Research on high performance LED cold light source for medical endoscope
Medical electronic endoscope has become a widely used medical instrument. Doctors can not only observe the tissue morphology of human internal organs and diagnose lesions through electronic endoscope, but also output and store images. Due to the dark environment inside the human body, an external illumination light source is required for auxiliary illumination when the electronic endoscope is imaging, and the illumination light is introduced into the body through a fiber bundle. Image quality is closely related to the color rendering, color temperature and illuminance of illumination light. At present, the light source of endoscope is mainly gas discharge light source, such as xenon lamp. Although the output luminous flux is large and the color rendering is good, there are problems such as large heat generation, short lifespan and high energy consumption. LED light source has the advantages of low energy consumption and long life. With the advancement of technology, the output luminous flux and color rendering of LED light source are also gradually improved. The purpose of this paper is to study the medical high-performance white light source using LED as the light-emitting element to meet the requirements of electronic endoscopes for color rendering, color temperature and illuminance. The research contents include LED chip selection, optomechanical system design, control circuit design, experimental system construction and testing, etc. According to performance requirements, two methods are proposed to obtain LED white light: RGB three primary colors are mixed to generate white light; high color temperature cool white light and red light are mixed to generate low color warm white light. According to the different characteristics of these two schemes, theoretical calculation, effect simulation and practical test are carried out respectively. The main work includes the following aspects: (1) Adopt OSRAM OSTAR SMT LE A/T/B/UW S2W complete LED chip solution, which has the characteristics of high power and large luminous flux, and design and apply the collimation of plastic aspheric surface according to its general optical characteristics Lens group to improve collimation efficiency. (2) The dichroic mirror is used as an optical element for mixing multiple light into a single light, and based on the X-cube light combiner composed of two dichroic mirrors, a light mixing system structure with strong versatility is designed. Two experimental schemes are implemented in one system. (3) Starting from the definition of the color rendering index, according to the luminous spectrum of the LED light source, the luminous flux ratio that can achieve the maximum color rendering index in the two schemes is calculated and simulated. After the experimental system was built, it was actually tested. The medical endoscope white LED lighting system designed in this subject has reached the international advanced level and has practical application value. The high color rendering warm white light generated by the combination of cold white light and red light can achieve a general color rendering index Ra of 93.9, and the output luminous flux can reach hundreds of lumens, which can meet the medical light source's requirements for high color reproduction and large luminous flux
