What Are Photoelectric Sensors?

A photoelectric sensor is a device that converts light signals into electrical signals. Its working principle is based on the photoelectric effect. Photoelectric effect refers to the phenomenon that when electrons irradiate certain substances, the electrons of the substances absorb the energy of photons and corresponding electric effects occur. According to the different photoelectric effect phenomena, the photoelectric effect is divided into three categories: external photoelectric effect, internal photoelectric effect and photovoltaic effect. Photoelectric devices include photocells, photomultiplier tubes, photoresistors, photodiodes, phototransistors, and photovoltaic cells. The performance and characteristic curves of photovoltaic devices are analyzed. ^[1]

The photoelectric sensor is generally composed of a processing path and a processing element. The basic principle is based on the photoelectric effect, which converts the measured change into a change in the optical signal, and then further converts the non-electrical signal into an electrical signal by means of the photoelectric element. The photoelectric effect refers to irradiating an object with light, which can be regarded as a series of photons with a certain energy bombarded on this object. At this time, the photon energy is transferred to the electron, and the entire energy of a photon is once Absorbed by the electrons, the state of the electrons will change after they get the energy transmitted by the photons, so that the object irradiated by the light will have a corresponding electrical effect. Photoelectric effects are generally divided into three categories: (1) the phenomenon that allows electrons to escape from the surface of the object under the action of light is called the external photoelectric effect, such as photocells, photomultiplier tubes, etc .; (2) can make objects under the action of light The phenomenon of resistivity change is called internal photoelectric effect, such as photoresistors, phototransistors, etc. (3) Under the action of light, the phenomenon that an object generates a certain direction of electromotive force is called photovoltaic effect, such as photovoltaic cells. ^[2]

Optics made from different principles of luminous flux on optoelectronic elements

Standard type

1) Diffuse reflection type: general type or energy type (-8), focus type (-8-H), type with background suppression function (-8-H)

Development direction of production

(1) The rapid development of the industrialization model of photoelectric sensors from theoretical research to production, and the leap-forward development path combining independent innovation and international cooperation, so that China will become a major sensor production country in the world;

(2) The structure of photoelectric sensor products is comprehensive, coordinated and sustainable. Product varieties should be tilted towards high technology and high added value, especially to fill "blank" varieties;

(3) The development of the production structure is specialized. That is, the production of sensor categories is small and sophisticated, and it specializes in the production of a certain type of sensor series required by an application field to obtain a high market share, and the specialized cooperative production of various sensor companies;

(4) The large-scale production technology of photoelectric sensors is developing towards automation. There are many types and types of photoelectric sensors, and the sensitive materials used are different, which determines the diversity and complexity of sensor manufacturing technology. Looking at the overview of the current photoelectric sensor process line, most of the processes have achieved single-machine automation, but there are still many difficulties from the full automation of the production process, which needs to be widely adopted in the future to adopt CAD, CAM and advanced automation equipment and industrial robots to break through;

(5) The key technological transformation of enterprises should strengthen the shift from relying on imported technology to the digestion and absorption of imported technology and independent innovation;

(6) Enterprise operations should accelerate the development from the domestic market to the internationalization of both domestic and foreign markets;

(7) The corporate structure will develop toward a pattern of "large, medium and small simultaneous development" and "group, specialized production coexist". ^[2]

Research directions

The rapid development of photoelectric sensing and related technologies has met the higher requirements of various control devices and systems, making the degree of automation in various fields increasingly higher, and the importance of photoelectric sensors has continued to increase. At present, the main research directions of photoelectric sensors are: (1) Multi-purpose. That is, a photoelectric sensor can measure not only one physical quantity, but also multiple physical quantities; (2) the development of new sensing materials and sensing technologies; (3) under severe conditions (high temperature, high pressure, etc.) Development and application of low-cost sensors (connection, installation, etc.); (4) development of micro-optical technology combining photoelectric sensors with other micro-technology. ^[2]

Prospect forecast

The sensor market report shows that the global sensor market capacity in 2008 was $ 50.6 billion, and the global sensor market is expected to reach more than $ 60 billion in 2010. The survey shows that Eastern Europe, Asia Pacific, and Canada have become the fastest growing regions of the sensor market, while the United States, Germany, and Japan are still the regions with the largest sensor market distribution. As far as the world is concerned, the fastest growing sensor market is still the automotive market, and the second is the process control market, which is optimistic about the prospect of the communication market.

Some sensor markets such as pressure sensors, temperature sensors, flow sensors, and level sensors have shown the characteristics of mature markets. The market scales of flow sensors, pressure sensors, and temperature sensors are the largest, accounting for 21%, 19%, and 14% of the entire sensor market, respectively. The main growth of the sensor market comes from emerging sensors such as wireless sensors, MEMS (Micro-Electro-MechanicalSystems) sensors, and biosensors. Among them, the compound annual growth rate of wireless sensors in 2007-2010 is expected to exceed 25%.

The global sensor market is showing rapid growth among constantly changing innovations. Relevant experts pointed out that the main technologies in the sensor field will be extended and improved on the existing basis, and countries will compete to accelerate the development and industrialization of new-generation sensors, and competition will become increasingly fierce. The development of new technologies will redefine the future sensor market, such as the emergence of new sensors such as wireless sensors, fiber optic sensors, smart sensors and metal oxidation sensors, and market share expansion. ^[4]

Intelligent development of photoelectric sensors

Intelligent photoelectric sensors are hotspots in the international scientific and technological circles, and there is no uniform and precise definition. At present, domestic and foreign scholars generally believe that intelligent photoelectric sensors are composed of a combination of traditional photoelectric sensors and microprocessors (or microcomputers). Adjust its internal behavior to optimize the collected data.

The functions of the intelligent photoelectric sensor are: self-compensation, self-calibration, self-diagnosis, numerical processing, two-way communication, information storage and memory, and digital output. With the development of science and technology, the function of smart sensors will be gradually enhanced. It will use artificial neural networks, artificial intelligence, and information processing technologies (such as sensor information fusion technology, fuzzy theory, etc.) to make sensors have more advanced intelligence and analysis, The functions of judgment, self-adaptation, and self-learning can complete complex tasks such as image recognition, feature detection, and multidimensional detection. ^[4]