page_title: Phase-contrast microscopy
section_title: Related methods
hierarchical_section_title: Phase-contrast microscopy / Related methods
caption_attribution_description: English: Saccharomyces cerevisiae cells in DIC microscopy. Imaging was performed with the Olympus BX61 microscope and a UPlanSApo 100× NA 1.40 oil immersion objective (Olympus). Pictures were acquired at room temperature in synthetic complete medium with a camera (SPOT; Diagnostic Instruments, Inc.) using MetaMorph software (MDS Analytical Technologies). Polski: Komórki drożdży piekarniczych (Sacharomyces cerevisiae) widziane w różnicowej mikroskopii interferencyjnej. Zdjęcie wykonane w syntetycznej pożywce kompletnej za pomocą mikroskopu Olympus BX61 wyposażonego w obiektyw imersyjny (olej) 100x NA 1,40 (Olympus) sprzężonego z kamerą SPOT (Diagnostic Instruments, Inc.). Użyto programu MetaMorph software (MDS Analytical Technologies).
context_page_description: Phase-contrast microscopy is an optical microscopy technique that converts phase shifts in light passing through a transparent specimen to brightness changes in the image. Phase shifts themselves are invisible, but become visible when shown as brightness variations.
  When light waves travel through a medium other than a vacuum, interaction with the medium causes the wave amplitude and phase to change in a manner dependent on properties of the medium. Changes in amplitude arise from the scattering and absorption of light, which is often wavelength-dependent and may give rise to colors. Photographic equipment and the human eye are only sensitive to amplitude variations. Without special arrangements, phase changes are therefore invisible. Yet, phase changes often convey important information.
  Phase-contrast microscopy is particularly important in biology.
  It reveals many cellular structures that are invisible with a bright-field microscope, as exemplified in the figure.
  These structures were made visible to earlier microscopists by staining, but this required additional preparation and death of the cells.
context_section_description: The success of the phase-contrast microscope has led to a number of subsequent phase-imaging methods.
  In 1952, Georges Nomarski patented what is today known as differential interference contrast (DIC) microscopy.
  It enhances contrast by creating artificial shadows, as if the object is illuminated from the side. But DIC microscopy is unsuitable when the object or its container alter polarization. With the growing use of polarizing plastic containers in cell biology, DIC microscopy is increasingly replaced by Hoffman modulation contrast microscopy, invented by Robert Hoffman in 1975.
  Traditional phase-contrast methods enhance contrast optically, blending brightness and phase information in a single image. Since the introduction of the digital camera in the mid-1990s, several new digital phase-imaging methods have been developed, collectively known as quantitative phase-contrast microscopy. These methods digitally create two separate images, an ordinary bright-field image and a so-called phase-shift image. In each image point, the phase-shift image displays the quantified phase shift induced by the object, which is proportional to the optical thickness of the object.
caption: S cerevisiae cells imaged by DIC microscopy
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