A device (20, 40, 69, 79) for measuring biological properties of an examined tissue comprising tissue layers (S1, S2, S3, S4, S5) that contain blood vessels, the device (20, 40, 69, 79) comprising: at least one light source (10, 10a, 10c, 62, 70) configured and operable to illuminate the examined tissue with light radiation of one or more wavelengths at a light illumination direction; and a light detector (12, 60c, 70c) configured to be located at a same side of said examined tissue and configured and operable to receive light components of said one or more wavelengths reflected from the examined tissue in response to the illuminated light radiation at a light detection direction, and to generate measurement data indicative thereof, wherein light components reflected from the blood vessels towards the light detector (12, 60c, 70c) introduce a pulsating AC component to the optical signals measured by the light detector (12, 60c, 70c), wherein light components reflected from non-perfused tissue layers (S1, S2) contribute to DC and noise components of the measured signal; at least one of said light illumination direction and detection direction is positioned at an angle (α) of at least 2° relative to an imaginary line perpendicular to the examined tissue or form an angle (α) of at least 2 0 between the light illumination direction and the detection direction, characterized in that: the device (20, 40, 69, 79) comprises a control unit configured and operable to activate said at least one light source (10, 10a, 10c, 62, 70) to illuminate the examined tissue, receive and process the measurement data generated by said light detector (12, 60c, 70c), and determine based on an AC/DC ratio of the optical signals, said biological properties; the at least one light source is oriented so as to direct the light illumination direction away from the light detection direction; and a distance between the at least one light source (10, 10a, 10c, 62, 70) and the light detector (12, 60c, 70c) is chosen to optimize the AC/DC ratio with respect to the angle (α) formed between the light illumination direction and detection direction, whereby as the angle (α) between the light illumination direction and the light detection direction is increased the distance between the light source (10, 10a, 10c, 62, 70) and the light detector (12, 60c, 70c) are respectively reduced, and vice versa. at least one light source (10, 10a, 10c, 62, 70) configured and operable to illuminate the examined tissue with light radiation of one or more wavelengths at a light illumination direction; and a light detector (12, 60c, 70c) configured to be located at a same side of said examined tissue and configured and operable to receive light components of said one or more wavelengths reflected from the examined tissue in response to the illuminated light radiation at a light detection direction, and to generate measurement data indicative thereof, wherein light components reflected from the blood vessels towards the light detector (12, 60c, 70c) introduce a pulsating AC component to the optical signals measured by the light detector (12, 60c, 70c), wherein light components reflected from non-perfused tissue layers (S1, S2) contribute to DC and noise components of the measured signal; at least one of said light illumination direction and detection direction is positioned at an angle (α) of at least 2° relative to an imaginary line perpendicular to the examined tissue or form an angle (α) of at least 2 0 between the light illumination direction and the detection direction, characterized in that: the device (20, 40, 69, 79) comprises a control unit configured and operable to activate said at least one light source (10, 10a, 10c, 62, 70) to illuminate the examined tissue, receive and process the measurement data generated by said light detector (12, 60c, 70c), and determine based on an AC/DC ratio of the optical signals, said biological properties; the at least one light source is oriented so as to direct the light illumination direction away from the light detection direction; and a distance between the at least one light source (10, 10a, 10c, 62, 70) and the light detector (12, 60c, 70c) is chosen to optimize the AC/DC ratio with respect to the angle (α) formed between the light illumination direction and detection direction, whereby as the angle (α) between the light illumination direction and the light detection direction is increased the distance between the light source (10, 10a, 10c, 62, 70) and the light detector (12, 60c, 70c) are respectively reduced, and vice versa. the device (20, 40, 69, 79) comprises a control unit configured and operable to activate said at least one light source (10, 10a, 10c, 62, 70) to illuminate the examined tissue, receive and process the measurement data generated by said light detector (12, 60c, 70c), and determine based on an AC/DC ratio of the optical signals, said biological properties; the at least one light source is oriented so as to direct the light illumination direction away from the light detection direction; and a distance between the at least one light source (10, 10a, 10c, 62, 70) and the light detector (12, 60c, 70c) is chosen to optimize the AC/DC ratio with respect to the angle (α) formed between the light illumination direction and detection direction, whereby as the angle (α) between the light illumination direction and the light detection direction is increased the distance between the light source (10, 10a, 10c, 62, 70) and the light detector (12, 60c, 70c) are respectively reduced, and vice versa.