Reference beam setup/alignment

  1. If pellicule beamsplitter is out, put it in between the CCD and the last lens of the 4f system. The engraved side should be facing away from the CCD. It should be at as much of a 45 degree angle as possible, given the space constraints. Make sure the beamsplitter is not clipping the sample beam.
  2. Direct the reference beam towards the CCD using reference mirrors 1 and 2.
  3. With all ND filters out, adjust reference mirror 1 so that the reference beam transmitted through the pellicule and the sample beam reflected off of it hit the same spot in the near field (close to the pellicule).
  4. Adjust reference mirror 2 so that the two spots overlap in the far field (farther away from the pellicule).
    1. When the spots are very close to overlapping, it may be beneficial to stop down both beams so that the spot sizes are small. Just make sure the iris’s used are centered!
  5. Put the ND filters back in, and make final adjustments to mirror 1 so that the two beams overlap perfectly.
    1. If this part of the alignment is correct, you should have circular fringes with good contrast.
  6. Put a sample of fixed beads into the system (larger beads make alignment easier).
  7. Place a bead on the edge of the elastic excitation beam, diagonal from the center. Adjust BS1 and reference mirror 1 so that the tilt fringes are nulled in the interferogram.
  8. Move the bead to the center of the excitation beam. Adjust the BS and mirror until the frequency of the tilt fringes approximately doubles in both x and y directions.
  9. Put in two pinholes along the reference beam path to make future alignments easier.

Aligning the IRAM system

Raman alignment (all in epi-illumination mode):

1) With the air objective and no condenser lens, and a glass coverslip in the sample plane, use the 1st Raman mirror to make the two reflections from the coverslip overlap on the hitachi CCD.

2) With no objective or condenser lens, and a mirror facing downwards in the sample plane, use the 2nd Raman mirror to make the retro-reflection exiting the microscope hit the same spot as the illumination beam. (This can be done by using the IR viewer and a piece of lens paper to see both beams.)

3) Repeat steps 1-2 until they converge.

4) Put in the oil objective and a glass coverslip in the sample plane. Adjust the 2nd Raman mirror so that as the objective goes in and out of focus, the beam of the hitachi CCD has equal power in each quadrant of the spot.

5) Put in two pinholes after the periscope. These pinholes designate the path of a vertical beam.

Elastic alignment (in trans-illumination mode):

6) Use the two Elastic mirrors to direct the beam through the pinholes before the periscope, using the 1st mirror to align to the first pinhole and the 2nd mirror to align the second pinhole.

7) To fine-tune the beam so that it is going through the center of the objective with no condenser lens: Adjust the 2nd Elastic mirror so that the beam is hitting the center of the objective (will need IR viewer to see this). Then adjust the 1st Elastic mirror so that the beam is still going through the pinholes before the periscope. Repeat until the two converge.

8) Put in the condenser lens, and adjust its focus and position.

Quick Alignment

1) In epi-mode: Adjust 1st and 2nd Raman mirrors so that the beam is going through the 1st and 2nd pinholes, respectively, in the Raman excitation path.

2) In epi-mode: Without the condenser or objective, adjust the periscope mirrors so that the beam is going through the two pinholes after the periscope.

3) In trans-mode: Adjust the 1st and 2nd Elastic mirrors so that the beam is going through the two pinholes before the periscope.

4) Put in the objective and condenser. Adjust the focus and position of the condensor.

 

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