相位差顯微鏡 Phase Contrast Microscope

相位差顯微鏡（Phase Contrast Microscope）由P．Zernike於1932年發明，並因此獲1953年諾貝爾物理獎。這種顯微鏡最大的特點是可以觀察未經染色的標本和活細胞。
相位差顯微鏡的基本原理是，把透過標本的可見光的光程差變成振幅差，從而提高了各種結構間的對比度，使各種結構變得清晰可見。光線透過標本後發生折射，偏離了原來的光路，同時被延遲了1/4λ（波長），如果再增加或減少1/4λ，則光程差變為1/2λ，兩束光合軸後乾涉加強，振幅增大或減下，提高反差。在構造上，相差顯微鏡有不同於普通光學顯微鏡兩個特殊之處：
1.環形光闌（annular diaphragm） 位於光源與聚光器之間，作用是使透過聚光器的光線形成空心光錐，焦聚到標本上。
2.相位板（annular phaseplate）在物鏡中加了塗有氟化鎂的相位板，可將直射光或衍射光的相位推遲1/4λ。分為兩種：
1.A+相板：將直射光推遲1/4λ，兩組光波合軸後光波相加，振幅加大，標本結構比周圍介質更加變亮，形成亮反差（或稱負反差）。
2.B+相板：將衍射光推遲1/4λ，兩組光線合軸後光波相減，振幅變小，形成暗反差（或稱正反差），結構比周圍介質更加變暗。


Phase contrast microscope by P. The Zernike invention, in 1932 and therefore received the Nobel Prize in Physics in 1953. The biggest feature of this microscope can be observed without staining of specimens and live cells.
The basic principles of phase contrast microscopy, visible light through the specimen optical path difference into a difference in amplitude, thereby increasing the contrast between the various structures, the various structures become visible. Refraction of light through the specimen from the optical path has been delayed at the same time the 1/4λ (wavelength), if the increase or decrease 1/4λ optical path difference becomes 1/2λ after the two-beam photosynthetic axis interference strengthened, the amplitude increase or decrease, increase contrast. In the construction phase contrast microscope, different from ordinary optical microscope two special features:
An annular aperture (annular diaphragm) is located between the light source and the condenser, the role of the formation of hollow light cone, coke gather specimens through the condenser light.
The two phase plates (annular phaseplate) added in the objective phase plate coated with magnesium fluoride can be direct light or diffracted light phase delayed 1/4λ. Divided into two types:
1.A + phase plate: will direct light to postpone 1/4λ two sets of light waves sympodial after the sum of light waves, the amplitude increased, the specimen structure is more light than the surrounding medium, the formation of bright contrast (or negative contrast).
2.B + phase plate: the diffracted light to postpone 1/4λ, two sets of light after the co-axis light waves subtract a small amplitude, the formation of dark contrast (positive contrast), the structure is more darken than the surrounding medium.