Comparison of spectacle-lens optical quality by modulation transfer function measurements based on random-dot patterns

Abstract

We present a method for comparing the optical quality of spectacle lenses based on determining the modulation transfer function ͑MTF͒ using random-dot patterns. Furthermore, we determine the precision of the method under repeatability conditions of measurement. The experimental device is composed of a laptop computer in which the LCD monitor presents the random-dot pattern, a liquid-crystal tunable filter, the lens under test, and a charge-coupled device detector connected to its control card installed in another computer. The method proposed has major advantages: the lenses can be characterized at different wavelengths; no additional sources to illuminate the pattern are required, the monitor's lighting source itself is used; and the characteristics of the pattern can be quickly and easily modified, as we install the control software in the laptop computer. We analyze three spherical spectacle lenses ͑+5 D͒ from different manufacturers and, in terms of MTF, the greatest difference found between them is 13.7%. The uncertainty associated with this method falls within the range of 0.001 and 0.06. Given the low uncertainty values, differences found between the lenses are significant. Therefore, the method proposed is a versatile and quick technique to distinguish the optical quality of spectacle lenses from different manufacturers. © 2010Society of Photo-Optical Instrumentation Engineers.

A method of generating amplitude masks with a constant power spectra and using them to measure the two-dimensional modulation-transfer functions of optical systems

“…[2][3][4] The basic principle of this method consists of recording a random mask and subsequently analyzing the spectrum of its image. Random masks are generated on a discrete raster.…”

“…The technique used to measure the MTF is based on the random-mask method. [2][3][4] A CPSM obtained by the method developed here and displayed on a liquid-crystal monitor screen with gamma correction switched off was used as the test scene. The mask was recorded by the test camera in such a way that one mask pixel corresponded to one camera pixel.…”

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“…Según Rubiño et. al [8,9] la MTF total viene dada en función de la lente y la cámara CCD a través de la siguiente relación:…”

Comparative analysis of resolution measurement methods for the optoelectronic systems

“…LCTF is, in fact, bandpass filter, based on LC controllable elements, transmitting one wavelength and cutting off the rest [17]. The filter application allows determining the MTF of the system using quasimonochromatic illumination and makes it possible to characterize it at different wavelengths [18]. There is an experimental setup scheme in Fig.7.…”