How to Adjust the Laser Intensity of Confocal Microscope
Laser intensity has two adjustment factors: power control knob, acousto-optic tunable filter
1. Power control knob: generally set it to 30% of the maximum value. If the output increases, the life of the laser will be shortened, and laser noise will also be generated. AOTF, PMT, etc. should be adjusted first to obtain the best intensity.
2. Acousto-optic tunable filter: control the excitation light beam and intensity, turn on or off the laser or adjust it to change between 0-100% within milliseconds. This makes it possible to use a different laser beam for each image point and to select the desired intensity.
Working principle: It uses the Bragg diffraction effect of the sound wave incident on the propagation medium when it propagates in various media. When a radio frequency signal of a certain frequency is input, the AOTF diffracts the incident polychromatic light, and selects a monochromatic light with a wavelength of λ. The wavelength of the output switch can be changed quickly and randomly. AOTF realizes continuous adjustment of laser intensity, and has a fast adjustment function, realizes local stimulation and scanning, and fast wavelength switching (microsecond level). Therefore, the brightness of the image can be adjusted by adjusting the voltage of the photomultiplier tube. In addition, the size of the pinhole (confocal pinhole) affects the amount of photons and can also adjust the brightness of the image. The photomultiplier tube is a special vacuum tube that is extremely sensitive to ultraviolet light, visible light and near-infrared light. It can increase the incoming weak light signal to 108 times the original, so that the light signal can be measured.
