Apparatus for light sheet microscopy, comprising - an illumination optical unit comprising an illumination objective for illuminating a sample, which is situated in a medium on a sample carrier, with a light sheet via an illumination beam path, wherein the optical axis of the illumination objective and the light sheet lie in a plane which includes an illumination angle (β) that differs from zero with the normal of a horizontal, plane reference surface in respect of which the sample carrier is aligned, - a detection optical unit comprising a detection objective in a detection beam path, the optical axis of which includes a detection angle (δ) that differs from zero with the normal of the reference surface, - a separation layer system comprising at least one layer made of a specified material with a specified thickness, which separates the medium from the illumination objective and the detection objective, wherein, by way of a base lying parallel to the reference surface, the separation layer system is in contact with the medium, at least in the region accessible to the illumination objective and the detection objective for illumination and detection, respectively, characterized in that - the apparatus comprises a detection correction lens system with at least one detection correction lens for reducing those aberrations arising as a result of the oblique passage of light to be detected through interfaces of the separation layer system, - wherein the at least one detection correction lens is configured as a free-form lens and is arranged between detection objective and separation layer system or forms the front lens of the detection objective, - wherein both lens surfaces are configured as free-form surfaces, which each satisfy a condition z x y = x 2 + y 2 / R 1 + 1 − 1 + k ⋅ x 2 + y 2 R 2 + ∑ m, n = 0 ∞ C m, n x m y n - where k denotes the conic constant, R denotes the radius of an imagined conic section at the apex of this surface, z(x,y) denotes the distance of the respective lens surface from a plane perpendicular to the optical axis at the apex of the conic section, in coordinates x and y, and Cm,n are coefficients of a polynomial and only differ from zero for even m, - and wherein, respectively for both free-form surfaces, k, R and the coefficients C m,n are predefined on the basis of the medium, the material of the at least one layer of the separation layer system and the thickness of the at least one layer of the separation layer system. - an illumination optical unit comprising an illumination objective for illuminating a sample, which is situated in a medium on a sample carrier, with a light sheet via an illumination beam path, wherein the optical axis of the illumination objective and the light sheet lie in a plane which includes an illumination angle (β) that differs from zero with the normal of a horizontal, plane reference surface in respect of which the sample carrier is aligned, - a detection optical unit comprising a detection objective in a detection beam path, the optical axis of which includes a detection angle (δ) that differs from zero with the normal of the reference surface, - a separation layer system comprising at least one layer made of a specified material with a specified thickness, which separates the medium from the illumination objective and the detection objective, wherein, by way of a base lying parallel to the reference surface, the separation layer system is in contact with the medium, at least in the region accessible to the illumination objective and the detection objective for illumination and detection, respectively, characterized in that - the apparatus comprises a detection correction lens system with at least one detection correction lens for reducing those aberrations arising as a result of the oblique passage of light to be detected through interfaces of the separation layer system, - wherein the at least one detection correction lens is configured as a free-form lens and is arranged between detection objective and separation layer system or forms the front lens of the detection objective, - wherein both lens surfaces are configured as free-form surfaces, which each satisfy a condition z x y = x 2 + y 2 / R 1 + 1 − 1 + k ⋅ x 2 + y 2 R 2 + ∑ m, n = 0 ∞ C m, n x m y n - where k denotes the conic constant, R denotes the radius of an imagined conic section at the apex of this surface, z(x,y) denotes the distance of the respective lens surface from a plane perpendicular to the optical axis at the apex of the conic section, in coordinates x and y, and Cm,n are coefficients of a polynomial and only differ from zero for even m, - and wherein, respectively for both free-form surfaces, k, R and the coefficients C m,n are predefined on the basis of the medium, the material of the at least one layer of the separation layer system and the thickness of the at least one layer of the separation layer system.