OPERATIONCarl Zeiss Illumination and contrasting techniques Axiovert 2003-34 B 40-080 e 03/013.3.2.3 Setting of transmitted-light phasecontrast on the Axiovert 200 /Axiovert 200 M• Swing phase contrast objective, e.g. Ph 1, intothe beam path.• Switch phase stop with the same description asthe phase contrast objective (e.g. Ph 1) in theturret of the condenser.• To check the centering and congruence of thebright phase stop (in the condenser) with thedark phase ring (in the objective), remove oneeyepiece from the tube and replace it with thecentering telescope. Use the correction facilityof the centering telescope to focus on thephase stop and the phase ring in the objectiveexit pupil.When the phototube is used, the Bertrand lens canalso be switched on for observation of theobjective exit pupil. When the Bertrand lens isused, the factor 1x must be set on the settingwheel of the Optovar turret.• If congruence is not perfect (3-19/A), two SW1.5 Allen keys (3-18/1) must be used torecenter the bright phase stop until completecongruence with the dark phase ring has beenachieved (3-19/B).• Finally, remove the centering telescope fromthe tube and replace it with an eyepiece, orswitch off the Bertrand lens.However, centering is normally not required, since the phase stops are centered in the factory.To enhance the image contrast, an interference wide-band filter, green 32 x 4, can be inserted in thefilter changer. Complete phase contrast is only achieved if the bright phase stop (in the condenser) andthe dark phase ring (in the objective) are exactly congruent in the illumination beam path (3-19/B). Adjustment of the phase rings must be performed for all phase contrast objectives used. Whenliquid objects are examined in small vessels, the beam path must be aligned to the center ofthe vessel, since liquids on the edge of a vessel have the same effect as lenses and impair themicroscope image.Fig. 3-18 Centering the phase stop on thecondenserFig. 3-19 Centering of phase stop (bright incondenser) with phase ring (dark inobjective)