Solid-state light sources are much more efficient than arc-discharge lamps at converting electricity into light. That’s a fact. However, because like any light source, the light output and lifetime of the sources both decrease with increasing temperature, the removal of heat generated in the process remains a critical engineering requirement.
Typical Lumencor light engines used for fluorescence microscopy generate watts of light output. A liquid light guide is used to deliver that light to the microscope, without transmitting vibrations emanating from the cooling fan. This solution, implemented in all our SOLA®, SPECTRA®, SPECTRA X® and AURA® light engines, is depicted in the upper panel of the graphic. In an alternative engineering solution, shown in the lower panel, the light generation and heat dissipation functions are performed by two separate but coupled modules. This dispenses with the need for a liquid light guide at the expense of adding a circulation hose to carry pressurized cooling fluid between the heat exchanger and light generation modules.
At Lumencor, our adoption of the on-board heat exchanger plus liquid light guide stems from three overriding considerations:
Minimum separation between a heat source and a dissipation conduit maximizes cooling efficiency and reliability.
A passive liquid light guide is more robust than a pressurized liquid circulation system.
Perceived deficiencies of liquid light guides are largely derived from their use with metal halide lamps. They are simply not relevant in the context of solid-state light engines.
We’ve sold many thousands of light engines and have not replaced even one light guide due to over heating, leaking or bubble formation. Our customers can confidently testify that they have never replaced a liquid light guide on a Lumencor light engine… that can be a significant cost savings over the long lifetime of these solid-state lighting products!
Lumencor’s AURA light engine is a high performance, state-of-the-art, bright set of solid state light sources. It can be tailored to provide for the spectral, spatial and temporal needs of the bioanalysis tool it is designed to support. Key features of the AURA light engine include:
Up to 5 independently controlled (on/off and intensity) light sources
A selection of outputs ranging from ultraviolet to near-infrared
High performance bandpass filters or unfiltered white light
Fast (~10 μs) switching between color channels
100–700 mW optical output power per channel (dependent on filtering)
Light guide or optical fiber coupling for vibrational isolation
Vertically or horizontally oriented installation options
TTL and serial control interfaces
Click Here for more information on the AURA light engine.
Despite the name change, metal halide lamps are still essentially improved mercury vapour lamps. The concept of adding metallic iodides for spectral modification of mercury arc discharge lamps dates back to US patent 1,025,932 granted to Charles Steinmetz in 1912. However, a typical 120W metal halide bulb used for fluorescence microscopy contains about the same amount of mercury (~20 mg) as a 100W mercury short arc bulb used for the same application. Along with the mercury content itself, the associated bulb replacement costs and hazardous material handling constraints remain as well.
Lumencor’s solid state light engines eliminate these constraints entirely while delivering spectral content and output power at least equivalent to and in most cases superior to that of mercury and metal halide lamps. While these economic and environmental issues are clearly important, it is the performance advantages of solid state illumination such as temporal stability (see below) that are most readily appreciable to end users. Because as imaging techniques become more complex and multidimensional, data quality counts more than ever.
Specimen: Uniform FITC slide (Chroma)
Microscope: Nikon Ti, 10X/0.3 NA, FITC filter set
Light sources: SOLA SE 365 (10% maximum output) or 120W metal halide (12.5% maximum output)
Data collection: 100 frames, 50 ms exposure, 50 ms intervals (10 fps), ORCA-Flash4.0 sCMOS
Fluorescence intensity = average gray level per frame, normalized to a value of 1.0 for the first frame.
Solid-state light engines are now displacing mercury, metal halide and tungsten-halogen lamps in many bio-optical applications. This trend is driven by a wide range of economic and performance benefits. Light engines are less expensive to operate and maintain than lamps because there are no bulbs or light guide replacements required. Output stability and electronic control of output intensity are dramatically superior to the decay, noise, flicker of any bulb.
An article by Lumencor’s Director of Technical Support, Iain Johnson, in the February 2017 issue of Laser Focus World describes how these benefits can be leveraged to deliver illumination solutions tailored for specific applications.