Mordern microscopes are more likely to use a camera than human viewing. This is accomplished by replacing the eyepiece in figure with a photo-ocular that focuses the image of the objectives to a real image on the sensor of a digital camera. A typical sensor is wide and consists of wide pixels. suppose a microscopist pairs a objectives with a photo-ocular
a. what is the field of view? That is what width on the microscope stage in fills the sensor?
b. The photo of a cell is in a diameter. what is the cell's actual diameter in ?
a. The field of view is .
b. The cell's actual diameter is .
We have given that:
Magnification of object,
width of typical sensor and
magnification of photo ocular.
We need to find the magnification M .
Let us find Magnification M:
(substitute values in equation.)
Therefore width will be,
substituting the values we get ,
Here, is the field of view.
We need to find the cell's actual diameter in
Firstly we have to find width of the photo of the cell:
Therefore Diameter is:
(substituting value in the equation.)
Here, is the cell's actual diameter.
The resolution of a digital cameras is limited by two factors diffraction by the lens, a limit of any optical system, and the fact that the sensor is divided into discrete pixels. consirer a typical point-and--shoot camera that has a lens and a sensor with pixels.
(a) . First, assume an ideal, diffractionless lens, at a distance of what is the smallest distance, in between two point sources of light that the camera can barely resolve? in answering this question, consider what has to happen on the sensor to show two image points rather than one you can use
(b) . You can achieve the pixel-limied resolution of part a only if the diffraction which of each image point no greater than the diffraction width of image point is no greater than pixel in diameter. for what lens diameter is the minimum spot size equal to the width of a pixel ? use for the wavelength of light.
(c). what is the of the lens for the diameter you found in part b? your answer is a quite realistic value of the at which a camera transitions from being pixel limited to being diffraction limited for smaller than this (larger-diameter apertures), the resolution is limited by the pixel size and does not change as you change the apertures. for larger than this (smaller-diameter apertures). the resolution is limited by diffraction and it gets worse as you "stop down" to smaller apertures.
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