Optimal rejection of the image extinction in confocal scanning microscopy

摘要

Confocal scanning microscopy(CSM) has been used in biomedical application, materials science, semiconductor quality measurement and forensic application. CSM consists of a beam projector with which a small spot is formed on a specimen, a point detector with a pinhole or slit, and a mechanism for two-dimensional beam scanning. An image distribution can be reconstructed by a correlation of spots with many advantages of non-contact, high speed, high resolution of thick specimen comparatively. But it is a serious problem for the high performance to align pinhole and other optical components. Especially, the parasitic motion of focus on the point detector gives rise to the fatal distortion of an image profile named the image extinction while the beam is scanned. The intensity of detecting signal truncated by the finite aperture of detector diminishes by the order of two ro more when the spot is focused with more than a half aperture. This paper shows the mathematical expression of the light such as the extinction curve in the optical fields of system using AO deflector, and the axial/lateral response experimentally when the error sources change. We propose the progressive methods for the rejection of image extinction as the following. At first, for having the corrected image, small spot and long scan range, this paper shows that the optimal design having the multi-objects can be used by choosing the unitary lens device in CSM. At second, in order to compensate for the intensity cancellation at the end profile that may be the cause of waviness for the optical image, this paper shows that it is efficient to schedule the frequency of scan. According to characteristics of the extinction curve and axial/lateral response having the error property, we can define the frequency and sensitivity of as their robustness.