Detector CCD camera

A video channel counting detector (CCD) camera transmits the image to the monitor where the indentation is displayed. The control unit reads the diagonals and calculates the microhardness. 

For detection of secondary ions a laterally resolving detector is necessary. In the first step a channel plate for amplification is used secondary electrons from the output of this device are accelerated either to a fluorescent screen or to a resistive anode. If a fluorescent screen is used the image is picked up by a CCD camera and summed frame by frame by use of a computer. The principal advantage of this system is unlimited secondary ion intensities, but compared with the digital detection of the resistive anode encoder the lateral and intensity linearity is not as well-defined. 

Fig. 1. Schematic diagram of the multimass ion imaging detection system. (1) Pulsed nozzle (2) skimmers (3) molecular beam (4) photolysis laser beam (5) VUV laser beam, which is perpendicular to the plane of this figure (6) ion extraction plate floated on V0 with pulsed voltage variable from 3000 to 4600 V (7) ion extraction plate with voltage Va (8) outer concentric cylindrical electrode (9) inner concentric cylindrical electrode (10) simulation ion trajectory of m/e = 16 (11) simulation ion trajectory of rri/e = 14 (12) simulation ion trajectory of m/e = 12 (13) 30 (im diameter tungsten wire (14) 8 x 10cm metal mesh with voltage V0] (15) sstack multichannel plates and phosphor screen. In the two-dimensional detector, the V-axis is the mass axis, and V-axis (perpendicular to the plane of this figure) is the velocity axis (16) CCD camera.

Figure 1. Schematic of the optical fiber system. Excitation light is launched into the fiber. Due to the refractive index differences between the fiber core and cladding materials, the light is internally reflected and travels through the fiber with minimal loss (see inset). The emitted light is carried back from the fluorescent sensor located on the tip of the fiber to a CCD camera detector. Reprinted with permission from Science, 2000, 287, 451-452. Copyright 2000 AAAS.

Neither of the CCD camera and IP has the ideal resolution of a single pixel, and in both detectors additional noises are introduced in the detection process. The recorded image can be generally expressed as... 

Considerable improvement over film detection can be obtained with either a slow scan CCD camera interfaced to a TEM or with imaging plates. The CCD camera attached to a YAG crystal can have a good linearity in intensity detection, however can present several drawbacks one is the presence of overflow artifacts when ED is recorded, but even more serious problem can be the potential damage of the CCD detector after continuous exposures to high diffracted ED beam intensities. 

With the aid of this prototype, an adequate scanning unit -interfaced to the TEM -scans with pre-determined step size resolution- a part or whole of ED pattern against a fixed detector. Electron beam is deflected by means of deflector coils in the TEM which are situated after the sample. Fixed detector can be either a combination of a scintillator and a photomultiplier or a Faraday cage (one or multiple). Detector is fitted at the bottom of the TEM column, but can also be adapted in the 35 mm port, if the port below the TEM column is occupied by e g. a CCD camera (see fig. 1). 

Detection — Primarily via fluorescence-based charge-coupled device (CCD) camera detectors. 

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