String_lens is a free Chrome add-on developed by Анощенков Дмитрий. This extension adds a button to the browser's toolbar, allowing users to input the desired optical system and calculate its paraxial characteristics.

With String_lens, users can enter a string that follows specific rules, and the extension can automatically determine the parameters of the system. Additionally, users have the option to specify the object size and front focal length to calculate the characteristics of the image.

This add-on provides a convenient and efficient way to perform quick calculations of paraxial characteristics for optical systems. Whether you're a professional in the field or simply curious about optics, String_lens can be a valuable tool in your browser.