This article commemorates the 150th anniversary of A. L. Gershun (1868-1915) who played a key part in the creation of optical industry in the pre-revolutionary Russia. He was a student of professor I. I. Borgman at St. Petersburg University, whose functions he later took up in the department. However, a number of circumstances did not allow him to get a job as a teacher. A. L. Gershun taught in various secondary and higher educational institutions both in Saint Petersburg and at the Artillery Officer Class in Kronstadt, where he became a professor. Pedagogical and scientific activities of A. L. Gershun closely intertwined with the work as an engineer and experimenter. He headed the Optical-Mechanical Department of the Obukhov Plant, participated in the construction and equipment of the Optical Plant (LOMO).