Circular Dot Calibration Board
The dot calibration grid is one of the most commonly used high-precision calibration tools in machine vision, industrial measurement, and computer vision (on par with the checkerboard calibration grid). It consists of an array of circular black and white dots, typically categorized as symmetrical or asymmetrical dot arrays.
1. Core Advantages and Features
(1) Extremely high sub-pixel accuracy: Dots possess natural geometric symmetry. By fitting the boundary of the entire circle or calculating the centroid, the algorithm can aggregate information from hundreds or thousands of pixels to determine the center position, achieving a positioning accuracy generally superior to traditional corner points (such as checkerboard corner points).
(2) Strong anti-distortion capability: Under conditions of wide viewing angles or severe lens distortion, feature extraction from dot arrays is more stable than from square corner points, reducing the likelihood of feature point drift or misidentification.
(3) High orientation discrimination: The asymmetric circle grid, by introducing a unique asymmetry in dot arrangement, allows the algorithm to automatically determine the orientation of the calibration grid in a single image, avoiding calculation errors caused by orientation reversal.
2. Main Application Scenarios
(1) Camera-based distortion calibration: Used to accurately calculate the camera's focal length, optical center, and lens distortion coefficient before machine vision 3D reconstruction, binocular stereo vision, or monocular ranging.
(2) Industrial high-precision measurement and photogrammetry: Commonly used in aerial photography, large workpiece 3D measurement, and automotive manufacturing, where high precision is required.
(3) Robot eye-hand calibration: Used in conjunction with the end-effector camera to establish precise mathematical transformations between the camera coordinate system and the robot arm coordinate system.
3. Customization Services (Parameters and materials can be customized; custom designs based on provided drawings are also available)
The dot calibration plate substrate is optional. Different substrates (such as glass, ceramics, film, aluminum plates, etc.) can be customized according to different application scenarios, environments, and precision requirements.
The following are some commonly used substrate parameter information:
1. Glass substrate parameters:
| Design |
Substrate
|
|
Manufacturing Process
|
Photolithography
|
Glass substrate
|
Quartz glass (fused silica)/soda glass
|
|
Minimum line width
|
1µm / 0.55µm
|
Transmittance rate(@550nm)
|
>95%
|
|
Feature accuracy
|
±1µm
|
Coefficient of thermal expansion
(20-200°C)
|
<5.0×10⁻⁷/K
|
|
Coating
|
Yellow chromium, bright chromium
, blue chromium (low reflectivity)
|
Expansion ratio(20-200°C)
|
0.00006% (0.6µm/°C of 1m)
|
|
Reflectance
|
< 13.4% @550nm
|
Surface flatness
|
<0.55µm (length<50mm)
|
|
< 1.8% @650nm
|
<2µm (length<100mm)
|
|
< 2.67% @750nm
|
<5µm (length>100mm)
|
|
Coating accuracy
|
120nm (±0.20nm)
|
Surface roughness
|
<0.025µm
|
|
Optical density OD
|
Yellow Chromium 3 (Blue 5)
|
Thickness
|
1mm,1.6mm,2.3mm,3mm(±0.2mm)(500*500*4.8)
|
|
White background
|
Minimum line width:10µm
|
Minimum/maximum size
|
Min: 2×2 mm
|
|
White background thickness: 40 µ m
(smooth white coating on the back)
|
Max: 800×960mm (±0.1mm)
|
|
Positive & negative shapes
|
Positive: pattern opaque
Negative: pattern translucent
|
Appearance and shape
|
Square
|
2. Ceramic substrate parameters:
|
Design
|
Substrate
|
|
Manufacturing Process
|
Photolithography
|
Type
|
Matte chromium on matte ceramics
|
Bright chrome on glossy ceramics
|
|
|
Type
|
Matte ceramic
|
Glossy ceramic
|
Ceramic substrate
|
Zirconia / Alumina
|
|
Minimum line width
|
4µm
|
2µm
|
Thickness
|
1mm (±0.1mm, common)
|
2mm (common)
|
3mm (±0.1mm)
|
|
Feature accuracy
|
±2µm
|
±2µm
|
Surface flatness
|
<30µm (length<100mm)
|
<60µm (length<200mm)
|
|
Appearance accuracy
|
±0.05mm
|
±0.05mm
|
Surface flatness
|
MIN: 2×2mm (±0.1mm);
MAX: 228×228mm (±0.1mm)
|
|
Coating
|
Chromium
|
Chromium
|
Surface roughness
|
<0.2-0.7µm
|
|
Light coating/matte coating
|
Matte chromium coating
|
Bright chrome coating
|
Coefficient of thermal expansion
(40-400°C)
|
<6.7×10⁻⁶/K
|
|
ReflectaCnce
|
< 12.88% @550nm
|
< 9.56% @550nm
|
Unit weight
|
≥ 3.66 g/cm³
|
|
< 10.62% @650nm
|
< 1.89% @650nm
|
|
< 12.23% @750nm
|
< 11.168% @750nm
|
|
Coating thickness
|
100-120nm
|
100-120nm
|
Rockwell hardness
|
≥80 HRA
|
|
Positive and negative shapes
|
Positive film: opaque pattern,
Negative film: transparent pattern
|
Appearance and shape
|
Laser cutting of any shape
|
Square
|
Ellipse
|
|
Protective layer
|
The thin film above the chromium layer
makes the chromium pattern more durable
|
Special shape
|
Punch
|
Chamfer
|
Oblique angle
|
3. Film substrate parameters:
|
Design
|
Film substrate
|
|
Manufacturing Process
|
Lithography
(Film Lithography Machine)
|
Application
|
Used for transmission/backlight
/functional testing
|
|
Minimum line width
|
10 µ m/30 µ m optional
|
Coefficient of expansion
|
Film shrinks when heated and expands when cooled
|
|
Feature accuracy
|
±10µm
|
10µm/°C of 1m
When the relative temperature is constant,
When the humidity changes by 1 ° C,
A film with a length of 1m will change by 10 µ m (one ten thousandth)
|
|
Coating
|
Silver bromide
|
Transmittance rate(400~700nm)
|
>90% ultraviolet<(400~700nm)>infrared
|
|
Coating thickness
|
2µm
|
Film substrate thickness
|
0.18mm (±0.01mm)
|
|
Optical density OD
|
OD>4 when 100% black
(OD value controllable in grayscale)
|
Maximum size
|
0.71×0.81m (±0.1mm)(minimum line width 10µm)
1.68×3.5m (±0.1mm)(minimum line width 30µm)
|
|
color
|
Black grayscale,
sine grayscale
|
Appearance
|
Laser cutting, straight edge cutting, and circular hole hollowing are available
|
Product Tags:
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Customizable Circular Dot Calibration Board With Chromium Coating Images
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