An exact expression is obtained that evaluates the error associated with angular-position measurement of an incoherently illuminated object when a quadrant detector is used in the image plane of an optical system. The accuracy of such a measurement is inversely proportional to the signal-to-noise voltage ratio associated with the four quadrants summed to act as a single detector. In the particular case of a circular object, the rms angular measurement error is given by the expression σ<sub>θ</sub> = π[(3/16)<sup>2</sup> + (n/8)<sup>2</sup>]<sup>½</sup>(λ/<i>D</i>)/SNR<sub>v</sub>, where n is the angular subtense of the object divided by the diffraction angle λ/<i>D</i>, SNR<sub>v</sub> is the signal-to-noise voltage ratio, λ is the wavelength of the light used, and <i>D</i> is the diameter of the limiting aperture in the optical system under consideration.
© 1982 Optical Society of America
Glenn A. Tyler and David L. Fried, "Image-position error associated with a quadrant detector," J. Opt. Soc. Am. 72, 804-808 (1982)