Partial aperture imaging by systems with annular phase coded masks

Abstract

Interferenceless coded aperture correlation holography is a recently developed technique for indirect 3D imaging of objects without two-wave interference. In such systems, the intensity response to a point is first recorded by modulating the light diffracted from a point object by a pseudorandom coded phase mask (CPM). The object intensity response is recorded under identical conditions and with the same CPM by mounting an object at the same axial location as of the point object. The image of the object is reconstructed by a crosscorrelation between the above two responses. In the present study, the imaging capabilities of a system with partial apertures are demonstrated by synthesizing the CPM in the shape of a ring. The partial aperture system demonstrates 3D imaging capabilities with an area as low as 1.4% of the total aperture area, which is beyond the limits of a regular imaging system. These superior imaging capabilities of the new technique might be useful for imaging with ground and space telescopes.

Review of 3D Imaging by Coded Aperture Correlation Holography (COACH)

“…One unique advantage of I-COACH concept implemented by PAIS technique is the ability to image through an annular aperture of diameter D with the similar resolution of a full-disc aperture of the same diameter D. To the best of our knowledge, [61] is the first study which shows that an annular aperture can image general targets without substantial reduction of the image resolution. Annular aperture imaging is a new technology to image objects through part of the aperture area with as close as possible resolution capabilities of the full aperture.…”

“…This statement has practical and theoretical importance. In the practical aspect, the method proposed in [61,72] offers much more efficient imaging in the sense of weight and aperture utilization. In the theoretical aspect, it was demonstrated that reducing the aperture by two orders of magnitude still enables us to transfer the same amount of information transmitted by the original clear aperture.…”

“…In this section, the partial aperture imaging capabilities of I-COACH is summarized and compared with equivalent direct imaging systems. The I-COACH systems with partial apertures are denoted as partial aperture imaging systems (PAISs) [61]. In order to retain the resolution of the full aperture, annular apertures are considered.…”

“…An experiment demonstrating PAIS was carried out [61] by a single optical channel to image an NBS object with 14 lp/mm. Three intensity patterns were recorded using three different annular CPMs synthesized from three different initial random phase profiles and composed into a complex hologram using phase shifts θ 1,2,3 = 0, 2π/3 and 4π/3.…”

Resolution-enhanced imaging using interferenceless coded aperture correlation holography with sparse point response

“…The object reconstruction is done by correlating the object hologram with a library of point spread holograms (PSHs), where each PSH is recorded for a point object placed at different axial location of the imaging system. I-CAOCH was further developed for extending the system's field of view 22 , for imaging through partial apertures 23 , for better resolving image details 8,24,25 and for seeing through scattering layers 26 . Due to the lack of two wave interference in the I-COACH holography, the optical configurations and calibrations are simpler in comparison to traditional holographic systems.…”