KOSEN 한인과학기술자네트워크

>제가 광 센서에 관한 소개와 원리를 20페이지 정도 ppt를 해야 합니다.. >광센서에 관련한 원리와 응용되는 분야 제품등 >여러 정보를 알려주셨으면 합니다.. 일본의 Hamamatsu사의 home page를 잘 보시면 아래 내용과 같은 여러가지 광detector 설명을 볼 수 있습니다. Photomultiplier tubes (PMT) are optical sensors having extremely high sensitivity. A typical PMT consists of a photocathode, focusing electrodes, an electron multiplier, and an anode (electron collector electrode) sealed in a vacuum tube. On October 2002, Dr. Masatoshi Koshiba (Professor emeritus at the University of Tokyo) received the Nobel Prize in Physics for the detection of cosmic neutrinos. This is still fresh in our memory and, since that time a huge amount of attention has been focused on the fact that Dr. Koshiba was using a large number of PMTs as high-sensitivity neutrino detectors. The PMT used by Dr. Koshiba had a diameter of 50 cm making it the largest size in the world. However, the PMT is available in a wide range of variations and sizes from 10 cm up to 50 cm in diameter. When light strikes the photocathode, it emits photoelectrons into the vacuum. These photoelectrons are then guided by the focusing electrodes towards the electron multiplier where the electrons are multiplied in a secondary emission process. Since this secondary emission process is repeated in the electron multiplier, the photoelectrons are increased one million to 10 million times or more, making the PMT the most sensitive optical sensor currently available. The PMT also provides a fast time response as well as many other outstanding characteristics. Compared to devices combining phototubes and signal amplifiers, the PMT delivers exceptionally low noise because the signals are amplified inside a vacuum tube. These facts all serve to prove that the PMT is the ideal optical sensor for low-level light detection. 1959 : First PMT product Around the mid-1950s when chemical analytical instruments incorporating PMTs first started making their appearance in Europe and the US, production of spectrophotometers for chemical analysis using PMTs also began in Japan. This served to abruptly focus the attention of Japan’s industry on the PMT and we also commenced making prototypes with the aim of full PMT production. PMTs at that time were produced by hand one at a time in a process that depended greatly on the skill and instincts of the worker. Though the multiplication or gain shown in tests varied somewhat from one PMT to another, most PMTs we produced were acceptable. Basically if the PMTs produced at that time had acceptable amplification, then they were judged as fully satisfactory for use. After successfully manufacturing prototypes in this way, the very first PMT product was sold in 1959. At that time, saying that a product was sold, meant that sometimes producing a prototype was successful and if that prototype could be shipped somewhere, then it instantly became a “sold” product. In other words, there was no product standardization in those days and improvements or modifications were made to the prototype while on sale. Our PMT started to get a commercial foothold in the 1960s when we beat our competitors in being the first to solve the problem of hysteresis (output overshoot or undershoot) which had been a serious problem up to that time. Eliminating this problem helped expand our sales. Hysteresis had proved to be a problem for PMTs in the period from 1962 through 1964 and grew more apparent as major manufacturers of analytical instruments gradually increased their orders for PMTs. High acclaim in the US Many different methods have been proposed to eliminate hysteresis. However, the hint that finally brought a real solution was the conductive film (so-called “nesa film”) coated on the inner surface of the glass of a phototube. This conductive film was used to prevent the electrostatic charges that occur on walls or partitions inside tubes to cause hysteresis. After a period of trial-and-error, a method was contrived for evaporating a conductive metal film on the inner surface of electrode support plates and maintaining it at the cathode potential. This method proved a great success in eliminating hysteresis and even today is effectively used as a major feature in our PMTs for photometric applications. Our hysteresis-free PMT was highly acclaimed by photometric equipment manufacturers in the US (especially spectrophotometer manufacturers). The American Society of Analytical Chemistry, which would be later known to be strict, stated that “The data cannot be trusted unless measured with a HAMAMATSU (brand name used in the US) PMT.” Carving out new markets one after another Following the above success, we constantly developed various types of PMTs one after another for applications such as high energy physics experiments and gamma cameras in response to lively new product demand. Moreover, the development of low-light-level measurement technology created a strong demand around 1965 in fields including Raman spectroscopy using lasers, astronomy measurement with spectrophotometry, thermal fluorescence measurement, and use of laser radar for air pollution analysis. This spurred intensive research into a photon counting technique using PMTs. This photon counting technique can count signals corresponding to individual photons and is even today the most sensitive optical detection method. The name “photomultiplier tube“ or “PMT“ has not changed in some 50 years, yet there has been a great deal of progress in what that name means. In the past, an array of multiple PMTs was required to measure a position. However, multianode PMTs made up of one PMT with multiple independent anodes have been developed for position measurement. Detection efficiency also tends to drop when using an array of cylindrical PMTs because of the gap between PMTs. This problem, in turn, led to development of square and hexagonal PMTs that vastly improve detection efficiency because they can be arrayed without gaps between them. High efficiency and miniaturization pushed to new levels! About 10 years ago, we developed a miniature PMT sealed in a metal package used for semiconductor devices. The size of this metal package PMT was as small as 15 mm in height and diameter. Since then, various metal package PMTs were developed including a 30x30 mm square type and multianode type. These are now widely used in many applications. All these developments were greatly supported by development of a multiplier called the metal channel dynode that is the direct result of our sophisticated design capabilities for electron trajectories and micromachinining technology. In recent years, the success of PMT technology has given rise to new concepts in high-sensitivity optical sensors. These include “flat panel PMT” that offers boosted detection efficiency in a small package, and “HPD“ photodetector devices that use “electron bombardment” in the electron multiplication process and deliver a high signal-to-noise ratio. Other innovative items include “EB-CCD“ imaging devices using GaAs (gallium arsenide) and GaAsP (gallium arsenide phosphor) crystal photocathodes. These and a host of other innovative devices are constantly being developed to open new applications. Ever widening fields of use The true roots of electron tube device development lies in “finding the farthest limits of performance” and judged by this standard, the PMT is without a doubt, the optical sensor that has accumulated the most results. Currently, PMT use is growing in a diverse range of fields where highly precise photometric capabilities are required. In the medical field, the PMT is used in clinical examination equipment (such as blood tests and biochemical tests) as well as nuclear medical imaging and diagnostic systems (such as gamma cameras and PET). In fields involving chemical analysis, the PMT is used in various types of analytical instruments including spectrophotometers, environmental measurement equipment, etc. In academic research fields, the PMT is used in satellite-borne instruments and high energy physics experiments. In the measurement and industry field, the PMT is used, for example, in oil well logging and radiometry; and in the optical field is used for laser scanning confocal microscopy (LSCM). The PMT is also widely used in the semiconductor field for wafer surface inspection, plasma process monitoring, and thickness measurement. It also finds use in applications like bulk mail and farm produce sorting. (The above information appeared in the July 2003 edition of “Science & Technology Journal” published by “The Japan Foundation of Public Communication on Science and Technology.)

>제가 광 센서에 관한 소개와 원리를 20페이지 정도 ppt를 해야 합니다.. >광센서에 관련한 원리와 응용되는 분야 제품등 >여러 정보를 알려주셨으면 합니다.. > 이 부분을 잘 아는 분을 소개시켜 드릴게요. 회사명: K-STAR 사장: 김 동현 휴대폰 번호: 019-489-4043