In recent years, tactile sensors have become an important interface for information devices. Our goal is to develop a simple and sensitive tactile sensor. We have proposed a reflection-image-based tactile sensor . The key points of this sensor were its simplicity and use of an optical device. In this study, we propose a design of a distributed-force sensitive touch panel following the previous developments. We employ an LED (light emitting diode) and PDs (photo diodes) in the new reflection-type tactile sensor. We investigate the illumination distribution and its changes under some simple deformation of the sensor surface with a ray-trace simulation. Then, based on the results of the experimental simulations, we also propose a method for estimating a given deformation from the illumination distribution.