Measuring instrument, light source, image

During the development of the second-dimensional image measuring instrument by Mingwei Vision, the use of LED light sources plays a vital role in the accuracy of the measurement: LED is an injection type electroluminescent device, which is mainly composed of P-type and N-type It is composed of type semiconductor materials. The schematic diagram of the appearance and structure of the LED is shown in Figure 3-9. In fact, the PN junction die is sintered on a metal or ceramic base with a lead frame, and then surrounded by epoxy resin that protects the inner core wire. LED shape and structure principle When the P-type semiconductor and the N-type semiconductor are in contact with the LED light-emitting mechanism, the PN junction is formed due to the balance of the diffusion movement of the carriers and the drift movement under the action of the internal electric field. If a forward voltage is applied to the PN junction, the barrier of the junction zone is reduced, which promotes the diffusion movement, that is, the electrons flowing from the N zone to the P zone and the holes flowing from the P zone to the N zone increase at the same time, so there is a large amount of The electron and hole meet and recombine in the PN junction. The essence is that the electron releases the energy from the high-level conduction band to the valence band and the hole recombine, releases excess energy in the form of photons, and directly converts electrical energy into Light energy, that is, luminescence. The LED light source has low power, long life, fast response speed, stable brightness, easy adjustment, and environmental protection (the light emitted by the LED has no stroboscopic light, almost no ultraviolet light and infrared light, and no harm to the human body and eyesight). The main disadvantages are The luminous efficiency is low, and the effective luminous surface is difficult to enlarge. In addition, there are very few materials that emit short-wave light (such as blue-violet), and the manufactured short-wave LED is expensive. If these shortcomings can be overcome, the role and application range of LEDs will increase dramatically. The application fields of R front LED light source mainly include display screens, traffic signal display light sources, backlight sources of small electronic products such as the automotive industry, mobile phones, building lighting and special solid-state light sources required for other occasions. The commonly used LEDs are as follows. (1) Gallium phosphide (Gap) LED. When zinc and oxygen are added to gallium phosphide, the composite formed can emit red light with a central wavelength of 0.69 m and a bandwidth of 0.1 m. When zinc and nitrogen are doped in Sichuan, the device can emit green light. The center wavelength of the light emission is 0.565 m, and the bandwidth is about 0.035 m. (2) Gallium arsenide (GaAs) LED. Gallium arsenide LED emits near-infrared light. Light, the center wavelength is 0.94 Hm, and the bandwidth is 0.04 Hm. When the temperature in Sichuan rises, the radiation wavelength shifts to the long wave direction. The biggest advantage of this kind of LED is high luminous efficiency and fast pulse response, so it can produce high-frequency modulated light beam, which is often used in fiber optic communication, infrared night vision and other fields. (3) Phosphorus gallium arsenide (GaAs). F-LED. When the material content ratio of phosphorous gallium arsenide is different, that is, when x changes from 1 to 0, its luminous light W can change from 565nm to 910nm. Therefore, it can be manufactured LEDs with different luminous colors. The characteristic of this LED is that the preparation of PN junction is relatively simple, and when the code current increases, the saturation of the luminous curve is not obvious. In addition, it is also suitable