Since the early 1970s, inversion techniques have become the most useful tool for inferring the magnetic, dynamic, and thermodynamic properties of the solar atmosphere. Inversions have been proposed in the literature with a sequential increase in model complexity: astrophysical inferences depend not only on measurements but also on the physics assumed to prevail both on the formation of the spectral line Stokes profiles and on their detection with the instrument. Such an intrinsic model dependence makes it necessary to formulate specific means that include the physics in a properly quantitative way. The core of this physics lies in the radiative transfer equation (RTE), where the properties of the atmosphere are assumed to be known while the unknowns are the four Stokes profiles. The solution of the (differential) RTE is known as the direct or forward problem. From an observational point of view, the problem is rather the opposite: the data are made up of the observed Stokes profiles and the unknowns are the solar physical quantities. Inverting the RTE is therefore mandatory. Indeed, the formal solution of this equation can be considered an integral equation. The solution of such an integral equation is called the inverse problem. Inversion techniques are automated codes aimed at solving the inverse problem. The foundations of inversion techniques are critically revisited with an emphasis on making explicit the many assumptions underlying each of them.

自 20 世纪 70 年代初以来，反演技术已成为推断太阳大气的磁性、动力学和热力学特性的最有用的工具。文献中已经提出了模型复杂性依次增加的反演：天体物理学推论不仅取决于测量，还取决于假设在谱线斯托克斯剖面的形成及其仪器检测方面占主导地位的物理学。这种内在的模型依赖性使得有必要以适当的定量方式制定包括物理在内的具体方法。该物理学的核心在于辐射传输方程（RTE），其中假设大气的特性已知，而未知数是四个斯托克斯分布。 （差分）RTE 的解决方案称为直接问题或前向问题。从观测的角度来看，问题恰恰相反：数据由观测到的斯托克斯剖面组成，未知数是太阳物理量。因此，反转 RTE 是强制性的。事实上，这个方程的形式解可以被认为是一个积分方程。这种积分方程的解称为反问题。反演技术是旨在解决反演问题的自动代码。对反演技术的基础进行了批判性的重新审视，重点是明确每个反演技术背后的许多假设。