I have just learned photoacoustic imaging for less than one week. I am confused about some issues of optic-resolution photoacoustic microscopy (OR-PAM) and acoustic-resolution photoacoustic microscopy (AR-PAM).The main difference of two modalities' system is the laser illumination part. In OR-PAM, before the last focused lens, the laser is collimated while it is defocused in AR-PAM. How does the illumination determine the resolution?
Many thanks to the people who concern my question.
It is due to the fact that the detected acoustic signal comes from the excited volume, defined by the illuminating spot (which depends on the laser wavelength and N.A, of the objective)
In PA imaging you may be exciting the specimen with light, but you are imaging acoustically. The resolution is based on acoustic diffraction. You cannot resolve finer than half the wavelength (speed of sound in the media divided by frequency) used to measure. If the wavelength is 100um, then if looking at some object that is less than 50um you cannot determine if you are seeing the front or the back of the object. It is diffraction limited.
Check this latest review about Photoacoustic microscopy, very good read I think!
Article Review on Practical Photoacoustic Microscopy
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