RO116930B1 - Portable miniaturized range finder - Google Patents

Abstract

The invention relates to a portable miniaturized Nd:YAG pulsed laser range finder, meant for determining/measuring distances targets, in a range of measurement of till 10 km and comprising a laser transmitter/emitter (EL) with Nd:YAG active medium, having a Galilean-type telescope for the laser beam collimation, a trigger circuit and a power unit (SALT) for supplying the laser transmiter/emitter (EL), the range finder comprising also an optoelectronic receiver (RO) provided with common path receiving lens, with a sighting telescope, a assembly/unit controlling and processing the signals (BCPS) and also a displaying device (DA), a controlling panel (PC), all these subassemblies being included in an optomechanical monobloc structure, ensuring a good stability to the optical axes parallelism, a minimal limit, a good sturdiness/robustness and an optimization of functioning allows a reduced consumption, maintaining the standard parameters, the range of distance, precision and sensitivity.

Description

RO 116930 B

The present invention relates to a portable, miniaturized, pulsed laser rangefinder with active medium Nd:YAG [neodymium and yttrium and aluminum garnet], intended for determining distances to various objects (targets) located in the measurement range (max. 10 km], with application in the civil and military fields.

Such rangefinders are known which operate according to a predetermined timing diagram and have a certain degree of complexity. A portable laser rangefinder, in the standard version, contains a laser emitter with the associated components: the emitter power supply, the energy storage capacitor, the trigger circuit and the emission scope [collimation], an optoelectronic receiver with the associated components: the source of receiver power supply and receiving objective, an electronic control block, an electronic signal processing block, a digital distance display indicator, a sight scope, a control panel and an electric power supply battery. The operation of the rangefinder consists, mainly, of emitting a power laser pulse, of short duration (7...30ns], constituting the START signal and receiving the laser pulse, reflected by the targeted target, constituting the STOP signal. During a measurement, can get one or more STOP signals as there are one or more objects on the measured azimuth By measuring the time interval between the 2 START and STOP pulses with a suitable time base it is determined, with a certain precision, the distance between the rangefinder and the target. The power pulse is generated by the laser active medium located in the resonant cavity, excited by the light pulse emitted by the flash lamp through which the energy stored in the storage capacitor is discharged. The emission scope provides a low divergence (<1 mrad) of the emitted laser beam. From the target, part of the reflected laser signal is processed by the receiving objective and applied to the avalanche photodetector, which provides an electrical pulse at the output. Denoting with At, the time interval between the moments of the appearance of the emitted pulse [START] and the reflected one [STOP], the distance d, between the rangefinder and the target, is:

d=0.5 c-At [1]

The quantity c represents the speed of propagation in the air of the radiation provided by the laser emitter at the wavelength λ=1060 nm:

[2]

The quantity n represents the refractive index at the specified wavelength. By choosing the frequency of the reference oscillator, existing in the signal processing block of 29.9708 MHz [value correlated with the refractive index], the measured distance is directly expressed in meters (m] and displayed on the digital indicator. The distance accuracy is ±5m.

the structure of a rangefinder includes specialized electronic and optoelectronic components, as well as general purpose components. Control and operation are provided according to a timing diagram.

The disadvantages of these rangefinders are the complexity of the construction scheme, the time diagram, the large size and the high consumption of electricity.

The telemeter according to the invention removes the mentioned disadvantages, in that, through a minimized number of sub-assemblies operating according to an optimized time diagram, it allows the reduction of the gauge and the consumption of electricity, while maintaining the parameters at the standard values.

An embodiment of the invention is indicated, in connection with fig. 1... 10 which represents:

RO 116930 B

- fig. 1, the block diagram in which, with a continuous line, the paths of the electrical signals were represented, and with a broken line, the paths of the optical signals, the following figures constituting the time diagram, namely;

- fig. 2, supply voltage ϋ _Λ during operation; it

- fig.3, the voltage U, for initializing the measurement,

- fig.4, indicates the charging voltage U _c of the storage capacitor up to the nominal value U _cni reached at a moment of time t _n ,

- fig.5, represents the U _R impulse, measurement validation or ready impulse that materializes the moment t _R , 55

- fig.6, indicates the synchronized ready validation pulse U _HS ,

- fig.7, which shows the external reset pulse U _RE ,

- fig. 8, the control signal of the timed supply U _CTD of the time-distance converter,

- fig.9, indicates the control pulse U _D of the ignition of the flash lamp, 60

- fig. 10, indicates the distance measurement window U _M .

