Depth resolution enhancement in optical scanning holography with a dual-wavelength laser source

Abstract

In this paper, we use two point sources to analyze the depth resolution of an optical scanning holography (OSH) system with a single-wavelength source. A dual-wavelength source is then employed to improve it, where this dual-wavelength OSH (DW-OSH) system is modeled with a linear system of equations. Object sectioning in DW-OSH is obtained with the Fourier domain conjugate gradient method. Simulation results show that, with the two source wavelengths at 543 nm and 633 nm, a depth resolution at 2.5 μm can be achieved. Furthermore, an OSH system emulator is provided to demonstrate the performance of DW-OSH compared with a conventional OSH system.

Depth resolution enhancement in double-detection optical scanning holography

“…A more sophisticated regularization method has been shown to deliver better results [14,25,26], but we choose this l 2 -norm regularization for better comparison with the original inverse imaging for OSH [9] and the dual-wavelength technique [18]. The solution to Eq.…”

“…We then move the object away from the scanning mirror by Δz 15 mm, such that z In order to evaluate the performance of the proposed method in a more precise system, we use an OSH simulator for the investigation. In the simulator, the finite diameter of the apertures together with the finite scanning step size of the scan process, and different kinds of noise are taken into consideration, the detail of which can be found in [18]. The system parameters are as follows: the pinhole aperture is r 2.5 μm, the diameter of the collimated beam is D 40 mm, and the focal length of the lens is f 50 mm.…”

“…12 and 13 that to improve the system performance we should use high numerical aperture in the optical setup. Further improvement can be achieved by increasing the sampling step size or the area for the recording holograms [18].…”

“…Using two point pupils, with one as the positive spherical source and the other as the negative one, the defocus noise is reduced and the depth resolution can be doubled. Recently, to improve the depth resolution, a method using a dual-wavelength laser source has been proposed [18]. By switching the dualwavelength laser between 632 and 543 nm, more information can be recorded, leading to a depth resolution of 2.5 μm.…”

Deviation influences on sectional image reconstruction in optical scanning holography using a random-phase pupil

“…While the in-focus sectional image of 3-D object can be reconstructed easily from the recorded electronic holograms, it is usually degraded by out-of-focus haze. The haze is a result of contributions from the other sections, which manifest as defocus noise in the in-focus section [3,4]. This defocus noise results from the decoding function used in the normal OSH method not being sensitive enough to the sectional location.…”