Negative dot array calibration targets
Clear circular features on an opaque field. A transmitted-light reference for machine vision, camera calibration and coordinate measurement.
Discuss your drawingView technical specifications
A bright point on a dark field
With a suitable backlight, light passes through the circular openings in the patterned layer while the surrounding field remains dark. The camera captures the point array, and calibration software matches detected image centres to the physical coordinates in the target drawing.
Polarity matters: software set up for dark dots may need different detection settings for a bright-dot target.
Compare the full dot-array rangeWhy use a circle grid?
Locate each centre
Circle-boundary fitting or centroid calculation can estimate an image centre from multiple pixels. Subpixel repeatability depends on focus, sampling, contrast and the selected algorithm; it is not the same as the manufactured point-position tolerance.
Sample the full field
Dots distributed across the image support lens-distortion and scale analysis from centre to edge. Strong perspective or uneven backlighting can still shift detected centres and must be checked in the capture workflow.
Identify pattern orientation
A supported asymmetric grid can identify row order and target orientation from one image. Its staggered coordinates must match the software model; a symmetric grid cannot simply be substituted.
Technical specifications
Glass and film figures below describe available configurations. Ceramic values are included for comparison, but ceramic is for reflective targets and cannot transmit light through clear dots.
Negative-polarity pattern
| Pattern polarity | Clear dots on an opaque field |
|---|---|
| Array layout | Symmetric or staggered; coordinates defined by drawing |
| Illumination | Transmitted light through the clear dots |
| Coordinate model | Dot diameter, X/Y pitch, row/column order and origin follow the drawing |
Glass target
Fused silica or soda-lime glass with a photolithographic dot pattern.
For this negative-polarity version, specify clear dots in the opaque coating. The optional white backing listed below is a separate glass configuration, not part of a transmitted-light target.
| Substrate | Fused silica / soda-lime glass |
|---|---|
| Process | Photolithography |
| Line-width tolerance | ±0.2 µm |
| Minimum feature width | 0.55 µm or 1 µm, by pattern configuration |
| Feature and overall accuracy | ±1 µm |
| Clear-area transmission | >95% at 550 nm |
| Chrome finish | Yellow, low-reflection blue or bright chrome |
| Optical density | Yellow chrome OD 3; blue chrome OD 5 |
| Glass thickness | 1, 1.6, 2.3 or 3 mm (±0.2 mm) |
| Large-format glass thickness | 4.8 mm for the 500 × 500 mm format |
| Outline size | From 2 × 2 mm up to 800 × 960 mm |
| Outline tolerance at maximum format | ±0.1 mm at 800 × 960 mm |
| Fused-silica expansion | <5.0 × 10⁻⁷/K at 20–200°C |
| Low-reflection chrome reflectance | <13.4% at 550 nm; <1.8% at 650 nm; <2.67% at 750 nm |
| Surface flatness | <0.55 µm for lengths <50 mm; <2 µm for lengths <100 mm; <5 µm for lengths >100 mm |
| Chrome coating thickness | 120 ±5 nm (1200 ±50 Å) |
| Surface roughness | <0.025 µm |
| Optional white backing | 40 µm coating; 10 µm minimum feature width |
| Outline shape | Square |
| Pattern polarity | Opaque dots or clear dots |
Ceramic target
Opaque ceramic plates with matte or bright chrome patterns for reflective imaging.
Ceramic is opaque. Its figures apply to reflective dot-array targets and cannot make a backlit clear-dot negative plate.
