Olympus introduced a 40x silicone oil microscope objective, its latest offering in silicone immersion microscope optics. The new objective fills out the company’s full line of silicone oil optics, which already includes 30x and 60x objectives designed for live cell and time-lapse imaging. Olympus silicone oil objectives are designed to improve optical performance for live cell confocal, widefield fluorescence, multiphoton, differential interference contrast (DIC) and other applications. Both the new intermediate-magnification UPLSAPO 40x and the existing UPLSAPO 60x objective are designed specifically to work with the Olympus Zero Drift continuous autofocus system for extended time-lapse imaging. In addition, all three of the objectives are compatible with protocols that use repeat-single-shot autofocus.

In contrast to water immersion objectives, silicone oil optics are useful in long-term imaging experiments where water evaporation is a pervasive issue. While water immersion lenses are traditionally used to reduce refraction index mismatch, they are not practical for long-term, time-lapse imaging because of moisture loss and low viscosity.

Compared to conventional oil immersion objectives, the new 40x, 1.25 numerical aperture (NA), 0.3mm working distance objective improves resolution and reduces loss of contrast due to spherical aberration. By reducing the mismatch between the refractive index of the specimen and that of the immersion medium into which the tip of the objective is dipped, silicone oil provides higher resolution and brightness, especially when using the microscope to image into thick samples. Glycerol immersion optics are another option, but glycerol is sometimes not ideal because it tends to draw moisture from the air, resulting in changes in refractive index over time.

Silicone oil is very stable and does not have any of these issues; in addition, it more closely matches the refractive index (N=1.404) of intracellular components, making the new objective useful for imaging into cells during for long-term, time-lapse experiments.

The silicon objective has a correction collar, so users can correct for the spherical aberration that is present when imaging into a specimen beyond a cover slip. Image resolution and contrast, along with fluorescence performance, are optimized and maintained by adjusting this collar.

Olympus America Inc., 800-455-8236, www.olympusamerica.com/40xSiliconeOil