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modulation, in communications. The Columbia Encyclopedia, Sixth Edition. 2001-07 (690 words) |
 | When the carrier is thus modulated, a fraction of the power is converted to sidebands extending above and below the carrier frequency by an amount equal to the highest modulating frequency. |
| In frequency modulation (FM), the frequency of the carrier wave is varied in such a way that the change in frequency at any instant is proportional to another signal that varies with time. |
| The modulation might vary the amplitude (PAM or pulse amplitude modulation), the duration (PDM or pulse duration modulation), or the presence of the pulses (PCM or pulse code modulation). |
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Nikon MicroscopyU: Modulation Transfer Function (4055 words) |
| Modulation of the output signal, the intensity of light waves forming an image of the specimen, corresponds to the formation of image contrast in microscopy. |
| Modulation is typically less in the image than in the specimen and there is often a slight phase displacement of the image relative to the specimen. |
| The modulation transfer function is also related to the point spread function, which is the image of a point source of light (commonly referred to as the Airy disk) from the specimen projected by the microscope objective onto the intermediate image plane. |
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