Long-Range Searchlight Product

Overview

A long-range searchlight throws a narrow, steerable beam far enough to pick out a liferaft, a border fence line, or an aircraft kilometres away. The performance figure that matters is peak beam intensity, candela, not lumens: a 2 kW unit emits less total light than a supermarket's worth of fixtures, but by compressing it into a beam under one degree wide it reaches 50–100 million candela on axis, enough to put 1 lux, roughly full-moon illumination, on a target 7–10 km out in clear air. Users are ships (SOLAS-mandated signalling and rescue lights), coast guard and naval vessels, border and perimeter security, airfields, and the entertainment skybeams descended from wartime anti-aircraft lights.

Optics: why a point source

Collimation is governed by source size: beam divergence is approximately the source diameter divided by the reflector focal length. That arithmetic is why the Xenon Short-Arc Lamp dominates the class. Its arc burns in a 2–6 mm gap between tungsten electrodes inside a quartz envelope holding xenon at 8–30 bar, forming a near-point source of about 6,000 K colour temperature, comfortably daylight-white. Placed at the focus of the Parabolic Mirror, a few-millimetre arc behind a 500 mm aperture collimates to a fraction of a degree. LED engines are taking over the lower power classes for their 20,000-hour life and instant restrike, but a large LED panel cannot match the arc's collimation, so the longest-range units remain xenon.

The mirror itself, coated in aluminium or rhodium and figure-accurate to fractions of a millimetre, returns over 90 % of the arc's light into the beam. It sits in a kinematic Mirror Mount Cell so clamping and thermal cycling do not distort its figure. The Focus Slide moves the arc axially through the focal point: pulled slightly off focus the beam spreads to a flood for area search, on focus it tightens to maximum reach. Lamp changes happen through the Rear Access Cap, with the new lamp's arc re-referenced to the axis by the Lamp Socket.

Power and ignition

A xenon arc is a negative-resistance load: once struck, its voltage falls as current rises, so it cannot run from a stiff voltage source. The Ballast / Driver Unit therefore behaves as a constant-current supply. Starting takes a ~30 kV pulse from the Lamp Igniter to ionise the gap; the Ballast PCB then takes over, its IGBT Power Module chopper holding 20–150 A at the lamp's 18–40 V running voltage, with the Output Choke smoothing switching ripple that would otherwise flicker or extinguish the arc. Several kilowatts of input become roughly half light and half heat; the Cooling System fans force air through the Cooling Air Duct across the envelope and electrodes, the Intake Dust Filter keeps grit off hot quartz where it would burn in permanently, and the Over-Temperature Switch kills the arc if airflow fails. Pressurised lamps are handled with face protection; a hot envelope failure is energetic.

Pointing

The barrel rides in the Gimbal Mount: a Gimbal Yoke on a Base Turret, each axis driven by a Servo Motor through a self-locking worm Helical Gear Pair so wind load cannot back-drive the aim. Encoder feedback on both axes gives repeatable pointing, which enables the features operators actually use: stored home positions, automatic horizon scan patterns, and slaving the light to a radar track or FLIR line-of-sight so the beam lands on a target the sensor already holds. The Gimbal Slip Ring passes lamp current and signals across the azimuth joint, allowing unlimited continuous rotation. Slew rates run 5–25°/s, fast enough to track a small boat at close range.

Control is remote by design; nobody stands next to a 50-million-candela aperture. The Control Joystick panel on a ship's bridge drives the axes proportionally through the Remote Interface PCB, which also exposes RS-485 and NMEA 0183 so the vessel's integrated bridge or a security system's video-management software can command the light directly over the Control Cable.

Service

Routine work is optical hygiene and lamp economics. The Front Cover Glass and mirror are cleaned with optical-grade materials, since film and scratches scatter exactly the on-axis light the instrument exists to deliver, and the O-Ring Set seals are renewed to hold the IP55–IP66 rating in salt spray. Xenon lamps are lifed at 500–2,000 hours and replaced on the ballast's hour counter before end-of-life instability sets in; the alignment check after every change, centring the new arc on the optical axis, is what separates a 5 km light from a 10 km one.