Optical tactile sensor using surface-emitting laser

There exists a growing demand for an ultra small tactile sensor used in future industrial and medical systems, such as a miniature robot for inspection and repair in an extremely small space and an endoscopelcatheter used in the minimum invasive, laparoscopic surgical system for diagnosis and treatment. An optical sensor has a high sensitivity and a large Electromagnetic Interference (EMI) tolerance, which is necessary and important in a practical use combined with any other electrical apparatus. However, a miniaturization and a product cost reduction of an optical sensor is very difficult because a conventional high sensitive optical sensor consists of a laser and many precisely assembled optical components such as a lens for a beam shaping, an optical isolator to prevent a lasing wavelength instability induced by an optical feedback, an optical beam splitter to construct an interferometric optical path. Recently, some optical pressure sensor using an optical fiber is developed[l],[2]. These sensor consists of a small sensing element and a rather large optical interferometer which is spatially separated from the sensing element. Although sensing tips of these fiber-optic sensors are rather small, they have a serious drawback that the change of fiber bending shape strongly affects on a sensor output to induce sensing error. A surface-emitting laser (SEL) has two advantages compared to a conventional edgeemitting laser for the sensing use. One is a lasing wavelength stability against an optical feedback. The other is a design flexibility for a divergence angle of radiation beam. Consequently, an optical sensor with SEL can realize a miniaturized sensor which does not needs any optical components such as lenses and an optical isolator. This paper describes a feasibility study for an optical tactile sensor using SEL as a light source. 2. Principle of Operation