From 1973 to 1980, in the meantime, laser guns in the optical system and signal processor has a great development.First is the rendering of integrated optical element, make the light path structure is compact, alignment is more convenient, thus have may carry out more cluttered and efficient optical systems, polarization beam expansion, spatial filtering, separation, frequency, color separation, such as optical frequency shift of modern optical skills have been used to the laser velocimeter, and become a part of the series no shortage of goods.In signal processing, frequency tracking, counter type processor and photon relevant equipment have become commodities and was put into market, they together with integrated optical system into a discussion and disorderly fluid useful things.In the Danish capital Copenhagen in 1975 "laser doppler velocimeter world symposium marks this skill.Domestic also presented some instruments to develop [2-4], although all experimental, but invented the conditions to promote the use.If say, the development of the computer to start invented material conditions, computational fluid dynamics, then, the development of modern measurement skills, founding the new situation of the experiment of fluid mechanics, and to verify the correctness of the numerical results supply according to the experiment, the laser guns on its speed or use are dominant.With the deepening of turbulent state activities for discussion, puts forward a new question for LDV skills, this is known as the uncertainty of doppler frequency.It first affects the measurement precision of turbulence.Now on the influencing factors of doppler frequency widening don understand, puts forward some correcting measures together.However, in most cases, it is usually not measure the key question.Particles after sex is another question, the theory and experiment confirmed that the particles in the micrometer range, follow the mercy sex usually can reach 99%.From the practical idea, this is can be bear.Because the counter type processor can apply to sparse particles, thus increasing use.The speed of sparse sampling particles formed offset, can make the calculation errors occur, this has always been to deal with the questions in practice.In addition, if the use of frequency tracking and counter type processor to get a large number of real-time information, also become a prominent question.Traditional analog meter cannot adapt to microscopic structure and the dynamic activity of turbulence characteristics such as deepening the discussion topic. |
