An alignment means of a measurement instrument, the alignment means comprising - a housing; - an optical component (106, 202, 302, 606) having a principal axis (204, 304) in a direction parallel to a desired alignment, the optical component being configured such that an eye of the user is to be aligned with the principal axis of the optical component; - a first light source (108, 206, 306, 620) positioned at a first distance S1 from the optical component and at a first height h1 from the principal axis; - a second light source (110, 208, 308, 622) positioned at a second distance S2 from the optical component and at a second height h2 from the principal axis; and - an angle barrier means (112, 210, 312,612), - a third light source (310, 624) arranged at a third distance S3 from the optical component (106, 202, 302, 606) and at a third height h3 from the principal axis (204, 304), wherein the optical component comprises a focal point, wherein the first light source, the second light source and the third light source are positioned between the optical component and the focal point; and wherein the housing, the optical component, and the angle barrier means are arranged to: - block visibility of the first light source along the principal axis at a distance superior to d1'; - block visibility of the second light source along the principal axis at a distance smaller than d2, wherein d2 is smaller than d1'; and - block visibility of the third light source along the principal axis at a distance smaller than d3, wherein d3 is greater than d1' and smaller than d2'; and - block visibility of the second light source (110, 208, 308, 622) along the principal axis (204, 304) at a distance superior to d2', wherein d2' is greater than d1 wherein d1', d2, d2' and d3 are distances from the optical component. - a housing; - an optical component (106, 202, 302, 606) having a principal axis (204, 304) in a direction parallel to a desired alignment, the optical component being configured such that an eye of the user is to be aligned with the principal axis of the optical component; - a first light source (108, 206, 306, 620) positioned at a first distance S1 from the optical component and at a first height h1 from the principal axis; - a second light source (110, 208, 308, 622) positioned at a second distance S2 from the optical component and at a second height h2 from the principal axis; and - an angle barrier means (112, 210, 312,612), - a third light source (310, 624) arranged at a third distance S3 from the optical component (106, 202, 302, 606) and at a third height h3 from the principal axis (204, 304), wherein the optical component comprises a focal point, wherein the first light source, the second light source and the third light source are positioned between the optical component and the focal point; and wherein the housing, the optical component, and the angle barrier means are arranged to: - block visibility of the first light source along the principal axis at a distance superior to d1'; - block visibility of the second light source along the principal axis at a distance smaller than d2, wherein d2 is smaller than d1'; and - block visibility of the third light source along the principal axis at a distance smaller than d3, wherein d3 is greater than d1' and smaller than d2'; and - block visibility of the second light source (110, 208, 308, 622) along the principal axis (204, 304) at a distance superior to d2', wherein d2' is greater than d1 - block visibility of the first light source along the principal axis at a distance superior to d1'; - block visibility of the second light source along the principal axis at a distance smaller than d2, wherein d2 is smaller than d1'; and - block visibility of the third light source along the principal axis at a distance smaller than d3, wherein d3 is greater than d1' and smaller than d2'; and - block visibility of the second light source (110, 208, 308, 622) along the principal axis (204, 304) at a distance superior to d2', wherein d2' is greater than d1 wherein d1', d2, d2' and d3 are distances from the optical component.