The present invention relates to an acoustic device for ultrasonic imaging of an object (21). The device comprises an acoustic transducer (10 and an acoustic lens (20) arranged to variably refract the said acoustic pulse to and/or from the acoustic transducer. The acoustic lens comprising a first (L1) and a second fluid (L2) being separated by an acoustic interface (7), the normal of the said acoustic interface forming a relative angle of incidence (AI) with the said acoustic pulse, e.g. an electrowetting lens. The first and the second fluid of the acoustic lens (20) are specifically chosen so that the acoustic interface (7) has a reflection minima at a non-zero relative angle of incidence (AI). The invention is advantageous for obtaining an improved acoustic device having a substantially lower reflection in a broader interval of incidence angles as compared to hitherto seen ultrasonic imaging utilising acoustic lenses with two or more fluids as the active acoustic refracting entities.