The case of green laser pointer is made of the metal

Received on the photomultiplier tube photocathode is the synthesis of light of two different frequencies of the scattered light. Set the frequency of two incident beams - beam 1 and beam 2 in their respective forward direction unit vector and the unit vector in the selected scattering direction, the beams 1 and 2 in the direction of the scattered light frequencies and Is the frequency of the synthesized and the two beams of light on the photomultiplier tube photocathode photomultiplier tube output frequency of the alternating current, which is the photomultiplier tube of the difference frequency effect. Here is the frequency difference of the two scattered light. In order to distinguish the Doppler shift, known as the Doppler frequency difference. Subtract two type can be given. It is specific to detecting and testing the power of   200mw laser pointer  .
Where is the Doppler frequency difference is the refractive index of the fluid, is the wavelength of incident light in a vacuum, is the projection of the velocity vector perpendicular to the beam incident angle bisector direction. Actually measured is the absolute value, so here also the absolute value. When perpendicular to the velocity direction and the incident angle bisector, the fluid flow rate. Laser Doppler velocimetry techniques. Laser Doppler velocimetry with the non-contact measurement, does not interfere with the measurement object, the measuring device can be away from the detected objects and advantages, has been widely applied in the field of biomedical, fluid dynamics, aerodynamics, combustion. It is for the manufacturer to test and detect the total output power of   green laser led  .
Measurement of blood flow. Laser Doppler velocimetry with a high spatial resolution, and then configure a microscope can be used to observe the flow of blood within the capillary. Figure 6-34 Laser Doppler microscope optical path, the combination of Doppler velocimetry and microscopy, microscopic observation of the object field illumination light source lighting to capture the target. Speedometer through the beam splitter double scattering signal toward the optical receiver, the measured point can be a particle diameter of 60μ. Figure 6-34 blood flow measurement of the optical system. The measured object is the organism, the beam is not easy to directly enter the organism inside the above speedometer measurement in vivo is not applicable. It is to meet different requirements of the customer towards  led flash light   .
Measurement in vivo require the measurement of the probe size is small, and can drill down to the corner of the difficult to measure. Fiber optic probes are small and easy to adjust the measuring position; and anti-interference ability, Sealed fiber optic probe directly into the liquid. Medical blood flow measurement using fiber-optic laser Doppler velocimetry. Figure 6-35 is a fiber-optic Doppler velocimeter schematics, it uses optical scattering reference, the reference light-routing the fiber end reflection. Eliminate reflective lens, polarizer placed in the incident laser polarization direction orthogonal to receive blood particle scattering and reference beams. Figure 6-35 blood flow measurement of the optical fiber laser Doppler velocimetry. It is to test and detect whether the real power of  led flash light    is higher or lower than the needed power requirement of the customer.
The measurement of the flow in the pipeline. Figure 6-36 is the measurement of Doppler flow velocity distribution within the tube or rectangular pipe system schematic diagram, is the most typical double scattering optical path. The light emitted by the laser was divided into two beams through holes diaphragm into the converging lens. The two beams of light will be gathered in the focus of the lens. When the measured particulate P through focus, the two beams of light scattering. Part of the two-beam scattering of light into the photomultiplier tube in front of the receiver lens. Produce interference fringes signal before the photomultiplier tube and converted into electrical signals. Filtered and amplified signal into a spectrum analyzer, the results of the last printed display output. Convergent lens focused at different points within the tube, you can measure the flow rate of the different locations. It is according to the tested and detected value of the power meter of  led flash light    .