is possible to apply the adhesive-backed retroreflective tape to the target surface, since this provides a strong return signal for optimum operation.

The LIR and LV models can be used in conjunction with the spinning mirror assembly and high speed interface card to make a laser line scanner for profiling scenes and objects.


Acuity's rangfinders are very unique distance measuring devices. They employ a modified time-of-flight measurement principle that leads to very fast and accurate measuring speeds.

The AR4000 differs from other long-distance rangefinders in that the laser emitter and return signal collection lens are concentric. The illustration to the right reveals the major functionality of the rangefinder. A collimated beam of laser light is emitted from a diode in the center of the fresnel collection lens. Light hits a target and is diffusely reflected, collected by the lens and focussed on an avalance photdiode. The AR4000 distance measuring technology is patented (US patent 5,309,212).

Engineers specify the AccuRange 4000 rangefinder for its speed, concentric optical path and its ability to be mated to the Acuity line scanner.

The standard speed of the rangefinder using RS232, RS422 or analog interfaces is approximately 770 Hz. This is the true frequency response updated to the selected interface. Additionally, the rangefinders can be ordered with High Speed Interface Cards (HSIF cards) which enable even faster sampling speeds. These cards are available in either 50 KHz or 200 KHz varieties, with either PCI or PC104 bus formats.

The concentric optical path means that the emitted and reflected signals travel down a single axis, unlike other rangefinders where the emitter and collecter are situated side-by-side. The concentric path allows users to measure down narrow paths and tubes.

The concentric design and fast sampling rates work well with the scanning capabilities of the AccuRange Laser Line Scanner. Here, a mirror sweeps the rangefinder beam through a full 360° to collect 2D polar coordinates.

The AR4000-RET distance measuring rangefinder is used with reflective tape supplied with the sensor. It is a low-power, Class I eye-safe device, with an accuracy of 0.1 inches (2.5 mm) with a range of 2 to 54 feet (16.5 m). This is the sensor of choice where it is possible to apply the adhesive-backed retroreflective tape (3M brand) to the target surface, since this provides a strong return signal for optimum operation. We suggest using either the 3M™ Scotchlite™ High Gain Reflective Sheeting 7610 or the 3M™ Scotchlite™ Photoelectric Grade Smooth Surface Sheeting 7590 (for weather-resistant applications). Because of the target requirement, the AR4000-RET is not a candidate for use with the scanner options.

Output interfaces

Acuity offers the following standard and optional outputs for the AR4000 laser rangefinder devices:

Standard RS-232 Serial Output

All sensors come with an RS-232 serial output on a 6 foot, 9 pin cable that connects directly to PC style serial ports. Serial output can be configured for one of several data formats. ASCII may be used for visual reading with a terminal device or emulation program, or a binary format can be used with application software. The data may include calibrated distance output only, uncalibrated range and other sample data only, or both. The other sample data includes reflected optical signal strength, background light level, and internal sensor temperature. These values are also available as voltage levels on the sensor's power/signal cable. They may be used for external calibration if the sample rate is too high for each sample to be calibrated internally. When the binary format calibrated distance output only is selected, the maximum sample rate is 700 samples per second. Baud rate is selectable from 300 to 34,800 baud.

Optional RS-422 Serial Output

For long distance communications (more than 20 to 30 feet, depending on the baud rate), the RS-232 serial output may be replaced with an RS-422 serial output. The available sample rates, formats and software configuration commands are all the same as for the RS-232. The sensor can also be ordered with RS-485 (half duplex version of 422), but the AR4000 does not presently support any standard 485 network protocols.

Optional Current Loop Output

A 4-20 milliamp current output may be ordered as an option. If the AR4000 is ordered with this output it uses the same output line as the pulse width output on the power/signal cable, so 4-20 output is not available on sensors configured for the High Speed Interface. Serial I/O is still available. The zero and span for the current loop output may be set at any location, with a minimum span of 9 inches. The span point (20 mA) may be made closer than the zero point if desired. Either calibrated or uncalibrated range may be selected. If serial output is turned off, calibrated output on the current loop allows sample rates of 1000 samples per second, and uncalibrated range output allows update rates up to 3,000 samples per second. The 4-20 mA output has a maximum voltage capability of 10 volts, and it is suggested that a 400 to 500 ohm load be used at the reading instrumentation for best accuracy.

