A wide range of imaging applications do not require the unique illumination capabilities of a laser but still demand for more precise control than a constant halogen illumination can offer. LED illumination has clear advantages over the alternatives. Known spectral characteristics together with low heat dissipation and the ability to work in pulsed mode come in a cost-efficient package for various fields of applications.
LaVision offers LED solutions for different purposes. The LED 35 Illumination Units can be used in a „quasi-CW“ operating mode (light pulses are perceived by the human eye as flicker-free light) or synchronized to other devices and events by DaVis software. They come with individual power supplies and are triggered or modulated by TTL signals up to 100 kHz.
Standard colors are white and blue. The LED 35 Illumination Units contain 9 high power LEDs each and are focused for efficient usage of the light. White illumination is highly efficient and matches any camera‘s sensitivity curve well. Blue illumination is advantageous when high temperatures or flames give a strong background radiation of visible or infrared wavelengths or for use with photogenic patterning.
Sometimes it is not possible to guarantee an optimal sample illumination over the entire measurement process. Light reflections on metallic or glossy surfaces that may arise due to movement or deformation of the sample, complicate the subsequent image analysis or make recordings even unusable. As a variant the LED illumination units can be equipped with a filter for producing polarized light, whereby these reflections are reduced significantly.
The Clip-on Frame with polarizing filter includes 1 frame for use with LED 35 Illumination devices.
If the specimen has a reflective surface, complex geometry, or undergoes large deformation during the experiment, shadows or reflections may occur on the specimen surface. This can make image evaluation difficult.
An alternative approach to white light illumination is Ultra-Violet (UV) light. When UV light is combined with a matching filter for the camera it is possible to avoid the potential issues described above. In order to use UV light the specimen surface must be prepared with a suitable speckle pattern: this can be achieved with fluorescent paint (photogenic patterning) matched to the light characteristics. UV speckle is robust and stable over time irrespective of the specimen’s movement, and through the use of a matched filter, changes in ambient lighting do not affect the image quality.
LaVision’s UV LED Panel offers a compact light capable of illuminating small or large areas together with matched camera filters and speckle application kit.
The LED Floodlight is an LED light of continuous high power. It allows to illuminate large fields-of-view for digital imaging measurements with flickerfree light. Although pulsed (strobe) light sources reach higher maximum brightness they often are not suitable to synchronize to high frame rates (with high-speed cameras) and continuous light is advantageous. For the use with short exposure times – to avoid motion blur – it is important to have a flickerfree light source to maintain equally exposed images throughout a recording.
Strain experiments with high-speed cameras require large amounts of light in a short time. The LED-Flashlight 300 provides an array of 72 high-power LEDs in an area of 300 x 100 mm². It is much more compact, made up only by the LED module itself and a small power supply, allowing easy transportation and mounting. The incoherent white light ensures high image quality with constant homogeneous brightness in time and space. The amount of light output is similar to high-repetition-rate lasers at a fraction of the cost. The LEDs are operated above the nominal LED current to generate short pulses at very high light intensities. In the free-trigger mode at lower peak power, the LED-Flashlight 300 can either be used for constant illumination (100 % duty cycle), e.g. for experimental adjustment, or can be triggered with an arbitrary pulse sequence, e.g. for dual-pulse or multi-pulse illumination.
|Size||337 x 117 x 153 mm³|
|Weight||5.3 kg (LED module)
1.6 kg (power supply)
|LEDs||72 white high power, high efficiency LEDs|
|Opening angle||10° (+/- 5°)|
|Working distance||typ. 500 mm – 2000 mm|
|Electrical power||avg. 300 W|
|Efficiency||20 % (free-trigger), 10 % (pulsed-overdrive)|
|Light pulse trigger||0 – 20 kHz, TTL-level|
|Jitter||< 10 ns|
|Mode selection||manual switch or remote (TTL)|
|Safety features||temperature control, LED trigger protection|