Cornelius DPC 230 Specifications download pdf (Page 40)

34 Typical Applications

Fig. 52: Fluorescence lifetime image recorded with DPC-230 and bh DCS-120 confocal scanning FLIM system

[4]. Data analysed by SPCImage data analysis routines of SPCM software [4, 6]. Intensity image, lifetime image,

decay curve and fit at cursor position.

Luminescence Lifetime Imaging in the Microsecond Range

Fluorescence lifetime imaging in the microsecond range requires low repetition rate of the

excitation pulses. Low repetition rate causes two problems. The first one is that the laser repe-

tition rate interferes with the pixel rate. Unless extremely slow pixel rates are used the result is

stripes in the image. Second, the ratio of peak power to average power becomes large. Espe-

cially if femtosecond or picosecond lasers are used the high peak power may cause mul-

tiphoton excitation and excited-state absorption. If the peak power is reduced the average

power becomes low, resulting in low emission intensity and long acquisition time.

The solution is to use excitation pulses of nanosecond or microsecond duration, and to syn-

chronise these pulses with the pixel clock of the scanner. The principle is shown in Fig. 53.

DPC-230 module

LVTTL

Inputs

Scan

head

Light

Laser Scanning Microscope

PMC-100

Detector

DCC-100

Detector

Controller

Scan

Clock

Pulses

SYNC

from

BDL-SMC Diode Laser

in CW mode

ON/

Off

Power

Pulse

Generator

SYNC

Pxl Clock

Trigger

DDG-200 card

or other

Pulse generator

Fig. 53: Microsecond FLIM. The laser pulses are synchronised with the pixel clock.

The general setup is the same as for FLIM in the nanosecond range, compare Fig. 47. How-

ever, the BDL-SMC laser is operated in the CW mode [5] and controlled by a bh DDG-200

card or another pulse generator. The laser is switched on for a specified time interval at the

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Cornelius DPC 230 Specifications Page 40

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