Standard Voltage Signals for Signal Strength

The AR4000 has 3 lines which transmit 0 to 5 volt analog signals representing reflected optical signal strength, ambient light in the target area, and internal sensor temperature. These may be used to monitor signal quality, and they are sampled by the High Speed Interface for high speed data acquisition. The same information is available through the serial interface; these lines provide an alternate, higher-bandwidth data path.

Optional Pulse Width Output (Standard with High Speed Interface)

All AR4000 sensors shipped with a High Speed Interface also have an uncalibrated pulse width output. The duration of the low portion of the pulse changes linearly with the uncalibrated sensor reading, and the period of the signal is controlled by the sample rate for which the sensor is configured. This output is typically used with the High-Speed Interface or application-specific hardware at sample rates beyond the 700 sample/second limit of the serial interface. Calibration may be performed externally using the signal strength and other voltage outputs in conjunction with the pulse width output.



Acuity laser rangefinders can be used for diverse distance measuring applications. Our three standard models may benefit from the use of options or accessories. An example of an application that would require accessories is an outdoor distance measurement application. If your needs are for faster sampling speeds, consider Acuity's offerings of High Speed Interface Cards.


The optional AC to DC power supplies for the AR4000 rangefinders provide operating power and temperature stabilization heater power to the sensors.

They are housed in NEMA-4 polycarbonate enclosures and are normally permanently attached to the AR4000 power/signal cable, with 6 feet (2m) of cable between the sensor and power supply.

An additional 4 feet of cable extends beyond the power supply for reading the sensor's optional current loop and other outputs. The LIR Power Supply also includes the keyswitch and interlock jack required for CFR certification for Class IIIb lasers.

Input voltage range for the power supplies is 80 - 240 VAC, 50-60 Hz. All 4000-LIR systems purchased by end users must include the power supply or the IR Interlock Box in order to meet FDA regulations.

OEM users that do not order sensors with these interlocks are responsible for supplying the required keyswitch, removable jack or another suitable interlock.

Power supply dimensions are 6.73 by 3.15 by 4.75 inches (171 x 80 x 121 mm). The power supplies are permanently attached to the sensors with 6 feet (2m) of cable.

The power supplies may be installed with the High Speed Interface. The High Speed Interface can supply power to the AR4000 sensors from the computer in which it is installed, but if the voltage level is inadequate (5.0 V min) or the current for the sensor is inadequate, an AR4000 power supply may be used instead to guarantee reliable sensor operation.

It is not uncommon for new customers of the Acuity laser rangefinder to apply the incorrect voltage to their laser rangefinder. In cases of insufficient voltage, the green LED on the back of the sensor will flash and the sensor will behave erratically. In cases of >6.0V, circuitry often controlling the laser power may burn out and must be repaired at the factory. Such repairs can not be carried out in the field.


The high power 20 mW laser diode option is only available for the AR4000-LIR model. It is recommended for measuring to dark targets at ranges beyond 30 feet (9.1 m), or in outdoor applications where the target surface may be sunlit.

The GaAlAs semiconductor high power laser has twice the drift and fluctuation in the range readings of the 8 mW version, so it is half as accurate as the 8 mW version, but it often works in situations where the lower power laser is not sensitive enough. The laser class remains IIIB and has a wavelength of 780 nm.

The High Power Laser Option is typically designated during manufacture. Changing the laser on an existing sensor entails additional cost, as it requires significant changes and recalibration. The lifetime of the laser diode is 50,000 hours. If you need higher power than 20 mW, please contact Acuity.


For sunlit or very brightly lit targets, or when the target is glowing in the visible or near IR (at a temperature of 1000° F or higher), the optical interference filter is recommended for the Acuity laser rangefinder. This is a narrowband filter matched to the laser wavelength and permanently installed in the AR4000 device in front of the photodiode.

The filter blocks 96% of light to which the 4000's detector element is sensitive. It is availabe for all three Acuity laser rangefinder models, the LIR, the LV and the RET. The filter is installed internally in the AR4000 at manufacture and the focusing of the collection optics is adjusted for it, so retrofitting the Optical Filter carries additional charges.


The sensitivity of the standard AR4000 rangefinder increases with distance from zero to 9 feet (2.7 m), and then gradually drops off from 9 feet to 54 feet (16.5m) All AR4000 models may be ordered with a close focus configuration.

If an application requires maximum sensitivity at less than 9 feet and does not require operation beyond 16 feet, the optical focus can be adjusted to move the point of greatest sensitivity to shorter distances. This is one way to get the best performance out of the AR4000 laser rangefinder when being used at close, known distance ranges. A typical application that necessitates CFO is transverse road profiling of asphalt. In this case, the road profiling engineers designate the maximum range based on the height of their scanner (using the laser sensor) above the endpoints of a car lane.

