Finite and infinite conjugate objectives

Reading time: 1 min 2 sec

An objective is nothing but a compound lens, like a normal lens, the only difference is they are much more potent in terms of numerical aperture, resolution and magnification. In microscopes, objectives are mainly used with two optical designs: finite or infinite conjugate designs. In a finite optical design, the light from a spot is focused into another spot with the aid of a couple of optical elements, and in an infinite conjugate design, the diverging light from a spot is made parallel.

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Taking Fourier plane out of an objective.

Reading time: 2 min 14 sec

We know that a lens is a Fourier transform engine, which does complicated Fourier calculations of a complex object, faster than any computer available today! An object placed at a distance d from the lens will form its Fourier image at the back focal length (f) of the lens. As we know, Fourier image is always formed at the focal plane of the lens, irrespective of the position of the object; it can be very close to the lens (d<< f) or very far away from the lens (d>>f).

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How to screen a femtosecond laser pulse stream on an oscilloscope?

Reading time: 1 min 42 sec

It is quite possible to view the pulse stream of a femtosecond output on an oscilloscope screen, especially to measure the repetition rate of the laser. It is to be noted that, we cannot see the pulse shape of the laser beam as the response time (rise and fall time) of the photodiode (PD) is quite higher than the pulse width of the femtosecond laser.

Things to be noted:

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