1. Optical performance
We need to focus on the magnification, numerical aperture (NA), working distance and calibration level of objective 10x achromatic objectives. The magnification is chosen according to the needs of the sample, e.g. 40x-100x for fine observation of cellular structures and 4x-10x for overall overview of tissues. Numerical Aperture (NA) is the decisive factor for resolution, the higher its value, the better the resolution (≈0.61λ/NA) and light collecting ability, e.g. 100x oil mirror needs NA≥1.25 to ensure clarity, but objective 10x needs to be used with immersion oil. Working distance (WD) is related to the applicability of samples, thick samples or live cell culture need to choose a long working distance objective lens labelled 'LWD', while the WD of high magnification objective lens is usually less than 0.2mm, so avoid collision with the samples during operation.
2. Physical compatibility
The interface between the objective lens and the microscope is a prerequisite for use. Thread interface standards need to be strictly checked, old microscopes mostly use RMS (20.32mm), modern infinity systems commonly used M25 or M32 thread, if the objective 10x interface does not match will not be able to install. Mechanical tube length determines the compatibility of the optical system, finite distance system (such as 160mm, 170mm) and infinite distance system (marked '∞') can not be mixed, the latter need to be used with the tube lens, otherwise it will lead to aberration distortion.
3. Purchase Avoidance Points
When purchasing objective 10x, you need to be alert to the edge blurring problem of low-priced 'pseudo-flat-field' objectives (e.g., 'Semi-Plan'), and check the integrity of the coating of second-hand objective lenses, to avoid scratches or de-coating that may affect the light transmittance. Oil lenses need to be cleaned thoroughly after use to prevent damage to the lens from oil residue. Domestic objective lenses are cost-effective, but the resolution and chromatic aberration correction level of high-magnification lenses need to be verified by actual measurement, it is recommended to ask for the optical performance test report, and give priority to the 'Plan Achromat' flat-field achromatic objective lenses.
