Light microscopy plays a fundamental role in biological research, indeed few cell biology papers appear without some element of imaging. Dynamic techniques such as time-lapse microscopy and particle tracking are also becoming more popular and, as such, high quality imaging is not just reserved for static characterizations like morphometry and immuno-staining. The DM4000 B is the entry-level model from Leica’s range of digital microscopes. The philosophy behind Leica’s digital microscopes is to simplify imaging and this thinking has clearly resulted in an extremely user-friendly microscope. Key features on the DM4000 B include push button operation, motorized optical elements, automatically reproducible illumination settings and excellent ergonomics.
In terms of optics, Leica’s automated microscopes are designed to be modular and are configured to match your applications. The microscope has an upright arrangement and comes equipped with light paths for both transmitted and fluorescence microscopy. Transmitted light can be set up for brightfield, darkfield or phase contrast depending upon your requirements (scopes in the higher range can be equipped for interference contrast). For fluorescence work, the microscope can be equipped with five filter cubes so a wide variety of fluorophores can be considered. The nosepiece accepts six objectives such that a large range of magnifications can be covered. The switching of light paths with the consequent selection of optical elements, changing of filter cubes and shuttering of incident light are all motorized and easily activated with electronic buttons.
As mentioned above, one of the key features of this microscope is reproducible and optimal illumination that is achieved through encoded objectives. This encoding allows the microscope to recognize an objective and recall illumination settings to maximize the light collecting capacity for that particular lens. In practice this means that the light intensity, aperture and field diaphragm are automatically and correctly set for a particular objective and the light path being employed. Although settings are programmed, they can be manually changed with electronic buttons to fine tune illumination for your particular sample. Current optical parameters, including the objective, light intensity and filter cube used, can be visualized on a clear liquid crystal display at the front of the microscope.
The microscope is extremely easy to operate. User comfort is excellent, the result of a collaboration between Leica and an ergonomics institute. The focus wheels can be turned whilst arms are resting on the table and the length of stage drives can be adjusted telescopically to meet your hands. The electronic function and setting keys are easily accessible and their positions are distinct enough that you don’t need to continually look at them. Simultaneous focus and stage movement can also easily be achieved. Depending upon the model chosen, eyepiece angle and reach can have a wide range of adjustment. The stage is well designed, accepts commonly used slides and rotates. Further, the z-axis has sufficient displacement such that high-powered objectives can be used in conjunction with the cell chambers and heating units I use for live cell imaging .
Many additional features demonstrate the degree of ‘attention to detail’ on this microscope. For instance the transmitted light source is pre-aligned and high-powered oil immersion objectives have a built in spring system so that you can avoid destroying glass slides. Models higher in the product range have additional features such as remote control units, motorized stages and objective turrets, touch-sensitive control screens and software integration. The microscope can also be supplied as an integrated system with CCD camera and imaging software. Personally, I feel the DM4000 B is sufficiently well equipped for the majority of cell biology applications and users. Further, the DM4000 B permits flexibility in camera and fluorescence illumination choice. The DM4000 B microscope in our lab has been equipped with an Exfo X-CITE 120 for fluorescence illumination and a Spot RT camera interfaced to a Mac. This complete system has been producing excellent images for a variety of applications, including immuno-staining, morphology and time-lapse cellular imaging, for a number of happy users.
Peter Haggie, Ph.D.
Post-Doctoral Fellow
University of California, San Francisco