Collimation device for an X-ray detection system, the collimation device comprising: a collimator comprising a substantially planar support made of a material with partial or zero radiotransparency, the support being rotatably movable about an axis of rotation (Δ) which passes through the support and which is perpendicular to a first face of the support which acts as an X-ray plane of incidence referred to as the main plane of the support (P), the support (D) being provided on the first face with a slit which is completely transparent to X-rays and which is configured to generate an X-ray flow when the collimator is exposed to an X-ray source, the slit extending longitudinally in the main plane of the support along an axis located at a non-zero distance (d) from the axis of rotation (Δ), the slit extending through the entire thickness of the support.