A novel tissue hardness measurement sensor (tactile sensor) capable of measuring the material constants of sensed objects has been fabricated and demonstrated in this study. The tactile sensor we proposed is composed of an elastic optical waveguide unit, a highresolution CCD camera unit, and an LED light source. The sensing element is formed on polydimethylsiloxane (PDMS) and illuminated along its four edges by LED light sources. The sensor operates on the principle of total internal reflection within an optical waveguide. When an object compresses the waveguide, the contact area of the waveguide deforms and causes the light to scatter. Since the scattered light is directly captured by a CCD camera, the tactile resolution of the proposed sensor is based on the resolution of the camera. Experiments were conducted to demonstrate the ability of the proposed sensing strategy in measuring Young's modulus of polymer samples within 23% error.