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 , each measuring channel comprising a light source configured to produce a measuring light beam and an optical sensor 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 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 , each comprising the light source , the optical sensor and the light beam , are non-parallel; characterised in that said method comprises the following steps: - measuring , by the optical sensors , 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 , 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 , each measuring channel comprising a light source configured to produce a measuring light beam and an optical sensor 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 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 , each comprising the light source , the optical sensor and the light beam , are non-parallel; characterised in that said method comprises the following steps: - measuring , by the optical sensors , 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 , 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 , <EOS>