CharuCo Targets
In CharuCo targets, fields are uniquely encoded, which makes it possible to calibrate using a partly occluded or with a non-ideal target location. It also improves robustness against image noise. These properties allow recording information from the very edges of images, which is ideal for accurate and robust determination of lens parameters. Also, the unique coding of feature points allows for stereo calibration in which corners may be partly non-visible.
CharuCo detection is implemented in the OpenCV 3 and OpenCV 4 contrib module, but is also available as a stand-alone library.
Our default selection of CharuCo targets use the DICT_5x5 dictionary. If your application requires further customization, please contact us, and we are able to accommodate any customizations of CharuCo boards. You can also provide a PDF drawing of your completely custom pattern.
Precision Manufactured
All of our calibration targets are made from aluminium/LDPE composite which offers excellent flatness and stiffness, while being lightweight. Additionally, the composite material offers good thermal stability and corrosion resistance.
The patterns are transferred to the composite material using a specialised precision direct UV (Ultra-Violet) printing process resulting in a durable matte finish. Through extensive testing, we have found this process to be ideal for machine vision applications, where both accuracy, good optical performance and physical robustness are of utmost importance.
Sizes
The following sizes are available:
| Size [mm] |
Size [inches] |
| 800 x 600 x 6 |
31.496 x 23.622 x 0.236 |
| 600 x 400 x 6 |
23.622 x 15.748 x 0.236 |
| 400 x 300 x 6 |
15.748 x 11.811 x 0.236 |
| 300 x 200 x 6 |
11.811 x 7.874 x 0.236 |
| 200 x 150 x 6 |
7.874 x 5.905 x 0.236 |
Patterns
We offer two pattern options, Fine and Coarse, which have been specifically designed to work optimally with high (Fine) and low (Coarse) resolution cameras. The following tables illustrate the available options:
Fine
| Plate Size [mm] |
Checker Width [mm] |
Marker Width [mm] |
Rows x Columns |
| 800 x 600 x 6 |
30 |
23.33 |
18 x 25 |
| 600 x 400 x 6 |
20 |
15.56 |
18 x 29 |
| 400 x 300 x 6 |
15 |
11.67 |
18 x 25 |
| 300 x 200 x 6 |
10 |
7.77 |
18 x 29 |
| 200 x 150 x 6 |
7.5 |
5.83 |
18 x 25 |
Coarse
| Plate Size [mm] |
Checker Width [mm] |
Marker Width [mm] |
Rows x Columns |
| 800 x 600 x 6 |
60 |
46.66 |
9 x 12 |
| 600 x 400 x 6 |
40 |
31.11 |
9 x 14 |
| 400 x 300 x 6 |
30 |
23.33 |
9 x 12 |
| 300 x 200 x 6 |
20 |
15.56 |
9 x 14 |
| 200 x 150 x 6 |
15 |
11.67 |
9 x 12 |
Note about marker widths
The white margin around the AruCo markers has the same width as the encoding checkers. Hence, for the DICT_5X5 ChAruco boards, the markers width is 7/9th of the checker width. Note that this size is only used during detection and not a critical dimension for the calibration.
Technical Specifications
| Weight |
6.6 kg/m² |
| Outdoor Lifetime |
up to 3 years |
| Temperature Resistance |
-50 °C to + 80 °C [-58 °F to +176 °F] |
| Specified temperature |
20 °C (ISO 1:2016)
|
| Linear thermal expansion |
~24 μm /(°C · m) |
| Rigidity E·J |
3840 kNcm2/m
|
