Lights

Backlights

Backlights sit behind the part and give the camera a sharp, high-contrast silhouette - the standard choice for gauging, outline and hole inspection, and for spotting contamination in clear film. Collimated versions keep edges crisp on thick parts; edge-lit versions are the thinnest.

Shop by colour: Red backlights · Blue backlights · Green backlights · White backlights · Infrared backlights · UV backlights

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Backlights

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LS-BKL-1465Flat Backlight, 150 x 100 mm, White White150 mm × 100 mm182 mm × 113 mm × 18 mm24 VDC25 W-$319.00Quote Ships in 2-3 weeks
LS-BKL-1477Flat Backlight, 250 x 150 mm, White White250 mm × 150 mm282 mm × 163 mm × 19 mm24 VDC46 W-$529.00Quote Ships in 2-3 weeks
LS-BKL-1485Flat Backlight, 300 x 200 mm, White White300 mm × 200 mm332 mm × 213 mm × 19 mm24 VDC66.1 W-$729.00Quote Ships in 2-3 weeks
LS-BKL-1473Flat Backlight, 200 x 200 mm, White White200 mm × 200 mm232 mm × 213 mm × 18 mm24 VDC66 W-$549.00Quote Ships in 2-3 weeks
LS-BKL-1445Flat Backlight, 50 x 30 mm, White White50 mm × 30 mm82 mm × 43 mm × 18 mm24 VDC3.3 W-$209.00Quote Ships in 2-3 weeks
LS-BKL-1453Flat Backlight, 80 x 80 mm, White White80 mm × 80 mm112 mm × 93 mm × 18 mm24 VDC14.7 W-$249.00Quote Ships in 2-3 weeks
LS-BKL-1461Flat Backlight, 120 x 120 mm, White White120 mm × 120 mm152 mm × 133 mm × 18 mm24 VDC22 W-$309.00Quote Ships in 2-3 weeks
LS-BKL-1457Flat Backlight, 100 x 100 mm, White White100 mm × 100 mm132 mm × 113 mm × 18 mm24 VDC25 W-$279.00Quote Ships in 2-3 weeks
LS-BKL-1441Flat Backlight, 30 x 30 mm, White White30 mm × 30 mm62 mm × 43 mm × 18 mm24 VDC2.4 W-$199.00Quote Ships in 2-3 weeks
LS-BKL-1449Flat Backlight, 50 x 50 mm, White White50 mm × 50 mm82 mm × 63.2 mm × 18 mm24 VDC5.1 W-$209.00Quote Ships in 2-3 weeks
LS-BKL-1390Flat Backlight with Center Hole, 250 x 250 mm, IR 940 nm Infrared250 mm × 250 mm282 mm × 263 mm × 19 mm24 VDC52 W940 nm$739.00Quote Ships in 2-3 weeks
LS-BKL-1408Flat Backlight with Center Hole, 450 x 320 mm, White White450 mm × 320 mm488 mm × 335 mm × 21 mm24 VDC198 W-$1,379.00Quote Ships in 2-3 weeks
LS-BKL-1391Flat Backlight with Center Hole, 250 x 250 mm, Red Red250 mm × 250 mm282 mm × 263 mm × 19 mm24 VDC48 W625 nm$739.00Quote Ships in 2-3 weeks
LS-BKL-1387Flat Backlight with Center Hole, 250 x 200 mm, White White250 mm × 200 mm282 mm × 213 mm × 19 mm24 VDC53 W-$639.00Quote Ships in 2-3 weeks
LS-BKL-1404Flat Backlight with Center Hole, 400 x 300 mm, White White400 mm × 300 mm438 mm × 315 mm × 21 mm24 VDC83 W-$1,209.00Quote Ships in 2-3 weeks
LS-BKL-1396Flat Backlight with Center Hole, 300 x 200 mm, Red Red300 mm × 200 mm332 mm × 213 mm × 19 mm24 VDC45.9 W625 nm$719.00Quote Ships in 2-3 weeks
LS-BKL-1379Flat Backlight with Center Hole, 200 x 200 mm, White White200 mm × 200 mm232 mm × 213 mm × 18 mm24 VDC48 W-$549.00Quote Ships in 2-3 weeks
LS-BKL-1397Flat Backlight with Center Hole, 300 x 200 mm, White White300 mm × 200 mm332 mm × 213 mm × 19 mm24 VDC54 W-$719.00Quote Ships in 2-3 weeks
LS-BKL-1383Flat Backlight with Center Hole, 250 x 150 mm, White White250 mm × 150 mm282 mm × 163 mm × 19 mm24 VDC41 W-$529.00Quote Ships in 2-3 weeks
LS-BKL-1372Flat Backlight with Center Hole, 120 x 120 mm, White White120 mm × 120 mm152 mm × 133 mm × 18 mm24 VDC16 W-$309.00Quote Ships in 2-3 weeks
LS-BKL-1368Flat Backlight with Center Hole, 100 x 100 mm, White White100 mm × 100 mm132 mm × 113 mm × 18 mm24 VDC11 W-$279.00Quote Ships in 2-3 weeks
LS-BKL-1569150 x 150 mm Ultraviolet light UV150 x 150 mm-24 V19.2 WUV: 365-405 nm$389.00 Ships in 2-3 weeks
LS-BKL-156550 x 50 mm Ultraviolet light, power 3.6 W UV50 x 50 mm-24 V3.6 WUV: 365-405 nm$209.00 Ships in 2-3 weeks
LS-BKL-156780 x 80 mm Ultraviolet light UV80 x 80 mm-24 V7.2 WUV: 365-405 nm$249.00 Ships in 2-3 weeks

How to choose a machine vision backlight

A backlight sits behind the part and shines toward the camera. The part shows as a dark silhouette on an even, bright field, so the edge position depends on geometry, not on surface colour, texture or print. That makes backlighting the first choice for gauging, hole and gap checks, presence checks and for finding particles or bubbles in clear material. Work through these points in order.

