Eyesafe Laser Rangefinder Research Articles

Efficient Embedded Hardware Architecture for Stabilised Tracking Sighting System of Armoured Fighting Vehicles

A line-of-sight stabilised sighting system, capable of target tracking and video stabilisation is a prime requirement of any armoured fighting tank vehicle for military surveillance and weapon firing. Typically, such sighting systems have three prime electro-optical sensors i.e. day camera for viewing in day conditions, thermal camera for night viewing and eye-safe laser range finder for obtaining the target range. For laser guided missile firing, additional laser target designator may be a part of sighting system. This sighting system provides necessary parameters for the fire control computer to compute ballistic offsets to fire conventional ammunition or fire missile. System demands simultaneous interactions with electro-optical sensors, servo sensors, actuators, multi-function display for man-machine interface, fire control computer, logic controller and other sub-systems of tank. Therefore, a complex embedded electronics hardware is needed to respond in real time for such system. An efficient electronics embedded hardware architecture is presented here for the development of this type of sighting system. This hardware has been developed around SHARC 21369 processor and FPGA. A performance evaluation scheme is also presented for this sighting system based on the developed hardware.

Design and Development of Compact Hand Held Target Acquisition Device

A compact, lightweight hand held target acquisition device, comprising of an infra red imager, colour CCD camera, eye safe laser range finder, global positioning system and digital magnetic compass has been developed. The aim was to develop a compact, lightweight, modular and man-portable multi function electro-optical system with a recognition range of 1 km for vehicles and 500 m for human movement enabling day and night time surveillance, target ranging capability, ability to generate coordinates of the operator and estimation of target coordinates. Hand Held target acquisition device operates on 12 V DC, has integrated signal processing for all the sensors and display electronics with a weight of 3 kg. Overview of the system, design methodology, performance modeling, range simulation of both the IR imager and colour CCD camera and field results have been presented.

Using an eye-safe laser rangefinder to assist active and passive electro-optical sensor performance prediction in low visibility conditions

Laser rangefinders are used in various electro-optical (EO) fire control systems. They often operate at eye-safe wavelengths around 1.55 μm, which extends their utility. The paper investigates the use of a modified eye-safe laser rangefinder at 1.55 μm to obtain information on atmospheric attenuation and couple that information to the performance of active and passive EO sensors with an emphasis of lower visibility conditions. Such information can be of great value both for estimating own sensor capabilities at a given moment as well as estimating the threat capability. One obvious example is ship defense where it is difficult to obtain visibility along variable and slant atmospheric paths, especially in darkness. The experimental equipment and the results from measurements of atmospheric backscatter along various atmospheric paths are presented. The backscatter curve is used to evaluate the extinction. These extinction values are compared with those deduced from a point visibility meter and from echo measurements against two similar nets positioned at two ranges from the sensor. TV and IR images of test targets along a 1.8 km path close to sea surface in the Baltic Sea were collected in parallel with the lidar. A weather station and a scintillometer collected weather and turbulence parameters. Results correlating the lidar attenuation with the imaging performance will be given.

Improved Monoblock laser brightness using external reflector

The Monoblock laser has become the laser of choice in long-range, eye-safe laser range finders. It is eye-safe with emission at 1570nm, high pulse energy, simple construction, and high efficiency when pumped by a laser-diode stack. Although the output beam divergence of a typical Monoblock with a 3 mm×3 mm cross section is relatively large (10-12mrad), it can be reduced to <1 mrad using a telescope with large magnification. In this paper we present a simple and compact technique for achieving significant reduction in the Monoblock beam divergence using a partial reflector that is placed a short distance from the optical parametric oscillator (OPO). Using a 38mm long Monoblock with a 10mm long potassium titanyl phosphate OPO, we achieved a beam divergence of <4 mrad, corresponding to a >2.5× reduction from the unmodified laser. Performance using this technique with various feedback and etalon spacings is presented.

对称式人眼安全激光测距仪光学系统的设计

对称式人眼安全激光测距仪光学系统的设计

An intelligent active range sensor for mobile robot guidance

The mechatronic design of an eye-safe laser rangefinder, based on the lateral-effect photodiode (LEP) and synchronised scanning, is described. The sensor acquires two-dimensional range data, which has been found sufficient to guide the local manoeuvres of a mobile robot in most environments. An analysis of LEP operation shows that image position measurement repeatability, normalised with respect to the detector half length, is equal to the signal current to noise current ratio. This result suggests a method for estimating the noise density of the measurement process and, along with a geometric model of the ranging process, allows accurate estimation of the variance of individual range measurements, making the sensor particularly amenable to statistically based range feature detection, tracking, and data fusion algorithms. The sensor is active, in the sense that it can change the orientation of its field of view, in order to track useful and stable range features. Range data acquisition, range feature extraction, and control of the active head behaviour are all implemented on a local network of six transputers. This parallel structure is described and it is shown how the sensor constitutes an intelligent agent in a balanced sensor suite for the guidance of close range mobile robot manoeuvres.

Formula omitted]-μm eyesafe laser rangefinders performance under adverse weather conditions

In this investigation, the performance of a CO 2 laser rangefinder at 10.6 μm and an erbium:glass rangefinder at 1.54 μm are evaluated and compared under various atmospheric conditions. Both systems and the trial site are described. The effect of atmospheric extinction and scattering is discussed. Also, the maximum range capability of the two laser rangefinders under these degraded weather conditions is assessed. The results show that the tested CO 2 laser rangefinder performed better than the Er:glass LRF used for the trials under all weather conditions. However, comparing two state-of-the-art systems does not lead necessarily to the same conclusion.