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P5881-2 Michelson’s laser interferometer II PDF Download page

  • Technical laser interferometer
  • Definition of length
  • Two mode HeNe-laser
  • Two beam interference
  • Optical homodyne detection
  • Fringe interpolation
  • Interpolation of interference
  • Calibration of µm dial gauge
Principle of operation
The beam of the laser is displaced by 5 mm by the rhomboid prism (BD). The polarising beam splitter (PBS) separates the two orthogonal modes of the laser. On mode travels to the triple reflector T1 and the other one to T2 which is attached to a translation stage. The measuring pin of the dial gauge touches the translation stage in such a way that when turning the micrometer screw the dial gauge displays the translation.


The linear polarisation of the returning modes are converted to circular by means of the quarter wave plate (QWP) and subsequently separated by the non polarising beam splitter (NBS) into two channels. Within these channels the modes are superimposed providing the necessary signals for counting and interpolating the fringes.
  • Examples of investigations and measurements
Set-up a technical interferometer
The beam splitter is replaced by a polarising beam splitter cube (9). To avoid unwanted back reflections into the laser tube, the beam is displaced by 5 mm using the rhomboid prism (10). Furthermore the mirrors are exchanged against corner cube or also termed as triple reflectors. One of the triple reflectors is mounted onto a translation stage (13) allowing a precise translation of 5 mm. The interference signals are generated by the fringe detection unit (11). The photo detectors are connected to the up and down counter providing the analogue signals to optimise the adjustment of the set-up. The goal of this part is to align the interferometer and by turning the micrometer screw of (13) up and down counting should occur.
Calibration of the µm dial gauge
Once the set-up has been properly set-up the calibration of the provided dial gauge takes place. It is placed into its holder (12) and positioned in such a way that the measuring pin touches the translation stage. The micrometer of the translation stage is turned and the read out of the dial gauge is monitored. In addition the counter reading is noted for each translation. The set value of the dial gauge and the interferometer reading are plotted and the calibration curve derived.
  • Technical laser interferometer II (P-5881-2) consisting of:
Item Code Qty Description
13L-03801BNC connection leads, set of 6
24B-02401Optic cleaning set
3ED-01101Fringe up and down counter FC-01 with quad input
4LS-01501HeNe Pilot laser Ø 30 mm
5MC-02502Profile Rail MG-65, 300 mm
6MC-02601Profile Rail MG 65, 500 mm
7MC-02702Laser adjustment holder, soft ring 30 mm, carrier 20 mm
8PM-00801Triple reflector in click 30 mm
9XM-01501 Angle joint mount OCM 650 cross-piece with adjustable prism stage, theta, phi
10XM-04401Beam displacer
11XM-04601Fringe detection unit with 4 quadrant photodiodes
12XM-04801Measuring gauge 5 mm / 1 µm with carrier 20 mm
13XM-04901Triple reflector with translation stage and counter bearer
14XM-10901Mounting Plate, including carrier 20 mm, C 25
 TP-01001Oscilloscope 100 MHz digital, two channel
 XM-04501Motorised translation unit with triple reflector, travel 50 mm