An opto-electrical ultrasound sensor, preferably for the use in medical diagnostics, comprising at least one light source (2),a photo detector (3) illuminated by the light source (2) and capable of producing an electrical signal indicative of the intensity of the light incident on the photo detector(3), and an optical ultrasound detector (4) located in the optical path between the light source (2) and the photo detector (3) and capable of modulating in response to an ultrasound signal the intensity of at least part of the light incident on photo detector (3) from the light source (2). The opto-electrical ultrasound sensor further comprises intensity adjustment means (5) for adjusting the intensity of the light incident on the photo detector (3) via the optical ultrasound detector (4).