High-quality lighting is very important for Digital Image Correlation (DIC). The ability of the technique to accurately measure contour (shape), displacement and strain can be achieved through using an illumination system that has the following properties: high-intensity brightness, homogenous distribution, monochromatic (single-wavelength) source and continuous (flicker-free) operation.
An illumination system is specifically required for the purpose of providing contrast, within the camera shutter time, so that the correlation algorithm can distinguish between the contrast of light & dark pixels. Illumination from a source creates image brightness.
The brighter an image appears, the quicker the shutter time can operate – allowing faster measurements to be performed.
Dantec Dynamics has a portfolio of illumination systems available, varying in: wavelength, illuminance output and optics. The selection of the most appropriate illumination system is dependent on the measurement test application.
The X- and SX-Illlumination Systems are offered in red (650–670 nm) wavelength or for high-temperature testing applications, in green (520–535 nm). Both systems are supplied with exchangeable LED array lenses with 15°, 25°, 45° & 75° optics, so users can better control the illumination distribution with respect to the test application, stand-off distance. All systems are supplied with a mounting bracket for possible connection to a polarization filter.
The XR- and XG-LED Illumination Systems are easy-to-use and adaptable for the FlexDIC, MulticamDIC or MSpeedDIC systems, with any low- or medium-speed testing applications. Consisting of a 36 LED array, the XR- & XG-LED Illumination Systems provide a flicker-free, medium-intensity light at a fixed, continuous illumination setting.
The SXR- and SXG-LED Illumination Systems are powerful and are designed to be used together with the MSpeedDIC or HSpeedDIC systems, for any medium- or high-speed testing applications.
Consisting of a 126 LED array, the SXR & SXG-LED Illumination Systems provide a flicker-free, high-intensity light at a fixed, continuous illumination setting.
The LED Illumination System is available together with the EduDIC system and for any small-area, low-speed (quasi-static) testing applications.
Consisting of a 156 white-light LED array, the LED Illumination System provides a flicker-free, low-intensity light that can be switched to various cool (3200°K) to warm (5600°K) colour-temperature settings. The system also features a dimmer whereby the intensity can be adjusted from 10% to 100%.
A polfilter filters transient light in only one direction/angle. The advantage of this is that polarized light from a surface can be filtered out, thus allowing a measurement to be performed. Using a polfilter, both for the illumination and lens, known as “cross-polarization”, is most effective for the minimization of glare and refraction, since the control of the refraction of the specific (application) viewing angle can be best controlled.
A polfilter is used to manage reflections and suppress glare that may occur when working through mediums (ie. glass windows) or with shiny-coated objects.