The rangefinder according to the invention has a block diagram [fig.1] with a minimal structure, being formed by the following subassemblies: a miniaturized EL laser emitter with active medium Nd: YAG and passive switch, fed from a power source [pumping] type fly-back with high switching frequency SALT, also containing a trigger circuit 65 of the discharge of the energy storage capacitor on the flash lamp, an optoelectronic receiver RO, with the avalanche photodiode having automatic adjustment, during amplification, and with the power supply of the avalanche photodiode obtained from the laser power supply, a BCPS control and signal processing block, provided with a DA display containing a 4-digit multiplexed digital indicator for distance and two LEDs M, and 70 respectively N indicating the absence of the target or multiple targets whose light intensity is controlled, in operation, by the ambient light through an economizer made with □ PIN-type FD photodiode, an optical-mechanical BER emission and reception-aiming block, equipped with a control panel PC equipped with a 3-position kl switch: off/on/external power supply 0/P/AE, a 75 AjPD distance gate adjustment potentiometer, a PB button for selecting telemetry/distance gate T/PD working mode, a distance measurement trigger button D, an external power jack MA, and a battery pack B.

When the PB push-button is pressed, the digital indicator shows the size of the distance gate, which represents the distance up to which the target or targets are not ranged on the intended line, i.e. on the same azimuth, and when it is not pressed, the distance measured up to the intended target that is greater than the disallowed range through the range gate. This prohibited distance is also known as blocked distance.

The BER emission-reception block is a monobloc mechanical body and has a Galilei-type scope for 8 5 collimation of the emitted laser radiation, and for reception-sighting a common-path reception objective with the sighting scope, using an optical dividing cube. It also has a prism that takes a fraction of the emitted laser beam and directs it to the receiving objective to provide the START signal needed to determine the distance.

The operation of the rangefinder is controlled by the BCPS 90 signal processing and control block, consisting of an EC electronic control circuit and a converter

Claims (1)

RO 116930 B After the last U _M waveform is played out, the rangefinder returns to standby mode, retaining the distance information until the next measurement and is ready for a new measurement. Distance information is read through the left OC eyepiece, and the target is aimed through the right one. 140 Claim Portable, miniaturized, pulsed laser range finder, with Nd:YAG active medium laser emitter, Galilei-type scope, for collimating laser radiation, 145 trigger circuit and laser emitter power supply, with optoelectronic receiver fitted with objective lens common path reception with the scope, the rangefinder also including a control and signal processing block, a display device and a control panel, characterized by: the fact that the laser emitter (EL] with active medium Nd:YAG is miniaturized, being provided with a passive switch, which, fed from a 150 power source (SALT] in high-frequency fly-back switching containing a trigger circuit, which starting from the battery voltage (U _fl ) and at the command of a pulse of initialization [U,] charges a storage capacitor up to the nominal value [U _CBJ ] of the charging voltage (U _c ), reached at a given time moment (tp), materialized by the appearance of a validation pulse țU _R ] for initiation measurement, laser emitter [EL] ce 155 emits a laser power pulse, triggered at a specified time moment (t _D ] due to a command pulse [U _D ] to ignite the flash lamp, a small part of which is reflected by the target targeted, being captured by an optoelectronic receiver [RO] made with an avalanche photodiode, provided with automatic adjustment, in time, of the amplification, with a power source of the avalanche photodiode obtained from the 16O laser power source (SALT), a control and signal processing block (BCPS), consisting of a control circuit (EC) and a time-to-distance converter [CTD], which receives the signals from the transmitter and receiver in a measurement time interval [U _M ], transforming them into the measured distance, having minimized consumption due to its timed supply, obtained during the application of the supply voltage (0^), voltage signal offset by 165 a preset delay from a synchronized validation signal [U _RS ] , the rangefinder being equipped with a multiplexed type display device (DA) with four digits to indicate the distance measured/locked and with two LEDs [IM and M respectively] indicating the absence of the target or the multiple target, and with the light intensity commanded by the level ambient luminosity through an economizer circuit made with a PIN-type photodiode [FD], 170 the rangefinder also comprising on the one hand, a monobloc mechanical body [BER] containing a Galilei-type scope for collimating the laser radiation, an objective of common path reception with the scope using a splitter cube, together with a prism that takes a small part of the emitted laser beam and directs it to the receiving objective, and on the other hand a control panel [PC] equipped with switch [K1 ] with positions 175 off/on/external power supply (O/P/AE), with working mode button (PB), with telemetry/distance gate positions (T/PD) with measurement trigger button [D], with external power plug (NIA), with separate eyepiece (DC] for reading the display and with battery pack (B), the rangefinder works on an optimized timing diagram and ensures standard parameters. 180 President of the examination committee: Eng. Popesou Liuia Examiner: Eng. Apostol Cristina