The axial resolution of a confocal microscope refers to its ability to distinguish between two points along the z-axis (depth) of a sample. In other words, it is the minimum distance between two points that can still be resolved as separate entities.
The axial resolution is typically measured by using a resolution test target, which consists of a series of lines or dots of decreasing size. The smallest line or dot that can be clearly distinguished is then used to calculate the axial resolution.
The primary factors that affect the axial resolution of a confocal microscope are the numerical aperture of the objective lens, the wavelength of light used, and the type and quality of the detector. Additionally, the refractive index of the sample and the type of immersion medium used can also impact the axial resolution.
To improve the axial resolution of a confocal microscope, one can use a higher numerical aperture objective lens, a shorter wavelength of light (such as blue or green), and a high-quality detector. Additionally, using a higher refractive index immersion medium or implementing techniques such as deconvolution can also improve the axial resolution.
The typical axial resolution achieved for a confocal microscope is around 0.5-1 micrometer, depending on the factors mentioned above. However, with advanced techniques and equipment, it is possible to achieve even higher axial resolutions of 0.1 micrometer or less.