Microscopy > Components > Imaging Devices > Galvo-controlled Scanning Mirrors

Galvo-controlled Scanning Mirrors

The unit is installed on the left emission port of the microscope. The excitation light passes through the dichroic filter, the scanning mirrors and the lens before entering the microscope; the fluorescence light follows the same path: from the microscope it passes through the descanning lens, the mirrors and it is finally reflected by the dichroic in a direction perpendicular to the excitation.

A peculiarity of the unit is in the way the dichroic if utilized: the excitation light traverses the dichroic whose transmission is around 80-90%; the fluorescence instead is reflected. In so doing the losses of fluorescence light are minimized. The scanning mirrors provide great distortion-free images on an area of about 100 Ám diameter. More importantly, they can be stopped at any XY location with no jitter, a condition required for the acquisition of FCS data.

For z-stack applications the scanning mirrors unit is used in conjunction with a z-axis piezo control of the objective.

Descanning lens
The descanning lens is key component of the scanning mirrors unit. It is a high aperture laser objective achromatic system (f=60 mm, NA=0.19) made of a cemented achromat and aplanatic meniscus lens with a 40 mm diameter. The lens features an anti-reflection ARB2-line coating (see Figure 6).

Scanning mirrors controller
The control electronics of the scanning mirrors unit is housed in a separate unit, which communicates to the computer through the USB communication port.

Mechanical

Rated Angular Excursion 40°
Rotor Inertia 0.125 gm*cm2, +/-10%
Torque Constant 6.17x104 Dyne-cm/Amp, +/-10%
Maximum Coil Temperature 110° C
Thermal Resistance, Coil to Case 1° C/Watt, Max

Electrical, Drive Armature

Coil Resistance 2.79 Ohms, +/-10%
Coil Inductance 180 µH, +/-10%
Back EMF Voltage 108 µV/Degree/Second, +/-10%
Current, RMS 3.9 A, Maximum
Current, Peak 20 A, Maximum
Small Angle Step Response 200 µs, with appropriate CTI Y mirror

Electrical, Position Detector

Linearity Over 99.9 %, minimum, over 40° optical
Scale Drift 50 PPM/oC, Maximum
Zero Drift 15 microradians/oC, Maximum
Repeatability 8 microradians, Maximum
Output Signal, Common Mode 155 A, with AGC Voltage of 30mA, +/-20%
Output Signal, Differential Mode 11.7µA/Deg,, with Common Mode of 155A,± 20%