Die optischen Instrumente

Abstract

THE aim of this little book, one of a series dealing popularly with various subjects of scientific or general interest, is to give a simple account of the development and modern theory of optical instruments, and to make clear to readers possessing no special technical knowledge the main features of their optical construction. The treatment is largely based on the work of Abbe; and in the introductory chapters, which deal with the general principles governing the formation of optical images and the consequences dependent on the characteristics of the eye, special attention is given to the question of aperture and the limits of the image-forming pencils, and to the manner in which the perspective of a picture may be modified in the image. In the application of these considerations to the photographic lens, the microscope, and the telescope, there is some novelty and interest. In other respects a clear and concise account is given of the main properties and aberrations of the different instruments, whether for objective or subjective use, with some brief historical notes. The section on the photographic lens is followed by useful particulars as to enlarging and projection apparatus; the description of the microscope includes a short explanation of Abbe's theory of microscopic vision, of the relation of “numerical aperture” to resolving power, and of the sine law, and even admits of reference to the possibilities of photomicrography with ultra-violet light. To the description of the ordinary forms of telescope are added some notes on the prism binocular as constructed by the Zeiss firm. The diagrams and illustrations are noticeably well drawn and clearly printed.