It's Just a Light Source. How Hard Can It Be?
Why developing illumination for an OEM instrument involves rather more than choosing a bright LED, attaching a lens and pointing it in approximately the right direction.
The conversation usually starts quite reasonably
“We already design complex scientific instruments. Surely we can build the light source ourselves. LEDs aren't exactly mysterious.”
And technically, that's true. LEDs are easy to buy. Drivers exist. Heat sinks exist. Lenses exist. With a little engineering effort, the first prototype can produce light surprisingly quickly.
Excellent. The glorified torch is complete.
Unfortunately, producing light and producing usable illumination for an OEM instrument are rather different achievements.
Bright isn't the same as useful
The instrument doesn't need an LED that looks impressive when it's switched on. It needs the correct optical power at the sample, detector, wafer or target.
That means accounting for optical losses, coupling efficiency, working distance, beam shape and field size. A very bright LED can still produce disappointing results if most of its output never reaches the place where it's needed.
The wavelength isn't simply a colour
OEM systems may need tightly defined spectral output, specific peak wavelengths or channels extending from UV through visible light and into NIR or SWIR.
Two LEDs carrying the same nominal wavelength can still differ in output, bandwidth and temperature response. Those differences become important when the light source forms part of a measurement or imaging system rather than a desk lamp.
Then somebody asks about uniformity
A bright centre surrounded by dim edges may be perfectly acceptable for a torch.
It's less useful for slide scanning, semiconductor inspection, machine vision, metrology or any application where performance needs to remain consistent across the whole field.
Suddenly the project involves optical modelling, diffuser selection, homogenisation, tolerances and a growing collection of test images containing suspiciously bright corners.
The torch has now acquired an optical engineering programme.
Heat quietly joins the project
LED output, wavelength and lifetime all depend on temperature. Thermal management therefore affects far more than whether the enclosure feels warm.
Heat influences optical stability, mechanical design, fan noise, reliability and component life. The solution then needs to work inside the final instrument, rather than on an open laboratory bench with plenty of air around it.
Now make it communicate
The light source may need TTL triggering, analogue control, USB, RS-232 or Ethernet. It may need to switch in microseconds, report its status and respond correctly when the wider instrument decides to do several things at once.
At this point, the bright LED has gained firmware, communications, timing requirements and a software interface.
And then there's production
Component tolerances, calibration, test procedures, supplier changes and quality control all affect whether every production unit behaves like the prototype.
The light source also needs to fit the available space, survive the intended environment and remain manufacturable for the expected lifetime of the OEM platform.
Then come electrical safety, EMC, environmental requirements, documentation and change control.
The LED was the easy bit.
Building in-house can still make sense
Some OEM manufacturers have the time, skills and resources to develop their own illumination successfully. The question isn't whether it can be done.
The question is whether illumination should become a separate engineering project when your team could be concentrating on the part of the instrument that makes your product different.
Working with an illumination specialist gives you access to established optical, electronic, thermal and manufacturing knowledge without having to discover each issue during development.
Because a light source may begin as a glorified torch. It rarely stays that way for long.
Still thinking of building one in-house?
Here at CoolLED, we know what we're talking about when it comes to LED illumination. In fact, we've written a whole White Paper about this very subject.
It's well worth a read if you're considering tackling the design and manufacture of a custom illumination system internally.
Spoiler alert: it's really hard.
Read Our White Paper on Creating Custom LED Illumination
