Point Source Microscope

Yes, the PSM comes with an internal source whose wavelength is 635 nm which is fiber coupled into the PSM via a FC/APC fiber connector. The internal source fiber can be unscrewed and stored in an adjacent storage fiber connector. An external source is then coupled into the now vacant active FC fiber connector. The external source fiber to the PSM must be terminated with a FC/APC connector for the PSM to work properly.

The beamsplitters in the PSM have broadband coatings so any source from 350 to 700 nm can be used and even beyond with some loss in sensitivity. The Thorlabs S1FCxxx fiber-coupled lasers sources are well suited as are similar sources from qphotonics that provide a wider range of wavelengths. Incandescent sources can be coupled in as well as long as the termination into the PSM is a FC/APC connector. The losses will be large getting the white light in but the PSM is quite sensitive to low light levels.

The spatial scale in the PSM is controlled using the “Calibration Factor” on the Cal Tab. For a 10x objective the Calibration Factor should be about 1.0 and then the units displayed on the right hand side of the PSM2 GUI under Spot will be correct in μm. For a 4x objective the Calibration Factor should be about 2.5.

Many things influence the precise PSM calibration including the pixel size in the camera and the make of the objective lens. For precise calibration of the spatial scale it is best to use a sample of known line width such as a stage micrometer or Ronchi ruling and measure the width using as much of the field of view of the objective as possible.

Use the arrow cursor to click on one edge of the line and then click on the other edge. Green crosses will appear with each click. On the Threshold tab the coordinates of the green crosses are listed. If the distance between the two crosses at either edge of the known line is not correct, change the Calibration Factor by the ratio of the measured value to the known value and repeat the measurement. One or two times making the measurement should get to 1% of the true spatial scale. Note that the coordinates of each cross is with respect to the reference cross.

Once this is done the scales is correct for all readings on the GUI unless the objective or camera are changed in which case the calibration must be repeated. The units on the scale bar and the crosshairs are also controlled by this calibration and will be correct once calibrated. Notice the scale bar at the bottom of the Cal tab. It can be made any length, have any number of divisions and be placed anywhere on the video screen.