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Hem / Case studies / Serial-code imaging on a dark cover
Application study · Electronics traceability

Serial marks on a dark cover: light the code without losing the part

The supplied capture shows a bright two-dimensional mark and small serial characters on a dark rectangular cover. A white bar provides a starting recipe for resolving the mark while controlling the bright edge around it.

Make the mark repeatable in the image before measuring traceability performance.

  • Light in sourceLS-2BS23738-RGBW · white
  • EvidenceReal application-lab image
  • Imaging kitCamera, lens and fixture proposed
  • AcceptanceValidate on representative parts
3D view of the inspection set-up: camera, lens, light and partDrag to rotate · scroll to zoom
3D illustration · real CAD where available
Walk through this setup 5 guided stops
From component to inspection

Understand each choice.

Choose a stop to frame the part in 3D and see why it belongs in this setup. The component notes and links remain available if 3D cannot load.

Camera and available lens CAD are published models. Lens and light envelopes use printed dimensions. The linked station uses its published base size and column height; carriage, brackets, fittings, parts and spacing are illustrative. Confirm load, travel, fasteners and clearances before ordering. Light paths explain the arrangement and do not simulate optical performance. Representative part geometry is illustrative, not reconstructed inspection evidence. The specimen and lighting angle are representative, not dimensions or settings recovered from the source capture.

From the demo to your test bench

Build around the parts you can buy.

Explore each component, check its specifications and compare alternatives. The proposed quote includes the linked test station; its catalog listing includes two lighting holders.

Mount the optics with intent

The station is an optical test bench, with its two lighting holders included in the catalog listing. The 3D column and base follow the published height and footprint. Carriages, clamps and part supports are schematic: confirm camera screw pattern, lens support, light fasteners, permissible load and actual travel before ordering.

Configure the mounting station →

Complete the electrical system

Select a controller against the exact light voltage, drive mode and power, then confirm camera data/power/I/O cables and a suitable PC. These are not silently added to the proposed optical kit.

Lighting application-lab catalog capture

Evidence you can inspect

Visible in the images

Small bright characters and a two-dimensional mark are visible inside the dark cover boundary.

What the source reports

The catalog labels the example serial-number identification under a white bar light.

How to use this evidence

One application image with no decoded payload, read statistics, code grade, source camera or working distance.

What the camera saw

Cropped from the source test sheet; original test annotations are retained. Captures are not generated or enhanced. Drag the comparison slider or use the image buttons.

Source white-bar image: the marked serial region is visible on the dark cover while its outer edge reflects brightly.
Source white-bar image: the marked serial region is visible on the dark cover while its outer edge reflects brightly.

The challenge

A small mark can be lost when the camera exposure is set by a much brighter outer edge.

The code and text may have different minimum feature sizes, and both can move with part placement.

How it was solved

The source identifies the white bar for serial-number identification. Its image shows the marked area inside a dark part rather than providing a decoded result.

Define a region of interest around the mark and use a repeatable cover fixture. Confirm illumination direction and focus on the actual surface finish before choosing a reader.

Why it works

  1. 1

    An oblique bar arrangement gives a direction to the reflected signal instead of lighting every surface identically.

  2. 2

    The code region is visible, but the source does not establish a symbology, payload, OCR recipe or successful-decode percentage.

From image contrast to a production decision

What to validate on your part

A useful sample image is the starting point. These are the checks that turn the concept into a defensible inspection.

  1. 01

    Collect actual marking variation

    Test faint, displaced, incomplete and overmarked samples with verified identities.

  2. 02

    Preserve the quiet region

    Keep the whole required code region and margins in focus without saturating adjacent reflective edges.

  3. 03

    Validate the complete reader

    Test both part localization and mark reading at the final fixture variation and exposure.

Explore your inspection requirements

How many pixels cover your feature?

Compare feature coverage, camera pixel requirements and exposure using your own planning inputs. These are calculated planning values, not inspection results or an accuracy specification.

Editable planning scenario. Adjust these example inputs for your application; they are separate from the source test and 3D setup. Motion allowance and target coverage are starting points to validate, not acceptance limits. Pixel count starts from the proposed camera's catalog resolution.

Object sampling0.04085 mm/px
Pixels across feature12.24 px
Horizontal pixels for target1000 px
Motion during exposure0.2448 px
Exposure ceiling from motion204.2 µs
Formulas and assumptions

The field, feature, speed and exposure start with neutral example values. They are not taken from the source test or the 3D illustration. Allowed motion starts at an editable 0.5-pixel example; it is not a recommended acceptance limit. Target coverage starts at an editable 5-pixel example; it is not a recommended detection or measurement threshold. The horizontal pixel count starts from the catalog Resolution row for MV-CS050-10GM(NPOE). Use the effective width after cropping, binning or decimation if those modes are enabled.

  • Object sampling (mm/px) = field width (mm) / horizontal pixels.
  • Pixels across feature = feature width (mm) / object sampling (mm/px).
  • Horizontal pixels for target = field width (mm) × target pixels across feature / feature width (mm), rounded up to a whole pixel.
  • Motion (px) = speed (mm/s) × exposure (µs) / 1,000,000 / object sampling (mm/px).
  • Exposure for allowed motion (µs) = allowed motion (px) × object sampling (mm/px) / speed (mm/s) × 1,000,000.

The exposure result is the maximum duration from this motion allowance alone. At zero speed, motion sets no exposure limit; the camera, lighting, saturation and other constraints still apply. A shorter exposure does not itself guarantee a reliable inspection.

Field width and feature width refer to the same object plane. The motion calculation assumes uniform linear motion parallel to the field-width direction and a single exposure. It does not model perspective, vibration, rolling-shutter distortion, diffraction, defocus or optical distortion. A strobe may change the effective exposure.

The target result is a horizontal sampling requirement, not a camera recommendation or a change to the selected camera. It uses the effective image width after cropping, binning or decimation and does not determine the vertical resolution or sensor size. Pixel coverage alone does not establish detectability or measurement accuracy. Validate contrast, lens performance, working distance, illumination, calibration, camera exposure limits and the inspection algorithm on representative parts. Changing field width does not change the 3D model or certify that the proposed lens can achieve that field.

The set-up and the parts

Tested lightLS-2BS23738-RGBW, white
Source camera / lensNot specified in the source image caption; proposed parts below
Proposed lens point0.1x at 152 mm, printed lens pair
Derived proposed field84.456 × 70.656 mm = sensor dimensions / 0.1x; not a source test field
Bar housing (printed)237 × 38 × 27 mm
Mounting (proposed)LS-BT-XZ-G-6-6045; 600 mm column, 600 × 450 mm base, glass tray and two included lighting holders

"Tested" identifies the part named in the source. "Our pick" is a proposed alternative or supporting part. The quote includes only cards marked "In proposed setup", with the quantities shown; other test arrangements are separate. Confirm colour, optics, controllers, power supplies, cables and mounting before ordering.

About this case study: the photos and camera images come from the application laboratory of the maker of the lighting and optics we sell, imaged on the parts shown; your results depend on your part, camera and set-up. This is an application-lab study, not a LumaSpec customer deployment. Source figures are reported results; proposed components require a fresh trial. The 3D scene illustrates the arrangement and does not simulate imaging performance.

More case studies

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Tell us the part size, smallest defect or tolerance, available working distance, material and line speed. Include what a good part and a reject look like.

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