Pulsed xenon.
Less Star Trek, more semiconductor inspection.
It sounds suspiciously like something fired from a spaceship, but pulsed xenon has spent decades doing a very real job inside high-speed industrial imaging systems. So what is it, why has it been so useful, and why are OEMs increasingly looking at LEDs instead?
What actually is pulsed xenon?
Inside a xenon flash lamp is a tube filled with xenon gas. Apply a sufficiently large electrical discharge and the gas produces an extremely bright flash of light, typically lasting just a few microseconds.
It is basically the same principle behind the classic photographic flash, except engineered for rather more demanding applications than embarrassing family photos.
The big attraction is intensity. Xenon flash lamps can produce extremely high peak optical output, together with broad spectral emission extending from ultraviolet through visible wavelengths and into the infrared.
Very bright
Large amounts of optical energy can be delivered during an extremely short exposure.
Very fast
Short flashes help freeze movement in high-speed inspection and imaging systems.
Very broadband
A single xenon source can provide emission across UV, visible and infrared wavelengths.
Why does semiconductor inspection use it?
Semiconductor inspection is not especially forgiving. A wafer, die or electronic component may be moving through an automated inspection system at speed, while the camera is expected to capture tiny defects, contamination, surface features or dimensional differences.
Motion blur is not terribly helpful when you are trying to inspect something microscopic.
A very short, very bright pulse gives the imaging system enough light while effectively freezing the subject.
Nothing. Until you ask whether you'd design it that way today.
Pulsed xenon is still useful technology, and there are applications where its combination of peak output and broadband emission remains a good fit.
But it comes with characteristics that an OEM has to design around.
The flash is created by an electrical discharge, so the system requires high-voltage circuitry and triggering. The lamp itself also changes with use. Electrodes wear, optical output ages and eventually the source becomes another component that needs replacing.
High-speed illumination has changed
LEDs have been replacing conventional lamps across scientific and industrial applications for years, but high-speed inspection presents a particular challenge.
It is not enough to produce plenty of light. You need to produce a lot of light, very quickly.
Modern high-power LED systems can now deliver short, precisely controlled optical pulses suitable for applications that once depended heavily on xenon flash.
Use the light you actually need
One of xenon's strengths is its broad spectral output. But that can also mean generating a huge range of wavelengths before filtering the light down to the region the application actually uses.
With LEDs, an OEM can approach the problem differently.
If an inspection process needs a particular UV, visible, NIR or SWIR wavelength, the illumination can be designed around that requirement. Multiple wavelength channels can also be independently selected and controlled.
That matters because changing wavelength can change what the imaging system sees. Different materials, coatings, structures and defects can respond very differently across the spectrum.
Don't replace the lamp. Reconsider the illumination.
For semiconductor equipment manufacturers, machine-vision companies and industrial OEMs, the interesting part is not simply exchanging xenon for LED. It is the opportunity to rethink how illumination works inside the system.
Choose your wavelengths
Build around the spectral regions that reveal the information your inspection process needs.
Choose the delivery
Configure illumination for fibre, liquid light guide, collimated output or application-specific optical integration.
Build it into the instrument
Synchronise illumination with cameras, software and automation using control architecture designed for the OEM system.
Still using pulsed xenon?
We are not suggesting you dramatically throw it into a skip. If it is doing the job, it is doing the job. But if you are developing the next generation of your system, it might be worth asking whether you still need it.
