Cameleon
The protein Calmodulin is a ubiquitous intracellular calcium sensor that responds to changes in calcium concentration. Each Calmodulin molecule has four binding sites for Ca2+. The molecule undergoes a conformational change after calcium- binding.

Cathodic vacuum etching
The prepared and scratch-free specimen forms the cathode in a vacuum glow discharge chamber. During the etching process the sample is bombarded by positive ions with high velocity. Hitting the sample surface the ions eject the ...

CCD
The acronym CCD stands for "charge-coupled device". CCDs are used as electronic light sensors: Photons hitting the surface of the device release electrons from outer shells which are collected and stored in capacitors. The accumulated electrons are ...

CCD Chip Size
The CCD chip size is often given in an inch measure: 1/2" chip, 2/3" chip, etc. Counter intuitively this does not refer to the chip diagonal in inch but has historical reasons. It relates the field-of-view of the camera to that of ...

CCD Chip Types
This is a rather expensive and delicate type of chips for high-end scientific-grade CCD, ICCD and EBCCD cameras which is, to put it simple, mounted upside-down in the camera. The illuminated back is thinned by ...

Ceramic specimen
A thin section of the ceramic sample is cut of (5 mm thickness). One surface is treated by a process of repeated lapping and cleaning. After drying it is mounted to the microscope slide with resin. The exposed face is now reduced to ....

Chemical Etching
After sectioning and grinding several cycles of etching and polishing removedisturbed metal layers from the surface of the sample. For the chemical etching acidic or basic chemicals in an aqueous or alcoholic solution can be used.

Chimeric proteins
The construction of chimeric proteins is an elegant approach for FRET analysis in living cells (e.g. Cameleon or chimeric peptides for substrate-enzyme reactions). A chimeric protein useful for FRET analysis usually is a molecule, which is ...

Chromatic aberration
see Aberration, optical

CMOS Chips
In an Active Pixel Sensor (=APS) Complimentary Metal Oxide Semiconductor chip each photodiode (pixel) is coupled to an individual amplifier. Also there is one A/D converter for each column of pixels so that the data of a row of amplifiers can be ...

Colour Images and Colour Mixing
The colour images produced by computer monitors and TV screens are generated by pixelwise mixing of the three primary colours red (R), green (G) and blue (B). This is called additive mixing of light. Digital images where the colour information is ...

Coma
see Aberration, optical

Concrete
Optical microscopy is an important tool to analyse concrete and related materials (building stones, bricks …). Semitransparent thin sections as thin as 20 µm of concrete can be analysed by optical microscopy in brightfield or ...

Confocal Laser Scanning Microscopy
A popular mode of optical microscopy in which a focused laser beam is scanned laterally along the x and y axes of a specimen in a raster pattern. The emitted fluorescence (reflected light signal) is sensed by a photomultiplier tube and ...

Conoscopy
The conoscopic image shows interference patterns of anisotropic specimen. To get a conoscopic image in a polarising microscope one eyepiece has to be removed from the tube. An auxiliary telescope or a Bertrand lens can be ...

Contrast
Contrast is the variation of signal intensity relative to the average intensity (Delta I / I). Together with resolution it is the most important factor determining the quality of an image. Contrast and resolution are linked by ...

Contrast Transfer Function
The CTF is a measure for the information transmission capability of an optical system. It is a somewhat abstract concept that shall not be discussed in detail here. Basically it is a function that relates the contrast produced by ...

Conversion Factor
The A/D converter divides the electronic charges of the CCD pixels that are readout from the chip by a certain factor, the conversion factor, thus delivering a digital signal measured in counts (or grey levels). The maximum possible conversion ...

Crossed Nicol position
If the polariser is oriented in East-West direction and the analyser is oriented in North-South direction no direct light can pass.

Curvature of field
see Aberration, optical