Optical lens designed for speckle measurement based on human eyes resolution cells on speckle pattern induced by laser projector

Abstract This paper presents an optical lens design for laser projector induced speckle measurement, based on resolution cells of human eyes. While the speckle pattern at the image plane was split up into hundreds of cells of human eyes resolution and formed cells pattern, its contrast become lower than that was calculated based on individual pixels. To evaluate the sensation of human eyes on the speckle pattern and perform a standardized speckle measurement, resolution of human eyes at the objective plane should be taken into consideration. Different lenses of a camera sensor usually have different field of views, therefore each pixel presents different size at the objective plane. The relationship between pixel size on the objective plane, human eyes resolution and F-number of camera lens was deduced, which is important for the optical design for speckle measurement. An optical design around an Aptina’s MT9P001 imaging sensor was developed, optimized and analyzed using Zemax. The results show that the MTF is above 0.3 when spatial frequency is 113.5 lp/mm, distortion is less than 1%, relative illumination is more than 90% at the max field of view, and the radius of the spot size is less than 2um, which has met the requirements for speckle pattern measurement based on human eyes resolution cell. Finally, we performed a sensitivity analysis of tolerance and Monto Carlo simulation to confirm that the lens could be fabricated.