Comprehensive Introduction of Optical Platform (Zhuoli Hanguang)

With the development of advanced equipment and processes, it is possible to measure at the nanometer level. For example, a phase-change optical interferometer measures the surface roughness of an object, and currently can achieve a resolution of 1 nanometer. In the field of semiconductors, integrated circuits with line widths in the sub-micron range have been produced, and precision requirements for measurement accuracy of less than 50 nanometers have been proposed.
Such an application puts extremely high requirements on the precision and stability of different components in the system.
For example, an imaging system that uses a microscope to magnify the image highly. The microscope and the photographic objective jointly determine the image of each point on the photo paper. If, during the exposure process, each part of the optical system (illumination system, sample, microscope optical system, imaging optical system, and photo paper plane) moves precisely together, there is no relative displacement, and the imaging will be clear. If the sample moves relative to the objective lens, the image will be blurred. In optical interferometry, holography, and the use of similar laws, it is important to control relative motion.
Within an ideal rigid body (only exists in theory), the relative position of any two points is unchanged. That is to say, in the case of vibration, static moment or temperature change, the size and shape of any entity are unchanged. If all components are firmly connected into an ideal rigid body, and there is no relative displacement between different components, the performance of the system will also be very stable.
The ideal rigid body does not exist. The system in reality can only be considered to be rigid, so its stability is affected by many factors. For example, external vibration sources, system weight, optical platform structure, etc.
In order to improve the stability of the system, we can proceed from the following aspects.
1. Isolate the system from the vibration source.
There are many sources of external vibration sources, such as ground self-vibration, various sounds, and so on. But the most influential are various low-frequency vibration sources, which are mainly concentrated in the frequency range of 10 to 100 Hz. Isolating the system from these vibration sources can effectively improve the stability of the system. The use of large damping air spring support can better isolate the system from the vibration source.
2. Control the role of vibration.
Assembling the system into a dynamic rigid structure can ensure the relative stability inside the system, and can reduce the chance of resonance under the influence of the outside world and improve the stability of the system
3. Control the effect of static torque.
The hard-to-weight ratio of the optical platform has an important influence on its resonance frequency. A higher hard-to-weight ratio can increase the resonance frequency of the platform, thereby reducing its vibration under external influence. And under the action of external force, a platform with a higher hard-to-weight ratio can produce the smallest deformation under the smallest weight, increasing the rigidity inside the system. The optical platform with a honeycomb-shaped supporting structure inside can fully increase the hard-to-weight ratio and achieve the purpose of improving system performance.
4. Control temperature changes.
As time goes on, irregular temperature changes will cause the structure to gradually bend. The key to reducing the temperature effect is to control the environment to reduce temperature changes. For example, avoid placing heat dissipation equipment under the platform to isolate heat source equipment and hardware, such as light sources and flames.
As far as possible, the table should be designed to be insensitive to temperature.
Good thermal conductivity can play a role, however, in extremely special applications, it is necessary to select special materials that do not change the size of the shape with temperature changes. For example, ultra-unexpanded steel has a very small coefficient of thermal expansion. One-meter-long ultra-inflatable steel has an expansion length of about 0.2 microns when the temperature changes by 1K.

The optical platform of our company adopts the structure of ferromagnetic stainless steel on the surface, supported by the honeycomb structure of the core. This structure not only gives full play to the advantages of ferromagnetic stainless steel materials with good rigidity, small temperature expansion coefficient, and corrosion resistance, but also improves the platform's hard-to-weight ratio, increases rigidity, reduces deformation, and improves static moment resistance . And ferromagnetic stainless steel is corrosion-resistant, can absorb the magnetic base, and can easily build various optical systems. It is suitable for systems with large load bearing and high vibration resistance requirements.
The optical plate of our company is made of high-quality aluminum. Compared with steel, aluminum has a large hard-to-weight ratio, has certain vibration resistance, good temperature conductivity, low temperature deformation in bad environments, beautiful after anodizing, and wear resistance, but aluminum has poor rigidity and can not bear more. Big weight. Therefore, it is generally used to carry a smaller system. And it should not be suspended in the air.