Detection arm

Schemes

Part list

Alignment

click on the image to enlarge

Since all the elements of the detection arm are mounted on a rail it is much simpler to emsemble and to align than the illumination one.

First of all mount the Camera on the rail using the base plate and the rail carriage. With the plastic cover of the CCD on, make sure that the heigh of the illumination path is correct, by pointing the laser beam on the center of the plastic. If you wish to have a higher design, then add a higher custom base plate.

Once you have check for the heigh, the rail can be attack to the table. The rail has to be placed perpendicular to the optical bench border, and parallel to the bench holes. Secure it with the clamps.

Tube lens

Remove the CCD cover and screw in the C-mount adaptor and the SM1E60 lens tube. Introduce the tube slip mounted in another rail carriage to hold the lens tube.

The distance between the tube lens and the camera CCD has to be 200 mm, so add a SM1E20 lens tube and the tube lens mounted on a SM1E10.

Objective support

The objective is mounted on an independent rail carriage. This will make easier to change the focal position when replacing the objective. The objective lenses we have are not parfocal. That means that when using the x16 objective the whole objective support should be moved towards the camera, and when using a x4 or x10 towards the sample. Moreover, when using air objectives the position of the chamber (and the amount of water between sample and objective) will slighty change the image plane.

This movement of the objective performs the coarse alignment in order to image, together with the tube lens, the light sheet onto the CCD. Fine alignment can be performed with the translational stage of the illumination arm, moving the illumination objective. But this movement has to be limited to small adjustments, in order to prevent the system from optical aberrations.

Final alignments

Now that all the elements are inserted on the system is time to mount the filter wheel and the sample sub-systems. Mount the x16 objective lens (or the longer objective that you have). Insert the filter wheel as close as posible from the objective support. Then move the camera-tube lens system closer to the filter wheel, but without touching it. Take into account that the filter wheel should rotate freely.

Now open the shutter and with 0 volts on the galvo mirror and an empty slot of the filter wheel move the objective mount in order to create an image of the laser beam on the CCD camera. Once you have a sharp image of you beam produce by scattering in the water, set a fluorescent filter and correct the objective position if needed. Then clamp the objective mount. Move again as closer as possible the filter wheel and the camera-tube lens assembly and clamp them.

Finally attach the sample mounting sub-system, adjusting the heigh and the z position, in such a way that you can scan your sample in all the axes (X/Y/Z). Fine alignment of the laser beam can be now performed using the manual translational stages on the illumination arm.

After that, when using the air objectives, place the chamber in a desired position. Then only adjust the objective support position to create the sharp image of your beam, without touching anything else.

Optional

Between the objective lens and the tube lens we have the so called infinity space. In that region beam travel in a collimated way. Is in this infinity space when we are allowed to introduce different optics such as filters or a dichroic mirror (mounted in the cage cube) for fluorescence illumination of the sample.

Basically the expanded beam is redirected using a flip-mount mirror to a lens (200 mm) that focus on the back focal apperture of the objective (after been reflected the dicrhoic mirror), creating an illuminated area on the sample. The fluorescence pass back through the dicrhoic mirror and is imaged with the tube lens onto the CCD camera. This option is useful for OPT fluorescence mode. (See diagram below)