A two-axis tilt sensor, consisting of two lenses and a CMOS image sensor, based on refractive law, is described here. This two-lens optical system, which has a bowl-shaped lens, is designed in such a way that one can find the tilt information for the total system. Indeed, the relationship between the tilt angle and the position of the light spot on the sensor is easy to observe directly. The reading tilt angle can be estimated with a resolution of better than 4.2 arcsec. This tilt sensor would be suitable for laboratory, civil engineering and industrial applications.