Contrast transfer function

About: Contrast transfer function is a research topic. Over the lifetime, 934 publications have been published within this topic receiving 26533 citations.

Verbesserung der Auflösung im Elekronenmikroskop durch Bildebenen-Holographie†

Abstract: Enhancement of resolution in electron microscopy can be achieved by use of electron image holography. In order to compensate for the aberrations of the electron lenses the reconstruction is performed with laser light in an optical system with suitably adapted aberrations. The partial coherence in connection with the aberrations of the electron lenses limits the possible resolution. The limits of resolution dependent on defocusing and spherical aberration are calculated.

Electron microscopy: Better vision with electron lenses.

Abstract: Lenses used in electron microscopy have aberrations that limit their resolution. Successful correction of spherical aberration is now possible, opening the door to three-dimensional, sub-angstrom imaging of atomic arrangements.

Using Contrast Transfer Function to Evaluate the Effect of Motion Blur on Microscope Image Quality

Abstract: Scanning of microscope slides is an important part of cytogenetic diagnosis. Metaphase chromosomes arranged in a karyotype reveal the nature and severity of cancer and other diseases. Searching for metaphases spreads is a lengthy and tedious process that can benefit from computer aided systems. When slides are searched by such systems in continuous motion, the image quality is reduced. The motion blur is a function of the scan speed, the camera frame rate and sample time, and the level of magnification. In this study, normalized contrast transfer function (CTF) is used to define the amount of image degradation.

Optical transfer function characterization using a weak diffuser

Abstract: We present a simple technique which uses a random phase object for single-shot characterization of an optical system's phase transfer function. Existing methods for aberration measurement typically involve holography, requiring complicated wavefront sensing optics or through-focus measurements with known test objects (e.g. pinholes, fluorescent beads) for pupil recovery from the measured wavefront. Here, it is demonstrated that a weak diffuser can be used to recover the pupil of an imaging system in a single measurement, without exact knowledge of the diffuser's surface. Due to its stochastic nature, the diffuser scatters light to a wide range of spatial frequencies, thus probing the entire pupil plane. A linear theory based on the weak object approximations predicts the spectrum of the measured speckle intensity to depend directly on the pupil function. Numerical simulations of diffusers with varying strength confirm the validity of the theory and indicate sufficient conditions under which diffusers act as weak phase objects. Using index matching oils to modulate diffuser strength, experiments are shown to successfully recover aberrations from an optical system using coherent illumination. Additionally, this technique is applied to the recovery of defocus in images of a weak phase object obtained through a commercial microscope under partially coherent illumination.