The Lambda DG-4 offers unprecedented speed and versatility for experiments requiring rapid light wavelength switching. It offers all the advantages of interference filter-based systems, yet eliminates the temporal constraints imposed by filter switching devices. Switching between any two wavelengths is achieved in less than the 1.2 msec vertical retrace period of a video signal, allowing you to perform real-time video imaging. For dual wavelength ratio imaging studies, the Lambda DG-4 enhances your ability to follow fast changes in ion concentrations by acquiring a ratio pair in two consecutive video frames.

Narrow bandpass systems, such as single cavity interference filters, grating monochromators, and A.O. modulators, will, by their nature, pass harmonics of the desired wavelength. With variable wavelength devices, it is not always possible to obtain sufficient blocking of out-of-band wavelengths. Modern interference filters, as used in the Lambda DG-4, have integral blocking characteristics 1000 times better than typical monochromator systems. In addition, it is difficult to adjust the intensity of one wavelength relative to another in a traditional system with a single optical path and a variable wavelength device. The dual galvanometer design of the Lambda DG-4 eliminates this problem.

HOW IT WORKS 
This unique optical design of the Lambda DG-4, is based on dual scanning galvanometers. The wavelength selection is done by interference filters. The standard version of the instrument, the Lambda DG-4, can host up to four 25mm interference filters. 

A five filter version (two 25mm and three 18mm), Lambda DG-5 is also available. The light coming from the 175W xenon arc lamp is focused on the first galvanometer mirror.  The light is then directed, via a parabolic mirror, through one of the optical channels that may contain an interference filter. The light passing through the filter is collected by another parabolic mirror and sent to a second scanning mirror that directs it to a liquid light guide. The light guide can be coupled to the illumination port of an instrument (e.g. epi-illumination port of a microscope).  The intensity of the output can be modulated by controlling the relative orientation of the two scanning mirrors. Thus this system can provide narrow band excitation at selected wavelengths over a range of intensities or can rapidly turn off the light source. Dwell time at any wave-length is arbitrarily set by the user. Transitions are achieved in less than 1.2msec.