How to adjust the laser intensity of confocal laser microscope
There are two adjustment factors for laser intensity: power control knob and Acousto-Optical Tunable Filter (AOTF).
1. Power control knob: Generally set to 30% of the maximum value. As the output increases, the life of the laser will be shortened and laser noise will be generated. AOTF, PMT, etc. should be adjusted first to obtain the best intensity.
2. Acousto-optic tunable filter: Controls the excitation light beam and intensity, and can turn the laser on or off within milliseconds or adjust it to change between 0-100%. This makes it possible to use a different laser beam for each image point and select the required intensity.
Working principle: It utilizes the Bragg diffraction effect of sound waves incident on the propagation medium when they propagate 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 in. There is a one-to-one correspondence between the wavelength of the monochromatic light and the radio frequency frequency f. As long as the electrical signal is tuned, that is The wavelength of the output switch can be changed quickly and randomly. AOTF realizes continuous adjustment of laser intensity and has a rapid adjustment function to achieve local stimulation and scanning, and rapid wavelength switching (microsecond level). In a laser confocal microscope, the photomultiplier tube cannot increase the intensity of the laser, but it can adjust the final imaged photoelectric The intensity 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 enhance the incoming weak light signal to 108 times its original value, allowing the light signal to be measured.
