Application of Vacuum Photoelectric Detection Technology in Super-Resolution System

Due to the wave characteristics of light, diffraction occurs when the light passes through the optical system, so that the resolution of the ordinary far-field optical system is limited by the size of the Airy disk diameter. There are various factors that cause image quality degradation during system detection and imaging, such as optical system aberrations, atmospheric interference, defocusing, system noise and so on. Super-resolution optical imaging technology is the most innovative breakthrough in the optical imaging and detection field in this century. It goes beyond the resolution limit of ordinary optical systems or detectors, and can get more details and information of the structure, providing unprecedented tools for various fields. Compared with ordinary optical systems, super-resolution systems have very high requirements on the signals to be detected, which cannot be met by ordinary detection techniques. Vacuum photoelectric detection and imaging technology is equipped with the characteristics of high sensitivity and fast response. It is widely used in super-resolution systems and has played a great role in super-resolution systems. In this paper, the principles and structure of the image-converter streak camera super-resolution system, scanning electron microscopy super-resolution system and laser scanning confocal super-resolution system will be sorted out separately, and the essential role of the vacuum photoelectric detection technology in the ultra-microscopic system will be analyzed.


Introduction
With the development of bioscience, high energy physics and other fields, people How to cite this paper: Gu, K., Liu, X.F., Zhang, Y., Zhao, H.W. and Liu, W.P. Therefore, more and more emphasis has been placed on super-resolution technology for the last few years. Super-resolution technology, being a cutting-edge research topic in the field of optical engineering, not only involves in the design of optical imaging system, but also concerns in the field of image acquisition and processing. According to the signal generation and transmission process, the resolution of the system can be regarded as consisting of three parts [1], including diffraction resolution, geometric resolution, and noise equivalent resolution.
People improve the above three resolutions by improving the optical system, improving the image processing ability, etc., in order to achieve the purpose of super resolution. Photoelectric detection is an indispensable link between a super-resolution system. Therefore, optimizing and improving the photoelectric detection capability helps to achieve the final imaging result of the system. In view of the high requirement of the super-resolution system for detected signals, ordinary detection technology cannot meet its requirements. Nevertheless, vacuum photoelectric detection technology is extensively applied to the super-resolution system on account of its high sensitivity and Short relaxation process [2], and played significant effect of the super-resolution system. This article lists three super-resolution systems and discusses the application of vacuum photoelectric detection and imaging technology.

Basic Working Principle of the System
The working principle of the image converted tube streak camera is shown in The ordinary imaging system can be regarded as a low-pass filter. When it is greater than the cut-off frequency, the transfer function is zero, and high-frequency information is limited. Therefore, in order to achieve super-resolution, we must get the information above the cut-off frequency [5] [6] [7]. Using a super-resolution restoration technique, information above the cut-off frequency can be obtained. According to the information superposition theory, the information above the cut-off frequency is superposed into the frequency component below the cut-off frequency by convolution. In other words, the frequency component below the cut-off frequency contains all the information about the object of a bounded restricted object. That is, for a bounded restricted object, the frequency component below the cutoff frequency contains all the information on the object. Then, the analytic continuation principle can be used to reconstruct the information above the cut-off frequency using signals below the cut-off frequency, so as to realize the super-resolution of the image and improve the temporal resolution of the camera.

Application of Vacuum Photoelectric Technology in the System
The Image converted tube streak camera super-resolution system is an optical The image converter is a kind of vacuum imaging device which can transform the invisible light image into the visible light band, including three parts: photocathode, electronic acceleration system and electro-optic conversion fluorescent screen. When the invisible ray such as X-ray is incident on the photocathode, photoelectrons will be excited. The photoelectrons are accelerated by the elec-

Basic Working Principle of the System
Scanning electron microscope can be divided into six systems, including vacuum system, electronic optical system, signal detection amplification and display system, image recording system, cooling circulating water system and power supply system [8] [9]. The working principle is as follows: The electron gun in the elec- The scanning electron microscope can magnify the sample of more than 10,000 times, achieving extremely ultra-high resolution.

Application of Vacuum Photoelectric Technology in the System
The three main systems in scanning electron microscope are electronic optical Optics and Photonics Journal system, signal detection amplification and display system and vacuum system. The electronic optical system and signal detection amplification and display system, whose working environment requires a high vacuum environment, are all placed in the vacuum system. Therefore, these three systems can be considered as a large vacuum photoelectric detector. The first reason why it is necessary to change the system into a vacuum is to protect the filament in the electron gun of the electronic optical system. Once the filament is exposed to the air, it will be rapidly oxidized and fail to emit electrons. Moreover, the vacuum degree of the system has a great relationship of the electron production efficiency of the electron gun. Secondly, it is conducive to increase the average free path of the electron, so as to obtain more electrons for imaging.
In the signal detection amplification and display system, owing to the interac-

Basic Working Principle of the System
The working principle of laser scanning confocal microscope is shown in Figure   2. The laser scanning confocal microscope takes the laser as the light source. Because of the excellent monochromatism and directivity of the laser, the chromatic aberration appears in the system imaging is eliminated fundamentally. In addition, the system adopts confocal technology, the specific principle of which

Application of Vacuum Photoelectric Technology in the System
In the traditional laser scanning confocal super-resolution system, a common photomultiplier tube is generally used to detect the signal. But for improving the resolution of system imaging, it is necessary to increase the power and time of to reduce the phototoxicity, you must reduce the power and time of the laser irradiation, which will prevent the ordinary photomultiplier tube from collecting the fluorescent signal. In order to solve this contradiction, a hybrid photodetector, which can better collect more fluorescent signals while using a lower power laser, can be used to take the place of the traditional photomultiplier tube.
The new hybrid photodetector incorporates a solid-state semiconductor anode chip into a traditional photomultiplier tube, which hits off the disadvantages of low signal-to-noise ratio and easy saturation of signal of the micro channel plate in the traditional photomultiplier tube, and realizes that the effect of doubling electrons is enhanced, and broadens the use of vacuum photoelectric devices. In the new laser scanning confocal super-resolution system, a gallium arsenide phosphide (GaAsP) hybrid photodetector is generally used [11].
Conventional laser confocal microscopy uses a photomultiplier detector.
When photons are incident on the photocathode, photoelectrons are obtained.
These electrons hit the anode through the action of high voltage to achieve electron multiplication. In the new GaAsP hybrid detector, incident photons generate photoelectrons through the gallium arsenide phosphorous photocathode.
These photoelectrons bombard the semiconductor chip at a very high speed under a voltage acceleration much higher than the acceleration voltage in the photomultiplier tube. The anode, which ultimately produces electron bombardment gain and avalanche gain, obtains better excitation effects than ordinary photomultiplier tubes [12]. Due to its higher sensitivity and lower background noise, a lower intensity laser can be used to illuminate the sample, which not only ensures the survival rate of cells, but also ensures the collection of fluorescent signals.

Conclusion
Vacuum photoelectric imaging and detection technology, due to its high sensitivity and fast response, has been widely used in super-resolution systems, and has played a great role in super-resolution systems. This article briefly summarizes the role of vacuum photoelectric detection technology in three super-resolution systems, and analyzes the role of related devices and technologies in different super-resolution systems. Finally, it is concluded that vacuum photoelectric technology is essential in the super-resolution system.