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随着光电倍增管及其附属测量电路的不断改进,使得光强测量的灵敏度不断提高.例如采用双光电倍增管的符合法电路已可能对单个光子进行计数.近十年来也发展了一种只用一只光电倍增管的单道脉冲幅度分析测量电路,这种电路比较适合于测量超微弱的生物发光,例如国外已对癌细胞、肝细胞的光辐射进行了测量,国内报导估计人体体表发光的频谱范围在3800埃～4200埃之间,其强度约相当于3×10~(-18)瓦.如此微弱的光强,如用人眼接收的话,大约每秒仅接收1.7个光子,人类的眼睛是不能够产生光感的.人眼对不同波长的光子的灵敏度阈值是不同的,例如波长为5100埃的光子,大约需要100个左右才能引起视觉感,若以实际到达并作用于视网膜敏感层的光子数来说,那么只需要5～14个光子就能产生光感,这样大小的光强约相当于3×10~(-17)瓦,若人体体表或生物细
With the continuous improvement of the photomultiplier tube and its associated measuring circuits, the sensitivity of the light intensity measurement has been continuously improved, for example, the photomultiplier tube with the compliance circuit has been possible to count a single photon .Also in the past decade has also developed a With a single photomultiplier tube single pulse amplitude analysis and measurement circuit, this circuit is more suitable for the measurement of ultra-weak bioluminescence, such as foreign cancer cells, liver cells have been measured by light radiation, domestic reports estimated body surface The spectral range of light emission is between 3800 angstroms and 4200 angstroms and its intensity is about 3 x 10 ~ (-18) watts. Such a weak light intensity, which is only about 1.7 photons per second if received by the human eye, Of the eye is not able to produce light perception.Human eyes on different wavelengths of photons sensitivity threshold is different, for example, the wavelength of 5100 angstroms photon, about 100 or so to cause visual sense, if the actual reach and act on the retina Sensitive layer of photons, then only 5 to 14 photons can produce light sense, so the size of the light intensity equivalent to about 3 × 10 ~ (-17) watts, if the human body surface or biological thin