An oximeter wristwatch, for measuring a blood oxygenation level at a wrist of an individual, comprising: - a back-case assembly with a lens, said lens comprising a flat disk portion, - a light emission assembly comprising a green LED, a red LED and an infrared LED, each configured to emit light rays toward wrist tissue through the lens, - a broadband photodiode configured to receive red and infrared light rays, - a selective photodiode configured to receive green light rays and to eliminate infrared wavelengths, - a control unit configured to collect electrical signals delivered by the selective and broadband photodiodes (2,3) upon selective activation of each LED of the light emission assembly, and configured to calculate therefrom a current blood oxygenation level, wherein the infrared LED is arranged to emit light rays at a first position, the red LED is arranged to emit light rays at a second position, the green LED is arranged to emit light rays at a third position, wherein the broadband photodiode is arranged to receive light rays from a red and infrared path at a fourth position (P4,P4a), such that the broadband photodiode is spaced from the first position of at least e4 =7mm, and such that the broadband photodiode is spaced from the second position of at least e4 =7mm wherein the selective photodiode is arranged to receive light rays from a green path at a fifth position (P5,P5a), such that the selective photodiode is spaced from the third position of at least e5 =2mm, wherein the emission assembly, the broadband photodiode and the selective photodiode are disposed according to an in-line arrangement, i.e. the selective photodiode is interposed between the emission assembly and the broadband photodiode, wherein the in-line arrangement is such that a first part of a light path in the wrist is common for the green path and the red and infrared path, wherein the selective photodiode forms a barrier for direct path between the light emission assembly and broadband photodiode. - a back-case assembly with a lens, said lens comprising a flat disk portion, - a light emission assembly comprising a green LED, a red LED and an infrared LED, each configured to emit light rays toward wrist tissue through the lens, - a broadband photodiode configured to receive red and infrared light rays, - a selective photodiode configured to receive green light rays and to eliminate infrared wavelengths, - a control unit configured to collect electrical signals delivered by the selective and broadband photodiodes (2,3) upon selective activation of each LED of the light emission assembly, and configured to calculate therefrom a current blood oxygenation level, wherein the infrared LED is arranged to emit light rays at a first position, the red LED is arranged to emit light rays at a second position, the green LED is arranged to emit light rays at a third position, wherein the broadband photodiode is arranged to receive light rays from a red and infrared path at a fourth position (P4,P4a), such that the broadband photodiode is spaced from the first position of at least e4 =7mm, and such that the broadband photodiode is spaced from the second position of at least e4 =7mm wherein the selective photodiode is arranged to receive light rays from a green path at a fifth position (P5,P5a), such that the selective photodiode is spaced from the third position of at least e5 =2mm, wherein the emission assembly, the broadband photodiode and the selective photodiode are disposed according to an in-line arrangement, i.e. the selective photodiode is interposed between the emission assembly and the broadband photodiode, wherein the in-line arrangement is such that a first part of a light path in the wrist is common for the green path and the red and infrared path, wherein the selective photodiode forms a barrier for direct path between the light emission assembly and broadband photodiode.