This paper describes a new type of tactile sensor intended for robotic applications. It is based upon the frustration of total internal reflection at an optical surface caused by an opaque elastic membrane. An optical image is created in which the intensity is monotonically related to the strains or pressures created by an impressed object. This image is subsequently converted to digital form by a CID camera. The performance characteristics of two planar tactile array sensors are presented. The first sensor is a tactile "table" with an active area measuring 7 x 12cm. A 128 x 128 pixel CID camera is used to image a 3.3 x 3.3cm section of the total active area, thereby resulting in an effective tactile element density of 1500/sq-cm. The second sensor is a small, compact unit designed for use on robot gripper fingers. A coherent cable of optical fibers convey the strain image to a remotely-located CID camera, resulting in a tactile element density of 54/sq-cm over an active area measuring 2.2 x 2.5cm. Such optical tactile array sensors are seen to offer significant promise in the area of robotics where they can provide the advantages of high spatial resolution and non-planar sensor geometries (e.g. cylindrical and hemispherical).