A spectroscope is an optical component that splits a beam of light into two beams with specific reflection and transmission ratios. Its core principle involves using a dispersion element (such as a prism) to decompose white light into light of different wavelengths, forming a continuous visible light spectrum. This characteristic allows the selective absorption patterns of pigments in gemstones to be used for gem identification, determining the type of gemstone and the cause of its coloration by identifying fixed absorption band positions. In optical paths, the spectroscope primarily functions to separate light source energy and alter the direction of the light path. It features a simple structure, minimal light absorption, and low loss after spectral splitting.

Classification and Structural Characteristics of Spectroscopes

Classification by Structural Form

• Cube Spectroscope: Composed of two right-angle prisms bonded together, with one prism's斜面 coated with a spectral splitting film, forming a cubic structure. Its advantages include high effective diameter utilization in all directions and ease of optical adjustment, making it suitable for compact optical systems. However, large-aperture products are heavier and more costly, and may produce a small amount of back-reflected light (within 1%).
• Plate Spectroscope: Designed based on a flat glass plate with a single surface coated with a spectral splitting film. It offers lower cost and lighter weight, making it suitable for applications with limited space or cost sensitivity. However, it suffers from issues such as optical path differences between reflected and transmitted light, which may cause astigmatism and beam displacement. At a 45° incidence angle, the effective diameter appears elliptical.