Optical micro displacement sensor using a composite cavity laser diode integrated with a microlens

We demonstrated an extremely small optical displacement sensor using a laser diode integrated with a microlens and based on the composite cavity principle, which is that the light output power from the laser diode changes with reflectance and displacement of the third mirror. The light output power from the device was modulated by the reflectance of the third mirror with the displacement in the lateral direction. The modulation depth was 0.1 when the third mirror reflectances were 70% and 4%, and the resolution in the lateral direction was 3 μm. The light output power was also modulated by the third mirror displacement in the axial direction with a period of 0.4 mu m, and a modulation depth of 0.047 was obtained.