Isolation principle of optical table

The optical table is a crucial foundational equipment in optical experiments and precision measurements. Its core function is to isolate external vibrations through structural design and technical means, ensuring the stability of the optical system.
The isolation principle of optical tables is mainly based on vibration control theory, which achieves table stability by blocking vibration transmission paths, reducing resonance effects, or actively canceling vibrations.
1. Passive isolation principle: Passive isolation is the most commonly used isolation method for optical tables, which reduces vibration transmission through material properties and structural design, mainly based on the following mechanisms:
Elastic support and damping absorption
Using elastic elements (such as air springs, rubber pads) to support the table, when external vibrations are transmitted to the table, the elastic elements absorb vibration energy through deformation, convert it into thermal energy or elastic potential energy, and attenuate the vibration amplitude. Meanwhile, damping materials such as metal internal resistance and viscoelastic materials can further consume vibration energy and shorten the duration of vibration.
Resonance frequency regulation
By designing the natural resonance frequency of the table, it is kept away from the main external vibration frequencies (such as ground vibration usually below 10Hz, and equipment vibration mostly between 50-100Hz). According to vibration theory, when the natural frequency of the system is lower than √ 2/2 times the external vibration frequency, the isolation effect is significantly improved. For example, the natural frequency of the table supported by air springs can be as low as 1-2Hz, effectively isolating high-frequency vibrations.
Quality and stiffness matching
Increasing table quality (such as using heavy metal or granite countertops) can improve inertia and reduce vibration acceleration; Simultaneously optimize the structural stiffness to avoid local resonance. The reasonable matching of quality and stiffness can reduce the response of the table to vibration.
2. Active isolation principle (some high-end tables): Active isolation monitors vibration in real time through sensors, and then generates reverse force through actuators (such as electromagnetic drivers) to counteract the vibration. The principle is as follows:
Vibration perception and feedback
The acceleration sensor detects the vibration signal of the table, and after processing by the controller, drives the actuator to generate a force opposite to the vibration direction, achieving "real-time cancellation".
Dynamic response compensation
Active systems can accurately compensate for low-frequency or periodic vibrations (such as the periodic shaking of precision instruments), compensating for the shortcomings of passive isolation in the low-frequency range.