| Substrate | Zirconia or alumina ceramic |
|---|---|
| Process | Photolithography |
| Line-width tolerance | ±0.2 µm |
| Pattern options | Matte chrome on matte ceramic; bright chrome on glossy ceramic |
| Minimum feature width | 4 µm matte; 2 µm glossy |
| Feature accuracy | ±2 µm |
| Outline accuracy | ±0.05 mm |
| Ceramic thickness | 1 mm (±0.1 mm), 2 mm or 3 mm (±0.1 mm) |
| Outline size | From 2 × 2 mm up to 228 × 228 mm |
| Outline size tolerance | ±0.1 mm at minimum and maximum formats |
| Flatness | <30 µm below 100 mm; <60 µm below 200 mm |
| Chrome coating | Matte chrome or bright chrome |
| Chrome thickness | 120 ±5 nm (1200 ±50 Å) |
| Surface roughness | 0.2–0.7 µm |
| Thermal expansion | <6.7 × 10⁻⁶/K at 40–400°C |
| Matte chrome reflectance | <12.88% at 550 nm; <10.62% at 650 nm; <12.23% at 750 nm |
| Bright chrome reflectance | <9.56% at 550 nm; <1.89% at 650 nm; <11.168% at 750 nm |
| Density | ≥3.66 g/cm³ |
| Rockwell hardness | ≥80 HRA |
| Optional protection | Thin protective layer above the chrome pattern |
| Edge and hole options | Laser-cut outline, hole, chamfer or bevel |
| Pattern polarity | Opaque pattern or clear pattern |
| Finish and shape | Matte or glossy; square, elliptical or drawing-defined cutouts |
Photographic film target
A thin, lightweight format for larger patterns where mounting and ambient conditions are controlled.
Film can be selected for larger backlit patterns where mounting, temperature and humidity are controlled.
| Process | Photographic-film lithography |
|---|---|
| Application | Transmitted-light or backlit functional testing |
| Minimum feature width | 10 or 30 µm |
| Feature accuracy | ±10 µm |
| Film thickness | 0.18 mm (±0.01 mm) |
| Temperature-related dimensional change | 10 µm per °C per metre |
| Environmental response | Film dimensions also respond to humidity; control temperature and relative humidity during coordinate measurement |
| Emulsion | Silver halide, approximately 2 µm |
| Clear-area transmission | >90% across 400–700 nm |
| Optical density | OD >4 in solid black; grayscale density can be specified |
| Maximum format | 0.71 × 0.81 m at 10 µm minimum width; 1.68 × 3.5 m at 30 µm |
| Maximum-format tolerance | ±0.1 mm for both maximum formats |
| Pattern and cutting | Black, grayscale or sinusoidal grayscale; straight, laser-cut or perforated outline |
Where it is used
Camera calibration and 3D visionKnown physical circle coordinates across multiple views support estimation of camera intrinsics and lens distortion for monocular or stereo workflows.
Industrial metrology and photogrammetryA point field supports image-to-plane mapping and image-scale checks across large components or camera-guided assemblies when the target coordinate record is defined.
Robot hand-eye calibrationCapture the same target coordinate frame at recorded robot poses to solve the camera-to-robot transformation.
Define the coordinate pattern
A negative pattern changes the illumination contrast, not the meaning of its coordinates. For calibration, the physical point list and the detector order must agree.
GeometryDot diameter, X/Y centre pitch, rows, columns and coordinate origin.
OpticsWavelength, backlight, opaque-field density and pattern-side direction.
InspectionPoint positions, diameter, missing features and the measurement record required.
Before you order
Does a negative target require backlighting?
Clear dots are normally imaged with transmitted illumination. Confirm the wavelength, light uniformity and camera exposure for the actual setup.
Can the same detector read dark and clear dots?
Not always. The detector must support the selected contrast polarity and the same row and column coordinate order as the physical target.
Does the photograph define the manufactured dimensions?
No. Dot diameter, pitch, plate outline and position tolerances are defined by the approved drawing.
Send us your pattern
Share the point coordinates, polarity, glass dimensions and camera setup so the target can be matched to your detector.
Request a quoteSelection notes
Negative circle-grid targets use transmitting circular features in an opaque field for suitable backlit camera-calibration arrangements.
Confirm detector polarity and illumination before capture. Overexposure can enlarge apparent dots and bias centre estimates; retain complete, sharply resolved features across useful poses.
Information for your inquiry
Transmitting-dot diameter, centre spacing, layout, active area, material, working distance, backlight and detector.
Can I change to negative polarity without changing the capture setup?
Check the detector, illumination direction, exposure and the coordinate map. Polarity changes image contrast but does not replace the geometry needed for calibration.