Modular machine vision lighting: one light, many inspection tasks

Lighting is the part of a vision system you re-spec most often. A new part family arrives, a defect shows up only at grazing angle, and last quarter's perfect light becomes a spare you never use. Modular machine vision lighting attacks the problem at purchasing level: one 24 V light body, a small set of interchangeable optics, one controller. You will leave with the technique list a single station can cover, the accessory set that does it, the brightness cost with its arithmetic, and a sizing worked example for a real field of view.

What is modular machine vision lighting?

Modular machine vision lighting is a light bought as a base unit plus interchangeable optics: diffuser plates, alternative-angle heads, polarizing film, wavelength filters and extension cables. One 24 V body serves direct, low-angle, dark-field and dome-style illumination instead of a single task.

Vendors sell the idea as angle changers and clip-on diffusers that re-aim or soften the same LEDs after installation. You get the same flexibility from a conventional catalog in three ways: order the same body family at a different beam angle or with a diffused window, bolt on the accessories the family lists, and let a controller change intensity and timing. The catalog is built for it: 414 of the 1,403 bar lights are diffused types and 258 of the 903 ring lights are diffused, so the like-for-like swap is a standard part number, not a custom build.

What you are really buying is fewer unique parts per station. One body plus optics carries one mounting, one cable standard and one spare strategy; three dedicated lights carry three of each. The rest of this page puts numbers on that trade.

Which lighting techniques can one light cover?

Four, from one body size: a 60° directed head for bright field, a diffused 0° window for dome-style fill on curved or shiny parts, a low-angle 0-15° head for grazing dark field on edges and scratches, and staggered sectors for photometric stereo.

The technique follows from three choices: emission angle, diffusion and working distance. Direct light from a 30-60° head is the default for matte, flat parts. When it fails, the cause is usually specular reflection rather than distance, as set out in direct incident light: when it works and fails. Dropping to 0-15° turns raised edges, engraved marks and scratches into bright lines on a dark field, the geometry compared in low-angle grazing light versus a dome for engraved text. A fully diffused head behaves like a small dome and wraps light around curved shiny parts, with the camera-hole caveat handled in fixing the dark spot from a dome light's camera hole.

Head size is the other half of the swap, and the ring light selection guide covers diameter, inner aperture and stand-off. Inside one diameter class, the optics do the rest:

Values as printed in each product's data sheet; open a part for its drawing and full specifications.

The LS-RNG-0100 sets its LEDs at 60° and 620 nm on a 120 mm body; the LS-RNG-0426 is its diffused 0° twin in white; the LS-RNG-0730 keeps a 48 mm inner aperture so the lens looks through the ring, with selectable angles from low angle (0-15°) to 85°. For surface texture and directional shading cues, photometric stereo ring lighting drives the sectors of a multi-zone ring in sequence.

What accessories turn a standard light into a modular one?

Five groups: diffuser plates that spread a bar light's hard LED line, same-body heads at other beam angles, crossed polarizing film for specular glare, bandpass filters that lock the image to the LED wavelength, and extension cables in 1, 3 and 5 m lengths on 4-pin connectors.

Bar lights take a dedicated diffuser plate that turns the LED line into an even strip:

That plate is the fastest route to dome-style behavior from a linear light. Glare and ambient light are handled optically instead. A crossed polarizer pair, film on the light and analyzer on the lens, strips specular reflection from shiny surfaces — crossed polarizers for glare suppression works the set-up. A bandpass filter matched to the LED center wavelength then blocks the room's lighting, with the numbers to match explained in bandpass filters: CWL and FWHM.

Cabling makes the kit portable between stations. The LS-LAC-0048 comes in 1, 3 and 5 m lengths on a 4-pin connector, so one controller shelf serves a head wherever the cell puts it.

When does one modular light beat several dedicated lights?

When the station's task changes faster than your spares shelf: three part families sharing one station need three dedicated lights, three mountings and three controller channels, while a modular kit holds the same coverage to one body, two swap-in optics and one channel.

Count parts, not applications. The dedicated route for a three-task station is three lights, three brackets, three cable runs, three channels and three spares. The modular route is one body, the optics that change the technique, one channel per head and optics as spares: roughly eight items down to four. The changeover becomes a bracket swap of minutes rather than a re-mount and re-teach of hours.

The trade reverses in three places. A frozen high-speed line running one part around the clock gains nothing from swappable optics and gives up a little peak brightness. A washdown or food-grade cell should not be opened routinely — what IP69K washdown ratings do not cover explains why frequent optic swaps fight the sealing — so specify the permanent configuration there. And when two fixed angles must fire every cycle, stacked ring lights switching angles hold both at once instead of swapping between them.

What does modularity cost in brightness and uniformity?

Peak output, not image quality, provided you strobe: every diffuser and angle plate absorbs light, but at 60 parts per minute a 3 ms flash loads the LEDs to 3 ms / 1,000 ms = 0.3% duty, which leaves headroom to pulse far above the continuous rating.

Worked example. One part arrives every 60 / 60 = 1 s, or 1,000 ms. The camera needs a 2 ms exposure; give the flash a 3 ms pulse to cover it with margin. Duty cycle = 3 ms / 1,000 ms = 0.3%. Pulse the head at ten times its continuous rated current during that flash and the mean thermal load is 10 × 0.3% = 3% of continuous — an order of magnitude of headroom. How large a pulse a given head accepts is set by its driver and the controller channel, so read those two as a pair: LED strobe duty cycle: matching lights and controllers works the matching, why your vision light needs a controller covers the current control, and integrated strobe drivers move the timing into the light itself.

Diffusion pays for itself in evenness with the same coin. A diffused window smooths the hotspots of individual LEDs — the reason roughly a third of bar light types are diffused — and the absorbed fraction comes back as strobe headroom. Uniformity across a wide field then becomes its own balancing act, covered in large field of view lighting.

How do you spec a modular lighting kit for one station?

Work outward from the field of view: lit length equals the FOV plus 20-40 mm of margin at each end, the angle class fixes the technique, 24 V ties the kit to a single controller type, and 1, 3 or 5 m cables close the distance.

Worked example, sizing. The part is 150 mm wide and the FOV is 160 mm. Allow 30 mm of margin at each end: required lit length = 160 mm + 2 × 30 mm = 220 mm. That lands in the 200-400 mm size class, and the model below sits in it:

At 290 mm of lit length against the 220 mm target you hold 70 mm of margin for part wander and bracket tolerance.

Standardize voltage before anything else: 1,390 of the 1,403 bar lights and 888 of the 903 ring lights run on 24 V, so a 24 V controller shelf accepts nearly any head you add later. Then fix the angle class per technique — 0-15° grazing, 30-60° directed, diffused for dome-style — and order the optics as your spares. The light finder filters size, angle, color and voltage in one pass:

• Field of view plus 20-40 mm of end margin sets lit length or head diameter.
• Technique sets the angle class: 0-15° grazing, 30-60° directed, diffused for curved shiny parts.
• White covers most tasks; red raises contrast on color-marked parts for mono sensors; 850 nm or 940 nm when ambient light must be ignored.
• 24 V everywhere, one controller channel per head, strobe input on the controller.
• Spares are optics — plate, alternative-angle head, polarizer pair — not whole lights.

Send the FOV, the part finish and the cycle rate to the configurator and it narrows heads and accessories to a buildable kit:

The lighting topic page collects the technique guides behind every choice above.