The customer specifies the minimum and maximum operating range and the optics are tuned accordingly. The optics are adjusted and permanently mounted at manufacture, so retrofitting the Close Focus Optics carries additional charges. The sensor is only calibrated in the specified range.


The NEMA-4 Interlock box supplies the keyswitch and removable jack power controls required for end use of all Class IIIb lasers (the 4000-LIR rangefinder).

This box is installed in-line in the AR4000 power/signal cable (dark-grey cable). Interlock box dimensions are 2.2 by 2.6 by 4.6 inches (56 x 66 x 117 mm).

Read more about laser safety here.

Touch Panel Display

The Acuity™ Touch Panel Display is a stand-alone terminal interface for use with Acuity laser distance sensors. These fully-enclosed units replace panel meters, alphnumeric displays and analog controllers by providing a modern interface through a full-color LCD and touch screen. The Touch Panel Display communicates with one or two Acuity sensors using their serial interfaces. Sensors can be easily configured using on-screen buttons to display and scale their distance outputs. Relative dimensions can be measured using a tare function. With dual RS232 serial inputs from two Acuity sensors, the touch panel serves as a thickness gauge and display, an application which previously demanded a PC computer and custom software programming. Using a single RS485 serial interface, the Panel can transmit thickness and dimensional information to external devices.



The AccuRange High Speed Interface (HSIF) is used to increase the sample rate capability of a AR4000 laser rangefinder while tracking the mirror position on the AccuRange laser line scanner, using any PC-compatible or PC-104 bus computer.

Acuity offers four models of HSIF cards including ones for ISA, PCI and PC104 formats. All cards enable a maximum sampling rate of 50,000 samples per second. A specialized PCI version is even capable of 200,000 samples per second and buffer the data for reading by the host computer.

The high speed interface card from Acuity represents a hassle-free means of increasing the sampling rate of the AR4000 laser rangefinder and tracking the mirror position through the optical encoder on the line scanner.

The board is available with a PCI, PC-104 or ISA bus interface. The AccuRange HSIF includes the interface, user's manual, demonstration / diagnostic software. The input to the card is a pulse-width output (square wave) from the rangefinder. It also takes the lower-level outputs of the laser rangefinder such as AMPLITUDE, AMBIENT LIGHT LEVELS and TEMPERATURE to calculate a calibrated distance reading.

The PCI version of the card is standard with a 64 KB buffer size as well as two motor controllers (voltage controlled) and two single-ended optical encoder readers. The card can be ordered with differential encoder readers as well. The ISA and PC-104 interface cards are standard with a 16K buffer size and a 2-channel motor power control and motor encoder reader.

Acuity offers software developer's kits to be used with the AR4000 in conjunction with the high speed interface cards.

The following are technical documents available for download. Data sheets are brief specification sheets describing the features of the product. User's manuals are installation and operating guides for Acuity products.

Download PCI High Speed Interface Data Sheet - File Size 163 KB

Download PCI High Speed Interface User's Manual - File Size 312 KB

Download ISA/PC-104 High Speed Interface Data Sheet - File Size 371 KB

Download ISA/PC-104 High Speed Interface User's Manual - File Size 289 KB



Software libraries for the laser rangefinder drastically ease the programmer's burden of writing application code. The product is written by Crandun Technologies. The AR4000 Software Library provides a "plug-and-play" software interface to the Acuity AR4000 laser measurement senor so you can concentrate on your application functionality, rather than on hardware interfacing or data collection details.

The library of functions are written in C, C++ and Visual Basic. Some Microsoft® Excel macros are included. The AR4000 software library is for the serial, RS-232 output only. Please specify Windows® or Linux® versions.

If you are using a high speed interface card with your AR4000 laser rangefinder, please consider using the Windows or Linux version of the developer's kit for the PCI, ISA or PC104 bus cards.

This software library is licensed on a per-sensor-basis and discounts are available for multi-sensor users. To convince yourself of the value of these software libraries, read our Top Ten reasons to purchase Crandun software libraries.

Download the AR200 Software Library from the Crandun website.
You will need to purchase a keycode to run this library with your sensor.

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Crandun software library for AR4000 using serial output - exe 124.68 KB

Mechanical drawing of AR4000 - pdf 18.94 KB


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