Objectives are categorized into performance classes on the basis of their transmission, chromatic correction, planarity, and others. From the point of view of the International Organization of Standardization (ISO), there are three groups of objective classes differing in quality of chromatic correction.
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Absolute Value(s) of Focus
up to 23 mm
between red and blue wavelength (2 colors) is ≤ 2x depth of field
for standard applications in the visual spectral range
up to 25 mm
for red wavelength and blue to green wavelength (3 colors) are ≤ 2.5x depth of field
for applications in the visual spectral range with higher specifications
up to 25 mm
for red wavelength and blue to green wavelength (3 colors) are ≤ 1x depth of field
for applications with highest specifications in the visual range and beyond
Depth of field:
Leica Microsystems has aligned all three performance classes of its range of objectives to the needs of its customers and the specific requirements of a wide variety of applications – while offering a convincing price-performance ratio.
Leica achromats are powerful objectives for standard applications in the visual spectral range, offering field flatness up to 23 mm.
The absolute value of the focus differences between red wavelength and blue wavelength (2 colors) is ≤ 2x depth of field of the objective.
HI PLAN objectives feature good chromatic correction at two wavelengths and flatness over the whole field of view. Even the edges of the image are sharp and require no refocusing. HI PLAN objectives are designed for visual fields up to 20 mm. Versions for phase contrast are available. Leica HI PLAN objectives offer good correction properties while being extremely reasonably priced.
The N PLAN objective class comprises further improved achromats with good field flatness up to 22 mm. N PLAN objectives are suitable for transmitted light and DIC, N PLAN PH for phase contrast. For incident light applications including differential interference contrast (DIC), N PLAN EPI objectives are available. The N PLAN EPI BD can also be used as a darkfield objective. The N PLAN EPI incident light objectives feature excellent image contrast and safe working distances.
FL PLAN objectives are modern universal objectives with outstanding chromatic correction and field flatness up to 23 mm. State-of-the-art coating techniques give FL PLAN objectives high transmission for fluorescence excitation. All contrasting methods are possible. FL PLAN objectives are optimized for fluorescence, PH and DIC.
Leica semi-apochromats are objectives for applications in the visual spectral range with higher specifications, offering field flatness up to 25 mm.
The absolute values of the focus differences for the red wavelength and the blue wavelength to green wavelength (3 colors) are ≤ 2.5x depth of field of the objective.
There are two semi-apochromat classes:
PL Fluotars are powerful universal objectives with outstanding chromatic correction for at least three wavelengths which makes them suitable for fluorescence imaging.
Field planarity (PL) is computed for a 25 mm field of view. They are made of special glass to enable maximum transmission. This makes them powerful photon collectors in fluorescence microscopy.
Leica’s Fluotar portfolio features various application-optimized correction collars (CORR) to compensate for external influences such as temperature, coverslip thickness and immersion media.
Leica’s PL S-