Scan clocks

A second requirement is that the scan clocks (i.e. a frame clock, a line clock, and a pixel clock) are available from the scan controller of the microscope. This is rarely a problem in modem scanning microscopes, which usually make the scan clocks available through an external connector. 

Scan is a technique where storage elements (latches and flip-flops) are changed to dual mode elements. For instance, Fig. 8.125 shows a normal flip-flop of an integrated chcuit. Also shown in Fig. 8.125 is a flip-flop converted to a scan register element. During normal operation, the D input and system clock control the output of the flip-flop. During scan operation, the scan clocks are used to control shifting of data into... 

The functioning of the counting circuits can be easily checked if they consist of individually accessible decades or binary counters. When one is dealing with LSI counters, where the output lines are time-shared by several decades, the functioning of each decade may be observed by externally triggering a scope with the scanning clock signal. 

The external trigger input allows automatic inspections and ultrasonic imaging. The clock signal of an encoder or of stepper motors can be used as a trigger for the pulser. An internal software controlled divider allows different scan resolutions. 

Dedicated TCSPC electronics is used in all practical TCSPC-FLIM implementations [21, 22]. There are several issues that should be noted. First of all, the lifetime acquisition has to be synchronized with the scanning of the confocal or multiphoton microscope. To this end, the pixel clock and often the line and frame synchronization signals of the scanning microscope are used. 

In subprograms for operating scanning devices, the primary algorithm may include a do and wait operation (for a stepper motor) or a do and look operation (for a servo system). Try to avoid problems that could arise if you move your software to a faster, newer PC. With a new PC running at a faster clock speed than an old one, the faster do operation will require a longer wait if the scanner operation is matched to the duration of do + wait. Thus, the CAM should be treated as three separate units the microscope, the interface, and the PC. The PC will become obsolete before the microscope. 

Fig. 2.19 Scanning electron micrographs of Tego Magnan powder (a) milled for 100 h under the high-energy impact mode (IMP68 with two magnets at six and eight o clock positions) and (b) after three cycles of desorption at 350°C under 0.1 MPaH pressure for 15 min/annealing at 350°C under pre-vacuum for 15 min/absorption at 350°C under 3.2 MPa pressure for 15 min...

Zimova et al. have determined chlorpromazine by differential pulse voltammetry in an acetonitrile medium [168]. The method involves oxidation of the derivative to the radical cation, with the reaction taking place in acetonitrile that is also 0.03M in perchloric acid. Maximum sensitivity was achieved with a scan rate of 2 mV/sec, a modulation amplitude of 50 mV, and a clock time of 40 seconds. 

The integration or exposure time of the arrays is controlled by the clock and a series of counters. The minimum integration time at room temperature of an array running with a 20 kHz clock is 15 milliseconds the maximum integration time is 205 milliseconds. The minimum time is limited by the scan time of the array the maximum time by thermal charge. 

The second hardware unit was an interrupt, skip-check control unit for the Reticon arrays. This unit allows the computer to see the end-of-scan and beginning-of-scan pulses generated by the arrays and allows the computer to have an on/off control of the external clock which is used to start the analog to digital converter. 

Although the laser is repetitively charged for firing on its own internal cycle (currently 55 seconds), the actual firing pulse of the laser is synchronized to the internal clock of the OMA. This is to enable the streaked image on the camera phosphor to appear during the 768 usees retrace interval between OMA target scans. 

During an experimental run, the laser wavelength is scanned by a variable-speed clock... 

Hardware. To employ the IDA, the user must supply a clock signal, a begin scan signal, and data acquisition hardware. The hardware to accomplish this has been based on a PDP 11/20 minicomputer or a KIM microcomputer plus additional external hardware (13-15). The clock signal determines the rate at which the diodes are interrogated during readout and was 33 kHz with the minicomputer and 125 kHz with the microcomputer. This means the time to read out all 512 diodes and hence the minimum integration time varies from 15 ms to 3.7 ms, respectively. For the microcomputer, direct memory access (DMA) circuitry was used to increase the data acquisition rate. 

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