Question

What are the differences between

(a) the negative impact on the images due to lenses, mirrors, atmosphere, sensor, and photon noise?

(b) Pre-Processing and Post-Processing

(c) Wavelet, Fourier transform, and convolution

Answer 1

a) It should be noted that simpler optical systems limit dispersion because they have fewer optical elements (lenses, mirrors, etc.) which are the primary site where dispersion arises. Since a dedicated two-photon instrument can be easily assembled with only a few optical elements (the required light path consists of approximately 3 cm of glass), dispersion can be kept low and excitation maximat. Thus, our strategy to overcome the effects of pulse dispersion is to minimize amount of glass in the system, hut obviously some glass is always required. In contrast, many recent commercial systems have suffered from the use of highly dispersive elements, notably large numbers of relay lenses as well as dispersive elements such as acousto-optic deflectors (AODS). The resultant loss in peak power made many of these extremely inefficient at producing the high peak powers that is necessary for producing the two-photon effect...

b) preprocessing:-

Any function performed by receiver is preprocessing...storage in the scan converter

: Scans anatomy creates image

: Image converted from analog to digital

: Sonographer Identify ROI (region of interest)...scan lines in ROI is greater than ROI of original image .More pixels = better spatial resolution...pixels are the same size as original

post-processing:-

After image information is stored in the scan converter

: Scans anatomy and creates image

: Image converted from analog to digital and stored

: Identify region of interest

: Pixels are enlarged, ROI fills screen

.Resolution loss

c)- A fourier transform (FT) will tell you what frequencies are present in your signal. A wavelet transform (WT) will tell you what frequencies are present and where (or at what scale). If you had a signal that was changing in time, the FT wouldn't tell you when (time) this has occurred.