product of the refractive index of the object space and the sine of the semi-aperture of the cone of rays entering the entrance pupil of the objective lens from the object point. The resolving power is proportional to the numerical aperture.
Ava saab valida poole ühiku kaupa. Mida suurem on avaarv, seda väiksem on ava. Valitav avade vahemik sõltub kasutatavast objektiivist. Võimalikud: 1,0-64. Väiksema avaarvuga pildistades saad head portreevõtted, kus taust jääb uduseks. Suur avaarv annab aga teravussügavuse- kõik fotol on terav.
A binocular microscope shall be used for counting and shall have the following features:
- Koehler illumination, ...
- a 40 times bar-focal positive phase-contrast achromatic objective with a numerical aperture of 0,65 to 0,70 and phase ring absorption within the range 65 to 85 %, ...
