Miniature High-NA
Objectives  

GRIN Needle Endomicroscopes (GRIN singlets and doublets) provide a unique and uncomplicated microscopic access with minimal invasiveness to deep tissue regions, especially as consumables. However, if numerical apertures greater than 0.6 (NA > 0.6) are required, or the field of view of pure GRIN lenses with high resolution is not sufficient, or chromatic aberration needs to be corrected over a wide spectral range, miniature high-NA objectives with diameters of 1.3 to 2.2 mm provide the solution for your needs. The different product versions differ in their complexity and thus also in the degree of correction of aberrations.

In 2009, GRINTECH has introduced the SpheroCor high-NA objectives with only 1.4 mm diameter, which increase the Numerical Aperture from 0.55 to 0.8 by a combination of GRIN lenses with plano-convex micro-lenses, which correct spherical aberration on-axis and significantly improve the resolution to image, for example, dendritic spines in vivo for neuro­scientists (see article here: Barretto, R., Messerschmidt, B. & Schnitzer, M. In vivo fluorescence imaging with high-resolution microlenses. Nat Methods 6, 511–512, 2009). However, chromatic aberration is not corrected and the field of view is limited in these least complex objectives.

Since 2016, GRINTECH offers the FieldAchromatic high-NA objectives. With a diameter of only 1.3 mm, they provide a tremendously increased field of view of up to 400 μm in tissue with sub-micron resolution due to the high NA of 0.7 – 0.8. This field correction is combined with a very broad correction of lateral and axial chromatic aberration from 488 to 900 nm, making these objectives the perfect optics for non-linear fiber-scanning endoscopes or coherent fiber bundle based endomicroscopic probe heads. Offering these high NA’s, a large field of view and small component diameter results in a stronger field curvature of up to 20 – 28 μm focus shift at the marginal field of view, which is often accepted when diagnosing volume tissues. A special version of the FieldAchromatic Series is the 178 mm long endomi­croscopic tube for CARS endomicroscopy providing a chromatic correction from 795 nm to 1029 nm.

In 2023, GRINTECH brought the ReduCurv high-NA objectives with diameters of 1.3 and 2.2 mm on the market, the latest generation which offers additionally a significant 70% reduction of field curvature in object space, while keeping high NA, large field of view and sub-micron resolution. Focus shifts from the center to the margin of the field of view are reduced to only 6 – 7 μm. These objectives are recommended for imaging of planar and very thin samples or where a very flat field of view is required.