Lau fringes and subjective refraction

Abstract

Lau fringes formed in the far field of a pair of gratings illuminated by spatially incoherent light are known to disappear when one grating is rotated slightly (+/-3 degrees ) with respect to the other. We observed that a cylindrical lens that was appropriately rotated could restore the high-contrast Lau fringes by bringing together the rays that are coherent with respect to each other. We have developed a new refractometer based on this phenomenon, the details of which are presented. Measurement of the cylinder power and axis of the human eye is possible with good accuracy and repeatability with this instrument.

Application of wavelet filtering techniques to Lau interferometric fringe analysis for measurement of small tilt angles

“…has been reported. It has also been used for fabrication of array illuminators [9], theta-encoder [10] and for realization of refractometer for testing the eye-sight [11]. The use of Lau interferometer for determination of the focal length of collimating lens [12], profiling of reflecting surface [13] and in vibration analysis [14] has also been demonstrated.…”

Automated collimation testing in Lau interferometry using phase shifting technique

“…Lau set up and its modified form has been used for low-cost measurement of various physical variables such as focal length [3], temperature [4], small tilt angles [5], refractive index [6], parallelism of the plate [7], degree of coherence [8], etc. It has also been used for fabrication of array illuminators [9], theta-encoders [10] and for realization of refractometers for testing the eye-sight [11]. Recently, we reported the use of Lau interferometer for the determination of the focal length of collimating lens [12].…”