A method for establishing a thickness map of an object, the method being implemented by a contactless measuring device comprising: - at least one pair of measuring channels (2, 3), each measuring channel (2, 3) comprising a light source (7a, 8a) configured to produce a measuring light beam (5, 6) and an optical sensor (7b, 8b) configured to produce distance measurements, - a reception zone for an object to be measured, the reception zone comprising an object plane and/or axis, wherein two measuring channels (2, 3) are arranged on either side of the object plane and/or the object axis so as to be able to measure the object from two opposite sides, and so that the planes of the measuring channels (7, 8), each comprising the light source (7a, 8a), the optical sensor (7b, 8b) and the light beam (5, 6), are non-parallel; characterised in that said method comprises the following steps: - measuring, by the optical sensors (7b, 8b), the light reflected and/or scattered by the zones illuminated by the light beams of two opposite surfaces of a reference object of thickness, e REF, which is known, to obtain a first and a second reference signal of the positions of the two reference surfaces, - measuring, by the optical sensors (7b, 8b), the light reflected and/or scattered by the zones illuminated by the light beams of two opposite surfaces of the object to be measured, to obtain a first and a second signal for measuring the positions of the two surfaces of the object, at a plurality of measurement points on the object, - determining, from the first and the second measurement signal and the reference thickness, e REF, a plurality of thickness values, e, for the plurality of measurement points, and - establishing a thickness map of the object from the plurality of thickness values of the object to be measured, the measurements of one surface of the object being desynchronised from the measurements of the other surface of the object. - at least one pair of measuring channels (2, 3), each measuring channel (2, 3) comprising a light source (7a, 8a) configured to produce a measuring light beam (5, 6) and an optical sensor (7b, 8b) configured to produce distance measurements, - a reception zone for an object to be measured, the reception zone comprising an object plane and/or axis, wherein two measuring channels (2, 3) are arranged on either side of the object plane and/or the object axis so as to be able to measure the object from two opposite sides, and so that the planes of the measuring channels (7, 8), each comprising the light source (7a, 8a), the optical sensor (7b, 8b) and the light beam (5, 6), are non-parallel; characterised in that said method comprises the following steps: - measuring, by the optical sensors (7b, 8b), the light reflected and/or scattered by the zones illuminated by the light beams of two opposite surfaces of a reference object of thickness, e REF, which is known, to obtain a first and a second reference signal of the positions of the two reference surfaces, - measuring, by the optical sensors (7b, 8b), the light reflected and/or scattered by the zones illuminated by the light beams of two opposite surfaces of the object to be measured, to obtain a first and a second signal for measuring the positions of the two surfaces of the object, at a plurality of measurement points on the object, - determining, from the first and the second measurement signal and the reference thickness, e REF, a plurality of thickness values, e, for the plurality of measurement points, and - establishing a thickness map of the object from the plurality of thickness values of the object to be measured,