A complete microscope system design is very complex, involving optical design, mechanical design, circuit design and other aspects of knowledge; most modern microscopes are combined with computer technology and automatic control technology, which is a high-tech product of the combination of optics, electronics and computing. I just want to do some simple knowledge summary based on my own microscope design practice in recent years. I hope you can give me more advice.

First of all, according to the requirements of the use of the microscope, the selection and design of the microscope should be carried out. Microscopes have been developed for hundreds of years, and there are many forms of microscopes. According to different requirements, the parameters of microscopes vary greatly. For example, biological microscope, metallographic microscope, stereomicroscope, measuring microscope, tool microscope and so on. Taking the simplest common biological microscope as an example, it can be divided into many categories, including upright and inverted according to the structure, bright field illumination and dark field illumination according to the lighting form, fluorescent microscope and laser microscope according to the light source, 195mm and infinity according to the conjugate distance, etc.

The second step is to select the shape, size, magnification, resolution and other main parameters. This step can be learned in engineering optics or applied optics courses in general universities. According to the national standard, the magnification of objective lens should be 1.6x, 2.5x, 4x, 6.3x, 10x, 16x, 40x, 63x and 100x. According to the degree of achromatic, it can be divided into achromatic objective, flat field achromatic objective, flat field semi achromatic objective and flat field achromatic objective. Of course, the better the achromatic effect, the more complex the structure, the higher the cost. Therefore, we should try our best to choose the one with lower cost that can meet the use requirements according to the use situation. The structure of microscope eyepiece is much simpler than that of objective lens, which is mainly divided into Huygens eyepiece, flat field eyepiece, wide field eyepiece, ultra wide field eyepiece and so on. The overall dimension mainly involves the axial dimension and transverse dimension of objective lens and eyepiece. The axial dimension includes focal length, conjugate distance, mechanical cylinder length, optical cylinder length, working distance, eyepiece exit pupil distance, position of aperture diaphragm and field diaphragm, etc. the transverse dimension includes aperture, aperture diameter, aperture angle, numerical aperture, etc. In addition to eyepiece and objective lens, other accessory optical elements should also be considered, such as field lens, reticle, filter, steering prism, polarizer, etc. It seems that the selection of these initial structures is simple, but it is very important for the subsequent detailed design. If the initial structure calculation is not correct, it may make the subsequent design unable to carry out, or it is found that the previous initial structure calculation is not correct until later, leading to the failure of previous work. Of course, the results of these calculations can not be static. There may be some adjustments later, but generally speaking, they should not be changed too much.

The third step is to design the optical system of objective lens, eyepiece and other accessory structures in detail. Modern optical design generally uses all kinds of optical design software, which greatly improves the degree of automation and reduces the labor of designers. In fact, optical design is the process of aberration elimination. It is always the pursuit of optical design institute to improve the resolution of the system and eliminate the aberration as much as possible. I believe that you know more about aberration theory than I do. I will not explain in detail what kind of structure can affect the elimination of various aberrations. What I want to emphasize is the problem of "aberration balance". Theoretically speaking, there is no optical system without aberration at all, so "aberration elimination" is only an ideal situation. More precisely, "aberration reduction" should be used to make the aberration not be perceived by the receiver or human eye, which achieves our goal. As we all know, there are seven kinds of geometric aberrations: monochromatic aberration includes spherical aberration, coma aberration, astigmatism, field curvature and distortion, and two kinds of polychromatic aberration: axial aberration and vertical aberration. We can't eliminate all these aberrations, we can only reduce some of them to meet our requirements. For example, only spherical aberration, coma, astigmatism and primary chromatic aberration need to be corrected for ordinary observation microscope, and there is no high requirement for field curvature and distortion; if the measurement microscope is to be designed, flat image field must be achieved to reduce measurement error.

The fourth step is to design the mechanical structure of the microscope. Because of the computer 3D design software, the mechanical structure design is not as complex as before, but the basic principle and basic requirements are still unchanged. I mainly use Pro / E and SolidWorks for mechanical design, because I am in the learning stage, so I am not very proficient in it. During the design, the reference books such as mechanical design manual and optical precision instrument design manual are indispensable, especially the mechanical assembly of eyepiece and objective lens, which involves very precise structure. At the same time, the mechanical design should also be carried out according to the actual production and processing level. To be honest, I think there is a big gap between the machining level of our country and that of Europe, America and Japan. Compared with some foreign famous brand products, I think the processing level of mechanical parts is higher than ours, so sometimes we can design a good lens, but it can't be realized. Another point is to pay attention to the appearance of beauty and humanization, which also involves the knowledge of ergonomics, psychology and so on. The microscope produced in China is not very good in this aspect. Compared with foreign products, it is not very comfortable, and it is not as convenient to use as foreign products. So industrial design ability is also a very important aspect of mechanical design level.

The fifth step is the design of dimming, auto focusing, automatic workbench and computer control. These are not necessary in the general microscope design, but some high-end research-oriented microscopes need to be designed in these aspects. Now the auto focus technology at home and abroad is developing very fast, and it is also one of the research hotspots. There are many auto focus algorithms. If you are interested, you can check more scientific papers.

The sixth step is software design. Some microscopic images need image processing and professional software, which should be carried out together with professional software designers.