According to the invention, the skull pot is provided with the following characteristics: a pot wall, a bottom and an induction coil which surrounds the pot wall and by means of which high-frequency energy can be coupled into the contents of the pot. In addition, the device comprises a support, functionally separated from the proof body, of generally annular shape, housing the rigid component and a flexible mass radially inserted between the support and the rigid component such that the contour of the measurement surface is bounded by the flexible mass, this flexible mass adhering to the support and to the rigid component. An image quality evaluation device and method provided in the present invention are used to analyze the parameters of an image with the image recognition technology to obtain parameter values and then generate the parameter values in line with the predetermined standard. The frequency converter provided in the present invention has a compact volume and fewer optical components, which means it is easy to be integrated, a big frequency converting range, a high frequency converting efficiency and a high output power.