Confocal microscopy via reciprocal optical fibre image detection

We describe a compact form of confocal scanning microscope using a semiconductor laser. Confocal operation is ensured by the use of a single mode optical fibre for both launching the light into the microscope and collecting the signal from the object. The collected light is allowed to re-enter the laser and the image is detected as a modulation on the signal from the laser power monitor diode. Images are compared with those obtained from traditional point detectors. The alignment tolerances of the reciprocal scheme are found to be greatly reduced over conventional confocal systems.