A computer-implemented method for computing and optimising an optical objective lens architecture with a determined focal length and intended to operate within a determined wavelength range and within a determined temperature range, characterised in that said method contains the following steps of: - Step 1: estimating the acceptable axial chromatic aberration threshold (Δ PV) and the acceptable thermal defocusing (ε(ΔT)); - Step 2: setting an optical combination in the paraxial domain of the "Petzval" type containing two convergent lenses (L1, L2) made from a first material; - Step 3: first optimisation of the optical combination for a first plurality of wavelengths at a constant reference temperature and a second plurality of temperatures at a constant reference wavelength; - Step 3bis: if the result of this first optimisation yields an optical combination whose residual axial chromatic aberration is greater than the acceptable chromatic aberration threshold or whose thermal defocusing is greater than a determined thermal defocusing, depending on the acceptable thermal defocusing, duplicating one of the lenses of the optical combination and/or replacing the first material of one of the lenses with a second material and/or adjusting the draw and the bulk of the optical objective lens and returning to step 3; - Step 4: if the result of this first optimisation yields an optical combination whose residual axial chromatic aberration is less than or equal to the acceptable chromatic aberration threshold and whose thermal defocusing is less than the determined thermal defocusing, second optimisation of the optical combination for the first plurality of wavelengths and for each temperature belonging to the second plurality of temperatures. - Step 1: estimating the acceptable axial chromatic aberration threshold (Δ PV) and the acceptable thermal defocusing (ε(ΔT)); - Step 2: setting an optical combination in the paraxial domain of the "Petzval" type containing two convergent lenses (L1, L2) made from a first material; - Step 3: first optimisation of the optical combination for a first plurality of wavelengths at a constant reference temperature and a second plurality of temperatures at a constant reference wavelength; - Step 3bis: if the result of this first optimisation yields an optical combination whose residual axial chromatic aberration is greater than the acceptable chromatic aberration threshold or whose thermal defocusing is greater than a determined thermal defocusing, depending on the acceptable thermal defocusing, duplicating one of the lenses of the optical combination and/or replacing the first material of one of the lenses with a second material and/or adjusting the draw and the bulk of the optical objective lens and returning to step 3; - Step 4: if the result of this first optimisation yields an optical combination whose residual axial chromatic aberration is less than or equal to the acceptable chromatic aberration threshold and whose thermal defocusing is less than the determined thermal defocusing, second optimisation of the optical combination for the first plurality of wavelengths and for each temperature belonging to the second plurality of temperatures.