Smart Optics or Intelligent Optics is a product of the combination of traditional optics and modern computer systems. Intelligent optics integrates modern technologies such as new materials, computer information, electronics, and close processing, greatly expanding the application fields of traditional optical systems.
Intelligent optics is based on adaptive optics and active optics technology, and has close connections with disciplines such as microelectronics, information optics, optoelectronics, etc. Intelligent optics and related disciplines promote and develop together.
Concept of Intelligent Optics
Foreign scientists (Greenaway) define intelligent optics as optical technologies and components that can achieve dynamic adjustment. Intelligent optics is a constantly evolving concept, initially based on a technology of adaptive optics and active optics - dynamic modulation of wavefront phase using reflective optical components as the main equipment. Here, a brief introduction will be given to adaptive optics and active optics.
1.1 Adaptive optics
Before introducing adaptive optics technology, let's briefly introduce the concept of "atmospheric turbulence". Atmospheric turbulence is essentially a form of motion in the atmosphere. Due to the presence of atmospheric turbulence, the horizontal and vertical exchange of water, heat, momentum, and pollutants in the atmosphere has been greatly enhanced, and the increasing trend of this motion intensity is much greater than the degree of molecular motion intensity.
We know that the atmosphere is one of the transmission media of light waves. When light waves propagate in the atmosphere, they are affected by atmospheric turbulence, resulting in wavefront distortion (wavefront changes after transmission through the transmission medium). The application of adaptive optics technology aims to compensate for wavefront distortion caused by atmospheric turbulence or other factors. At present, adaptive optics mainly plays an important role in intelligent optics to realize high-speed and small amplitude wavefront modulation using deformable mirrors.
1.2 Active Optics
Active optics is a wavefront correction technique aimed at correcting the deformation of telescope optical systems and their supports caused by factors such as temperature and gravity. In addition to the influence of atmospheric turbulence, factors such as temperature, pressure, and gravity may cause interference in the normal observation of telescopes (wavefront deformation). Through active optical technology, computer actuators can be controlled to adjust their working state based on wavefront deformation to monitor and eliminate wavefront deformation in real-time. In short, active optics is a technology that actively changes the shape of the mirror surface to improve image quality through the built-in "corrector" of the telescope.
With the further development of intelligent optics, the concepts of intelligent optics based on adaptive optics and active optics have been further supplemented, namely optical technologies, components, and systems with dynamic adjustment, automatic control, and measurable capabilities.
At present, refractive diffraction optical components and optoelectronic components are also widely used in the process of measurement, control, and modulation of wavefront phase; The application of dynamic adjustment optical components in intelligent optics further expands the functions of the optical system, achieving modulation and measurement of parameters such as wavefront amplitude, polarization, wave frequency, and light intensity.
Intelligent optics has further promoted the development of traditional optics. For some optical systems that are complex in design and difficult to achieve through conventional processing, the use of intelligent optics can effectively simplify the design of optical systems and improve their performance. Intelligent optics has extensive applications in fields such as astronomy and medicine.
2 Dynamic optical modulation
As mentioned earlier, wavefront distortion is an important factor affecting optical imaging, and both adaptive optics and active optics technologies in intelligent optical systems aim to achieve correction or compensation for wavefront distortion. Dynamic optical modulation, as one of the core technologies of intelligent optics, is also used to correct or compensate for wavefront distortion, thereby improving the performance of optical systems. This article focuses on the modulation (correction or compensation) of wavefront distortion and introduces several commonly used dynamic optical modulation techniques.
2.1 Wavefront dynamic modulation technology
The wavefront modulator is the core optical component to realize the dynamic modulation technology of wavefront, which is used to modulate the wavefront phase or amplitude (some wavefront modulators have the function of both wavefront phase and wavefront amplitude modulation). The wavefront modulator is usually composed of a reflector and an actuator (the two are combined into an array). According to the different structures of the spliced mirror surface and the whole mirror surface of the reflector, the wavefront modulator can be divided into discrete and continuous forms. The commonly used actuators for adaptive optics and active optics include electromechanical actuators, pressure actuators, piezoelectric actuators, and microcomputer actuators.
Active optics technology is mostly applied to large aperture reflective telescopes, which can achieve low speed and large amplitude wavefront modulation, so it needs strong support. Electromechanical actuators and pressure actuators are the main units that constitute the active optical dynamic support structure, which plays a role in providing sufficient support force for the active optical dynamic support structure.
2.2 Other dynamic modulation technologies
Light intensity dynamic modulation technology: Light intensity dynamic modulation technology mainly relies on spatial light modulators and is applied in the field of projection display optics. The modulators used for dynamic modulation of light intensity are generally discrete structures.
Spectral dynamic modulation: Spectral dynamic modulation mainly uses acoustooptic tuning filters and liquid crystal tuning filters to dynamically filter the spectrum. This technology has extremely wide applications in many optical systems, such as micro imaging, remote sensing imaging, and other fields. The response speed of the acoustooptic tunable filter is relatively high, but its image quality is relatively insufficient; The image quality of the liquid crystal tuning filter is higher, but its corresponding speed is lower.
3 Dynamic optical detection
Dynamic control of optical modulation based on optical characteristics of wavefront phase and light intensity information. The foundation for achieving dynamic control of light intensity and wavefront is various photoelectric sensors. For example, photomultiplier tubes, avalanche diodes, optocoupler devices, etc. Photoelectric sensors can directly detect light intensity information; Photoelectric sensors and other optical devices can form wavefront detectors to detect wavefront information. According to the different detection positions of wavefront detectors, they can be divided into two categories: pupil wavefront detectors and focal wavefront detectors; According to the different processes of wavefront reconstruction, it can be divided into two categories: linear wavefront detectors and nonlinear wavefront detectors.
4 Intelligent optical systems
In summary, we can define an intelligent optical system as an optical system with dynamic optical modulation or (and) dynamic optical detection functions that can be dynamically controlled based on optical characteristics. Currently, the dynamic control function of intelligent optical systems can be divided into two categories: open-loop control and closed-loop control. The open-loop control system mainly includes two parts: a modulator and a controller; The closed-loop control system mainly includes three parts: modulator, detector, and controller. Intelligent control systems can be divided into two categories: adaptive control systems and active control systems.
Active optical systems are mainly used in reflective and large aperture telescopes to modulate the wavefront distortion of the telescope's main mirror. Currently, active optics has become an essential technology for large aperture telescopes.
As the aperture of telescopes continues to increase, some space-based telescopes are also adopting active optical technology to improve image quality. For example, the famous James Weber Space Telescope achieved ideal image quality using a complex mosaic mirror active optical system.
References
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