Laser confocal microscope laser intensity adjustment
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 large value, the output increases, the laser life will be shortened, but also produces laser noise, should be adjusted first AOTF, PMT, etc. to obtain the best intensity.
2. Acousto-optic tunable filter: control the excitation beam and intensity, can be turned on or off the laser in milliseconds or adjusted to change between 0-100%. This makes it possible to use a different laser beam for each image point and select the desired intensity.
Principle of operation: The Bragg diffraction effect of sound waves propagating in various media on the incidence into the propagation medium is utilised. When the input of a certain frequency of radio frequency signals, AOTF diffraction of incident polychromatic light, from which the wavelength is selected into the monochromatic light, monochromatic wavelength and radio frequency f has a one-to-one correspondence, as long as the electrical signal tuning can be quickly and randomly change the wavelength of the output off. AOTF to achieve the continuous adjustment of the laser intensity, and have a rapid adjustment function, to achieve the local stimulation and scanning, rapid wavelength switching ( In laser confocal microscopy, the photomultiplier does not increase the intensity of the laser, but regulates the intensity of the photoelectricity that is imaged, so the brightness of the image can be adjusted by adjusting the voltage of the photomultiplier. In addition, the size of the confocal pinhole affects the amount of photons, which also adjusts the brightness of the image. A photomultiplier is a special vacuum tube that is extremely sensitive to ultraviolet, visible, and near-infrared light, and can enhance the incoming weak light signal up to 108 times its original value so that the light signal can be measured.
