A spectrometer comprising - an entry slit configured to receive a one-dimensional image slice of light for spectral analysis along a straight object line shape; - projection optics (2,3,4) configured to project a spectrally resolved two-dimensional image of the straight object line shape onto a detector array; and - correction optics formed by a monolithic block of material disposed in an optical path directly behind the entry slit and in front of the projection optics, wherein the correction optics comprises ∘ an internal reflection surface forming a cylindrical mirror with its curvature around a first cylinder axis in a direction perpendicular to a length of the entry slit for providing a first reflection of light originating from the entry slit; ∘ a curved entry surface forming a collimation compensator configured to counteract decollimation of parallel principal light rays (Lc,Le) of the light caused by the first reflection; and ∘ a flat mirror surface extending in a direction parallel (//) to the first cylinder axis for providing a second reflection of the light, wherein the correction optics is configured to warp the straight object line shape of the entry slit into a curved object line shape from a point of view of the projection optics (2,3,4), wherein the warping of the correction optics is configured such that a curvature of the curved object line shape counteracts an otherwise distorting curvature in a projection of the straight object line shape by the projection optics (2,3,4) without the correction optics, wherein the spectrally resolved image comprises a plurality of parallel straight projected line shapes formed by spectrally resolved projections of the straight object line shape. - an entry slit configured to receive a one-dimensional image slice of light for spectral analysis along a straight object line shape; - projection optics (2,3,4) configured to project a spectrally resolved two-dimensional image of the straight object line shape onto a detector array; and - correction optics formed by a monolithic block of material disposed in an optical path directly behind the entry slit and in front of the projection optics, wherein the correction optics comprises ∘ an internal reflection surface forming a cylindrical mirror with its curvature around a first cylinder axis in a direction perpendicular to a length of the entry slit for providing a first reflection of light originating from the entry slit; ∘ a curved entry surface forming a collimation compensator configured to counteract decollimation of parallel principal light rays (Lc,Le) of the light caused by the first reflection; and ∘ a flat mirror surface extending in a direction parallel (//) to the first cylinder axis for providing a second reflection of the light, ∘ an internal reflection surface forming a cylindrical mirror with its curvature around a first cylinder axis in a direction perpendicular to a length of the entry slit for providing a first reflection of light originating from the entry slit; ∘ a curved entry surface forming a collimation compensator configured to counteract decollimation of parallel principal light rays (Lc,Le) of the light caused by the first reflection; and ∘ a flat mirror surface extending in a direction parallel (//) to the first cylinder axis for providing a second reflection of the light,