Image Enhancement of Computational Reconstruction in Diffraction Grating Imaging Using Multiple Parallax Image Arrays

Abstract

This paper describes an image enhancement method of computational reconstruction for 3-D images with multiple parallax image arrays in diffraction grating imaging. A 3-D imaging system via a diffraction grating provides a parallax image array (PIA) which is a set of perspective images of 3-D objects. The parallax images obtained from diffraction grating imaging are free from optical aberrations such as spherical and chromatic aberrations that are always involved in the 3-D imaging via a lens array. The diffraction grating imaging system for 3-D imaging also can be made at a lower cost system than a camera array system. However, the parallax images suffer from the speckle noise due to a coherent source; also, the noise degrades image quality in 3-D imaging. To remedy this problem, we propose a 3-D computational reconstruction method based on multiple parallax image arrays which are acquired by moving a diffraction grating axially. The proposed method consists of a spatial filtering process for each PIA and an overlapping process. Additionally, we provide theoretical analyses through geometric and wave optics. Optical experiments are conducted to evaluate our method. The experimental results indicate that the proposed method is superior to the existing method in 3-D imaging using a diffraction grating.

Computational Three-Dimensional Imaging System via Diffraction Grating Imaging with Multiple Wavelengths

“…Figure 2 shows basic geometries to explain the ray analysis in diffraction grating imaging, where a point object, its parallax images, and an imaging lens are introduced [ 20 , 21 , 22 ]. Here, a point object is located at ( x O , y O , z O ) and a diffraction grating is located at a distance d away from an imaging lens in the x – y plane.…”

“…Recently, a diffraction grating imaging (DGI) system has been introduced to acquire and process a 3-D image [ 18 , 19 , 20 , 21 , 22 ]. The optical configuration of a DGI system consists of an amplitude diffraction grating in the form of a transmissive film, a camera, and a laser as a light source [ 18 ].…”

“…One is an optical pickup process, using a diffraction grating. The other is a computational reconstruction process, producing a 3-D volume [ 20 , 21 , 22 ]. In the optical pickup process, 3-D objects are illuminated with a laser beam, and then the laser rays are scattered from the objects.…”

“…Also, the speckle noise of a laser source deteriorates the image quality in computational reconstruction [ 20 ]. Although some techniques were addressed to solve these problems [ 21 , 22 ], there are still many problems such as speckle noises from a laser source, artifacts from crosstalk between parallax images, and blurring from back-projection in computational reconstruction. Thus, it is required to continue researching new techniques to overcome these shortcomings and to improve the image quality in diffraction grating imaging.…”

Lensless Three-Dimensional Imaging under Photon-Starved Conditions

“…In particular, lensless 3D imaging is free from diffraction and aberrations that occur in lens array-based acquisition methods, and has advantages over camera array or moving camera-based acquisition methods in point of view for cost effectiveness and system complexity. Diffraction grating imaging [ 11 , 12 , 13 , 14 ], which is one of lensless 3D imaging, consists of a transmission grating to generate diffraction images and a camera or image sensor to acquire the generated diffraction image array. These diffraction images are used for the computational 3D reconstructions [ 11 , 12 , 13 , 14 ].…”