Phase contrast microscope is a special microscope, especially suitable for observing objects with high transparency, such as biological slices, oil films, phase gratings and so on. When light waves pass through these objects, they often only change the phase of the incident light waves, but not the amplitude of the incident light waves. Because the human eye and all energy detectors can only distinguish the difference of light wave intensity, that is, the difference of amplitude, but can not distinguish the change of phase, it is difficult to observe these objects with ordinary microscope.
Objects with high transparency are also called phase objects. Phase contrast method (also called phase contrast method) is to convert the phase information of the object into the corresponding amplitude information through a spatial filter, thus greatly improving the resolution of transparent objects. Therefore, in this sense, phase contrast method is an optical information processing method and one of the earliest achievements of information processing, so it is of great significance in the history of optical development. 1935, according to Abbe imaging principle, Zelnik first proposed a phase contrast method to improve the imaging contrast of transparent objects by changing the phase of the spectrum. 1953, Zelnik won the nobel prize in physics. This is one of the few optical related awards in the Nobel Prize for Physics.
The practical method is to add a drop of liquid in the center of the glass substrate, and the optical path of the drop causes a certain phase shift, thus forming a phase plate, which is placed on the back focal plane of the microscope as a spatial filter. Under the irradiation of coherent light, an image related to the phase information of the object appears on the image plane. The light intensity distribution on the image plane has a linear relationship with the phase of the sample, that is, the phase distribution of the sample modulates the light intensity on the image plane.
Zelnik 1888 July 16 was born in the family of a math teacher in Amsterdam, the Netherlands. His parents are both math teachers. My father worked as a primary school principal and compiled mathematics textbooks, which is famous for paying attention to teaching methods. Zelnik's brothers and sisters are university professors and cultural celebrities.
Zelnik inherited his father's interest in physics. He had his own library of experimental equipment when he was a child. Greek and Latin often fail because they prefer science courses. When he was a student, he spent a lot of time doing experiments, especially color photography. Due to limited funds, he had to prepare his own alcohol for color photography. He also made a camera and a small astronomical observer by his own wisdom, which can take pictures of comets with the clockwork in the old record player. He also solved many math problems with his parents.
1905 Zelnik entered the University of Amsterdam, majoring in chemistry and minoring in mathematics and physics. 1908 won the gold medal in mathematics. It is said that people asked him whether he wanted to win a gold medal or a bonus before awarding the prize, and he replied, "I want money." Because he has enjoyed the honor of winning the gold medal. 19 15 Zelnik received his doctorate in applied Gibbs statistical mechanics. In the future, he will continue his research in cooperation with others in this field.
19 13 Zelnik accepted the invitation of Kapteyn, professor of astronomy at the University of G? ttingen, as his assistant. 19 15 years as a lecturer at the university of g? ttingen, teaching mathematical physics. 1920 promoted to full professor. He wrote a lot of articles about statistical physics. In the experiment, it is famous for its sensitive vibrating mirror design. Later, this sensitive galvanometer was mass-produced and widely used by manufacturers. 1930, he returned to the field of optical research and wrote a book on the aberration and spatial coherence of concave gratings. From 1938 to 1948, he cooperated with his students to study the influence of lens aberration on diffraction patterns.
The phase contrast method was discovered not by a microscope, but by Zelnik when he was working in other optical fields. This starts with 1920 zel Nik's interest in diffraction gratings. This kind of reflective grating consists of a plane or a concave mirror plate, and a large number of equidistant notches are engraved on the lens surface. The slight error of groove position will obviously affect the optical effect of grating. The error of periodic repetition of engraving machine makes the optical path difference change accordingly, and the observer will see that the mirror surface seems to be uneven when observing it. The fine lines on the grating surface are invisible to the naked eye, and only thick lines with wide intervals appear on the mirror surface. The spectrum formed by this grating is often accompanied by a series of messy weak lines on both sides of each intensity line, which is called "Roland ghost line". A perfect grating, as big as the palm of your hand, looks rich and colorful under uniform illumination, showing various colors in the visible spectrum. However, in fact, some gratings look like "scars" everywhere, and thick lines are superimposed on the ribbon. In 1902, H.S.Allen claims that these thick lines are not true, but the result of interference and cancellation between the main spectral line and its ghost line. Zelnik disagreed with this statement when he studied gratings in 1920. He believes that these "scarred" surface views provide more information than spectral photos taken by photographic negatives. The surface field of view gives the relative phase of the ghost line, but the photo loses the phase information of the ghost line. Zelnik is engaged in the research of statistical physics at this moment, so he keeps this problem in his heart for future research.
In about 1930, Zelnik's laboratory got a large concave grating and installed it on the support. Soon people saw the "scar" on the grating surface. Because the grating is 6m away from the human eye, it can't be seen clearly, so Zelnik tried to observe it with a small telescope. Then something unexpected happened. The linear scar is very clear, but when the telescope is accurately focused on the mirror, the line disappears completely! What's going on here? Zelnik remembered the thinking of 10 years ago. He realized the significance of this phenomenon and immediately concentrated on studying this optical problem. With the help of Abbe's imaging theory, he finally made a successful explanation after a series of experiments and calculations. It turns out that this is an interference phenomenon caused by the phase difference of waves. 1935, Zelnik further developed the phase contrast method according to the phase theory and invented the phase contrast microscope. In his first design, he used a linear strip aperture stop and placed the corresponding linear strip aperture stop on the back focal plane of the objective lens. In his acceptance speech for the Nobel Prize, Zelnik said: "However, this device makes the microscopic image of the object structure dizzy, because the diffraction effect makes the strip image of the object details spread in the direction perpendicular to the strip, thus turning the small bright spots on the image into short segments. In order to avoid this observation, I used an annular diaphragm to make the halo spread in all directions, but the halo became so weak that it was actually completely meaningless. "
As early as 1932, Zelnik successfully trial-produced the first phase contrast microscope, and applied for a German patent on April 26th of the same year. After Zelnik's continuous efforts, the German Patent Office approved his application with 1936 four years ago. 1933 held a professional meeting in Vakhnin, the Netherlands. He submitted a paper entitled "A new method of microscope observation", but when he reported his experiments and theories to the conference, he was given the same cold shoulder. Participants were not interested in his invention and did not ask any questions. When he demonstrated the function and production of phase contrast microscope to Zeiss in Jena, Germany, he did not get enthusiastic support. The same thing happened when he negotiated with E.Leitz in wetzlar. The phase contrast microscope was hit by World War II before it entered the market. It was not until 194 1 that Zeiss company produced phase contrast objective lenses and accessories. Zelnik overcame many difficulties with perseverance, continued to carry out experiments and constantly improved, and finally made the phase contrast microscope widely used all over the world. From 65438 to 0944, in Utrecht, Zelnik cooperated with Brink, an optical instrument manufacturer, to develop the objective lens of achromatic phase village microscope, in which a phase plate was installed. In 195 1 year, H.Heine developed a ring lighting device with condenser for phase contrast equipment. Later, other companies began to produce phase contrast microscopes, such as Zeiss Winkle of G? ttingen, American Optical Company and Cook, Troughton & Simms Co., Ltd. At present, there are many companies that produce phase contrast microscopes all over the world. Phase contrast microscope is widely used in bacteriology and pathology research in biology and medicine, and it is also effectively used in the micromorphology of mineral crystals. With this special microscope, the dynamic observation of crystal surface growth can be carried out. In view of the great significance of phase contrast method and phase contrast microscope to science and social life, 1953 Nobel Prize in Physics was awarded to Zelnik. Zelnik died soon after 196 1 March 10.