1. Size: cover the field of view at the backlight, plus a margin

Every edge you measure must fall on uniform light. With a standard (entocentric) lens the viewing cone widens behind the part, so the area the camera sees at the backlight plane is larger than the field of view at the part. Size the backlight to that larger area and add 10-20 % on each axis: brightness falls off toward the frame of any backlight. For long webs, sheets or extrusions, a narrow strip backlight under a line of interest is often enough.

2. Colour and wavelength

In a silhouette the colour does not change the contrast much, but it changes edge sharpness, ambient rejection and what the light passes through:

  • Blue (455-470 nm): the shortest visible wavelength gives the least diffraction blur at the edge, the usual choice for precise measurement with a mono camera.
  • Red (625 or 660 nm): good mono-sensor response and easy to isolate from room light with a red bandpass filter.
  • Infrared (730, 850 or 940 nm): passes through many dyed plastics, inks and thin papers that block visible light, and is invisible to operators. Needs a mono camera or one without an IR-cut filter.
  • UV (365-405 nm): many clear plastics and coatings absorb UV, so a transparent film that disappears on a visible backlight shows up dark.
  • White: for colour cameras, for example checking the colour of a liquid in a clear container.

3. Construction: standard, edge-lit, collimated or with a centre hole

  • Standard (direct-lit): LEDs behind a diffuser. The most output per area; housings are commonly 18-30 mm high.
  • Edge-lit: LEDs at the edge of a light-guide plate. About 7-11.5 mm thick where stated, for tight machines, with less output than a direct-lit panel of the same size.
  • Collimated: near-parallel light. Paired with a telecentric lens it gives the sharpest edges on thick or round parts. See collimated lights.
  • With centre hole: a round or square opening (20-80 mm where stated) so the camera can look through the panel and use it as a flat front light, or so a second light can shine through.

Some panels take a polarizing film or a light-control (parallel) film to narrow the emission angle.

4. Drive: constant, dimmable or strobed

Panels without a driver need an external light controller. Panels with an in-line driver take 24 V DC directly and dim with an analog voltage; versions with a PNP trigger input can be pulsed above their continuous rating (overcurrent strobe) to freeze moving parts. Work out the exposure the line allows with the motion blur calculator, then check that the light's shortest pulse and strobe frequency fit it.

5. Environment and mounting

IP50 suits dry cabinets; wash-down lines need IP67, IP68 or IP69K. Check the mounting (T-slot channel, tapped holes, nut grooves), the cable exit and length, and whether the connector is flying leads or M12.

What the range covers

ParameterRange in this category
Lit areaFrom about 25 x 25 mm to 700 x 700 mm; strip backlights 25.4 mm wide with lit lengths beyond 2 m
ColoursWhite, blue 455/470 nm, cyan 505 nm, green 520/530 nm, amber 590 nm, red 625/660 nm, IR 730/850/940 nm, UV 365-405 nm
Supply24 V DC on almost every model
Strobe (where offered)Pulses from 30 µs, typically up to 2,000 Hz, some to 4,000-5,000 Hz
ProtectionIP50 to IP69K

Filter by colour: white, red, blue, infrared and UV backlights.

Typical applications

  • Diameter, length and profile of turned, stamped or extruded parts, and wire or rod diameter.
  • Hole count, position and size in sheet metal, gaskets and PCBs.
  • Connector pin presence and straightness seen from the side.
  • Fill level, bubbles and particles in clear bottles, vials and film.
  • Edge and gap tracking of webs, labels and cut sheets.

Common mistakes

  • Sizing the backlight to the part instead of to the field of view at the backlight plane, so the corners go dark.
  • Running the panel too bright or the exposure too long. Light spills around the edge and the silhouette shrinks: the measured size then depends on intensity. Fix the brightness and exposure before calibrating.
  • Measuring thick parts with a diffuse panel and a standard lens. The camera sees the side wall, not the edge; use a collimated backlight and a telecentric lens.
  • Placing the panel inside the depth of field, so dust and scratches on the diffuser appear in the image. Move it further back.
  • Pairing an infrared backlight with a colour camera that has an IR-cut filter.

Questions

Diffuse or collimated backlight?
Diffuse panels are tolerant of alignment and suit presence, hole and fill checks on thin parts. Collimated panels give sharper, more repeatable edges on thick, round or reflective-edged parts, and are normally paired with a telecentric lens.

How far behind the part should the backlight sit?
Far enough that its surface is out of focus, so diffuser texture and dust blur away, and close enough that the panel still covers the viewing cone. Then size the panel for that distance.

Can a backlight inspect transparent parts?
Yes. Bubbles, particles, cracks and edges in glass or clear plastic bend or scatter the light and show as dark marks. For clear film that a visible backlight cannot show, try UV.

What else do I need?
A lens and camera that resolve the edge and, for strobing or several lights, a controller. Build the system to match them, or see the lighting guide to compare backlights with other light types.