Moor Instruments moorLDI2-VR - ELEMENTS of the Moorldi2; The Laser Source; The Mirror; Optics and Light Detection

MOOR INSTRUMENTS moorLDI2 RESEARCH USER MANUAL
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The laser Doppler technique is used to its best advantage when assessing microvascular function:
before and after drug treatment, surgical procedure or a test stimulus. The moorLDI2 Repeat Scan
mode and processing is well suited to this type of assessment.
4.4 ELEMENTS OF THE moorLDI2
4.4.1 THE LASER SOURCE
The laser wavelength, accessible power and laser classification depend on the moorLDI2 version.
1. moorLDI2-VR and moorLDI2-HR Class 3R visible laser.
Either a Helium-Neon gas laser wavelength 633nm, maximum accessible power 2.5mW.
Maximum scan area with large scan setting approximately 60 x 60 cm.
2. moorLDI2-IR and moorLDI2-HIR Class 3R near infra-red laser.
A laser diode wavelength 785nm or 830nm, maximum accessible power 2.5mW.
The near infra-red laser is combined with a visible red aiming beam.
Maximum scan area with large scan setting approximately 60 x 60 cm.
During set up a solenoid actuated attenuator reduces the intensity of laser beam emitted to less than
200 µ W. The attenuated beam is a class 1 laser.
4.4.2 THE MIRROR
The incident laser light is deflected to the tissue surface by a front silvered mirror. Two DC motors
manipulate the mirror so that a raster pattern is executed by the beam across the tissue surface.
Geometrical correction algorithms are employed to ensure that a rectilinear pattern is followed. The
light scattered by blood and tissue is directed back via the mirror and other optics onto two detectors.
4.4.3 OPTICS AND LIGHT DETECTION
A unique arrangement of optics in the moorLDI2 enables operation over a wide range of distances in
ambient lighting. Extraneous light does not significantly influence the detector because only the laser
spot and a small area around it is 'seen' by the detectors. Optical filters for the particular laser
wavelength being used also help to eliminate extraneous light.
4.4.4 OPTIC WINDOW
The laser aperture region of the scanner front panel is sealed by a glass window. This is anti
reflection coated and easily damaged by touching or by attempts to clean by wiping.
See Section 18.6 for advice on removing dust from the external surface of the window.