Scan stages

TLC plate which is wetted with reagent solution when it leaves the dipping bath before laying it on the hotplate, laboratory bench or scanning stage. 

Many laboratories are equipped with commercial video frame grabbers and video image analysis systems, the operation of which is nicely explained by Russ (5). Many of the concepts involved apply both to video analysis and to the analysis of matrices obtained with a mechanical scanning stage driven by a stepper motor. Video scanning is very rapid, but slow mechanical scanning can be very precise and accurate. 

Programming instructions for scanning-stage stepper motors (or monochromator stepper motor, etc.) may contain a bit pattern that reflects the structure of the motor. For example, to step in one direction the POKE instructions to the motor address may be 3,6,12, and 9, which may look illogical until you consider the respective bit patterns, 0011,0110,1100, and 1001. Sending in reverse order will step the motor in the opposite direction. 

Figure 5. The scanning stage subsystem in the Perkin-Elmer Micralign...

The image analysis of UV photomicrographs is carried out by means of a microdensitometer using an X-Y scanning stage or a TV camera. However, the absorbance value obtained may be influenced by the methods of film development or by unevenness of illumination. It is difficult to eliminate the latter completely from the optical system of a UV microscope. 

Fig. 1. Diagram of the optical path of a fluorescence-imaging system (ACAS 570 Interactive Laser Cytometer). This system consists of a tunable 5W Argon ion laser, an acousto-optic modulator (AOM) to control the duration and intensity of excitation, an inverted microscope with an X-Y scanning stage, a Z-axis stepper motor, and two photomultiplier (PMT) tubes. A computer performs command, control, and analytical routines.

Smith MJ, Leigh-Jones P (1985) An antomated microscope scanning stage for fission track dating. Nucl Tracks 10 395-400... 

Another aetive mode, called Scan XY Out sends digital position signals to a seaimer. This simplifies the control of a scan stage considerably. Due to the limited number of signal input and output lines, multidetector operation and multiplexing are usually not applicable. 

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