Effect of non-contact preheating on fog spots of molded infrared lenses

When the aspheric infrared lens is molded, the lens press-cutting time can be shortened by increasing the temperature of the molding stage, thus improving the molding efficiency. However, it is easy to produce the fog spots on the lens surface, like a bad lens. Through the analysis of the formation mechanism of lens fog spots, a non-contact preheating molding process was adopted to reduce the formation of it, and the molding experiments were carried out on a multi-station molding press, in which the elements of fog spots were detected and analyzed by using an energy spectrometer. In this molding experiment, the non-contact preheating method was used to increase the molding temperature from 206℃ to 211℃ when the preheating gap was 1 mm, with no fog spots formed on the lens surface, and the press-cutting time was shortened by 21 s. The results show that the non-contact preheating method in the multi-station molding press can effectively eliminate the formation of lens fog spots. The test results show that the volatilization of the lens material in the molding stage plays a dominant role in the formation of fog spots.