Method to Measure the MTF of Imaging Spectrograph with Multi-line Scanning

摘要

The Modulation Transfer Function(MTF) is a very important performance parameter to an optical iamging system which is used as a remote sensor. Over a long period of time we applied ourselves to study the emthod to detect the MTF of an imaging system with single detector and continuous output. For an imaging spectrograph adopting linear array detectors with reading out circuit and with "discrete " output, it is more difficult to analyze and detect the MTF of such imaging system than that of the former. After deducing from the linear system theorem in this paper, an imaging spectrograph with linear array detectors and with multi-line scanning can be regarded as a low-passed filer plus a sampling process in its scanning direction. by adopting "over-sampling" method, using periodical spatial square wave function with the same frequency as the system's Nyquist frequency as input, the MTFs of its different detectors to different wavebands were obtained. From the square wave response function of this system, we can easily find that there are the same peak values corresponding to the periodical square wave peak values, the only one difference among them is that they had differnet vale depths, that is to say their MTFs were differnet, so we can make a conclusion that the method to measure the MTF is feasible.